Kate D Alexander, Northwestern University - CIERA
Cosmic Extremes: Probing Energetic Transients with Radio Observations

February 25, 2019 (9:20 AM - 9:40 AM)

Radio observations provide a unique window into a wide variety of transient events, from gamma-ray bursts (GRBs) to supernovae to tidal disruption events (TDEs) in which a star is torn apart by a supermassive black hole. In particular, GRBs and TDEs have emerged as valuable probes of some of the most extreme physics in the Universe. In these high-energy laboratories, the longer timescale of radio emission allows for extensive followup and characterization of the event energies and the densities of surrounding material. I will present high-cadence broadband radio studies of GRB afterglows and TDEs undertaken with the goal of learning more about their physical properties, the physics underlying the formation and growth of relativistic jets and outflows, and the environments in which these events occur. These insights derived from these studies will be invaluable for designing and interpreting the results from future radio transient surveys.
Elias Aydi, Michigan State University
A "shock" to the system - classical novae emitting gamma-rays

February 26, 2019 (2:55 PM - 3:10 PM)

Co-authors: Laura Chomiuk, Kirill Sokolovsky, and Adam Kawash
Classical novae are transient events powered by thermonuclear runaways on the surface of accreting white dwarfs in interacting binary star systems. The recent discoveries of gamma-ray emission from several classical novae by Fermi-LAT has altered the field and our understanding of these enigmatic objects. For several decades, the standard model assumed that the optical luminosity of the outburst originates from energy released near the hot white dwarf which is reprocessed through the ejected material. However, GeV gamma-ray emission challenge this model as strong shocks are required to explain the high energy emissions. These shocks might also account for a considerable share of the optical luminosity emitted during the eruption. In this talk, I will present a review of the efforts done in the last five years towards a better understanding of Gamma-ray emitting novae with emphasizes on an ongoing multiwavelength study of a remarkable nova, namely ASASSN-18fv.
Damiano Caprioli, University of Chicago
Towards a Comprehensive Theory of Diffusive Shock Acceleration

February 25, 2019 (2:00 PM - 2:20 PM)

I discuss the recent developments in the theory of diffusive shock acceleration (DSA) by using both first-principle kinetic plasma simulations and analytical theory based on the solution of the Parker equation. In particular, I show how simulations are revealing that the standard theory of DSA, which predicts universal energy spectra E^-2, has to be revised, in better agreement with the significantly steeper particle spectra inferred with multi-wavelength observations of radio-SNe and young SN remnants. Then, I introduce a new code for calculating particle acceleration at non-relativistic shocks: CRAFT (Cosmic-Ray Analytical Fast Tool). In few seconds on a laptop, CRAFT can return the particle spectrum, the self-generated magnetic turbulence, and the global non-linear structure of a shock where the dynamical back-reaction of accelerated particles and amplified magnetic fields are taken into account self-consistently. CRAFT will be a useful tool for better modeling non-thermal emission of steady sources, such as SN remnants, and transients such as radio SNe, novae, and kilonovae.
John Carlstrom, Astronomy and Astrophysics, University of Chicago

February 25, 2019 (9:00 AM - 9:10 AM)
Deep Chatterjee, University of Wisconsin Milwaukee
Predicting Supernova Rates Using iPTF: Estimating the transient detection efficiency

February 25, 2019 (3:05 PM - 3:20 PM)

Co-authors: Peter Nugent, Chris Cannella, David Kaplan, Patrick Brady
The intermediate Palomar Transient Factory (iPTF) was in operation between 2013 and 2016. It located about 50,000 non-moving transients, confirmed more than 1000 supernovae, and also located some "fast" transients, evolving in timescale of days. When it comes to a statement on transient rates, a robust quantification of the number of transient missed for every one detected is required. In this work, the transient detection efficiency for iPTF is calculated. Once equipped with the efficiency, volume sensitivity to any transient type, hence the rate, could be computed. Here, we consider the type Ia supernovae (SNIa) sample in the survey.
Deanne L Coppejans, Northwestern University
Multi-wavelength studies of Fast-evolving Blue Optical Transients

February 25, 2019 (10:10 AM - 10:25 AM)

In recent years, surveys have identified a new class of luminous transients with an extremely rapid rise to maximum (of a few days) and blue colours. These transients, refered to as Fast Blue Optical Transients (FBOTs), are generally attributed to stellar explosions, but their properties challenge traditional supernova models. Alternative scenarios for FBOTs include failed supernovae (SNe), the detonation of a helium shell on a white dwarf, SN shock breakout from a dense circumstellar medium, or other engine-driven mechanisms. Multi-wavelength studies that include radio and x-ray data allow us to probe the relativistic material. I will discuss how we are using these observations to constrain the nature of this new class of transient.
Sean Couch, Michigan State University
The Turbulent Frontier in Massive Stellar Death

February 26, 2019 (10:50 AM - 11:05 AM)

I will discuss the recent developments in the study of the supernova mechanism and progress toward a predictive theory of massive stellar death. In particular, I will discuss the emerging picture of the importance of turbulence in the supernova mechanism and the impact of realistic 3D initial conditions for supernova simulations. Such realistic 3D initial conditions turn out to be favorable for successful explosions, in large part because they result in stronger turbulence behind the stalled supernova shock. I will also discuss new work on the role of ubiquitous rotation and magnetic fields in altering the character of supernova explosions. I will conclude with a discussion of the impacts of improved physics on observational features of supernovae, including on the gravitational wave emission from these stellar explosions.
Zoheyr Doctor, Uchicago
Search for Optical Emission from Binary-Black-Hole Merger 170814

February 26, 2019 (4:15 PM - 4:30 PM)

Co-authors: DES + external collaborators
We searched for optical Emission from black hole merger GW170814 with the Dark Energy Camera. Two candidates were found, neither of which is likely to be associated with GW170814
Vikram Dwarkadas, University of Chicago
Introduction and Logistics

February 25, 2019 (9:10 AM - 9:20 AM)
Brian Fields, University of Illinois
When Stars Attack! Confirmation, Identification, and Localization of a Recent Near-Earth Supernova

February 26, 2019 (11:50 AM - 12:05 PM)

Supernovae are major engines of nucleosynthesis, and create many of the elements essential for life. Yet these awesome events take a sinister shade when they occur close to home, because an explosion very nearby would pose a grave threat to Earthlings. We will show how radionuclides produced by supernovae can reveal nearby events in the geologic past, and we will highlight isotopes of interest. In particular, geological evidence for live 60Fe has recently been confirmed globally in multiple sites of deep-ocean material, in cosmic rays, and in lunar samples (!). We will review astrophysical 60Fe production sites and show that the data demand that one or more core-collapse supernovae exploded near the Earth ∼ 3 Myr ago, and explain how debris from the explosion was transported to the Earth as a “radioactive rain.” The 60Fe measurements represent a new tool: sea sediments and lunar cores as telescopes, probing supernova nucleosynthesis and possibly even indicating the direction towards the event(s). The ~ 1 Myr measured duration of 60Fe deposition is surprisingly long, likely pointing to dust dynamics and evolution effects within the Local Bubble. We will conclude by showing how the 60Fe gradient on the Moon could help localize the explosion site.
Aprajita Hajela, Northwestern University
Developing New Technique to Measure the Ambient Density of GW170817

February 26, 2019 (4:30 PM - 4:45 PM)

Co-authors: Raffaella Margutti
We present a new method to constrain the density of the environment of GW170817 based on diffuse X-ray emission from the host galaxy from hot ionized gas. The measurement being independent of the inferences based on conventional afterglow modeling will help us break the degeneracies.
Chelsea E Harris, Michigan State University
Which SNe Ia Come from the Single Degenerate Channel? The Answer Will Shock You.

February 25, 2019 (2:20 PM - 2:35 PM)

The biggest open question in SN Ia research is what their progenitors are, with research typically aimed at identifying the mass-donor companion star to the white dwarf. There are myriad theoretical candidates, but we typically frame experiments with the question, "single degenerate xor double degenerate?". The single degenerate channel with a red giant donor is now strongly disfavored for producing normal SNe Ia. But not all SNe Ia are normal -- about 10% are the hot and bright "91T-like" sub-type, which are included in cosmological samples. I will present recent theoretical and observational results that suggest 91T-like SNe Ia may represent the single-degenerate channel.
Gil Holder, University of Illinois
Transients in CMB Surveys

February 26, 2019 (9:50 AM - 10:05 AM)

CMB surveys are now reaching a sensitivity where GRBs and nearby supernovae should be detectable at mm wavelengths in regular survey data. For example, SPT-3G (at the South Pole) covers a 1500 square degree survey region almost daily with a daily sensitivity of several mJy at wavelengths of 90, 150, and 220 GHz. Surveys from Chile, such as the ongoing Advanced ACTPol and future Simons Observatory and CMB-S4, can access roughly half the sky for transient detection at mm wavelengths.
A. Miguel Holgado, University of Illinois at Urbana-Champaign
On the Formation of Double Neutron Stars from Supernova Natal Kicks

February 25, 2019 (2:50 PM - 3:05 PM)

Co-authors: Paul Ricker
A neutron star emerging from the common-envelope phase may be paired with a helium-star companion. The helium star may eventually undergo a supernova explosion and form a double neutron-star system. The transition from the pre-supernova to the post-supernova state is often treated as an instantaneous process in binary population-synthesis codes. We investigate this phase transition with a more sophisticated model that accounts for the finite timescales of the supernova mass loss and natal kick. We compare how treating the finite timescales affects the final orbital characteristics with those predicted from the prescriptions often used in binary population-synthesis codes.
David Kaplan, UW-Milwaukee
Radio Followup of Binary Neutron Star Mergers

February 26, 2019 (3:55 PM - 4:15 PM)

Co-authors: Tara Murphy, Dougal Dobie, Samaya Nissanke, Kenta Hotokezaka, Kunal Mooley, Dale Frail, Gregg Hallinan, Alessandra Corsi
I will discuss the major uncertainties regarding the geometry, energetics, and environment of the first EM/GW binary neutron star merger GW170817. In particular I will look at the origin of the radio emission, how it differs from the early-time optical/infrared emission, and what that tells us about how the explosion proceeded. I will show how constraints from the radio lightcurve, polarization, and Very Long Baseline Interferometry helped answer these questions, and what we can expect from future events.
Mansi M. Kasliwal, Caltech
First results from the Zwicky Transient Facility

February 26, 2019 (9:00 AM - 9:20 AM)

Co-authors: On behalf of the ZTF (Zwicky Transient Facility) and GROWTH (Global Relay of Observatories Watching Transients Happen) collaboration
Adithan Kathirgamaraju, Purdue University
The non-thermal counterparts of GW170817: current observations and what we can expect in the future

February 26, 2019 (4:45 PM - 5:00 PM)

Co-authors: Rodolfo Barniol Duran, Paz Beniamini, Dimitrios Giannios, Alexander (Sasha) Tchekhovskoy
Utilizing 3D GRMHD simulations, I will demonstrate how a jet launched by an accreting black hole in a post-merger system, naturally reproduces the observed properties of GRB170817A. I will also explore another electromagnetic counterpart of GW170817 which may be detectable in the near future, the afterglow associated with the kilonova, and discuss what we can learn from its detection.
Maxim Lyutikov, Purdue
Transients following white dwarfs merger

February 25, 2019 (10:25 AM - 10:40 AM)

Co-authors: Silvia Toonen
We suggest that fast-rising blue optical transients (FBOTs), and the brightest event of the class AT2018cow, result from electron-capture collapse following a merger of a massive ONeMg white dwarf (WD) with another WD. The model explains many of the puzzling properties of FBOTs/AT2018cow: host galaxies, fast and light anisotropic ejecta producing bright optical peak, afterglow with high energy emission of similar luminosity to optical, hard X-ray and infra-red features, presence of dense wind environment, late powerful radio emission.
Jessica E Metzger, University of Chicago
A Neutrinosphere Model for Kilonova Photometry

February 25, 2019 (4:15 PM - 4:30 PM)

Co-authors: James Annis, James Annis, Ken Herner, Kamile Lukosiute, Marcelle Soares-Santos
On August 17th, 2017 we observed the first binary neutron star merger (BNS) in gravitational waves, and soon afterwards located the electromagnetic counterpart, the kilonova. Models of this electromagnetic emission are interesting and useful in deducing properties of the merger. We present a unified, physically motivated kilonova model for the UV to IR lightcurves. We parametrize the composition through a neutrinosphere model of neutrino luminosity, and account for ejecta anisotropy and viewing angle effects in producing the observed lightcurves. We are able to describe the data from GW170817, and present fits of the UVOIR lightcurves. Our resulting parameters show some deviations from previous estimates. We also fit blackbodies to the early-time optical photometry, accounting for the blueshift of the expanding ejecta. Our velocity and temperature fits are slower and, for the most part, colder than previous estimates.
Danny Milisavljevic, Purdue University
Connecting Distant Supernovae with Nearby Supernova Remnants

February 25, 2019 (11:50 AM - 12:05 PM)

I will review key connections between extragalactic supernovae and resolved supernova remnants that provide valuable information about supernova progenitor systems, their nearby environments, and supernova explosion dynamics. Links between long-lasting, “middle-aged” (10–100 years) supernovae and young (<1000 years) supernova remnants that uniquely inform about the origins of explosive mixing, high-velocity jets, and the formation of dust in the ejecta will be highlighted. I will conclude with a discussion about future facilities that will enable transformational progress to be made on our understanding of the SN-SNR transition.
Jon Miller, University of Michigan
X-ray Observations of Tidal Disruption Events

February 25, 2019 (9:40 AM - 9:55 AM)

X-ray studies of AGN are particularly adept at revealing the innermost regions of relatively steady accretion flows onto massive black holes. Similarly, X-ray studies of tidal disruption events probe the nature of nascent, highly variable, and potentially super-Eddington accretion onto massive black holes. This talk will review some recent key developments, including X-ray reflection, QPOs, and outflows, and look ahead to prospects with future telescopes and mission concepts.
Anya E Nugent, Northwestern University
Analysis of A Short Gamma Ray Burst in an Old Galaxy Cluster

February 25, 2019 (9:55 AM - 10:10 AM)

Short gamma ray bursts (SGRBs) are high-energy explosions that last from just a few milliseconds to two seconds and are thought to originate from the merging of a binary neutron star system. Typically, SGRBs are found in a range of stellar populations, and about 30% of them occur in early-type host galaxies. However, in one rare instance an SGRB was observed in a faint galaxy cluster (SGRB 161104A). In this talk, I will discuss multi-band photometry of several galaxies within the cluster. Furthermore, I will present preliminary models of their spectral energy distribution (SED) using Prospector to determine stellar population properties, such as stellar mass, stellar population age, and dust extinction.We plan to perform this analysis not only for SGRB 161104A, but also for a large sample of other host galaxies of SGRBs to find common environments in which SGRBs originate.
Michael A Pajkos, Michigan State University
Gravitational Wave Features from Rotating Core-Collapse Supernovae

February 26, 2019 (11:05 AM - 11:20 AM)

Co-authors: Sean M. Couch, Kuo-Chuan Pan, Evan P. O'Connor
I explore the influence of progenitor mass and rotation on the gravitational wave (GW) emission from core collapse supernovae, during the post bounce, pre explosion, accretion phase. I present the results from 15 two-dimensional (2D) neutrino radiation-hydrodynamic simulations from initial stellar collapse to 300 ms after core bounce for a variety of progenitor masses and rotation rates. The GW strain immediately around core bounce is fairly independent of ZAMS mass and—consistent with previous findings—that it is more heavily dependent on the core angular momentum. At later times, all nonrotating progenitors exhibit loud GW emission, attributed to vibrational g-modes of the protoneutron star, excited by convection in the post shock layer and the standing accretion shock instability (SASI). However, increasing progenitor rotation rates results in muting of this accretion phase GW signal due to centrifugal effects that inhibit convection in the post shock region, quench the SASI, and flatten the protoneutron star vibrational modes.
Antonella Palmese, Fermilab
Gravitational wave astrophysics and cosmology with DES galaxies

February 25, 2019 (4:30 PM - 4:45 PM)

Co-authors: Marcelle Soares-Santos, DES. LVC
In the occasion of the exciting discovery of the electromagnetic counterpart of the GW170817 gravitational wave event, the Dark Energy Survey (DES) collaboration produced a series of studies covering different aspects of the event. In this talk, I will present the Dark Energy Survey gravitational wave follow up program and how observations of the GW170817 host galaxy can provide information about the formation of the binary neutron star that merged, producing the gravitational wave signal. The synergy between gravitational wave data and new generation large galaxy survey such DES can be further extended to binary black hole events. This will allow precision measurements of the Hubble constant within a few years and insights into the nature of black hole binaries.
Chris Pankow, Northwestern University
Astronomy and Astrophysics with Gravitational Waves

February 25, 2019 (4:45 PM - 5:00 PM)

The first two observing runs of the LIGO/Virgo gravitational-wave interferometer network have produced ten binary black holes and the historic detection of a binary neutron star. In this talk, I will review the current inventory of detections during those runs and how their measured properties are shaping our understanding of compact object populations and multi-messenger astrophysics. I will also project forward over the next five years to give a picture of what the future holds; e.g., incremental sensitivity improvements with new and current instruments, hundreds of detections, and increasingly precise estimations of sky location.
Rachel A Patton, The Ohio State University
Optical Depth Constraints on the Supernova Impostors SN 1954J and SN 1961V

February 26, 2019 (10:05 AM - 10:20 AM)

Co-authors: Chris Kochanek, OSU; Scott Adams, Caltech
There are a subset of massive stars which seem to experience violent outbursts that are spectroscopically similar to Type IIn supernovae. The most energetic of these non-terminal eruptions are not cleanly separated from the least energetic supernovae. SN 1954J in NGC 2403 and SN 1961V in NGC 1058 were two bizarre, luminous transients whose definitive classification as either non-terminal eruptions or supernovae remains elusive. A critical question is whether a surviving star can be obscured by a large amount of dust produced in the transient. This dust has been invoked to explain the lack of each object’s observed brightening, but the evolution of the dust implies that the optical depth should fall off as at least {tau}^-2 as the ejecta expand, causing the star to brighten. We use four probes of optical depth, SED modeling of new HST optical/NIR data, photometric variability, and H{alpha} evolution and variability, to argue that the candidate survivors are not significantly optically extincted.
Matthias Raives, The Ohio State University
The Antesonic Condition for Core-Collapse Supernovae

February 26, 2019 (11:35 AM - 11:50 AM)

While the neutrino mechanism is understood to be the driving force behind core-collapse supernovae (CCSNe) explosions, the physics of this mechanism in multidimensional simulations are not fully understood. We extend the "antesonic condition" formulated by Pejcha & Thompson (2012) to time-dependent, polytropic models. We find that high spatial resolution is necessary for accurate determination of simulation properties near the critical curve, and low resolution simulations explode less readily. We also find that there is an important physical connection between the critical mass accretion rate at explosion and the mass loss rate of the post-explosion wind.
Noel D Richardson, University of Toledo
eta Carinae: A stellar system 170 years after a Great Eruption

February 25, 2019 (3:20 PM - 3:35 PM)

The binary system eta Carinae contains one of the most massive stars in the Galaxy, and was the second observed system to have an LBV outburst. During the 1840s, the brightness of the star grew to rival Sirius and expelled about 40 solar masses of material. Several groups have now managed to have state-of-the-art observations and theoretical developments over the past 20 years. I will review what we know about the closest supernova imposter and outline future directions for understanding the system.
Wilson Ricks, University of Chicago
Excavating the Explosion and Progenitor Properties of Type IIP Supernovae via Modelling of their Optical Lightcurves

February 25, 2019 (11:20 AM - 11:35 AM)

Co-authors: Vikram Dwarkadas
The progenitors of Type IIP supernovae (SNe) are known to be red supergiants, but their properties are not well determined. We employ hydrodynamical modelling to investigate the explosion characteristics of eight Type IIP supernovae, and the properties of their progenitor stars. We create evolutionary models using the MESA stellar evolution code, explode these models, and simulate the optical lightcurves using the STELLA code. We fit the optical lightcurves and Fe II 5169 ̊A velocities to the observational data. Recent research has suggested that the progenitors of Type IIP SNe do not exceed ∼ 18 solar masses. Our fits give progenitor zero age main sequence (ZAMS) masses ≤ 18 solar masses for seven of the supernovae. Where previous progenitor mass estimates exist, from various sources such as hydrodynamical modelling, multi-wavelength observations, or semi-analytic calculations, our modelling generally tends towards the lower mass values. This result is in contrast to results from previous hydrodynamical modelling, but is consistent with those obtained using general-relativistic radiation-hydrodynamical codes. We do find that one event, SN 2015ba, has a progenitor whose mass most likely exceeds 18 solar masses, although we are unable to fit it well. We also derive the Ni-56 mass required to describe the tail of the lightcurve, and find values generally larger than previous estimates. Overall, we find that it is difficult to characterize the explosion by a single parameter, and that a range of parameters is needed.
Sumit K Sarbadhicary, Michigan State University
Drilling deep into the transient radio sky with the CHILES-VERDES survey

February 26, 2019 (9:20 AM - 9:35 AM)

Co-authors: Laura Chomiuk, Adam Stewart, Evangelia Tremou, Jack O' Brien, Christina Conner, Charee Peters, Chris Hales, Tara Murphy, Rob Fender, Eric Wilcots, Jacqueline Van Gorkom, Emmanuel Momjian
High-energy transients such as supernovae, GRBs, compact binary mergers and tidal disruption events leave unique footprints in radio wavelengths that can be essential for understanding the underlying physics. Radio can also probe through dusty lines of sight, revealing transients that would otherwise be obscured in optical surveys. In this talk, I will discuss the CHILES-VERDES survey, which is poised to become the deepest survey of the radio transient sky in the pre-SKA era. The survey utilizes 1000 hrs of VLA continuum observations of the COSMOS field as part of the CHILES (COSMOS HI Large Extragalactic Survey) project. With each 3 hr epoch reaching 10 muJy sensitivities, CHILES-VERDES is expected to uncover both short and long-duration transients (by co-adding epochs) with unprecedented sensitivities. In addition, the plethora of existing multi-wavelength data in the COSMOS field will allow us to relate our radio observations with the multi-wavelength properties of transients, as well as identify their host galaxy properties.
Kirill Sokolovsky, Michigan State University
Classical novae as X-ray transients: the case of Nova Carinae 2018

February 26, 2019 (3:10 PM - 3:25 PM)

Co-authors: Laura Chomiuk, Koji Mukai, Elias Aydi, Raimundo Lopes De Oliveira
Novae are known for their spectacular optical outbursts, but are also accompanied by thermal X-ray emission produced by either 1) plasma heated by internal shocks within the nova ejecta or 2) the hot surface of the nuclear-burning white dwarf that becomes visible as the ejecta clears (the super-soft source stage). The rapid response capability of the contemporary X-ray observatories shed new light on the shock-powered emission. We present results of NuSTAR, Swift and XMM-Newton observations of the bright southern nova ASASSN-18fv/Nova Carinae 2018 and discuss them in the context of its gamma-ray detection by Fermi and AGILE.
Niharika Sravan, Purdue University
A comprehensive population-scale modeling of Type IIb supernova progenitors

February 26, 2019 (2:35 PM - 2:50 PM)

Co-authors: Pablo Marchant, Vicky Kalogera, Raffaella Margutti, Dan Milisavljevic
The mechanisms driving removal of envelopes of stripped-envelope supernova (SE SN) progenitors is a key challenge to our understanding of massive star evolution. Type IIb SNe are particularly valuable for addressing this challenge because of the wide variety of observational constraints available for them, most notably, direct progenitor/companion identifications in several cases. We undertake an unprecedented population-scale modeling effort using MESA to test our ability to reproduce all observational constraints for Type IIb SNe. Our comprehensive grid of ~150,000 models span the full parameter space occupied by single and binary SN IIb (in progenitor mass, mass ratio, orbital separation, and mass transfer efficiency) at solar and low metallicities. As already widely suggested, we find that Type IIb SN fractions imply that binaries comprise of the vast majority of Type IIb SNe. However, the models require significantly lower wind mass loss rates at solar metallicity and highly inefficient mass transfer. We find observational parameter spaces that are currently unprobed but highly constraining for mass loss rates due to stellar winds and eruptions. In particular, our models indicate the presence of a population of highly-compact nearly-fully-stripped progenitors and episodic mass loss in progenitors in the years leading up to core-collapse.
Albert Stebbins, Fermilab
Vacuum Pair Production and EMP for Short Radio Transients

February 26, 2019 (2:00 PM - 2:15 PM)

Vacuum pair production (the Schwinger Mechanism) limits the brightness of short radio transients such as nanoshots and possibly Fast Radio Bursts. We show how the electromagnetic pulse (EMP) produced can easily propagate through dense plasmas with frequency content well below the plasma frequency. Thus short radio transients observed at GHz frequencies could easily have originated very near the surface of neutron stars.
Elad Steinberg, Columbia University
Emission from Radiative Shocks

February 26, 2019 (2:15 PM - 2:35 PM)

Co-authors: Brian Metzger
Radiative shocks, behind which gas cools faster than the dynamical time, play a key role in many astrophysical transients, including classical novae and young supernovae interacting with circumstellar material. The dense layer behind high Mach number radiative shocks is susceptible to thin-shell instabilities, creating a “corrugated” shock interface. We present two and three-dimensional hydrodynamical simulations of optically-thin radiative shocks to study their thermal radiation and acceleration of nonthermal relativistic ions.
Tuguldur Sukhbold, The Ohio State University
Life and Death of Massive Stars

February 25, 2019 (11:00 AM - 11:20 AM)
Giacomo Terreran, Northwestern University
The ''He-rich'' Type Ic SN 2016coi and its massive progenitor

February 25, 2019 (11:35 AM - 11:50 AM)

I will present the multi-wavelength follow-up of the energetic H-stripped SN 2016coi (aka ASASSN-16fp) spanning the gamma-rays, X-rays and optical bands, acquired within the first hours to ~420 days since explosion. Our campaign confirms the presence of He mixed into the inner layers of the SN ejecta, and a bolometric light-curve with long time-scales of evolution, which is indicative of large ejecta mass to kinetic energy ratio Me~4-7 Msun, Ek~7-8 x 10^51 erg. Furthermore we find a small [Ca II] 7291,7324 to [O I] 6300,6364 ratio suggestive of a large progenitor core mass at the time of collapse. SN 2016coi is a luminous source of X-rays with Lx>10^39 erg/s in the first ~100 days since explosion, similar to relativistic SNe. However, for SN 2016coi we infer a large pre-explosion progenitor mass-loss rate Mdot~3-7 x 10^-5 Msun/yr and a sub-relativistic shock velocity v~0.25c, in stark contrast with relativistic SNe and similar to normal SNe. Finally, we find no evidence for a SN-associated shock breakout gamma-ray pulse with energy E>2 x 10^46 erg. While we cannot exclude the presence of a binary companion, taken together these findings allow for the possibility that SN 2016coi originated from a massive single star progenitor experiencing substantial mass loss in the years leading up to core-collapse, but unable to achieve complete stripping of its outer layers.
Patrick Vallely, Ohio State University
ASAS-SN: Big Science with Small Telescopes

February 26, 2019 (9:35 AM - 9:50 AM)

Co-authors: K. Z. Stanek, C. S. Kochanek, J. Shields, T. A. Thompson (Ohio State), B. J. Shappee (IfA-Hawaii), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), M. Stritzinger, S. Holmbo (Aarhus)
The All-Sky Automated Survey for Supernovae (ASAS-SN) is a global multi-telescope project that surveys the entire sky down to 18th magnitude every night in order to detect astronomical transients. ASAS-SN has now been operating for over five years, and with recent developments, including the deployment of additional telescope units in Texas and South Africa and a shift from V-band observations to g-band, the survey is now more productive than ever. I present an overview of the ASAS-SN survey and also highlight a number of its interesting discoveries.
Xilu Wang, University of Notre Dame
Sandblasting The R-Process: Spallation Of The R-Process Nuclei Ejected From A NSNS Event

February 25, 2019 (4:00 PM - 4:15 PM)

Co-authors: Rebecca A Surman, Brian D Fields
Neutron star mergers are r-process nucleosynthesis sites, which eject materials at high velocity ranging from 0.1c to 0.3c for different regions. Thus the r-process nuclei ejected from a neutron star merger event are sufficiently energetic to have spallation nuclear reactions with the interstellar medium particles. The spallation reactions tend to shift the peak positions of the r-process abundance patterns, towards the solar data. The spallation effects depend on the r-process ejecta velocity, spallation cross section, the astrophysical trajectories and nuclear data adopted in the r-process nucleosynthesis simulation.
MacKenzie Warren, Michigan State University
Multimessenger signals from the landscape of core-collapse supernovae

February 26, 2019 (11:20 AM - 11:35 AM)

Co-authors: Sean Couch, Evan O'Connor
We have developed a new method for artificially driving core-collapse supernova explosions in 1D simulations. Turbulence is important for understanding the CCSN explosion mechanism, since turbulence may add a >20% correction to the total pressure behind the shock and thus aid in the explosion. Including turbulence results in successful explosions in spherical symmetry without altering the neutrino luminosities or interactions, as is commonly done to produce explosions in spherical symmetry. This better replicates the physical explosion mechanism and more reliably produces the thermodynamics and composition, which is vital for accurately predicting the nucleosynthesis that occurs in the supernova environment. We have applied this model to explore the multi-messenger observable signals - light curves, neutrino emission, and GW emission - for the landscape of supernova progenitors from 9 - 120 M⊙. We have explored correlations between the underlying stellar structure and physics of the CCSNe mechanism with observable quantities.
Charlotte Wood, University of Notre Dame
The Slowly Fading Light Echo Around Type Ia Supernova 2009ig

February 25, 2019 (2:35 PM - 2:50 PM)

Co-authors: Peter Garnavich, Peter Milne, Dina Drozdov
The light echo around Supernova 2009ig (SN2009ig) is the sixth known and most luminous around a type Ia supernova. Light echoes can provide information on the local environment around supernovae, which is particularly important for type Ias since they are used as standard candles. The presence of gas and dust in the local environment of a type Ia can affect the observed luminosity and could impact measurements of the Hubble constant. Using photometric data from the Large Binocular Telescope between 2010 and 2018, we present new observations of the SN2009ig light echo that confirm a slow fading of the echo over the past 6 years since its discovery in 2013. The fading is similar to that seen in the light echo of SN1991T and suggests that some of dust producing the echo may be local to the event.