# Deciphering the Violent Universe

## Rationale

High energy astrophysics is an exciting laboratory of fundamental physics. Exotic and transient astrophysical phenomena reveal the violent and capricious nature of the Universe. Wide-field and all-sky monitoring has already led to a wealth of discoveries such as pulsars and gamma-ray bursts which probe extreme realms of physics and yet were not anticipated prior to their discovery. While huge progresses have been made in recent years, our understanding remains incomplete.

The goal of this conference is to present and discuss our current understandings of high energy transients, in particular:

1. Gamma-Ray Bursts
2. Core-Collapse Supernovae
3. Thermonuclear and Super-Luminous Supernovae
5. Tidal Disruption events
6. Exotic transients (magnetars, soft gamma repeaters, neutrinos, etc)
7. Gravitational Wave Sources
8. Future missions

Each session will consist of invited and contributed talks. In addition, time for discussion will be allocated at the end of each session.

## Program (.pdf)

Monday morning. Session I: Accretion disks, jets, and particles
8.50-9.00 Welcome and opening remarks
9.00-9.30 Sasha Tchekhovskoy The role of accretion disks in transient sources
9.30-10.00 Pawan Kumar Relativistic jets in high energy transients
10.00-10.15 Elena Pian Blazars in outburst as probes of extragalactic jets formation and propagation (.pptx)
10.15-10.45 Grzegorz Kowal Particle acceleration mechanisms
###### The first observations of high-energy radiation, commonly known as cosmic rays, took place over one hundred years ago. Soon after the discovery of cosmic rays, Victor Hess in 1912 confirmed with his observations, that they are mostly of galactic or extra-galactic origin. Their origin and nature, however, still puzzles the modern astrophysics and is considered one of the unresolved problems. In the first part of my talk I will briefly describe what we know about the properties of cosmic rays from observations and discuss the physical mechanisms, such as diffusive shock acceleration and turbulence, believed to be responsible for accelerating thermal particles to high energies. Finally, in the last part I will present the results of our studies on first-order Fermi acceleration by fast turbulent reconnection.
10.45-11.00 Elisabete de Gouveia Dal Pino Magnetic reconnection particle acceleration and gamma-ray emission around black hole sources (.pdf)
11.00-11.30 Coffee Break & Posters
11.30-12.00 Dafne Guetta Neutrinos from astrophysical sources
###### One of the key goals in high energy astrophysics is to understand the formation and the dynamics of astrophysical jets and discover the sources of Ultra High Energy Cosmic Rays (UHECR). Cosmic Rays are extremely high energy charged particles that travel the universe at nearly the speed of light. Though they were discovered nearly a century ago, the research community is still puzzled by the origin of these high energy particles. Since neutrinos rarely interact, huge detectors covering an area of more than 1 km2 are required to make a statistically significant measurement. The South Pole in Antarctica is the host of IceCube, the first 1 km2 scale high energy neutrino detector that was completed in 2011. In this talk I will review the main mechanisms that may lead to the production of High Energy Neutrinos (TeV-PeV) from astrophysical sources. I will give an overview on the characteristic of these emissions and an estimate of the fluxes and rates that can be detected at the future and present neutrino telescopes. I will discuss the constraints given on these sources from the results of IceCube and future ultra high energy telescope ARA.
12.00-12.15 Nissim Fraija PeV Neutrino and UHECRs connexion around the Lobes of the nearest radio galaxies
###### Ultra-high-energy cosmic ray (UHECR) detections could give an indirect signal of PeV neutrino emission. Recently, Pierre Auger observatory reported the distribution of arrival directions of the highest energy cosmic rays in 10 years of operations. The IceCube neutrino telescope reported the detection of 54 extraterrestrial neutrinos in the High-Energy Starting Events catalog. The highest-energy neutrino event (IC35) reported in this catalog had an energy of ∼2 PeV and was located centered at RA=208.40 and DEC=-55.80 (J2000). Being Centaurus A and Centaurus B the nearest radio-loud active galactic nuclei and ones of the best potential candidates for accelerating cosmic rays up to 1020 eV, we investigate the possible association of UHECRs with the lobes of these radio galaxies and also the conditions so that the PeV-neutrino event (IC35) reported in the HESE catalog by the IceCube Collaboration could be associated to UHECRs detected by PAO around the giant radio lobes.
12.15-12.45 Discussion Elisabete de Gouveia dal Pino
Monday afternoon. Session II: Tidal disruption events
16.00-16.30 James Guillochon Models of tidal disruption events
16.30-16.45 Cristina Romero Cañizales The TDE ASASSN-14li and its host resolved with high-resolution radio observations
###### It is well established that the merger among gas-rich galaxies can trigger both starbursts and the onset of an active galactic nucleus (AGN). We present results on European very long baseline interferometry (VLBI) Network (EVN) observations toward PGC043234, a post-starburst galaxy which seems to be the remnant of a merger with current negligible star formation. This system recently hosted the tidal disruption event (TDE) ASASSN-14li. Our EVN observations have allowed us to resolve the system into two components 2pc apart. The components resemble a core-jet/outflow system, whose secondary component can be related directly to ASASSN-14li, if its motion is superluminal, or to a past AGN flare or TDE if its motion is subluminal. The exciting possibility exists that both components are instead a binary BH system. These possibilities will be tested in upcoming EVN observations, from which we will show preliminary results.
16.45-17.00 Katie Auchettl The nature of the soft X-ray emission of tidal disruption events
###### If a star passes within the tidal radius of a supermassive black hole, it will be disrupted, and subsequently accreted, producing a luminous X-ray flare. Over the last few decades, a significant number of tidal disruption events (TDEs) have been discovered, however for only a handful of these events has the X-ray emission from these source been studied in detail. In this talk, I will present the results of a comprehensive, systematic study of the soft X-ray emission from arising from TDEs, while highlighting observationally how the X-ray emission from these events differ from those of AGN. In particular, I will show that the X-ray emission of a TDE evolves significantly with time and decays with power-law indices that are much shallower than the canonical −5/3. In addition, I will show that the long lifetimes of TDEs are consistent with what one would expect from a main sequence star being disrupted by a viscously slowed BH with mass < 107 M☉, while the isotropic luminosities of jetted and non-jetted events are separated by a ”reprocessing valley”, which we suggest is naturally populated by optical/UV TDEs whose X-ray emission is being reprocessed into lower energies.
17.00-17.30 Coffee Break & Posters
17.45-18.00 Brenna Mockler Weighing black holes with TDEs
###### While once rare, observations of tidal disruption events are quickly becoming commonplace. To continue to learn from these events it is necessary to robustly and systematically compare our growing number of observations with theory. Here we present a tidal disruption module for the new Modular Open Source Fitter for Transients (MOSFiT) and the results from fitting 12 tidal disruption events (TDEs). Our model uses hydrodynamical simulations to generate accretion rates and passes these accretion rates through viscosity and light reprocessing modules to get theoretical light curves. It then uses an MCMC fitting code to compare these theoretical light curves with observations. This procedure provides a relatively robust method for measuring the masses of supermassive black holes because the shape of a TDE light curve depends strongly on the black holes mass. We find that the events we fit have black hole masses in the range from 1 × 106 − 1 × 108 M☉, and that the masses we derive are mostly consistent with other methods used in the literature. We also find that none of the events appear to show long viscous delays, supporting the theory that our current observing strategies are missing a significant fraction of viscously delayed events.
18.00-18.15 Nathaniel Roth Interpreting the spectral properties of tidal disruption events (.pptx)
###### Wide-field optical surveys are detecting TDEs at optical wavelengths, but the origin of this optical emission remains poorly understood. Discriminating between various models for this emission requires careful analysis of the observed spectra, which display a large amount of diversity. I will present results from radiative transfer calculations designed to connect the underlying hydrodynamics of the disrupted star to what is observed, showing how the combined effects of electron scattering and gas kinematics can shape the line profiles. In particular, I will demonstrate how the line profiles from several TDE spectra can be interpreted as evidence for massive, radiatively launched outflows.
18.15-18.45 Discussion Enrico Ramirez Ruiz
Tuesday morning. Session III: Core collapse Supernovae
9.00-9.30 Matteo Cantiello The Uncertain Evolution of Core Collapse Supernova Progenitors
###### I will review the current status of our understanding of massive stars evolution, emphasizing both recent progress and areas where we still lack a physical picture of the dominating processes at work. I will discuss possible ways to move forward, stressing the emerging synergies between theoretical and computational efforts, and the new observational probes.
9.30-9.45 Jeremiah Murphy A Unifying Explosion Condition for Core-collapse Supernovae
###### The fundamental challenge in core-collapse supernova (CCSN) theory is to explain why massive stars explode. We present a new integral condition for explosion that provides a deeper understanding of why stars explode. This explosion condition is a promising explodability measure for CCSN simulations. As a result, this condition provides a means to quantitatively explore which physical effects enable explosion. For example, using this condition, we show how turbulence enables core-collapse supernova explosions. An important result in core-collapse supernova (CCSN) theory is that spherically-symmetric, one-dimensional simulations fizzle, while multi-dimensional simulations explode. Recent multi-dimensional investigations suggest that turbulence eases the condition for explosion, but how has not yet been clearly defined. We develop a turbulence model for neutrino-driven convection, show that this turbulence model reduces the condition for explosions in concordance with multi-dimensional simulations, and identify which turbulent terms enable explosions. We find that turbulent ram pressure is not the dominant factor in reducing the condition for explosion. Instead, we find that there are many contributing factors, turbulent dissipation being the dominant.
9.45-10.00 Alexey Tolstov The first supernovae in the early Universe: radiation hydrodynamics simulations (.pdf)
10.00-10.15 Jennifer Andrews Progenitors of Type IIn Sne
###### Approximately 8-9% of core collapse supernovae (CCSNe) show the presence of narrow (∼100 km/s) hydrogen emission lines in their spectra, due to the photoionization or shock heating of the surrounding, slow moving circumstellar medium (CSM). These CCSNe are classified as Type IIn and while they all have narrow emission lines, they are far from homogeneous. They vary in peak absolute magnitude and some exhibit bright hydrogen emission for years or decades after explosion. To date, no definitive progenitor scenario seems to exist for these interacting SNe, and it is likely that they can arise from a wide variety of progenitor masses and mass-loss histories. Red supergiants and yellow hypergiants will have slower wind velocities and lower mass-loss rates than luminous blue variables, creating very different explosion environments. Many SNe IIn also have asymmetric CSM, whether it be bipolar or in the form of a disc or torus. Through continuous optical monitoring of a sample of IIn SNe we have found that the addition of CSM asymmetry in Type IIn SNe allows for a continuum among the non-super luminous IIn, and opens the door for RSGs to be common progenitors for all but the brightest SNe IIn.
10.15-10.30 David R. Aguilera Dena Unified progenitor models for long-duration gamma ray bursts and Type I superluminous supernovae
###### We model the late evolution and mass loss history of rapidly rotating Wolf-Rayet stars in the mass range 5 M☉ ... 100 M☉. Such stars, when they are hydrogen-free and contain little helium, represent the prime progenitor candidates for long-duration gamma-ray bursts, superluminous supernovae and broad-line Type Ic supernovae. We obtain corresponding models from simulating rapidly rotating quasi-chemically homogeneously evolving single stars. We find that such models with enhanced mixing retain very little helium and are compatible with Type Ic supernovae. The relatively long post-core helium burning time scale in our lower mass models (M < 20 M☉) allows for angular momentum transport, leading to core angular momenta in the range expected for magnetar driven SLSNe. Due to their faster contraction, our more massive models retain core angular momenta suitable to produce long-duration gamma-ray bursts in the collapsar scenario. Due to the absence of a significant helium envelope, the rapidly increasing neutrino emission after core helium exhaustion in our models leads to an accelerated contraction of the whole star. This contraction induces a strong spin-up, and centrifugally driven mass loss at rates of up to 10-2 M☉/yr. Since the angular momentum transport in our lower mass models enhances the envelope spin-up, they show the largest relative amounts of centrifugally enforced mass loss, i.e., up to 25% of the expected ejecta mass. Our massive models evolve into the pulsational pair-instability regime, where again large amounts of CO-rich matter may be ejected preceding an expected engine-driven Type Ic supernova. Signs of such mass loss should be observable at early epochs of the supernova explosion, and may be related to bumps observed in the light curves of SLSNe, or the massive circumstellar CO-shell deduced for some SLSNe.
10.30-10.45 Giacomo Terreran Hydrogen-rich supernovae beyond the neutrino-driven core-collapse paradigm
###### Type II supernovae (SNe) are the final stage of massive stars (above ∼ 8 M☉) which retain part of their hydrogen-rich envelope at the moment of explosion. They typically eject up to 10-15 M☉ of material, with energies of the order of 1051 erg and peak magnitudes of -17.5 mag. Although more luminous events are commonly discovered, their explosion energies are mostly in the range of a few times 1051 erg, explainable by neutrino-driven explosions and neutron star (NS) formation. We present our study of OGLE-2014-SN- 073, one of the brightest non-interacting Type II SN ever discovered, with an unusually broad lightcurve combined with high ejecta velocities. From our hydrodynamical modelling we infer a remarkable ejecta mass of 60 M☉, and a relatively high explosion energy of 12.4 x 1051 erg. We show that this object belongs, with a very small number of other hydrogen-rich SNe, to an energy regime that is not explained by standard core- collapse neutrino-driven explosions. We compare the quantities inferred by the hydrodynamical modelling with the expectations of various exploding scenarios, trying to explain the high energy and luminosity released. We find some qualitative similarities with pair-instabilities SNe, although a prompt injection of energy by a magnetar seems also a viable alternative to explain such extreme event. This is an object with no precedent in literature and it has the potential to stand as the archetypal of a new category. Our work has been recently accepted for publication on Nature Astronomy.
10.45-11.00 Vikram Dwarkadas Investigating the Highest Luminosity X-ray Supernovae
###### Type IIn supernovae (SNe) are characterized by narrow lines on a broad base in the optical spectrum. A wide diversity in their lightcurves, and in SNe that exhibit IIn features, has greatly complicated the task of identifying their progenitors. IIns have the highest X-ray luminosity of all SNe, generally exceeding 1040 ergs s −1 at early times, and 1038 ergs s-1 after several thousand days, and are observable in X-rays decades after explosion. Many of the lightcurves tend to fall off rather steeply at late times, although one interesting case displayed a rising light curve for several thousand days. These characteristics, along with their high luminosities at other wavelengths, imply initial expansion in a very dense medium. At later times the densities decrease faster than expected for expansion in a steady wind. Their X-ray spectra generally show distinct lines, suggesting that the emission is thermal in origin. We have aggregated together data available in the literature, or analysed by us, to compute the lightcurves of almost all young SNe that have been detected in X-rays. We will show the lightcurves of all IIns that have been observed in X-rays, and compare their lightcurves and spectra to those of other types of SNe. We will review the known properties of the X-ray emission from Type IIn, and explore the implications for the SN environment, progenitor mass-loss and the identity of the progenitors.
11.00-11.30 Coffee Break & Posters
11.30-12.00 Alex Heger Stripped Core-collapse Supernovae (.pdf)
12.00-12.15 Ori Fox A HST Search for the Binary Secondaries of Nearby Stripped-Envelope Supernovae (.pptx)
12.15-12.30 Yudai Suwa Ultra-stripped Type Ic supernovae generating double neutron stars (.pdf)
12.30-12.45 Tamas Szalai Searching for signs of circumstellar interaction in supernovae: a mid-IR investigation (.pdf)
12.45-13.00 Poster Session
Tuesday afternoon. Session IV: Core collapse Supernovae II
16.00-16.30 Raffaella Margutti GRB-supernova association (.pdf)
16.30-16.45 Emanuele Sobacchi A Common Central Engine for Long-Soft Gamma Ray Bursts and Type Ib/c Supernovae?
###### Long-duration, spectrally-soft Gamma-Ray Bursts (GRBs) are associated with Type Ic Core Collapse (CC) Supernovae (SNe), and thus arise from the death of massive stars. In the collapsar model, the jet launched by the central engine must bore its way out of the progenitor star before it can produce a GRB. Most of these jets do not break out, and are instead choked inside the star, as the central-engine activity time, te, is not long enough. Modelling the long-soft GRB duration distribution assuming a power-law distribution for their central-engine activity times, ∼ te-a for te > tb, we have found a steep distribution (a∼4) and a typical GRB jet breakout time of tb ∼ 60s in the star’s frame (Sobacchi et al. 2017; arXiv:1705.00281). The latter suggests the presence of a low-density, extended envelope surrounding the progenitor star, similar to that previously inferred for low-luminosity GRBs. Extrapolating the range of validity of this power law below what is directly observable, to te < tb, by only a factor of ∼ 4 − 5 produces enough events to account for all Type Ib/c SNe. Such extrapolation is necessary to avoid fine-tuning the distribution of central engine activity times with the breakout time, which are presumably unrelated. We speculate that central engines launching relativistic jets may operate in all Type Ib/c SNe. In this case, the existence of a common central engine would imply that (i) the jet may significantly contribute to the energy of the SN; (ii) various observational signatures, like the asphericity of the explosion, could be directly related to jet’s interaction with the star.
16.45-17.00 Dario Carbone Identifying Engine-Driven Supernovae: an Optimized Radio Follow-up Strategy
###### How exactly massive stars die is still an open question as the zoo of supernovae (SNe) explosions is very wide and variegate. The most extreme and rare type of supernova explosion is an engine-driven supernova associated with relativistic ejecta (gamma-ray burst; GRB), and bright radio emission. In the near future, several synoptic optical surveys (e.g., ZTF and LSST) will offer the unprecedented opportunity of discovering larger samples of the rarest forms of core collapses. Therefore, we need to have an efficient radio follow-up plan to detect and correctly identify engine-driven SNe, as well as promptly distinguish them from other types of radio bright (but non-relativistic) explosions such as e.g. CSM-interacting SNe. In this talk, I will present two new statistical methods that allow us to quantify the efficacy of radio follow-up strategies in detecting and classifying radio bright SNe, as well as potential off-axis GRBs. These methods allow us to optimize the follow-up so as to maximize either the detection probability in general, or the accuracy in identifying relativistic events in particular. I will conclude by providing an example follow-up strategy that correctly identifies most of the relativistic SNe, about half the CSM-interacting SNe, and about a third of the off-axis GRBs.
17.00-17.30 Coffee Break & Posters
17.30-18.00 Paolo Mazzali Super luminous Supernovae
18.00-18.15 Ragnhild Lunnan A Circumstellar Shell around a Superluminous Supernova Revealed in a Light Echo
###### Superluminous supernovae (SLSNe) are a rare class of transients with peak luminosities 10-100 times those of normal core-collapse and Type Ia SNe, and whose progenitors and energy sources are still debated. Here, I will report on a surprising result from a late-time spectroscopic survey of SLSNe: the discovery of a shell of circumstellar material (CSM) around the SLSN, revealed by both absorption and subsequent re-emission in Mg II from the shell, in an echo of the SLSN light. The blueshift of the absorption lines allow us to measure the velocity of the CSM shell, while the time delay between the blueshifted and redshifted emission lines directly constrains the size of the shell. While pre-supernova mass loss is not uncommon in massive stars, this kind of observation is nearly unique, with the closest observed analogue being the ionization of the ring around SN1987A by the supernova flash. I will discuss both the circumstances that allowed us to observe it in this particular instance, and the implications for SLSN progenitors and mass loss mechanisms. In this case, the high shell velocity ( 3000 km/s) and implied time of the eruption ( 50 years prior to explosion) may point to a pulsational pair-instability origin.
18.15-18.30 Akihiro Suzuki Dynamical evolution of supernova ejecta powered by a central engine in multi-dimension
###### One of the remarkable results of recent un-biased transient surveys is the discovery of superluminous super- novae, a special class of extremely bright supernovae. Hydrogen-poor superluminous supernovae are among the most mysterious, because of their still unknown energy source. A plausible scenario for the extreme brightness of hydrogen-poor supernovae assumes that the compact object (neutron star or black hole) left at the center of the supernova ejecta deposits additional energy in some way to give rise to bright emission. We have recently been working on multi-dimensional simulations of dynamical evolution of supernovae ejecta powered by the central energy source. When the total amount of the injected energy is much larger than the original kinetic energy of the supernova ejecta, the energy redistribution process in the ejecta associates with multi-dimensional turbulent motion and efficient mixing of the ejecta. We present recent results of our numerical calculations and discuss their implications for observations of hydrogen-poor superluminous supernovae.
18.30-19.00 Discussion Elena Pian (.pptx)
Wednesday morning. Session V: Thermonuclear SNe and fast radio bursts
9.00-9.30 Ryan Foley The Diversity of thermonuclear transients
9.30-9.45 Aleksandar Cikota Spectropolarimetry of Supernovae Ia
###### Spectropolarimetric observations of SNe Ia allow us to (i) study the geometry of the ejecta by observing the polarization of absorption lines, and (ii) study the dust along the line of sight to SNe Ia by observing the ISM continuum polarization. Understanding the effect of dust extinction on SNe Ia is essential for accurate measurement of cosmological parameters and the expansion history of the Universe. Different studies of the host galaxies dust extinction from SNe Ia yielded diverse values of the absorption to reddening ratio, R v , ranging from R v = 1 to R v = 3.5 (see e.g. Cikota et al. 2016). Studies of dust along the lines of sight of SNe Ia might lead to conclusions on the progenitor system, because the single degenerate (SD) and double degenerate (DD) models imply different circumstellar environments. Furthermore, studeis of line polarization of SNe Ia might imply different explosion scenarios. Polarization models of SNe Ia predict different polarization signatures for the violent merger scenario, compare to the double-detonation and delayed-detonation models (Bulla et al. 2015, 2016). We will discuss the peculiar continuum polarization profiles of SNe Ia sight lines, and present preliminary results extracted from our spectropolarimetric observations of a sample of ∼ 35 SNe Ia observed with VLT at more than 120 epochs in total.
9.45-10.00 Tyrone E. Woods Supernova Archaeology: Unveiling the origin of Type Ia supernovae
###### About half of the iron in our blood was born in the thermonuclear explosion of a white dwarfa Type Ia supernova (SN Ia). However, we still do not know why a white dwarf would undergo such an explosion. Evolutionary models can be grouped into either ”accretion” or ”merger” scenarios, with accretion models typically implying a hot, luminous phase prior to explosion. These objects are significant sources of ionizing radiation; therefore, the environment surrounding SN Ia progenitors as well as nearby remnants should be strongly ionized, and traced by faint nebular emission. Such ”relic” nebulae should extend out to dozens of parsecs and linger for roughly 100,000 years. Here we report deep upper limits which rule out accreting, nuclear-burning white dwarfs as the progenitors of several young SN Ia remnantsin particular, that of Tycho’s supernovaas well as in older stellar populations.
10.00-10.15 Arturo Avelino Toward a near-infrared SN Ia Cosmology (.pdf)
10.15-10.30 Brian Williams The Three-dimensional Expansion of the Ejecta from Tycho’s Supernova Remnant
###### We present the first 3D measurements of the velocity of various ejecta knots in Tychos supernova remnant, known to result from a Type Ia explosion. Chandra X-ray observations over a 12 yr baseline from 2003 to 2015 allow us to measure the proper motion of nearly 60 tufts of Si-rich ejecta, giving us the velocity in the plane of the sky. For the line-of-sight velocity, we use two different methods: a nonequilibrium ionization model fit to the strong Si and S lines in the 1.2-2.8 keV regime, and a fit consisting of a series of Gaussian lines. These methods give consistent results, allowing us to determine the redshift or blueshift of each of the knots. Assuming a distance of 3.5 kpc, we find total velocities that range from 2400 to 6600 km s-1, with a mean of 4430 km s-1. We find several regions where the ejecta knots have overtaken the forward shock. These regions have proper motions in excess of 6000 km s-1. Some SN Ia explosion models predict a velocity asymmetry in the ejecta. We find no such velocity asymmetries in Tycho, and we discuss our findings in light of various explosion models, favoring those delayed-detonation models with relatively vigorous and symmetrical deflagrations. Finally, we compare measurements with models of the remnants evolution that include both smooth and clumpy ejecta profiles, finding that both ejecta profiles can be accommodated by the observations.
10.30-11.00 Coffee Break & Posters
11.00-11.30 Emily Petroff Fast Radio Bursts: Recent Discoveries and Future Prospects
###### Two general types of coherent emission mechanisms for fast radio bursts (FRBs) are considered maser and antenna mechanisms. We use the observed properties of FRBs to constrain the physical conditions needed for these two mechanisms. The most favorable case is curvature antenna mechanism near the surface of a magnetar.
Free afternoon and excursion to Tulum
Thursday morning. Session VI: Gamma ray bursts
9.00-9.15 Josiah Schwab Accretion-Induced Collapse and its Progenitors (.pdf)
9.15-9.45 Agniezka Janiuk Accretion in GRB central engine
###### We study the structure and evolution of the accreting plasma in gamma ray burst central engines. The modeling is based on the general relativistic MHD simulations. The nuclear equation of state adequate for dense and degenerate plasma can be incorporated to the numerical scheme. Plasma is cooled by neutrinos and energy is extracted from the rotating BH by magnetic fields. We discuss our results in the frame of the observable GRBs, and speculate about the origin of variability in observed GRB emission. We also discuss the possible contribution of elements synthesized in the winds launched from GRB engine to the kilonova emission.
9.45-10.00 Felix Ryde Emission from accelerating jets in GRBs
###### We will discuss the narrowest spectra expected from gamma-ray bursts. We will present an analytical function for the spectrum that is emitted from the photosphere of a radiation-dominated flow that is under acceleration and numerical spectra from photospheres occurring during the transition into the coasting phase of the flow. Using these spectral models, we reanalyse Fermi observations of GRB100507 and GRB101219 and show that the bursts can be fitted by the spectral models: For GRB101219 the spectrum is consistent with the photosphere occurring below or close to the saturation radius, while for GRB100507 the photosphere position relative to the saturation radius can be determined as a function of time. In the latter case, we find that the photosphere initially occurs in the acceleration phase and thereafter transitions into the coasting phase. We also find that this transition occurs at the same time as the change in observed cooling behaviour: the temperature is close to constant before the break and decays after. We argue that such a transition can be explained by an increasing mass outflow rate. Both analysed bursts thus give strong evidence that the jets are (initially) radiation dominated.
10.00-10.15 J. Michael Burgess GRBs, Spectral Width, and Fitting Emission Models
###### The spectral width and sharpness of unfolded, observed GRB spectra have been presented as a new tool to infer physical properties about GRB emission via spectral fitting of empirical models. Following the tradition of the line-of-death, the spectral width has been used to rule out synchrotron emission in a majority of GRBs. This claim is investigated via examination of both cataloged GRB spectra as well as reanalyzed spectra leading to the introduction of another empirical characterization of the spectra: the data width. This new auxiliary quantity is a direct measure of the folded datas width. Examination of the distribution of data widths suggests that a large fraction of GRBs can be consistent with synchrotron emission. To assess this prediction, a sample of peak-flux GRB spectra are fit with an idealized, physical synchrotron model. It is found that many spectra can be adequately fit by this model even when the width measures would reject it. Thus, the results advocate for fitting a physical model to be the sole tool for testing that model.
10.15-10.30 Jean-Luc Atteia The maximum isotropic energy of gamma-ray bursts (.pdf)
10.30-10.45 Christopher Irwin X-Ray Flares During the Steep Decay Phase from High-Latitude Subjets (.pdf)
10.45-11.00 Hüsne Dereli A study of GRBs with low luminosity afterglows (.pdf)
11.00-11.30 Coffee Break & Posters
11.30-12.00 Jonathan Granot Magnetic fields in Gamma-ray bursts
###### Magnetic fields likely play an important role in most aspects of the GRB phenomena, from the launching and acceleration of the relativistic outflow, through the jet dynamics and stability, to the energy dissipation, particle acceleration and the production of the radiation that we observe. I will review some of the recent progress in our understanding of the role of magnetic fields in GRBs.
12.00-12.15 Paz Beniamini Constraints on millisecond magnetars as the engines of prompt emission in gamma-ray bursts (.pdf)
12.15-12.30 Christina Thöne Abundances and kinematics in GRB hosts in 3D
###### Long GRBs are connected to massive star-formation and possibly require other special circumstances such as low metallicites, as has been claimed by progenitor modeling. GRB hosts are hence star-forming galaxies but most of these hosts remain unresolved due to their large distances. This also makes it difficult to determine whether the properties of the entire host reflect appropriately the properties at the GRB site. Here we present the most recent results from two samples of integral-field spectra of GRB hosts using FLAMES and MUSE that allow us to study those hosts at both high spatial and spectral resolution. In particular, we compare the properties of the GRB site with other regions in the host and its global properties to determine whether we can infer anything on the measurements of unresolved hosts on the properties of GRB progenitors. Although GRB sites are somewhat less extreme in terms of metallicity, age and star- formation than demanded by progenitor models, they tend to occur is the more extreme regions in their hosts. In addition, kinematical studies reveal frequent outflows and interesting kinematics even in the smallest GRB hosts. Finally, we will also put this into context of other massive stellar explosion hosts and their properties, in particular super-luminous SN hosts. Future facilities will soon allow us to extend these studies to higher redshift to study possible differences.
12.30-12.45 Susanna Vergani Tackling the origin of GRBs and SLSNe through the study of their host galaxies
###### Despite their extremely powerful explosions, our knowledge on the progenitors of LGRBs and SLSNe remains very poor. Indeed, massive stars can end their lives in very different ways. Mass, binarity, metallicity, rotation rate, mass-loss and magnetic fields play critical roles in determining the final fate of a star. In most cases it is not possible to have direct observation of the star before its explosion, making the progenitors of different classes of cosmic explosions still unknown. This is the case for LGRBs and SLSNe. Indirect information on the progenitor star conditions of both phenomena can be inferred by the study of the properties of their host galaxies. I will present the results of our recent studies which took advantage of both photometry and spectroscopy of carefully selected samples of SLSN and LGRB host galaxies, as the Swift/BAT6 complete sample of LGRBs up to z∼3. I will show in particular which are the implications of our results on the properties of the progenitor stars of both classes of objects (binarity, metallicity, masses,...), that can be tested by theoretical progenitor models.
12.45-13.00 Cyril Lachaud The SVOM Gamma-ray Burst mission
###### Scheduled for a launch in 2021, SVOM (”Space-based multi-band astronomical Variable Objects Monitor”) is a Sino-French space mission dedicated to the study of the transient sky, focusing on the Gamma-Ray Bursts (GRBs). The satellite payload encompasses a coded-mask telescope operating in the 4-150 keV energy range for real-time detection and localization of all known types of GRBs, a non-imaging gamma-ray monitor extends the GRB spectroscopy up to MeV energies, and two narrow-field follow-up telescopes to refine the GRB positions and to study their afterglow emission in the X-ray and visible bands.The pointing strategy of the satellite has been optimized to favor the detection of GRBs located in the night hemisphere, in order to enhance ground-based observations in the first minutes and to facilitate GRB redshift measurements by the largest telescopes. The SVOM ground segment combines a wide-field camera to catch the GRB prompt emission in the visible band and two robotic telescopes to measure the photometric properties of the early afterglow in the NIR/visible band. We will present the scientific objectives of the SVOM mission, the operations, the instruments and their expected performance for GRB studies. We will also outline the prospects for GRB science with SVOM in the context of the multi-wavelength and multi-messenger panorama for the next decade.
Thursday afternoon. Session VII: Short gamma ray bursts and high energy emission
16.00-16.30 Wen-fai Fong Short gamma-ray bursts
16.30-16.45 Davide Lazzati Numerical simulations of dynamics and radiation from gamma-ray bursts (.pptx)
16.45-17.00 Antonio de Ugarte Postigo  OCTOCAM: Gemini’s future multichannel imager and spectrograph, optimized for transient studies
###### OCTOCAM is an 8-chanel imager and spectrograph capable of obtaining simultaneous imaging in g,r,i,z,Y,J,H, and Ks bands of a field of view of 180”x180”. It will also perform long slit spectroscopy covering the range ̊ with a resolution of ∼4000. Finally by using state of the art detectors OCTOCAM from 3700 to 23500 A will be able to perform high-time resolution observations and minimize the dead time between exposures. In this talk I will present the project, which is currently in the preliminary design phase, and discuss its scientific potential for the study of the transient sky.
17.00-17.15 Rosa Becerra COATLI and DDOTI, the new telescopes to catch transients (.pdf)
17.15-17.45 Coffee Break & Posters
17.45-18.15 Magda González HAWC: recent results
###### The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view TeV instrument. It has been operating since March 2015 from the Volcano Sierra Negra in the State of Puebla, Mexico, at an altitude of 4100 m. above sea level. HAWC operates continuously over a 95% of the time and observes two thirds of the TeV sky. HAWC sensitivity peaks at energies between 2-10 TeV which is close to an order of magnitude higher than IACTs, making their observations complementary. After more than 2 years of operation, HAWC has achieved its second steady source catalogue with both, previously known and new sources, the observation of extended sources and, a search for TeV transient and variable sources as well as follow-up alerts from other instruments such as Fermi, LIGO, etc., among other results. This talk will present recent highlights from the first years of HAWC operations.
18.15-18.30 Simone Dichiara Search of very high energy emission to constrain the physics of GRBs
###### The nature emission coming from gamma-ray bursts (GRBs) up to very high energy is far to be fully understood. Especially the study of their GeV-TeV component represent one of the most challenging and important task needed to unveil the physics of these peculiar events. We perform a search of TeV emission coming from a sample of GRBs detected by Fermi and Swift satellite. Using the data collected by the HAWC observatory we search for possible extended or delayed signal with respect to the prompt phase. Under the framework of the external shock model scenario, we use the flux upper limits derived for each event to constrain the microphysical parameters and the bulk Lorentz factor. Theoretical interpretation will be discussed and the parameter constrains will be presented under different assumptions.
18.30-19.00 Discussion Pawan Kumar
20.00-22.30 Conference dinner
Friday morning. Session VIII: GW and EM counterparts
9.00-9.30 Nergis Mavalvala GW: observations
9.30-9.45 Charles Kilpatrick Optical discovery and follow-up of kilonovae
###### 11 hours after the LIGO and Virgo collaboration detected GW170817, the first detection of gravitational waves from a binary neutron star merger, my team, the One-Meter Two-Hemisphere (1M2H) collaboration, discovered the optical counterpart Swope Supernova Survey 2017a (SSS17a). Within 24 hours of this discovery, follow-up observations spanning the electromagnetic spectrum confirmed that SSS17a was the counterpart to GW170817 and that it was a kilonova resulting from r-process material generated in the merger. I will discuss our observing strategy for finding SSS17a, which involved targeting high-mass galaxies within the LIGO/Virgo error volume and enabled rapid identification and follow up of the optical counterpart, including the only optical spectrum of a kilonova within 24 hours of merger. I will discuss application of this strategy to future gravitational wave sources, especially for more distant sources in an expanded LIGO/Virgo binary neutron star detection volume. Finally, I will discuss the optical and near-infrared properties of SSS17a, which involved a combination of both "blue" and "red" kilonova emission, which will inform the timescales and luminosities of sources for future GW-targeted kilonova searches.
9.45-10.00 Chris Pankow Gravitational-wave measurements of the merger and kilonova properties of GW170817
###### GW170817/GRB170817A was a watershed moment for multi-messenger astronomy and the astrophysics of neutron stars. In addition to the first discovery of a binary neutron star in gravitational waves and confirming the long-held association of short GRB with neutron star mergers, a wealth of observations of the post-merger dynamics in several electromagnetic bands has allowed a nearly full picture of the previously elusive phenomena of kilonova. This was enabled by the detection of the inspiral in gravitational waves, spurring a momentous effort to determine the properties of the pre-merger binary. I will describe the gravitational-wave measurement of the properties of the binary from its inspiral. Then I will explain how, in tandem with studies in numerical relativity, one can determine the properties of the kilonova which are consistent with those inferred from electromagnetic observations. In the future, this information can be synthesized with electromagnetic data to further constrain the neutron star equation of state as well as independently aid in observational campaigns for binaries detected in gravitational waves.
10.00-10.15 Nial Tanvir Observing kilonovae associated with compact binary mergers: lessons from GW170817
###### The electromagnetic detection of events that are also detected as gravitational wave (GW) sources has long been a holy grail" of astrophysics, allowing, as it does, determination of redshifts, distance estimates and characterisation of galactic environments and linking these to source properties. This ambition was finally realised in August 2017 with the discovery of the binary neutron star merger GW170817 by LIGO/Virgo, and the subsequent detection of counterparts across the electromagnetic spectrum. I will review what we have learnt from this event, particularly regarding the UV/optical/IR kilonova emission, and consider implications for future studies.
10.15-10.30 Alan Watson Discovery of the X-ray Counterpart to GW170817 (.pdf)
10.30-10.45 Wen-fai Fong The Environment of GW170817 on Sub-Parsec to Kiloparsec Scales
###### GW170817 marks the first direct detection of a merger of two neutron stars from gravitational waves, followed by the detection of electromagnetic emission across ten orders of magnitude in wavelength. GW170817 was localized to NGC4993, a galaxy in our own cosmic neighborhood, allowing us to study the properties of the merger and its environment in unprecedented detail. Here, I discuss the environment of GW170817 on sub-parsec to kiloparsec scales. I will present radio and X-ray observations, which constrains the make-up of the local environment, as well as HST observations and archival data, which constraints the galaxy-scale stellar population. I also discuss the inferred properties of the environment in the context of cosmological short GRBs.
10.45-11.15 Coffee Break & Posters
11.15-11.45 Rosalba Perna Electromagnetic counterparts of compact object binary mergers
###### Mergers of two compact objects in a binary, in addition to being sources of gravitational waves, may also be accompanied by strong electromagnetic radiation. I will discuss the expectations for double neutron star and neutron star-black hole mergers, and the evidence that they may be associated with short Gamma-Ray Burts. I will then speculate on the novel possibility that electromagnetic signatures may be produced also in the merger of two black holes.
11.45-12.15 Stephan Rosswog Multi-Messenger signals from gravitational wave sources
12.15-12.30 Masaomi Tanaka Kilonova/Macronova Emission from Neutron Star Mergers
###### Kilonova/macronova,optical and near-infrared emission powered by radioactive decays of r-process nuclei, is one of the most promising electromagnetic counterparts to gravitational sources. The opacity in the ejecta is a key factor to determine the emission properties, but lack of systematic atomic data limits our understanding. We recently performed new set of atomic structure calculations and performed detailed radiative transfer simulations with the new atomic data. For various element abundances, we study expected properties of kilonova/macronova emission, such as brightness, color, and timescale. We show that the presence of post-dynamical ejecta (e.g., viscosity-driven wind) can enhance optical brightness by > 2 mag, and that such emission reaches the observed magnitudes of 21.0 mag (100 Mpc) and 22.5 mag (200 Mpc) in optical, which can be detectable with 1m or 2m-class telescopes.
12.30-12.45 Ariadna Murguia-Berthier Unraveling GW170817: shedding light on the neutron star binary merger
###### LIGO recently discovered gravitational waves from a binary neutron star merger, mark- ing the beginning of a new era in high energy astrophysics. Aside from the gravitational wave signal, the event was serendipitously observed in the entire electromagnetic spectrum. In my talk I will argue the non-thermal processes that describe the nature of the relativis- tic ejecta can be probed by the γ-ray, X-rays and radio observations, while the thermal processes, originated in the decay of r-process elements from material torn from the system can be probed by the optical and infra-red observations. I will discuss how the prompt emission and multi-wavelength observations are consistent with a typical short γ-ray burst seen off-axis.
12.45-13.00 Ramandeep Gill Lessons from the short GRB 170817A and off-axis emission from GRB jets (.pdf)
Friday afternoon. Session IX: GW Sources
14.30-15.00 Fred Rasio Merging Black Hole Binaries as GW Sources
###### I will review recent work making theoretical predictions for the properties and merger rates of black hole binaries detectable by LIGO and Virgo. In particular I will contrast the properties of GW sources formed through the evolution of massive binaries in the field to those of sources assembled dynamically through gravitational interactions in dense star clusters, and I will discuss the prospects for distinguishing between these two formation channels with upcoming LIGO/Virgo observations.
15.00-15.15 Jeff Andrews Binary Population Synthesis with Markov-Chain Monte Carlo
###### With the detection of merging stellar mass black hole binaries (BHBHs) by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the study of binary stellar evolution transformed almost overnight. As traditionally employed, binary population synthesis codes interpreting these merging systems have dif- ficulty generating sufficient statistics because merging BHBHs are exceedingly rare; only a small fraction of simulated systems evolve into binaries similar to those observed. I will introduce a fundamentally new approach to studying stellar binary populations that employs a Markov-Chain Monte Carlo algorithm to efficiently explore the binary evolution parameter space. In addition to being substantially more efficient than traditional methods for studying high mass binaries, I will demonstrate how this technique seamlessly incorporates observational constraints and their corresponding uncertainties. Finally, using this algorithm I will demonstrate what we can learn about the merging BHBHs detected by LIGO under the assumption that they were formed through classical binary evolution channels.
15.15-15.30 Tassos Fragos 1D hydrodynamic simulations of the common envelope phase: the formation of binary compact objects
###### To date, the common envelope (CE) phase remains vital in our understanding of a wide variety of astrophys- ical problems, including the formation of XRBs, double compact objects, short and long gamma-ray burst progenitors, and type Ia supernova progenitors. The recent detection of gravitational waves from coalescing binary black holes sparked a renewed interest in the CE phase as one of the proposed formation channels, namely the “classical” binary evolution channel, requires a CE phase that will eject the envelope of the second-born black hole progenitor and bring the first-born black hole and the stellar core of the second-born BH in a close orbit. In this talk, I will present new 1D hydrodynamic models, that include heat, radiation and angular momentum transport, of the inspiral of compact objects, black holes or neutron stars, in the envelopes of massive giant stars. These models self-consistently follow the inspiral of the compact object and the ejection of the common envelope, while they avoid the use of free parameters such as the infamous α CE and ad-hoc definitions of the core-envelope boundary, and lead to physical predictions of the end-state of the common envelope phase. Finally, they are computationally efficient, in contrast to 3D simulation, allowing for broader parameter studies.
15.30-15.45 Enrique Moreno Méndez The jet-accretion feedback during common envelope with a compact object
###### A large percentage of massive stars are part of a binary system which will interact. It is evermore clear that binary interactions are a very important, if not critical, ingredient in the formation of many transient phenomena, e.g., sort and long GRBs, GWs, SNe, HNe, kNe, etc. Thus, the importance of understanding the common envelope (CE) phase is hard to overstate. We study the interaction between a jet and a stellar envelope focusing in the particular cases where a giant star engulfs a compact object; we include the cases of a NS, as well as that of a BH. We further study the feedback between the jet-induced cocoon and the accretion rate. We discuss the implications this may have in partially or fully removing the CE. We find that the energy, luminosity, as well as the timescale, are in line with those of ultra-long GRBs. Thus, we suggest CE events of a red-giant or supergiant with a BH or NS are interesting candidates for this rare type of GRB, and/or an exotic, high-energy, transient.
15.45-16.00 Aldo Batta On the formation of rapidly rotating BHs in High Mass X-ray Binaries
###### High mass X-ray binaries (HMXRBs) like Cygnus X-1, host some of the most rapidly spinning black holes (BHs) known to date, reaching spin parameters greater than 0.84. However, there are several effects that can severely limit the maximum BH spin parameter that could be obtained from direct collapse, such as tidal synchronization, magnetic core-envelope coupling and mass loss. Here we propose an alternative scenario where the BH is produced by a failed supernova (SN) explosion that is unable to unbind the stellar progenitor. A large amount of fallback material ensues, whose interaction with the secondary naturally increases its overall angular momentum content, and therefore, the spin of the BH when accreted. Through SPH hydrodynamic simulations, we studied the unsuccessful explosion of a 8 M☉ pre-SN star in a close binary with a 12 M☉ companion with an orbital period of 1.2 days, finding that it is possible to obtain a BH with a high spin parameter (larger than 0.8) even when the expected spin parameter from direct collapse is 0.3. This scenario also naturally explains the atmospheric metal pollution observed in HMXRB stellar companions.
16.00-16.15 Alejandro Vigna Gomez Gravitational-wave sources and Galactic double neutron stars via isolated binary evolution (.pdf)
16.15-17.00 Discussion Vicki Kalogera
17.00 Farewell

## Posters:

Edilberto Aguilar Ruíz Study of the PeV Neutrinos, γ-Rays and UHECRs around the lobes of Centaurus A
###### Ultra-high-energy cosmic ray (UHECR) detections could give an indirect signal of PeV neutrino emission. Recently, Pierre Auger observatory reported the distribution of arrival directions of the highest energy cosmic rays. These events were collected in 10 years of operations with declinations between -90° and +45°. The IceCube neutrino telescope reported the detection of 54 extraterrestrial neutrinos in the High Energy Starting Events catalog. The highest-energy neutrino event (IC35) reported in this catalog had an energy of 2004 TeV and was located centered at RA=208.4° and DEC=-55.8° (J2000). Being Centaurus A the nearest radio-loud active galactic nucleus and one of the best potential candidates for accelerating cosmic rays up to ~ 1020 eV, we show that UHECRs with E > 58 EeV around the direction of Centaurus A (15° radius) could be accelerated inside the giant lobes. These comic rays unavoidably interact with external radiation fields and ambient gas whereas they propagate through the lobes and their paths to Earth. We show that the proton luminosity extrapolated at 1 TeV contributes to the faint $\gamma$-ray fluxes reported by Fermi Collaboration. Using the buoyancy ages of the giant radio lobes instead of their spectral ages, and those UHECRs in the direction of the IC35 event, we found that the IC35 event cannot be generated inside the giant lobes. Additionally, considering the closest Galaxies around Centaurus A and the hadronic interactions in their paths to Earth, we found that IC35 event could be created in this environment.
Igor Andreoni Deeper Wider Faster: proactive observations to chase the fastest bursts
###### The seconds-to-hours transient time domain is widely unexplored and includes events resulting from a variety of physical mechanisms such as supernova shock breakouts, kilonovae, dark gamma-ray bursts, fast radio bursts and gravitational wave event counterparts. I will present the Deeper, Wider, Faster (DWF) program designed to probe the fast transient Universe. DWF is an Australian based multi-facility, multi-wavelength program that coordinates simultaneous observations with the Parkes, Molonglo, and ATCA telescopes (radio), the DECam imager and REM telescopes (optical/IR), and the NASA Swift satellite BAT, XRT and UVOT (gamma-ray, x-ray, and UV/optical). Our custom real-time data analysis pipeline allows rapid spectroscopic and photometric follow-up of interesting sources with small to big telescopes including Gemini, SALT, and possibly VLT and Keck.
Jennifer Barnes Gammay-ray bursts and broad-lined Ic supernovae from a single central engine
###### While the unusually high velocities (~ 0.1 c) and correspondingly high kinetic energies observed in an intriguing subset of Type Ic supernovae established the broad-lined c supernova (SN Ic-bl) subclassification on empirical grounds, the central engine model capable of self-consistently generating these extremely energetic explosions remains an outstanding question. A clue to the explosion mechanism may lie in the fact that all supernovae that accompany long-duration gamma-ray bursts belong to the Ic-bl class. This study uses a combination of two-dimensional relativistic hydrodynamics and radiation transport calculations to demonstrate that the central engine responsible for long gamma-ray bursts can also trigger a SN Ic-bl. We find that a reasonable gamma-ray burst engine injected into a stripped Wolf-Rayet progenitor produces a relativistic jet with energy ~ 1 foe, as well as a SN whose synthetic light curves and spectra are fully consistent with observed SNe Ic-bl during the photospheric phase. I will discuss our engine and progenitor model, review the hydrodynamical and radiation transport calculations we employ, and discuss the resulting photometry, including the effects of viewing angle on the SN's radiative signature
Wlodek Bednarek Model for the delayed GeV gamma-ray emission from Gamma-ray Bursts
###### We propose that delayed hard GeV gamma-ray emission observed from long Gamma-ray Bursts (GRBs) can be produced when the hyper-relativistic jet encounters the radiation of stars, within the stellar cluster, which happens to be immersed in the jet. The hard X-ray to soft gamma-ray radiation from the jet, heats the surfaces of encountered stars to temperatures above those expected from nuclear burning. Then, relativistic electrons in the jet can efficiently Inverse Compton up-scatter stellar radiation to the GeV energies. We have performed numerical calculations of the gamma-ray spectra produced in the IC e-p pair cascade initiated by relativistic electrons in a dense stellar radiation field. The gamma-ray spectra produced in such scenario form additional component in the GRB spectrum which is delayed in respect to the main emission, coming from the central part of the GRB engine, since stars can be encountered up to a parsec distance scale from the GRB. Such mechanism is discussed for the delayed GeV emission recently observed from the powerful GRB 130427A.
Damien Bégué Radiative striped wind model for gamma-ray bursts
###### In my talk, I will revisit the striped wind model in which the wind is accelerated by magnetic reconnection. In our treatment, radiation is included as an independent component, and two scenarios are considered. In the first one, radiation cannot stream efficiently through the reconnection layer, while the second scenario assumes that radiation is homogeneous in the striped wind. We show how these two assumptions affect the dynamics. In particular, we find that the asymptotic radial evolution of the Lorentz factor is not strongly modified whether radiation can stream through the reconnection layer or not. On the other hand, we show that the width, density and temperature of the reconnection layer are strongly dependent on these assumptions. We then apply the model to the gamma-ray burst context and find that photons cannot diffuse efficiently through the reconnection layer below radius rDδ ~ 1010.5 cm, which is about an order of magnitude below the photospheric radius. Above rDδ, the dynamics asymptotes to the solution of the scenario in which radiation can stream through the reconnection layer. As a result, the density of the current sheet increases sharply, providing efficient photon production by the Bremsstrahlung process which could have profound influence on the emerging spectrum. This effect might provide a solution to the soft photon problem in GRBs.
Mikhail Beznogov Thermal Evolution of Neo-Neutron Stars (.pdf)
Mukul Bhattacharya Explaining GRB prompt emission spectrum with photospheric emission
###### We study the sub-photospheric Comptonization of fast cooled synchrotron photons while the electrons and protons are accelerated to relativistic energies by repeated dissipative events. Unlike previous simulations, we implement realistic photon to electron number ratio ~1e5 in addition to incorporating continuous energy transfer to electrons through Coulomb collisions. Using our Monte-Carlo code, we have successfully generated the observed photon spectrum for electrons accelerated to highly relativistic energies with Lorentz factor ~100 by ~40 dissipative events starting from moderate values of optical depth ~20. We find that the shape of the photon spectrum is independent of the initial photon energy distribution and baryonic energy content of the jet, as expected.
Peter J. Brown Ultraviolet-Optical-Infrared Aggienova Templates of Explosive Transients
###### The Swift satellite has made ultraviolet and X-ray observations of over 500 supernovae and other transients. The photometry for over 200 supernovae is already available from the Swift Optical Ultraviolet Supernova Archive. We use this photometric database to characterize the behavior of different supernova types and the increased variety in the ultraviolet. We combine the multi-epoch photometry with ground-based optical and near-infrared observations and spectral templates to create spectrophotometric templates. These better represent the ultraviolet and cover a larger sample of subtypes than previously possible and can be used to predict the brightness of these explosive transients out to cosmological distances where the rest-frame ultraviolet is redshifted into the optical and infrared.
Vikas Chand Spectral, Timing and Polarization properties of GRB 160509A & GRB 160802A: a tale of two GRBs with polarization measurements by AstroSat/CZTI
###### The bright GRBs 160509A and 160802A are observed in both Fermi and AstroSat/CZTI. We analyze these GRBs for temporal, spectral and polarization properties of the prompt emission. In GRB 160509A, the LAT high energy (LAT-HE) emission (> 100 MeV) is highly correlated to its counterpart at immediate low energies. The single pulse as seen in the main burst at its low energies can be resolved into two separate pulses at the high energies. This main episode of the burst is followed by a precursor. The precursor has a thermal spectra which smoothly evolves during the main episode. The spectrum of the main burst shows a cut-off at an energy that falls in the window 30 MeV - 150 MeV. The LAT-HE emission can be separated into two temporal and spectral components. Further, a high degree of polarization (96 ± 40%) is also detected for this GRB from the Compton double scattering events during the main burst. The top-hat like spectrum, the existence of a high energy emission that can extend from a few hundred MeVs to GeVs, a sub-dominant thermal component, the clues from afterglow emissions (a reverse shock) and the existence of high polarisation are incompatible with the existing mainstream models of the GRBs. GRB 160802A is surprisingly faint at ≲ 2 MeV energies. In the time resolved spectroscopy of this GRB, we found that low energy index of Band function α crosses the synchrotron line of deaths for cooling. This is a well known severity of the GRB spectral models. The availabilty of the AstroSat/CZTI observation forms an opportunity to study polarisation of such GRBs. Surprisingly, the polarisation for this GRB is also high and well constrained (polarization fraction 85 ± 29 %).
Ian Christie Pulsars in the Galactic Center
###### The discovery of radio pulsars within the inner most pc of our Galactic Center (GC) poses a unique challenge for both observational and theoretical astrophysics. These objects are highly sought after for their potential as probes of Sgr A*, the compact radio source associated with the supermassive black hole (SMBH) in our GC, as well as interpreting the surrounding interstellar medium. Despite numerous searches, the only detected pulsar residing in the GC is a magnetar located ∼0.1pc from the SMBH. The presence of a pulsar population can be revealed by their interactions with the gas surrounding Sgr A* and its accretion disk which results in the relativistic winds of the pulsars being terminated by a strong shock. Relativistic electron-positron pairs, accelerated at the shock front, can enter the disk while cooling via synchrotron radiation, thereby producing a non-thermal, year-long X-ray flaring event and a substantial contribution to the GHz radio emission. Here, I will present X-ray and radio light curves, produced from a fiducial population of pulsars interacting with Sgr A*’s accretion disk, and compare against X-ray and GHz observations of Sgr A*. I will also discuss the impact of the pulsar population on the dynamics of the accretion flow itself.
Kishalay De iPTF14gqr: A hot and fast ultra-stripped supernova in the outskirts of its host
###### Early observations of young supernovae (SNe) provide vital information on the structure and immediate environment of the progenitor, and have greatly improved our understanding of the pre-explosion evolution of massive stars. In this paper, we present the intermediate Palomar Transient Factory discovery and multi-wavelength follow-up observations of a fast type Ic SN, iPTF 14gqr. Discovered in the far outskirts (projected offset ~ 30 kpc) of a tidally interacting spiral galaxy, the transient exhibits a double peaked light curve composed of a rapid (~ 1 day) first peak and a longer timescale (~ 7 days) second peak. With rapid spectroscopy initiated within a few hours of discovery, we find the early spectra to be composed of featureless blue continua superimposed with flash ionized lines of He and C, making this the first Type I SN for which such features have been detected. The photometric and spectroscopic evolution of the main (second) peak of the light curve suggest a low Ni mass, ejecta mass and explosion energy of ~ 0.03 M☉, ~ 0.17 M☉ and ~ 1050 ergs respectively. The first peak can be well modeled by shock cooling emission from an extended progenitor envelope, which along with modeling of the early flash ionized spectra, suggest that the progenitor was surrounded by a He rich envelope with mass of ~ 0.01 M☉ and radius of ~ 1014 cm. Deep spectroscopic limits on the presence of star formation at the location of the transient argue against in-situ formation of the progenitor, and suggest that it was likely ejected from the host galaxy, possibly due to a preceding SN explosion in a binary system or due to tidal interactions of the host galaxy. Taken together, all derived parameters point to iPTF 14gqr as being perhaps the first confirmed ultra-stripped Type Ic SN candidate, that are suggested to be progenitors of the crucial double neutron star system targets of current and future gravitational wave observatories.
Rosa Wallace Everson Effects of the Common Envelope Phase on Binary Black Hole Evolution
###### The detection of gravitational wave signals from binary black hole (BBH) mergers in recent years has raised pressing questions about the formation and characteristics of these systems. In order for BBHs produced in the traditional formation channel to merge in a Hubble time, the pair must undergo a common envelope (CE) phase to dramatically reduce the separation distance of the progenitors prior to CE ejection. Recent work on the CE phase has shown that density gradients in the envelope material produce a significant departure from drag and accretion rates of the embedded compact object as predicted by Hoyle Lyttleton accretion formalism; these effects, in turn, have implications for mass and angular momentum transfer between the donor star and compact object. Using a range of simplified progenitor systems in which a massive, stellar-mass black hole (BH) dynamically inspirals through the envelope of a giant stellar companion, we examine these CE effects on the final mass and spin of the BHs in the resulting binary.
Christoffer Fremling Stripped envelope supernovae discovered by the (i)PTF
###### We present a spectral analysis of all stripped-envelope SNe discovered by the PTF and iPTF collaborations. We find SNe Ic to have stronger and faster oxygen absorption features in their spectra compared to SNe IIb and Ib. This is inconsistent with low-mixing models for SNe Ic, where helium could be hidden due to it not being nontheremally excited. Instead, we propose that SNe Ic lose helium due to stellar winds or binary interactions, and do not hide it. SNe Ib are faster compared to SNe IIb in their helium absorption lines, consistent with SNe Ib lacking significant hydrogen envelopes.
Edwin Antonio Galván Gámez Search of late time emission from GRB 170817A
###### The discovery of the gravitational wave GW170817 marks the beginning of a new era for multi-messenger astrophysics. It was originated from a merger of 2 neutron stars at 40 Mpc from us. Electromagnetic counterparts of this merger are observed at different wavelength with emission starting from 2 second up to several days after the gravitational wave detection. Fermi/GBM firstly identified the gamma ray counterpart classified as a short gamma-ray burst (GRB) called GRB 170817A. This source starts to emot in X-rays and in radio 9 and 15 days after, respectively. We use the High Altitude Water Cherenkov (HAWC) gamma-ray observatory, installed at an altitude of 4100 m asl in the state of Puebla (Mexico) to look for possible emission in the TeV range at early and late times. We report the results of this analysis providing the significance of the signal for each transit of the source inside the field of view of HAWC up to 20 days after the detection. No significant flux is observed during this period. Our upper limits indicates that the off-axis scenario is the most reliable one to explain the emission coming from this peculiar event.
Ramandeep Gill What’s powering the magnetar wind nebula around Swift J1834.9-0846? (.pdf)
Andreia Gomboc Optical polarimetry and photometry of GRBs with RINGO2
###### We present a catalog of early-time (~ 102 - 104 s) photometry and polarimetry of all GRB optical afterglows observed with the RINGO2 imaging polarimeter on the Liverpool Telescope. We discuss the results for the sample in the context of the reverse- and forward-shock afterglow scenario, and show that GRBs with detectable optical polarization at early time have clearly identifiable signatures of reverse-shock emission in their optical light curves. This supports the idea that GRB ejecta contain large-scale magnetic fields, and it highlights the importance of rapid-response polarimetry.
Diego Götz Investigating the Violent Universe with THESEUS
###### The Transient High Energy Sky and Early Universe Surveyor (THESEUS) is an ESA M5 candidate space mission (scheduled for 2029), whose goal is to increase our knowledge on transient high energy sources over the entire comic history. In particular THESEUS will make use of Gamma-Ray Bursts as beacons to investigate the early Universe up to the re-ionisation era, and at the same time it will perform an unprecedented deep monitoring of the X-ray transient Universe allowing THESEUS to play a prominent role in time domain and multi-messenger astronomy. THESEUS will carry a suite of high-energy telescopes (based on focussing "Lobster Eye" and coded mask techniques) capable of a wide and deep monitoring in a broad energy range (0.2 keV - 20 MeV) and a follow-up NIR (0.7-1.8 microns) telescope with moderate spectroscopic capabilities for immediate transient identification and redshift measurement. We will present the complete THESEUS science case, its mission profile, as well as the three instruments (the Soft X-ray Imager, the X-Gamma ray Imaging Spectrometer and the Infra-Red Telescope) we designed in order to reach them.
James Guillochon Systematic light curve fits to superluminous supernovae: insights from the full literature sample
###### I will present the findings from a study analysing 38 superluminous supernovae (SLSNe), comprising virtually all spectroscopically confirmed events with published light curves. Assuming magnetar central engines, we fitted the multi-band photometric evolution with our new public light curve code, MOSFiT, to derive posterior distributions for key parameters such as ejecta mass, spin period and magnetic field. We show that while SLSN light curves are diverse, the relevant magnetar parameter space is well constrained by current data. The ejecta masses and spin periods, along with the observed SLSN rate and preference for dwarf galaxies, may be used to place interesting constraints on the progenitor stars. (Nicholl, Guillochon and Berger, https://arxiv.org/abs/1706.00825)
Francisco S. Guzmán Accretion of winds onto black holes in 3D
###### We present the accretion of neutral and magnetized supersonic winds onto a rotating black hole in three dimensions. We select representative spin-wind orientations in order to illustrate its effects on the evolution and morphology of the shock cone with no symmetries. The most important finding in the magnetized case (MHD), unlike the purely hydrodynamical scenario (HD), is the formation of rarified spots where the magnetic field pressure dominates with \beta<1. In these rarified spots, in the case of a winds perpendicular and diagonal to the spin of the black hole, whirlpools are formed within the shock cone. We also study the subsonic case and present the dynamics near and around the black hole of the gas in the HD case and the plasma in the MHD case. In this analysis we solve the fluid and plasma equations for the matter on top of the background space-time of a black hole described in penetrating coordinates, which allows one to track down the accretion process all the way through the black hole's event horizon.
A. Miguel Holgado Gravitational Waves from Accreting Neutron Stars in the Common-Envelope Phase
###### The common envelope phase is a likely formation channel for close binary systems containing compact objects, which may eventually lead to gravitational-wave sources and/or high-energy electromagnetic transients. Neutron stars in common envelopes accrete at a fraction of the Bondi-Hoyle-Lyttleton accretion rate, since the stellar envelope is inhomogeneous, but may still be able to accrete at hypercritical rates (though not enough to become black holes). We show that common envelope systems consisting of a neutron star with a massive primary may be gravitational wave sources detectable in the advanced LIGO band as far away as the Magellanic Clouds. From the range of possible accretion rates relevant to common envelope evolution, we find that these systems may be significantly louder gravitational wave sources than low-mass X-ray binaries like Sco X-1, which are currently the target of directed searches for continuous gravitational waves. We also find that their strain amplitude signal may allow for novel constraints on the orbital separation and inspiral timescale in common envelopes when combined with pre-common envelope electromagnetic transient observations.
Thomas W.-S. Holoien Recent Supernova and Tidal Disruption Event Results from ASAS-SN
###### With 20 telescopes telescopes spread between the northern and southern hemispheres, the All-Sky Automated Survey for Supernovae (ASAS-SN or “Assassin”) is now monitoring the entire visible sky to a limiting magnitude of roughly 17.5 every night. ASAS-SN has now found over 550 bright supernovae (SNe) and 3 bright tidal disruption events (TDEs), all of which are bright enough to study with a wide wavelength coverage and for long periods of time. Here we present updated statistics on our overall SN sample as well as results of recent follow-up studies of individual TDEs and SNe..
Adithan Kathirgamaraju Off-axis short GRBs from structured jets as counterparts to GW events (.pdf)
Kelsie Krafton CSM Interaction and Dust Formation in SN2010jl
###### The origin of dust in galaxies less than 1 billion years old has remained an unsolved mystery for over a decade. One proposed solution is dust produced by core collapse supernovae. Theorists have shown that 0.1-1M☉ of dust must be produced per supernova for this to work as an explanation for the dust in young galaxies. SN 1987A has produced 1 M☉ of dust since its detonation. However, most supernovae have been found to only produce 10-4-10-2M☉ of dust. The energetic Type IIn SN 2010jl is located in UGC 5189, in a dense shell of CSM. As dust condenses in the SN ejecta, we see, (1) a sudden decrease in continuum brightness in the visible due to increased dust extinction, (2) the development of an infrared excess in the SN light curve arising from dust grains absorbing high-energy photons and re-emitting them in the infrared, and (3) the development of asymmetric, blue-shifted emission-line profiles, caused by dust forming in the ejecta, and preferentially extinguishing redshifted emission. A dense CSM may increase the dust production by supernovae. We observe signs of strong interaction between the SN ejecta and a dense CSM in SN 2010jl. SN 2010jl has been a source of much debate in the CCSN community, particularly over when it formed dust and how much dust it formed. The light curve shows strong signs of dust formation after 260 days. Arguments over these subjects have been based on the evolution of the light curve and spectra. We present new optical and IR photometry, and spectroscopy of SN 2010jl over 2000 days. We estimate dust masses using the DAMOCLES and MOCASSIN radiative transfer codes.
Jamie Law-Smith Tidal Disruptions of Stars with Realistic Structures and Compositions
###### A detailed theoretical understanding of tidal disruptions, coupled with high-resolution observations, can help us understand the properties of massive black holes and nuclear stellar populations, the physics of super-Eddington accretion, and the dynamical mechanisms operating in galactic centers. I will present the first simulations of tidal disruptions of stars with “realistic” structures and compositions. We calculate the signatures of the disruption of stars of a range of masses and ages, and track the composition of the debris that falls back onto the black hole. I will present new predictions from these simulations, and place our results in the context of current observations.
Kin Lopez Mendoza Analysis of the co-spatial and temporal correlation of gamma ray bursts with high-energy neutrinos
###### The IceCube Collaboration initially reported on the detection of 54 extraterrestrial neutrinos in the TeV-PeV energy range. The reconstructed neutrino events were obtained during three consecutive years of data collection, from 2010 to 2013. Currently, although it has been discussed that these events have an extra galactic origin, they have not been correlated with any known source. Therefore, in this work a comprehensive correlation analysis of these 54 high-energy neutrinos with GRB data of BAT, XRT and UVOT onboard SWIFT space laboratory and the LAT and GBM instruments onboard FERMI was done. Additionally, a theoretical model to relate these events is presented.
Tatsuya Matsumoto Is the Macronova (Kilonova) in GW170817 Powered by the Central Engine?
###### The gravitational wave event GW170817 from a binary neutron star (NS) merger is accompanied by electromagnetic counterparts, and the optical and near-infared emission is called a macronova (or kilonova). Although the radioactivity of synthesized r-process elements is widely discussed as an energy source, it requires a huge ejecta mass from the NS merger. We discuss a macronova powered by the central engine activities, and show that the engine model allows much broader parameter spaces, in particular smaller ejecta mass (∼ 10−4 − 0.01 M⊙) than the r-process model. The blue macronova is naturally explained by a cocoon powered by the jet from a black hole, while the red macronova by the merger ejecta heated by X-rays from the fall-back matter, which is very similar to the X-ray excess observed in GRB 130603B with the right power-law slope of the energy injection. On the other hand, we clarify that the r-process elements are required as the opacity source to reproduce the long duration of the red macronova. Early or late multi-wavelength observations are useful for revealing the central engine of short gamma-ray bursts and the r-process nucleosynthesis.
Jonah Miller Nonlinear Stability of Kerr Black Holes with Massive Boson Hair (.pdf)
Gibran Morales Rivera Thermal Neutrino opacity within the wind medium generated by a binary neutron star merger
###### The recent GW170817 event constitutes the first Gravitational Wave detection with LIGO and Virgo collaboration and its electromagnetic multiwavelength counterpart detected with many space and ground-based telescopes, confirming the Binary Neutron Star merger scenario as the progenitor of short Gamma-Ray Bursts. No MeV-EeV neutrino emission in directional coincidence with the host galaxy NGC4993 was detected with ANTARES, IceCube and Pierre Auger collaborations. In this work, we estimate the neutrino opacity of the stellar winds surrounding the central engine of this merger in both magnetically-driven (NS-NS) and neutrino-driven (NS-BH) wind scenario. We found that whereas MeV neutrinos leave the central engine isotropically due to a neutrino-driven wind, these neutrinos due to magnetically-driven wind can only be detected at viewing angles less than 45 degrees. Using these results we show an effective criterion to determine which is the most plausible progenitor of sGRBs based on the line of sight of these events
Claudia Moreno Obtaining gravitational waves emitted by a black hole interacting with accretion discs
###### We investigate the physical consequences of the interaction between a black hole and scalar and electromagnetic fields halos in terms of gravitational waves (GW) by solving Teukosky's master equation with sources. The black hole is taken as a static and spherically symmetric gravitational source; we work within the test field approximation, considering that the field lives in the curved space-time outside the black hole. We analyze the scalar, electromagnetic and gravitational waves as well as the quasinormal modes emitted by this system.
Takashi Moriya Ultra-stripped supernovae leading to coalescing double neutron stars
###### If a supernova progenitor is in a close binary system with a compact star like a neutron star, it can lose significant amount of its mass before the explosion. Such supernovae are called "ultra-stripped" supernovae. They only eject ~ 0.1 M☉ with the 56Ni mass of ~ 0.01 M☉. Because of the small ejecta mass, such supernovae may be a major path to make coalescing double neutron stars that will be detected in gravitational observatories. We followed the evolution of ultra-stripped supernova progenitors until core collapse and investigated their light-curve and spectral properties. We found that their light curves typically peak at around 1042 erg/s or -16 mag with the rise time of 5-10 days. By comparing synthesized and observed spectra, we found that SN 2005ek, some of so-called calcium-rich gap transients, and SN 2010X may be ultra-stripped supernovae. If these supernovae actually lead to the formation of coalescing double neutron-star systems, about 1% of core-collapse supernovae are likely to make such systems. Future detections of coalescing double neutron stars can test if the ultra-stripped supernovae are the major path to form coalescing double neutron stars.
Andrea Nagy Comparison of early- and late-time light curve fits of stripped-envelope supernovae
###### Stripped-envelope (Type Ib/c) supernovae form a special group of core-collapse SNe, because their progenitor lost the H and He layers during the presupernova evolution. Due to their complex physical nature, theoretical models are essential to understand better the physics of this kind of exploding stars via the analysis of their emitted radiation. One possibility to model the light curve of stripped-envelope SNe is the construction of a simplified semi-analytic model, which can be used for getting order-of-magnitude estimates of the basic physical properties. As previous studies (e.g. Clocchiatti & Wheeler, 1997, ApJ, 491, 375; Wheeler et al., 2015, MNRAS, 450, 1295) revealed, there are some discrepancies between the physical parameters derived from early- and late-time light curve fits. The aim of the present study is to improve the light curve fits in order to ease the tension between the estimated physical parameters. First, we consider the effect of poor light curve sampling, which may result in large offsets in explosion date as well as the slope of the late-time light curve. Next, we examined the frequently used assumption that the R-band light curve is a good approximation of the true bolometric light curve. Our results show that this approximation has limitations, because the slope of the light curve tail slightly depends on the filter used, which can strongly influence the derived masses. Finally, we analyze the effect of gamma-ray and positron trapping, that play an important role in forming the shape of the late-time light curve of stripped- envelope supernovae.
Sam Oates Exploring the behaviour of long GRBs with an intrinsic multi-wavelength afterglow correlation
###### We present a correlation observed in both the optical/UV and X-ray afterglows of long duration Swift Gamma-ray Bursts (GRBs), between the initial luminosity (measured at restframe 200s) and average afterglow decay rate. This correlation does not depend on the presence of specific light curve features, and is potentially applicable to all long GRB afterglows. We explore how the correlation decay parameters from the optical/UV and X-ray bands relate to each other and to the prompt emission phase. We will also investigate the implications and test whether the standard afterglow model is consistent with the observations.
Dan Patnaude The Role of Metallicity in Supernova Evolution
###### Surveys of nearby galaxies have thus far turned up scant evidence for young, evolving supernova remnants. This is in contradiction with the expected supernova rate of 1 event per century. A possible reason for the lack of young SNR is the metallicity of the host environment. In the case of low metallicity, the progenitor will not deposit much mass into the CSM, as the line driven winds are expected to be weak. When the progenitor explodes, it will remain in nearly free expansion, resulting in a low surface brightness remnant. In contrast, a higher metallicity will result in rapid evolution of the remnant into the Sedov phase. Here we present new models for the evolution of supernovae in high and low metallicity environments. We discuss the role that the metallicity has on the remnant dynamics and spectral qualities.
Giuliano Pignata Supernova rates from the SUDARE survey
###### Supernova (SN) rates as a function of cosmic time and their link with the properties of the galaxy parent population is a powerful tool to investigate the nature of progenitor stars and to shed light on the origin of SN diversity. I will present Supernova rates per unit volume and per unit of mass computed from the data collected by the Supernova Diversity and Rate Evolution (SUDARE) experiment. We monitored the Cosmic Evolution Survey (COSMOS) and Chandra Deep Field South (CDFS) fields in the g,r,i filters with the VLT Survey Telescope (VST) between 2011 and 2015. I will also show the correlation between the rates of SNe of different type and the main parameters of the host galaxies.
Graziella Pizzichini Search for particular properties of long GRBs at high redshift (.pdf)
Paul Plucinsky The Expansion of the SMC SNR 1E 0102.2-7219 (.pdf)
Isidro Ramírez Ballinas γ-Ray emission in supernova remnants
###### The $\gamma$-rays are results of the interaction of high energy particles acellerated for the shock waves of the Supernova Remnants (SNRs) with interstellar medium. It has been commonly assumed that 10% of the explosion energy of a supernova is transfering to the accelerated particles.It is accepted in the literature that the hard X-ray emission detected in many young SNRs is synchrotron emission from electrons accelerated to energies of tens of TeV (e.g. Koyama et al. 1995) by means of the diffusive shock acceleration process. The radiation at γ-rays energies is expected from collisions of these high energy electrons with low energy photons from the ambient radiation e.g. cosmic microwave background -which leads to very-high-energy (> 100 GeV) via Inverse Compton Scattering (leptonic model). In regions of high mass density, e.g. the interaction of a SNR with a molecular cloud, the γ-rays can be due to proton-proton collision (hadronic model). An argument in favor of a leptonic origin for the γ-rays emission is the spatial correlation found between γ-ray and X-ray brightness distributions, which suggests that both are originated from the same population of particles: electrons. The Large Magellanic Cloud was observed with Fermi γ-Ray telescope and X-ray space observatory XMM-Newton, see Figure 2. We show that hard-X ray emission, white contours, coincides with the peak emission in gamma at 30 Doradus region that contain the SNR 1987A. In the other hand, hadronic model have been proposed successfully for SNRs: IC443, W51C, W44 and W49B, see Figure 3. The nature of γ-rays is controversial, an example is the SNR J1713.7-3946, studies indicate that the dominant contribution is leptonic and other hadronic.
Kenia Joseline Ramírez Millán Inspiral and Ringdown Analysis of the LIGO Data From a Binary System of Black Holes
###### Recent direct detections of gravitational waves (GW) from coalescing binary black holes systems open a new era in the observational astronomy, as well as in experimental verifications of the theories of gravity. The detection of the GW events GW150914, GW151226 and GW170104 made by LIGO are a fascinate discovery that required three fundamental developments: (i) theoretical and numerical solutions of the Einstein's equations; (ii) the ground-based detector Laser-Interferometer Gravitational-Wave Observatory (LIGO) and (iii) computational models and data analysis algotithms. In this work,we will focus in the analytical model of the (i) and (iii) phases in black hole binaries: the phase (i) leads us to understand how the system works in the inspiral phase and how it produces GW. Late, we analyze the ringdown phase (iii) and be able to apply digital signal processin using machine learning and data science techniques, whose aim is to pull out gravitational waveforms from the noisy measurements provided by ground-based detectors and to estimate the physical parameters of the sources responsible of the detected signals.
Armin Rest A Fast-Evolving, Luminous Transient Discovered by K2/Kepler (.pdf)
Francisco Rivera Evolution of jets driven by relativistic radiation hydrodynamics as Long and Low Luminosity GRBs
###### We carry out an analysis of three-dimensional numerical simulations of jets modeled with Relativistic Radiation Hydrodynamics (RRH), that evolve on two environments: i) a stratified surrounding medium and ii) 16TI progenitor model. We consider particular processes of interaction between the fluid and radiation, specifically, Bremsstrahlung emission and Thomson scattering. In this simulations, we assume initially, that the radiation field and matter are in local thermal equilibrium, which is broken immediately after initial time. We explore a variety of initial conditions, with different radiation energy densities and Lorentz factors of the beam, in particular, mildly and ultra-relativistic jets, together with hydrodynamical and radiation pressure dominated scenarios. In order to investigate the impact of the radiation field on the evolution of the jets, we compare our results with purely hydrodynamical jets. Comparing among jets driven by RRH, we find that radiation pressure dominated jets propagate faster than gas pressure dominated ones. Finally, we construct the luminosity Light Curves (LCs) associated with all these cases. The construction of LCs is natural in the model, because the radiation is fully coupled to the hydrodynamics equations during the evolution. The LCs measured on the stratified surrounding medium are of the same order of magnitude as the gamma-ray luminosity of typical Long Gamma-Ray Bursts, that is, 1050-1054 erg/s, whereas, the LCs measured on the massive stellar envelope are of the order range of magnitude 1046-1048 erg/s, resembling a typical event of low-luminosity GRBs.
Ramón Daniel Rodríguez Soto Prototype detector of gravitational waves by laser interferometry (.pdf)
José Rodrigo Sacahui Reyes Strange star - strange planet coalescing binary systems - Their importance as a source of gravitational waves and the possible electromagnetic counterpart
###### Theoretical physicist have predicted that compact binary systems are the most important sources of Gravitational Waves (GW). Even thoug binary systems of Neuntron Star (NS) and Black Holes (BH) are the most favoured Strange Star (SS) systems have also being considerated as candidates. In this work we present the GW sign of a SS-Strange Planet system and with some prediction about the energies expected in the EM counterpart considering an external shock model.
Alberto Santos Morales A supervised learning approach to estimate parameters of binary black-holes from gravitational waves
###### In sixteen months the LIGO (Laser Interferometer Gravitational-wave Observatory) has reported three direct detections of gravitational waves (GW) from binary systems which suggests that the merger of two black holes is more frequent than we expected. Detection of GWs consists of measuring and identifying small deformations of the space-time (i.e., strain) that are produced by astronomical massive objects. The inverse problem in GWs consists on identifying the astrophysical source parameters, e.g., mass ratio, spin, distance, orbital phase, among others. This work proposes to estimate the mass ratio of colliding binary black-holes (BBH) using an artificial neural network (ANN) algorithm which is trained with a waveform dataset created from numerical relativity. A systematic evaluation with different architectures of feedforward-nets and deep neural networks was made to assess the algorithm performance. Preliminary results indicate a mean square error (MSE) of 0.2 solar masses in the estimations and a correlation coefficient of 0.85 between the estimations and the parametrical data. We conclude therefore that it is possible to use a supervised learning approach to estimate parameters of BBH from GW waveforms.
Josiah Schwab Modelling the progenitors of accretion-induced collapse (.pdf)
Sophie Schroder Can we constrain Black Hole Spin in Field Binaries?
###### In the classical scenario, the merger of the black hole binary that was detected as GW150914 must have come from the direct collapse or "failed" supernova explosion of two stars in an isolated binary system that underwent more than one mass transfer episodes. Through SPH simulations we explored different scenarios of the formation of the second BH, where a WR star suffers either a mild supernova explosions or a direct collapse, resulting in the formation of a massive BH but with considerably different spins depending on strength of the supernova.
Pablo Omar Sotomayor Checa Accretion and ejection in X-ray binaries of Population III
###### We present the first results obtained in the elaboration of a complete model of a microquasar where the donor star is from Population III. These stars do not have stellar winds so we consider that the mass loss is due exclusively to matter overflowing the Roche’s lobe towards the compact object, a maximally rotating black hole. The rate of accretion should be extremely super-Eddington, with an intense mass loss from the system in the form of winds and jets. We calculate the relativistic particle content of the jet and the corresponding spectral energy distribution (SED) considering a lepto-hadronic model. Prospects for the cosmological implications of these objects are briefly discussed.
Tomoya Takiwaki Oblate Supernova Explosions Aided by Rotation
###### We report results from a series of three-dimensional (3D) rotational core-collapse simulations for 11.2 and 27 M☉ stars employing neutrino transport scheme by the isotropic diffusion source approximation. By changing the initial strength of rotation systematically, we find a rotation-assisted explosion for the 27M☉ progenitor, which fails in the absence of rotation. The unique feature was not captured in previous two-dimensional (2D) self-consistent rotating models because the growing non-axisymmetric instabilities play a key role. In the rapidly rotating case, strong spiral flows generated by the so-called low T/|W| instability enhance the energy transport from the proto-neutron star (PNS) to the gain region, which makes the shock expansion more energetic. The explosion occurs more strongly in the direction perpendicular to the rotational axis, which is different from previous 2D predictions.
Gerardo Urrutia The effects of initial conditions on the dynamics of GRB jets and their afterglow emission

## Venue

The conference will be held at the all-inclusive resort Iberostar Quetzal, in Playa del Carmen, on the Mayan Riviera, Mexico.

The hotel offers special rates for conference participants: 2,335 Mexican pesos per day (about US$130-140 depending on the Mexican Peso/US Dollar daily exchange rate) for a single room and 1,681 Mexican pesos per day per person (about US$90-100) for a double room. Participants may use this link to reserve a room from Mexico and this link to reserve a room from the rest of the world. We recommend to reserve as early as possible because December is high season in the Mayan Riviera.

## Travel information

The hotel is located in Playacar, 60 km from the Cancún International Airport (about 50 minutes by car/bus) and 3 km from the center of Playa del Carmen (10 minutes by taxi/ 45 minutes walking).

The Cancún International Airport has a large number of direct flights from Europe, USA and Latin America. Low cost companies connect Playa del Carmen with main destinations in Mexico, including Mexico City.

There are several ways to go from the airport to Playa del Carmen. From the most expensive to the cheapest:

• By Taxi: taxi costs about ~US$60. We recommend to use only official taxis by buying tickets inside the airport terminal. We will coordinate the arrival of participants who want to share taxis from the Cancun airport. • By Shuttle: Shuttle costs about ~US$25 per person (buy a ticket inside the terminal).
• By Bus: Buses leave from the parking lot, just next to the terminal exit. The bus company is named "ADO". Buy a ticket at the booth next to the bus. The cost is about 180 Mexican pesos and the duration of the trip is 1 hr and 10 minutes. From the "ADO" bus station in Playa del Carmen take a taxi to the hotel (~US\$5).

## The Mayan Riviera and Playa del Carmen

The Mayan Riviera beaches are among the most beautiful in the world. In addition to idyllic beaches, the Yucatan peninsula hosted the Maya civilization, with its many archaeological sites, including Chichen Itzá, with the first astronomical observatory in the continent (built in 906 A.D.), Cobá and Tulum, a pre-Columbian Mayan walled city serving as a major port for Cobá.

The Yucatan peninsula is also famous for the peculiar "cenotes" (sinkholes), underground lakes (connected by rivers flowing underground) resulting from the collapse of the surrounding rock.

Playa del Carmen is one of the main touristic destination of the Mayan Riviera. The 1.5 km long "5a Avenida" is the main touristic street in Playa del Carmen and offers a dynamic nightlife (with restaurants, bars, night-clubs) and shops selling different types of Mexican art-crafts.

## Weather

Winter is the most enjoyable season in Playa del Carmen. Temperatures are between 18 and 28 degree Celsius (64-83 Farenheit) and rain is not frequent: 7 days a month on average (hurricane season ends in November). The water of the Caribean sea mantains a temperature of 27 degrees Celsius (about 80 Farenheit). Do not forget your swimming suit and sunscreen!

## Visa requirements

Citizens from most countries do not require a visa to enter in Mexico. A list of countries for which a visa is required is available here (official webpage, in Spanish) or here (in English). Contact the LOC for assistance in case you need a VISA.

## Invited Speakers

Matteo Cantiello - Flatiron Institute
The Uncertain Evolution of Core Collapse Supernova Progenitors
###### I will review the current status of our understanding of massive stars evolution, emphasizing both recent progress and areas where we still lack a physical picture of the dominating processes at work. I will discuss possible ways to move forward, stressing the emerging synergies between theoretical and computational efforts, and the new observational probes.
Ryan Foley - University of California, Santa Cruz
The Diversity of thermonuclear transients
Wen-fai Fong - Northwestern University
Short gamma-ray bursts
Maria Magdalena González - UNAM
HAWC: recent results
###### The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view TeV instrument. It has been operating since March 2015 from the Volcano Sierra Negra in the State of Puebla, Mexico, at an altitude of 4100 m. above sea level. HAWC operates continuously over a 95% of the time and observes two thirds of the TeV sky. HAWC sensitivity peaks at energies between 2-10 TeV which is close to an order of magnitude higher than IACTs, making their observations complementary. After more than 2 years of operation, HAWC has achieved its second steady source catalogue with both, previously known and new sources, the observation of extended sources and, a search for TeV transient and variable sources as well as follow-up alerts from other instruments such as Fermi, LIGO, etc., among other results. This talk will present recent highlights from the first years of HAWC operations.
Jonathan Granot - The Open University of Israel
Magnetic fields in GRBs
###### Magnetic fields likely play an important role in most aspects of the GRB phenomena, from the launching and acceleration of the relativistic outflow, through the jet dynamics and stability, to the energy dissipation, particle acceleration and the production of the radiation that we observe. I will review some of the recent progress in our understanding of the role of magnetic fields in GRBs.
Dafne Guetta - ORT-Braude
Neutrinos from astrophysical sources
###### One of the key goals in high energy astrophysics is to understand the formation and the dynamics of astrophysical jets and discover the sources of Ultra High Energy Cosmic Rays (UHECR). Cosmic Rays are extremely high energy charged particles that travel the universe at nearly the speed of light. Though they were discovered nearly a century ago, the research community is still puzzled by the origin of these high energy particles. Since neutrinos rarely interact, huge detectors covering an area of more than 1 km2 are required to make a statistically significant measurement. The South Pole in Antarctica is the host of IceCube, the first 1 km2 scale high energy neutrino detector that was completed in 2011. In this talk I will review the main mechanisms that may lead to the production of High Energy Neutrinos (TeV-PeV) from astrophysical sources. I will give an overview on the characteristic of these emissions and an estimate of the fluxes and rates that can be detected at the future and present neutrino telescopes. I will discuss the constraints given on these sources from the results of IceCube and future ultra high energy telescope ARA.
James Guillochon - Harvard University
Models of tidal disruption events
Alexander Heger - Monash University
Stripped Core-collapse Supernovae
###### It is the current paradigm that massive stars - if single, if of not too high initial mass, initial metallicity, or initial rotation - are expected to keep their hydrogen-rich outer layers until their death and the typical Type II supernovae - in their different varieties - results as the star dies. That is a lot of "if"s. In practise, as you may guess, some, if not several, of these conditions may be violated for many stars. It now known that most massive stars live in "close" binaries, close enough to interact in their lifetime, transfer mass and angular momentum, or even lose the envelope due to interaction with the companion stars, e.g., in a common envelope phase. We also know that stellar rotation leads to mixing; for very rapid rotation the star may evolve chemically homogeneous during hydrogen burning, with significant mixing possibly lasting until helium burning - significantly shrinking or even entirely removing the hydrogen envelope. Lastly, massive stars also blow winds from their surface, more fiercely the more massive, more metal-rich, or more luminous the star is. All of this leads to a different set of supernovae classes: stripped supernovae. These may range from objects just above the critical mass for core collapse all the way to very massive stars exploding as pair instability supernovae or making intermediate-mass black holes; stripped stars are also prime candidates for long-duration gamma-ray bursts as they are can be more compact than stars with hydrogen envelope. In this talk I will attempt to give an overview of core collapse supernovae that have lost the hydrogen-rich envelope, with focus on the progenitors and their evolution.
Agniezka Janiuk - Center for Theoretical Physics, PAS
Accretion in GRB central engine
###### We study the structure and evolution of the accreting plasma in gamma ray burst central engines. The modeling is based on the general relativistic MHD simulations. The nuclear equation of state adequate for dense and degenerate plasma can be incorporated to the numerical scheme. Plasma is cooled by neutrinos and energy is extracted from the rotating BH by magnetic fields. We discuss our results in the frame of the observable GRBs, and speculate about the origin of variability in observed GRB emission. We also discuss the possible contribution of elements synthesized in the winds launched from GRB engine to the kilonova emission.
Grzegorz Kowal - Universidade Cruzeiro do Sul
Particle acceleration mechanisms
###### The first observations of high-energy radiation, commonly known as cosmic rays, took place over one hundred years ago. Soon after the discovery of cosmic rays, Victor Hess in 1912 confirmed with his observations, that they are mostly of galactic or extra-galactic origin. Their origin and nature, however, still puzzles the modern astrophysics and is considered one of the unresolved problems. In the first part of my talk I will briefly describe what we know about the properties of cosmic rays from observations and discuss the physical mechanisms, such as diffusive shock acceleration and turbulence, believed to be responsible for accelerating thermal particles to high energies. Finally, in the last part I will present the results of our studies on first-order Fermi acceleration by fast turbulent reconnection.
Pawan Kumar - University Texas, Austin
Relativistic jets in high energy transients
Raffaella Margutti - Northwestern University
GRB-supernova association
Nergis Mavalvala - MIT
GW: observations
Paolo Mazzali - Liverpool University
Super luminous Supernovae
Rosalba Perna - University of Stony Brook
Electromagnetic counterparts of compact object binary mergers
###### Mergers of two compact objects in a binary, in addition to being sources of gravitational waves, may also be accompanied by strong electromagnetic radiation. I will discuss the expectations for double neutron star and neutron star-black hole mergers, and the evidence that they may be associated with short Gamma-Ray Burts. I will then speculate on the novel possibility that electromagnetic signatures may be produced also in the merger of two black holes.
Emily Petroff - ASTRON
Fast Radio Bursts: Recent Discoveries and Future Prospects
###### Fast radio bursts (FRBs) are quickly becoming a subject of intense interest in time-domain astronomy. FRBs have the exciting potential to be used as cosmological probes of both matter and fundamental parameters, but such studies require large populations. Advances in FRB detection using current and next-generation radio telescopes will enable the growth of the population in the next few years. Real-time discovery of FRBs is now possible with a significant number of FRBs now detected in real-time. I will discuss the developing strategies for maximising real-time science with FRBs as well as the properties of the growing FRB population. I will also discuss upcoming efforts to detect FRBs across the radio spectrum using a wide range of new and refurbished radio telescopes around the world and how these discoveries can inform next generation surveys and pave the way for the enormous number of FRB discoveries expected in the SKA era.
Fred Rasio - Northwestern University
Merging Compact Binaries as GW Sources
###### I will review recent work making theoretical predictions for the properties and merger rates of compact binaries containing black holes and neutron stars. In particular I will contrast the properties of GW sources formed through the evolution of massive binaries in the field to those of sources assembled dynamically through gravitational interactions in dense star clusters, and I will discuss the prospects for distinguishing between these two formation channels with upcoming LIGO observations.
Stephan Rosswog - Stockholm University
Multi-Messenger signals from gravitational wave sources
Alexander Tchekhovskoy - Northwestern University
The role of accretion disks in transient sources

## Scientific Organizing Committee

 Miguel Alcubierre - UNAM Edo Berger - Harvard University Fabio De Colle (co-chair) - UNAM Elisabete de Gouveia Dal Pino - Universidade de São Paolo Gabriela Gonzalez - Lousiana State University Vicky Kalogera - Northwestern University
 Andrew King - Leicester University Davide Lazzati - Oregon State University William Lee - UNAM Diego López Cámara (co-chair) - UNAM Elena Pian - INAF-Bologna, SNS Enrico Ramírez Ruiz - University of California, Santa Cruz

## Local Organizing Committee

 Rosa Becerra - UNAM Fabio De Colle (co-chair) - UNAM Diego López Cámara (co-chair) - UNAM Enrique Moreno Méndez - UNAM

## Important Dates

 Abstract submission deadline July 31 Preliminary program Mid August Registration fee payment deadline September 30 Hotel reservation deadline at a special price October 25 (subject to availability) Conference December 11-15

## Participants

Edilberto Aguilar Ruiz
Instituto de Astronomía, UNAM (Mexico)
David Ramón Aguilera Dena
Argelander Institut für Astronomie (Germany)
Miguel Alcubierre
ICN-UNAM (Mexico)
Igor Andreoni
Swinburne University of Technology (Australia)
Jeff Andrews
FORTH/University of Crete (Greece)
Jennifer Andrews
University of Arizona (USA)
Jean-Luc Atteia
IRAP - Toulouse (France)
Katie Auchettl
The Ohio State University (USA)
Arturo Avelino
CfA, Harvard (USA)
Jennifer Barnes
Columbia University (USA)
Aldo Batta
University of California, Santa Cruz (USA)
Rosa Becerra
Instituto de Astronomía, UNAM (Mexico)
Wlodek Bednarek
University of Lodz (Poland)
Damien Bégué
MPE (Germany)
Paz Beniamini
George Washington University (USA)
Mikhail Beznogov
Instituto de Astronomía, UNAM (Mexico)
Mukul Bhattacharya
University of Texas, Austin (USA)
Peter J. Brown
Texas A&M University & Mitchell Institute for Fundamental Physics and Astronomy (USA)
J. Michael Burgess
Max-Planck-Institut für extraterrestrische Physik (Germany)
Matteo Cantiello
CCA, Flatiron Institute & Princeton University (USA)
Dario Carbone
Texas Tech University (USA)
Vikas Chand
Tata Institute of Fundamental Research - Mumbai (India)
Ian Christie
Purdue University (USA)
Aleksandar Cikota
ESO Garching (Germany)
Kishalay De
Caltech (USA)
Fabio De Colle
Instituto de Ciencias Nucleares, UNAM (Mexico)
Elisabete de Gouveia Dal Pino
Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo (IAG-USP) (Brazil)
Antonio de Ugarte Postigo
Instituto de Astrofísica de Andalucía (IAA-CSIC) (Spain)
Hüsne Dereli
KTH Royal Institute of Technology, Sockholm (Sweden)
Simone Dichiara
UNAM (Mexico)
University of Chicago (USA)
Rosa Wallace Everson
UC Santa Cruz (USA)
Ryan Foley
University of California, Santa Cruz (USA)
Wen-fai Fong
Northwestern University (USA)
Ori Fox
STScI (USA)
Tassos Fragos
DARK/CTA, NBI, University of Copenhagen (Denmark)
Nissim Fraija
IA-UNAM (Mexico)
Christoffer Fremling
CalTech (USA)
Edwin Antonio Galván Gamez
IA-UNAM (Mexico)
Ramandeep Gill
The Open University of Israel (Israel)
Andreia Gomboc
University of Nova Gorica (Slovenia)
Sebastian Gomez
Harvard-Smithsonian Center for Astrophysics (USA)
Maria Magdalena González
Instituto de Astronomía, UNAM (Mexico)
Jonathan Granot
The Open University of Israel (Israel)
Dafne Guetta
ORT-Braude (Israel)
James Guillochon
Harvard University (USA)
Francisco S. Guzmán
Universidad Michoacana de San Nicolás de Hidalgo (Mexico)
Alexander Heger
Monash University (Australia)
Vicente Hernández
Playa del Carmen Planetarium (Mexico)
University of Illinois at Urbana-Champaign (USA)
Tom Holoien
The Observatories of the Carnegie Institute of Science (USA)
Christopher Irwin
Tel Aviv University/Hebrew University of Jerusalem (Israel)
Agnieszka Janiuk
Center for Theoretical Physics, PAS (Poland)
Alejandra Jiménez Rosales
Max-Planck-Institut für Extraterrestrische Physik (Germany)
Vicky Kalogera
Northwestern University (USA)
Purdue University (USA)
Charles Kilpatrick
University of California, Santa Cruz (USA)
Grzegorz Kowal
Kelsie Krafton
Louisiana State University (USA)
Pawan Kumar
University of Texas, Austin (USA)
Cyril Lachaud
APC - University Paris Diderot (France)
Jamie Law-Smith
UC Santa Cruz (USA)
Davide Lazzati
Oregon State University (USA)
Diego López Cámara
Instituto de Astronomía, UNAM (Mexico)
Kin López Mendoza
IA-UNAM (Mexico)
Wenbin Lu
University Texas at Austin (USA)
Ragnhild Lunnan
Stockholm University (Sweden)
Pablo Marchant
Northwestern University (USA)
Raffaella Margutti
Northwestern University (USA)
Tatsuya Matsumoto
Kyoto University (Japan)
Nergis Mavalvala
MIT (USA)
Paolo Mazzali
Liverpool University (UK)
Rogelio Alan Medina
ICN-UNAM (Mexico)
Jonah Miller
Los Alamos National Laboratory (USA)
Brenna Mockler
UC Santa Cruz (USA)
Gibrán Morales Rivera
IA-UNAM (Mexico)
Claudia Moreno
Enrique Moreno Méndez
UNAM (Mexico)
Takashi Moriya
National Astronomical Observatory of Japan (Japan)
University of California, Santa Cruz (USA)
Jeremiah Murphy
Florida State University (USA)
Andrea Nagy
University of Szeged (Hungary)
Sam Oates
University of Warwick (UK)
Chris Pankow
CIERA / Northwestern University (USA)
Dan Patnaude
Smithsonian Astrophysical Observatory (USA)
Rosalba Perna
University of Stony Brook (USA)
Emily Petroff
ASTRON (Netherland)
Elena Pian
INAF, IASF Bologna & Scuola Normale Superiore, Pisa (Italy)
Giuliano Pignata
Graziella Pizzichini
INAF/IASF Bologna (Italy)
Paul Plucinsky
Smithsonian Astrophysical Observatory (USA)
Isidro Ramírez Ballinas
IA-UNAM (Mexico)
Kenia Joseline Ramírez Millán
Enrico Ramírez Ruíz
UCSC (USA)
Fred Rasio
Northwestern University (USA)
Armin Rest
STScI (USA)
Jorge Reyes Iturbide
Tecnológico de Tianguistenco (Mexico)
Francisco Rivera
Universidad Michoacana de San Nicolas de Hidalgo (Mexico)
Ramon Daniel Rodriguez Soto
Cristina Romero Cañizales
Núcleo de Astronomía, Universidad Diego Portales (Chile)
Stephan Rosswog
Stockholm University (Sweden)
Nathaniel Roth
University of Maryland, College Park (USA)
Felix Ryde
KTH Royal Institute of Technology, Sockholm (Sweden)
José Rodrigo Sacahui Reyes
Instituto de Investigación en Ciencias Físicas y Matemáticas, ECFM-Universidad de San Carlos de Guatemala (Guatemala)
Filip Samuelsson
KTH Royal Institute of Technology, Sockholm (Sweden)
Jesús Alberto Santos Morales
Instituto Tecnológico y de Estudios Superiores de Monterrey (Mexico)
Sophie Lund Schrøder
University of Copenhagen, NBI (Denmark)
Josiah Schwab
UC Santa Cruz (USA)
Emanuele Sobacchi
The Open University of Israel & Ben Gurion University of the Negev (Israel)
Pablo Omar Sotomayor Checa
Facultad de Ciencias Astronómicas y Geofísicas - Universidad Nacional de La Plata (Argentina)
Yudai Suwa
Yukawa Institute for Theoretical Physics, Kyoto University (Japan)
Akihiro Suzuki
Kyoto University (Japan)
Tamas Szalai
University of Szeged (Hungary)
Tomoya Takiwaki
National Astronomical Observatory of Japan (Japan)
Masaomi Tanaka
National Astronomical Observatory of Japan (Japan)
Nial Tanvir
University of Leicester (England)
Alexander Tchekhovskoy
Northwestern University (USA)
Giacomo Terreran
Northwestern University (USA)
Christina Thöne
HETH/IAA-CSIC (Spain)
Alexey Tolstov
Kavli IPMU, The University of Tokyo (Japan)
Gerardo Urrutia Sánchez
ICN-UNAM (Mexico)
Susanna Vergani
CNRS - Paris Observatory (France)
Alejandro Vigna Gomez
University of Birmingham (UK)
Alan Watson
IA-UNAM (Mexico)
Brian Williams
Space Telescope Science Institute (USA)
Tyrone E. Woods
Monash University (Australia)