Submitted Abstracts
Invited Talk: AGN Variability Studies with the Nancy Grace Roman Space Telescope
By: Triana Almeyda
Abstract: The Nancy Grace Roman Space Telescope will be an integral facility in the rapidly growing field of time-domain Astrophysics. In this talk I will discuss how, along with other large time domain surveys such as the Square Kilometre Array (SKA), Legacy Survey of Space and Time (LSST), and Sloan Digital Sky Survey- V (SDSS-V), the Roman Telescope will give us a better understanding of some of the most luminous and variable sources in astronomy, active galactic nuclei (AGN). AGN are observed when supermassive black holes (SMBHs) that reside in the centers of most massive galaxies are actively accreting interstellar gas while releasing vast amounts of energy in the form of electromagnetic radiation, gas outflows, and jets of ionized plasma. With the millions of AGN that are predicted to be discovered with these surveys, we will be able to study the AGN luminosity function, AGN growth across varied cosmic environments, the highest redshift AGNs, different AGN variability types, and transient SMBH fueling events. Thus time-domain, multiwavelength studies of these objects will yield a better understanding of the SMBH growth phase and its role in galaxy evolution across the entire Universe.
Invited Talk: Eruptions and Explosions of Massive Stars
By: Jennifer Andrews
Abstract: Prior to their terminal endpoints, massive stars can go through large amounts of episodic mass loss. Some of these events can be eruptive, with brightnesses between classical novae and supernovae. Often dubbed “SN imposters”, they likely arise from a variety of initial stellar masses and are caused by physical mechanisms ranging from instabilities in nuclear burning as the object evolves off the main sequence to stellar mergers in binary star systems. While their eruptions mimic those of SNe, these transients appear to be non-terminal, leaving some form of the progenitor behind after eruption. Even more puzzling are those massive stars that blink out of existence without a bright eruptive event, either from being enshrouded in copious amounts of dust, or possibly collapsing directly to a black hole. I will discuss these puzzling non-terminal transients and what role Roman will play in the discovery and understanding of them.
Co-Authors: N. Smith, J. Jencson, D. Sand, S. Van Dyk
Invited Talk: Synergies between Roman and other surveys: the case of microlensing
By: Etienne Bachelet
Abstract: A new revolution in our understanding of the exoplanets demographic is expected from the Roman microlensing survey. Indeed, with more than 1500 'cold' planets and hundred of rogue planets, this survey will bring unprecedent constraints on the planet population located beyond the snowline of their system. The Roman microlensing fields are located towards the Galactic center and potentially overlap with other mission footprint, such as the Legacy Survey of Space and Time at Rubin Observatory or the Euclid space mission. I will present the potential of mission overlaps and how combining the various datasets could bring unique constraints on the microlensing events analysis, difficult to obtain with Roman alone.
Poster: Environmental correction in supernovae standardization
By: Anastasia Baluta
Abstract: Standardization of type Ia supernovae (SN Ia) is necessary for a more accurate measurement of the cosmological parameters of the Universe using the Hubble diagram. In the SALT2 SN Ia light-curve fitting model 2 standardization parameters are used — the color parameter c and the stretch parameter x1. The stretch parameter dependence on the host galaxy morphology and other supernova environment parameters is known from literature on this topic. In our work we reproduce the Hubble diagram fit according to Pantheon data, and also explore the possibility of introducing various standardization equations for SN exploded in early-type and late-type galaxies.
Co-Authors: Pruzhinskaya Maria
Poster: Pitfall of FFP parallax parameter accuracy between Euclid and Roman
By: Makiko Ban
Abstract: We presented the expectation of the free-floating planet microlensing observations in parallax between Euclid and Roman (Ban 2020), and here we have extended results for the accuracy of the FFP parameter estimation. The Einstein parallax is a parameter to be derived from the differential light curve parameterised in the unit of time and amplification. We found a pitfall in the accuracy of the Einstein parallax formula in the case of the spacial combination between Euclid and Roman. At ~5 days from the equinoxes season, the orbital plane of the Euclid and Roman centering at Lagrangian Point 2 forms ~0-degree inclination to the line-of-site when targetting at the Galactic bulge (l,b)=(1.00,-1.75). At this season the limited spatial condition of the telescopes can yield the distinguishable parallax observation. Even though the event is observed in simultaneous parallax, the calculative telescope separation in the lens plane is likely to be close to zero which causes to overestimate the Einstein parallax. Modelling the event with full kinematics of the source, lens, and observers for the curve fitting and deriving the Einstein parallax directory from their coordinates have the potential to overcome the pitfall.
Invited Talk: Multi-messenger astronomy with the Roman Space Telescope
By: Jennifer Barnes
Abstract: The study of electromagnetic and gravitational-wave emission from merging compact object binaries provides a pathway to study many pressing questions in astrophysics, including the architecture of neutron stars, the formation and evolution of relativistic jets, and the origin of heavy elements produced by rapid neutron capture nucleosynthesis.
The kilonova that accompanied the first confirmed neutron star merger (GW170817) demonstrated the importance of near infrared observations for understanding merger-driven mass ejection and nucleosynthesis. Detailed NIR observations of future mergers over a range of timescales—including nebular-phase observations—will be critical for refining the lessons learned from GW170817. This positions the Roman Space Telescope as a significant tool for multi-messenger astronomy. I will discuss the role that Roman can play in furthering our understanding of compact object mergers, their nucleosynthesis, and their electromagnetic emission.
Invited Talk: Completing Exoplanet Census with Roman Galactic Exoplanet Survey
By: Aparna Bhattacharya
Abstract: In this talk, I will describe how the Roman Galactic Exoplanet Survey (RGES) will observe time domain data in different epochs over 5 years and detect thousands of exoplanets up to Mars mass just beyond the snowline. I will talk about how the observations will be done, data will be processed, how we are preparing with precursor observations and what results we expect from the survey. This would show what science outcomes we expect by the end of the prime mission of Nancy Grace Roman Space Telescope and how that would shape the future exoplanet studies and missions.
Contributed Talk: Astrometric microlensing with Roman: a public code and perspectives for detection
By: Valerio Bozza
Abstract: The detection of the astrometric shift of the source during a microlensing event may provide a very useful complement to the photometric amplification. By constraining the Einstein angle and the relative proper motion, we may significantly extend the number of planets with precise mass measurements. We discuss the perspectives for the detection of such effect within the Roman survey and present the implementation of astrometry in VBBinaryLensing, a fast and efficient public code for microlensing computation.
Contributed Talk: Microlensing with the Roman Galactic Exoplanet Survey
By: Sebastiano Calchi Novati
Abstract: The Roman Galactic Exoplanet Survey has the main goal of carrying out a census of exoplanets using the microlensing method. The survey is expected to be sensitive to detect low-mass planets at orbital separation greater than about 1 AU and to free-floating planets down to the mass of Mars.
Poster: Enhancing Time-Domain Astronomy Through Joint Survey Processing
By: Ranga Chary
Abstract: Joint Survey Processing (JSP) is the pixel level combination of ground- and space-based datasets. It is particularly important for mitigating source confusion which affects 50\% of the sources in deep seeing-limited datasets such as those that will be taken by Rubin/LSST. By using location and morphology priors on static sources derived from space-datasets such as Euclid and Roman, and estimating accurate time- and location-dependent point spread functions for the ground-based data, one can model the scene in individual frames forward. The residuals after subtracting the modeled scene from the data, reveal transient events down to the shot noise limit of the individual images or in time-integrated coadds, even in crowded fields. This significantly improves the detectability of transient events, both in number and in faintness. JSP is therefore highly relevant for detection of microlensing events, moving objects, supernovae, and tidal disruption events close to the high surface brightness centers of galaxies. In addition, JSP will derive accurate multi-band photometry on galaxies which will lead to accurate photometric redshifts and galaxy physical parameters. These can be used to select host galaxies and transient electromagnetic counterparts for multi-messenger studies where the positional error circles can be large (e.g. LIGO gravitational wave events, ultra high-energy cosmic rays or fast radio bursts).
Co-Authors: Ranga-Ram Chary (Caltech/IPAC), Sergio Fajardo-Acosta (Caltech/IPAC)
Contributed Talk: A Roman Program for Very Fast Transients
By: Jeff Cooke
Abstract: Fast transients with milliseconds-to-hours duration exist at all wavelengths. Infrared fast transient astronomy is in its infancy compared to other wavelengths, largely as a result of the lack of sensitive wide-field facilities and technological challenges, leaving much of this parameter space unexplored. We propose a coordinated program to capitalize on the exceptional depth and wide-area of Roman to explore and characterize the infrared fast transient sky. We will build on the successful Australian-led Deeper, Wider, Faster multi-wavelength search program and coordinate sensitive wide-field telescopes in the radio, mm, optical, UV, x-ray, and gamma-ray to observe the same fields at the same time with Roman to obtain all possible data on fast transients before they quickly fade. The proposed program aims to intercept Roman data after it is received by the New Norcia Observatory in Western Australia and apply fast-processing techniques to identify fast transient candidates in real time, thereby eliminating crucial seconds time lag. Program-coordinated rapid-response radio, 8m-class optical-infrared telescopes and space-based high-energy telescopes will be triggered to obtain deep spectroscopy and imaging of high-priority Roman candidates to redshift and characterize events and to uncover the nature for new classes. This program has the potential to discover and classify a broad range of rare, fast transient events andto determine unobscured fast transient rates. We will discuss any changes to the existing mission requirements for this program and the pros and cons of using data from planned Roman time domain surveys.
Co-Authors: Jeff Cooke, Umaa Rebbapragada, Jason Rhodes, Jielai Zhang, Eric Huff
Invited Talk: Following Nancy Grace Roman Telescope in the Exploration of the Most Powerful Cosmic Explosions
By: Antonino Cucchiara
Abstract: The advent of the Nancy Grace Roman Telescope (Roman) represents a leap forward in our search for transient sources. Long Gamma-ray Bursts are the most powerful single-star explosions occurring in the Universe, probing a wide range of key scientific questions, from the origin of the first stars, to the cosmic metal enrichment, or the final evolutionary phases of >30 solar mass objects. On the other end, Short GRBs represents the key ingredient to fully comprehend the final stages of compact object mergers, the subsequent Kilonova emission, and their elusive gravitational wave emission. In this talk I will cover the recent past of GRB studies and present some of Roman key discoveries that will likely change our understanding of GRBs (long and short) and their contribution in shaping the Universe as we know it. The instruments on-board, its wide field-of-view, and ad-hoc and coordinated observing campaigns, Roman is set to nicely bridge the gap between the success of the pioneering Neil Gehrels Swift mission and the next generation of time-domain space probes as recommended by the Astro2020 Decadal survey.
Invited Talk: Obscured transients in the Galactic plane with the Roman Space Telescope
By: Kishalay De
Abstract: Eruptive transients in the Galactic plane, ranging from novae to X-ray binaries, offer a unique window into the population of accreting compact binaries in the Milky way. While all-sky optical surveys have been instrumental at identifying nearby and common populations of sources, infrared time domain surveys offer a whole new opportunity to i) study rarer events that are obscured behind large columns of dust and ii) construct complete samples of events to study their demographics. I will present recent results from a systematic census of the dynamic infrared sky using the Palomar Gattini-IR infrared time domain survey. By monitoring 8000 square degrees of the sky every night, Palomar Gattini-IR has unveiled a plethora of optically missed novae, symbiotic stars, X-ray binaries and young stellar objects. With its exquisite near-infrared sensitivity, spatial resolution and field of view, the Roman space telescope will be a revolutionary instrument to study the dynamic Galactic plane. I will highlight the science opportunities combining Roman Galactic plane surveys with long-term monitoring from ground-based surveys like the Rubin observatory to discover rare transients and study their progenitor systems.
Poster: Classification conundrum in Gamma Ray Bursts: Signatures of collapsars in high redshift short GRBs
By: Dimple Dimple
Abstract: GRBs are classically categorised into two types - short bursts (T90 < 2 sec) and long bursts (T90 > 2 sec) based on their gamma-ray emission duration. It is widely accepted that the two populations originate from two distinct progenitor channels residing in different host galaxy environments. However, the characteristics of two short GRBs (090426 and 200826A) hinted toward collapsar as plausible progenitors as opposed to compact object mergers. These short GRBs lie at a relatively higher redshift as compared to the median redshift (z=0.47) of short GRBs. We investigate the properties of short GRBs at low and high redshifts employing the prompt, afterglow and host galaxy information. A careful examination of the characteristics of short GRBs at different redshifts reveals that some short GRBs at high redshifts have properties similar to long GRBs indicating a collapsar origin. Further studies can aid in understanding the progenitors of GRBs and the true classification of GRBs.
Co-Authors: Dimple, K. Misra, D. A. Kann, K. G. Arun, A. Ghosh, R. Gupta, L. Resmi, J. F. Agüí Fernández, C. C. Thöne, A. de Ugarte Postigo, S. B. Pandey, L. Yadav
Contributed Talk: Wide-Field Instrument time-domain processing at the Science Operations Center
By: Henry Ferguson
Abstract: The Science Operations Center at STScI will produce a few standard data products that will support time-domain astrophysics with the Wide-Field Instrument. Plans include processing and cataloging difference images and conducting forced photometry. While not intended to support near-real-time transient detection, these data products should be useful for longer term monitoring or archival studies. Community input on science use cases and and feedback on the evolving plans for algorithms, processing strategy and data products will be particularly valuable in 2022.
Contributed Talk: Keck Infrared Transient Survey
By: Ryan Foley
Abstract: The Roman Space Telescope through both the High-Latitude Time Domain Survey and other Guest Investigator programs will perform an especially large and detailed infrared time-domain survey. The step up from current infrared surveys is both scientifically exciting and problematic for planning and eventual interpretation. Infrared data, and especially infrared spectroscopy, for transients is sorely lacking. To alleviate this problem, help plan for Roman observations, and to aid in the analysis of Roman data, a team of >50 scientists are performing an 18-night Keck Key Strategic Mission Support program, the Keck Infrared Transient Survey (KITS), which will start a few days after the conclusion of this conference and will obtain ~400 NIR spectra of transients ranging from Type Ia supernovae to kilonovae to tidal disruption events. I will present the motivation and strategy for this KITS, anticipated results, and discuss ways more scientists can get involved.
Co-Authors: The Keck Infrared Transient Survey Team
Contributed Talk: A Proposed extended Time Domain Survey (eTDS)
By: Ori Fox
Abstract: In light of the recent call for a Roman Early-Definition Astrophysics Survey, our team submitted a white paper for a proposed extended Time Domain Survey (eTDS). Since the original Roman Surveys were defined, there have been several significant developments, most notably the addition of the F213 filter. Roman's extreme wide field of view and near-IR sensitivity provide our only route for probing the Initial Mass Function (IMF) and stellar populations at high redshifts by finding intrinsically rare explosions. The Roman Deep High-Latitude Time Domain Survey (HLTDS) provides a powerful ability to detect explosive transients, but our analysis shows that extending the current HLTDS in both time (Cycles 1 & 2) and wavelength (K-band) is needed to color select high-z events. An extended TDS (eTDS) can generate an unparalleled transient database in terms of combined supernova (SN) redshift reach, area, and timescale. It would make Roman a discovery engine for rare, extreme high-z SNe and, for the first time, build a sample of thousands of normal high-z core-collapse (CC) SNe. Just as the GOODS observing strategy of repeated visits was designed to serve both time-domain and deep static-sky science, the eTDS will provide exceptionally deep and wide imaging comparable to COSMOS-Webb in depth (F158=29.5/F213=27.5 mag), but 8x larger in area! eTDS costs ~360 hours, a small fraction of HLTDS. This proposal is an updated modification of Moriya et al. (2021; arXiv:2108.01801) that differs in the following ways: (1) different integration times and (2) more details regarding high-z IMF science.
Co-Authors: Lead Author: Ori Fox (STScI) Co-Authors: Eddie Baron (Oklahoma), Mia Bovill (TCU), Ting-Wan Chen (Stockholm University), Alexei V. Filippenko (UC Berkeley), Ryan Foley (UCSC), Ryan Ridden-Harper (University of Canterbury), Suvi Gezari (STScI), Sebastian Gomez (STScI), Isobel Hook (Lancaster), Andy Howell (UCSB), Alessa Ibrahim (TCU), Patrick Kelly (Minnesota), Anton Koekemoer (STScI), Rubina Kotak (Turku), Seppo Mattila (Turku), Justyn Maund (Sheffield), Takashi Moriya (NAOJ), Saul Perlmutter (UCB, LBNL), Robert Quimby (SDSU), Justin Pierel (STScI), Eniko Regos (Konkoly Observatory), Armin Rest (STScI), David Rubin (Hawaii), Lou Strolger (STScI), Nao Suzuki (Kavli IPMU), Tea Temim (Princeton), Qinan Wang (STScI), Yossef Zenati (Johns Hopkins, STScI)
Poster: Finding Missing Supernovae with Roman
By: Ori Fox
Abstract: We recently conducted a two year Spitzer/IRAC 3.6 um survey for dust-extinguished supernovae (SNe) in forty Luminous InfraRed Galaxies (LIRGs) within 200 Mpc to test SN rate predictions in galaxies where dust obscuration may have a large effect. In general, ground-based surveys have discovered a factor of 3-10x fewer SNe than predicted, which they often attribute to both a variable point-spread function (PSF) and high dust extinction in the nuclear regions of star-forming galaxies. This inconsistency has potential implications on our understanding of star-formation rates, initial mass functions, and massive star evolution, particularly at higher redshifts, where star-forming galaxies are more common. Our Spitzer survey provides access to both longer wavelengths and a stable PSF to improve our sensitivity to dust-obscured and/or nuclear transients. The asymmetric Spitzer PSF results in worse than expected subtraction residuals when implementing standard template subtraction. Forward-modeling techniques improve our sensitivity by ~1.5 mag. We report the detection of nine SNe, five of which were not discovered by optical surveys. After adjusting our predicted rates to account for the sensitivity of our survey, we find that the number of detections is consistent with the models. While this search is none the less hampered by a difficult-to-model PSF and the relatively poor resolution of Spitzer, we discuss how it will succeed with the Roman Space Telescope.
Co-Authors: Khandrika, Harish (STScI) ; Rubin, David (Hawaii); Casper, Chadwick ; (Glint Photonics) Li, Gary Z. ; (The Aerospace Coorporation) Szalai, Tamás ; (University of Szeged, Hungary) Armus, Lee ; (IPAC) Filippenko, Alexei V. ; (Berkeley) Skrutskie, Michael F. ; (UVA) Strolger, Lou ; (STScI) Van Dyk, Schuyler D. (IPAC)
Poster: Constraining the Size of the Torus of NGC 6418
By: Ashley Lynn Frank
Abstract: One of the main components of the unified model of AGN is the circumnuclear torus consisting of dusty molecular gas. It is important to understand the size and structure of the torus, as it often obscures our view of the central engine of the AGN. Although it is not possible to resolve the torus in images obtained with existing single telescopes, it can be studied by reverberation mapping. In this technique, the time variations of the UV/Optical (UVO) emission from the accretion disk can be analyzed with the infrared (IR) response of the torus dust. The time lag between the driving UVO emission and the IR response can be used to constrain the size of the torus.
Our group used the Spitzer Space Telescope to observe 12 AGN over a period of 2.5 years during Spitzer cycles 8 and 9, at the wavelengths of 3.6 and 4.5 microns. Here, we present the cross-correlation analysis results for one of the objects, NGC6418, which exhibited the largest variations seen in our sample. A large optical flare occurs at the beginning of Cycle 9, after which the reverberation lag increases. The increase in the lag is most likely due to an increase in the inner radius of the torus, due to destruction of dust grains in the inner regions by sublimation.
Co-Authors: Andy Robinson, Michael Richmond, Triana Almeyda
Poster: The Wide-Field Infrared Transient Explorer (WINTER)
By: Danielle Frostig
Abstract: The Wide-Field Infrared Transient Explorer (WINTER) is a new time-domain instrument which will perform a seeing-limited survey of the near-infrared sky. I will present the design and science goals of the WINTER instrument, which will be deployed on a dedicated 1-meter robotic telescope at Palomar Observatory. Among the many near-infrared targets of interest, WINTER is principally designed for follow-up of kilonovae from binary neutron star and neutron star-black hole mergers detected in gravitational waves. WINTER will be sensitive to kilonovae with 90% localization areas smaller than 150 (450) square degrees out to a distance of 350 (200) Mpc. In addition to kilonova follow-up, WINTER will conduct a wide range of time-domain surveys to a depth of J=21 magnitudes, building up a deep co-added image of the near-infrared sky and studying near-infrared transients including supernovae, tidal disruption events, and transiting exoplanets around low mass stars. WINTER’s custom camera combines six commercial large-format Indium Gallium Arsenide (InGaAs) sensors, observing in Y, J, and a short-H (Hs) band filters (0.9-1.7 microns), and employs a novel tiled optical design to cover a >1 degree squared field of view with 90% fill factor. I will include updates on the final integration of the WINTER instrument and commissioning at Palomar Observatory.
Co-Authors: Danielle Frostig, John W. Baker, Kevin B. Burdge, Richard S. Burruss, Kishalay De, Mark Egan, Gabor Furesz, Nicolae Ganciu, Allan A. Garcia-Zych, Erik Hinrichsen, Mansi M. Kasliwal, Viraj R. Karambelkar, Nathan P. Lourie, Andrew Malonis, Robert A. Simcoe, and Jeffry Zolkower
Contributed Talk: The Simulated Catalog of Optical Transients and Correlated Hosts (SCOTCH)
By: Alexander Thomas Gagliano
Abstract: At present, we are only able to trigger follow-up for 10% of transients discovered by our current generation of photometric surveys. Spectroscopic resources will be further outpaced by the upcoming surveys launched by Roman and Rubin, demanding novel tools for early event characterization. To motivate these efforts, we have constructed a catalog of >3M simulated transients and the properties of their host galaxies for the Extended Astronomical Time-Series Classification Challenge (ELAsTiCC). In this talk, I will motivate the use of contextual information for low-latency transient analysis and outline our methodology for generating the ELAsTiCC dataset. I will then discuss our techniques for validating the embedded host-galaxy correlations and conclude with a comment on the exciting landscape of host-galaxy studies enabled by Roman. The ELAsTiCC catalog will enable robust validation of transient analysis pipelines at high-z and ensure the scientific yield of upcoming missions.
Co-Authors: Martine Lokken, Gautham Narayan, Renée Hložek, Richard Kessler, Laura Salo, John Franklin Crenshaw, and the ELAsTiCC team
Poster: From short GRBs to neutron star natal kicks
By: Nicola Gaspari
Abstract: The detection of GW 170817 and GRB 170817A secured the connection between binary neutron star (BNS) mergers and at least some short-duration gamma-ray bursts (sGRBs). Since the number of mergers detected through gravitational waves is still small, we can exploit the BNS-sGRB connection to study the physics underlying BNS mergers through the much larger and variegated sample of sGRBs. Here I present a sample of sGRBs with their putative host galaxies, and discuss the implications for neutron stars' natal kicks. The sample is built on the literature and enhanced with an additional host catalogue from archival observations and a recent robust distinction between long- and short-GRBs based on a machine learning approach. For each host, I reproduce the galactic potential from observations and seed synthetic binary stars in it, to then evolve their orbits and record the location of BNS mergers. This allows me to compare the actual locations of sGRBs with those expected from population synthesis, and test the requirements on natal kicks to explain the observed sGRB population.
Co-Authors: Andrew J. Levan, Ross Church
Contributed Talk: Notional Parameters, Extensions, and Auxiliary Science of the Roman Galactic Bulge Time Domain Survey
By: Bernard Scott Gaudi
Abstract: The Galactic Bulge Time Domain Survey (GBTDS) will provide an unprecedented census of extrasolar cold and free-floating planets detected by gravitational microlensing of background stars. The notional survey design involves seven WFI fields (with a total area ~2 sq. degrees) monitored continuously every 15 minutes during six 72-day bulge seasons when the Galactic Bulge from Roman. This survey will also enable a broad range of auxiliary science, including the measurement of the compact object mass function over ten orders of magnitude, the detection of 100,000 Transiting Planets, astroseismology of 1,000,000 bulge giants, the detection of 5000 trans-Neptunian objects, and measurement of parallaxes and proper motions of 6,000,000 bulge and disk stars. Although the parameters of the GBTDS are relatively tightly constrained, some alterations and/or augmentation may result in significant additional science without sacrificing the core science requirements.
Poster: Search for merger ejecta emission in Short Gamma Ray Bursts from very late time radio observations
By: Ankur Ghosh
Abstract: Coalescence of inspiral binary neutron stars (BNS) system, giving rise to short Gamma-Ray Bursts (GRBs), are one of the most probable candidates for Gravitational Waves (GWs). If the resultant product of the merger is a millisecond magnetar, a significant proportion of the rotational energy is deposited to emerging ejecta that produces late-time radio brightening from the interaction with the surrounding ambient medium. Detection of this late-time radio emission from short GRBs can have profound implications for understanding the physics of the progenitor. This study presents the deepest and an extensive search for radio emission at late times following a short GRB to date incorporating proper frequency regime, wider observation span, and relativistic correction. Five short GRBs were observed with the Giant Meter Wave Radio Telescope (GMRT) at 1250, 610, and 325 MHz band $\sim$ 2 - 11 years since the burst to search for radio emission from the merger ejecta. The estimated upper limits at the burst location are used to constrain the parameters of the burst and its surrounding environment. The magnetar model, with appropriate modifications, constrains the number density of the ambient medium for these bursts to be between $10^{-4}$ - $10^{-2}$ $cm^{-3}$. Our analysis rules out a stable magnetar with the energy of $10^{53}$ erg for four out of the five GRBs in our sample.
Co-Authors: S. V. Cherrukuri L. Resmi Kuntal Misra K. G. Arun Amitesh Omar and N. K. Chakradhari
Contributed Talk: Optimizing the Search for Exotic Transients
By: Sebastian Gomez
Abstract: The field of time domain astronomy continues to grow with new and bigger surveys coming online every few years. We are already at the point where we can only spectroscopically classify about 10% of all the transients discovered by all-sky surveys, and this fraction is only expected to keep going down. Given our limited resources, we must be careful when selecting which transients are worthy of spectroscopic follow-up. Towards this goal we developed FLEET (Finding Luminous and Exotic Extragalactic Transients), a machine learning algorithm that over the past year has been accurately selecting superluminous supernovae candidates from all-sky surveys. More recently, we began the expansion of FLEET to cover other exotic transients such as tidal disruption events. The Roman Space Telescope is expected to find tens of thousands of supernovae during its five year mission. Tools like FLEET will be not only useful, but necessary, when attempting to select which of these are the most likely exotic transients.
Co-Authors: Edo Berger Suvi Gezari Griffin Hosseinzadeh Peter Blanchard Ashley Villar
Poster: Probing into emission mechanisms of GRB 190530A using time-resolved spectra and polarization studies: Synchrotron Origin?
By: Rahul Gupta
Abstract: Multi-pulsed GRB 190530A, detected by the GBM and LAT onboard Fermi, is the sixth most fluent GBM burst detected so far. This paper presents the timing, spectral, and polarimetric analysis of the prompt emission observed using AstroSat and Fermi to provide insight into the prompt emission radiation mechanisms. The time-integrated spectrum shows conclusive proof of two breaks due to peak energy and a second lower energy break. Time-integrated (55.43 $\pm$ 21.30 \%; 2.60 $\sigma$) as well as time-resolved (53.95 $\pm$ 24.13 \%; 2.24 $\sigma$ for the third pulse) polarization measurements, made by the Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat, show a hint of a high degree of polarization. The presence of a hint of a high degree of polarization and the values of low energy spectral index ($\alpha_{\rm pt}$) do not run over the synchrotron limit for the first two pulses, supporting the synchrotron origin in an ordered magnetic field. However, during the third pulse, $\alpha_{\rm pt}$ exceeds the synchrotron line of death in a few bins, and a thermal signature along with the synchrotron component in the time-resolved spectra is observed. Furthermore, we also report the earliest optical observations constraining afterglow polarization using the MASTER telescope(P $<$ 1.3 \%), making it the first GRB for which both the prompt and afterglow polarization have been investigated. Additionally, we present the redshift measurement ($z$= 0.9386) of GRB 190530A obtained with the 10.4m GTC telescope. The broadband afterglow can be described with a forward shock model for an ISM-like medium with a wide jet opening angle. We determine a circumburst density of $n_{0} \sim$ 7.41, kinetic energy $E_{\rm K} \sim$ 7.24 $\times 10^{54}$ erg, and radiated $\gamma$-ray energy $E_{\rm \gamma, iso} \sim$ 6.05 $\times 10^{54}$ erg, respectively.
Co-Authors: S. Gupta, T. Chattopadhyay, V. Lipunov, A. J. Castro-Tirado, D. Bhattacharya, S. B. Pandey, S. R. Oates, Amit Kumar, Y.-D. Hu, A. F. Valeev, P. Yu. Minaev, H. Kumar, J. Vinko, Dimple, V. Sharma, A. Aryan, A. Castell\'on, A. Gabovich, A. Moskvitin, A. Ordasi, A. P\'al, A. Pozanenko, B.-B. Zhang, B. Kumar, D. Svinkin, D. Saraogi, D. Vlasenko, E. Fern\'andez-Garc\'ia, E. Gorbovskoy, G. C. Anupama, K. Misra, K. S\'arneczky, L. Kriskovics, M. \'A. Castro-Tirado, M. D. Caballero-Garc\'ia, N. Tiurina, P. Balanutsa, R. R. Lopez, R. S\'anchez Ram\'irez, R. Szak\'ats, S. Belkin, S. Guziy, S. Iyyani, S. N. Tiwari, Santosh V. Vadawale, T. Sun, V. Bhalerao, V. Kornilov, and V. V. Sokolov
Poster: Classifying Transients and Variable Objects with SCONE
By: Erin Elizabeth Hayes
Abstract: In this work, we expand the use of the Supernova Classifier with a Convolutional Neural Network (SCONE) to include classification of an additional two classes of transient objects and five classes of variable objects. SCONE has been adapted for these additional types of objects by updating its data processing pipeline to better handle variable objects, which exhibit repeated changes in brightness over time, as well as introducing class weights to ensure the model picks up on the nuances of the imbalanced training and test sets (both pulled from the PLAsTiCC dataset). Preliminary results show SCONE is capable of classifying transients with 90% accuracy and variable stars with 70% accuracy. To further improve its performance, we are now working on an original method of simulating light curves using templates found in the PLAsTiCC dataset to create a larger and more representative test set.
Co-Authors: Helen Qu and Masao Sako
Poster: The multiband evolution of novae
By: Yael Hillman
Abstract: Over the course of a nova cycle, a white dwarf (WD) quiescently accretes (mostly) hydrogen from its less evolved companion for a long period of time, until finally igniting a thermonuclear runaway (TNR). This causes the outer layers of the WD to rapidly expand and expel mass. The nature of this phenomenon entails orders of magnitude changes in the surface temperature, seemingly favoring observations in different bands at different epochs of the cycle. However, to better understand the evolution of a nova cycle, it would be extremely informative to have simultaneous observations of the system in multiple bands. To date, such data is sparse. I will present models of multiple nova cycles for various systems, to demonstrate how this feature and others, may assist in identifying the parameters of observed systems and better understanding them.
Invited Talk: Exploring Our Solar System's Minor Body Populations with Roman
By: Bryan J Holler
Abstract: Despite not being required to support moving target tracking, the Nancy Grace Roman Space Telescope is still more than capable of revolutionizing the study of the minor body and irregular satellite populations within our own solar system. The large field-of-view and sensitivity of the Wide Field Instrument (WFI) will enable deeper, more efficient imaging than any previous survey, revealing smaller and more distant minor bodies. In this talk I will discuss 4 high-value solar system investigations uniquely suited to Roman:
1. Roman’s placement at L2, combined with its field of regard, will allow for year-round searches for Earth Trojan asteroids, of which only one is definitively known. Identification of additional objects and comparison to minor body populations on Earth-crossing orbits could reveal the origins of Earth Trojans, either as primordial or temporary captured objects. These minor bodies are also potential targets for future robotic and even manned spaceflight missions.
2. The irregular satellites of the giant planets are believed to have been captured from heliocentric orbit and undergone collisional processing to form families. The entire population of irregular satellites down to a few kilometers in diameter could be detected and their orbits characterized in only a few tens of hours with Roman. Comparison to the size-frequency distributions of asteroid families will inform collisional processes across the solar system.
3. Roman will enable extremely efficient searches for the most distant known objects in our solar system, both through large sky coverage at each pointing and the resulting decrease in overheads for slewing. Deep searches with the F146 wide-band filter should help uncover additional Extreme trans-Neptunian objects (ETNOs) in order to test the Planet 9 hypothesis. Such surveys also present the possibility of discovering additional objects currently in excess of 100 au from the Sun, of which only 2 are currently known. The Roman Survey for Extreme TNOs (RoSET) concept submitted to the early-definition Astrophysics Survey call will be discussed.
4. The WFI is composed of 18 detectors and each one can obtain a guide star during a given observation. Read-out of a subarray surrounding the guide star at 5.8 Hz, and transmission of these data back to Earth, will enable the detection and characterization of small minor bodies throughout the solar system, but specifically in the trans-Neptunian region, through serendipitous stellar occultations. At present, such events are the only means of detecting the smallest solar system objects that are too faint to be seen in reflected light.
Poster: Millimeter to 𝛄-Ray Variability of AGN found in the SPTpol 500 degree2 field
By: John Calven Hood
Abstract: Cosmic Microwave Background (CMB) telescopes are now providing an option for daily monitoring of these objects within limited fields of view. While continuous, high-cadence monitoring of active galactic nuclei (AGN) is now common at gamma-ray, optical, and radio frequencies, AGN monitoring in the millimeter (mm) band has mostly been restricted to short campaigns on targeted sources. Here we use the South Pole Telescope (SPT), which was designed to observe the CMB at arcminute and larger angular scales, to monitor AGN. Between 2013 and 2016, the SPTpol instrument (the second-generation mm-wave camera mounted on the SPT) was used to continuously scan a 500 deg2 field, covering the entire field several times per day with detectors sensitive to polarization and radiation in bands centered at 95 and 150 GHz. This data set enables the monitoring of tens of mm-bright AGN on timescales from years to days at high signal to noise (S/N > 10 in a 36-hour coadd). We use SPTpol 150 GHz observations to monitor the variability of the sources in the mm-waveband and directly compare that to other frequencies. In a pilot study, we focus on the source PKS 2326-502, which has extensive, day-timescale monitoring data in gamma-ray, optical, and now mm-wave data between 2013 and 2016. We present a search for evidence of correlated variability between SPTpol (150 GHz), SMARTS (O/IR) and Fermi (gamma-rays) observations. This pilot study is paving the way for AGN monitoring with current and upcoming CMB experiments like SPT-3G, SO and CMB-S4, including multi-wavelength variability studies with upcoming facilities such as VRO-LSST.
Co-Authors: On behalf of the SPT collaboration.
Contributed Talk: Bridging our knowledge gap of supernova properties in the infrared
By: Eric Hsiao
Abstract: In preparation for the launch of the James Webb Space Telescope (JWST) and the Roman Space Telescope (RST), this talk gives an overview of our current state of knowledge on the infrared properties of supernovae. Carnegie Supernova Project-II (CSP-II) gathered the largest near-infrared spectroscopic data set for each class of supernova with the goals of 1) understanding their explosion mechanisms and progenitor systems and 2) providing concrete improvements for future dark energy experiments such as that onboard the RST. Our observations and studies clearly demonstrate that the infrared wavelengths provide independent information not available in the optical. In a few surprising discoveries, the more complete picture obtained from the combined optical and near-infrared data set led to conclusions contradicting those reached using optical data alone. Examples in hydrogen-rich, stripped-envelope, and thermonuclear supernovae will be presented.
Co-Authors: Carnegie Supernova Project-II Collaboration
Contributed Talk: Extremely Late-time Light Curve Evolution and Progenitor Constraints of Calcium-rich Transients
By: Wynn Jacobson-Galan
Abstract: We present multi-wavelength (X-ray to radio) observations of the most nearby calcium-rich transient, supernova (SN) 2019ehk, located in Messier 100. Because of its close proximity, SN 2019ehk had a plethora of Hubble Space Telescope (HST), Spitzer and Chandra pre-explosion imaging for ~2 decades prior to explosion. These observations allowed for the tightest constraints to be made on a Calcium-rich SN progenitor system to date, which, despite no detected progenitor source, constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (<10 Msun ) in binaries that lost most of their He envelope, or white dwarfs (WDs). We will discuss how the Nancy Grace Roman Space Telescope will increase the number of Calcium-rich transients with deep pre-explosion imaging, which will allow for us to probe the nature of their unknown SN progenitors in much greater detail. Furthermore, we present HST observations of SN 2019ehk at >300 days after explosion, the latest multi-band detections of a Calcium-rich transient to date. These observations provided the first opportunity to analyze the late-time bolometric evolution of an object in this observational SN class and provides constraints on the SN nucleosynthesis. We will discuss how Roman will be instrumental in increasing the sample size of extremely late-time Calcium-rich SN light curves, which will enable some of the best constraints on the elusive progenitor system for these peculiar explosions.
Co-Authors: Raffaella Margutti, Ryan Foley, Charles Kilpatrick, Daichi Hiramatsu, Hagai Perets, D. Andrew Howell, John Raymond, Edo Berger, Peter K. Blanchard, Alexey Bobrick, Sebastian Gomez, Griffin Hosseinzadeh, Danny Milisavljevic, Giacomo Terreran, Yossef Zenati, David J. Sand, Joel Shepherd, Stephen J. Smartt, Daniel Kasen, Ken Shen
Invited Talk: Revealing Core-Collapse Supernovae and Failed Explosions with Roman
By: Jacob Jencson
Abstract: As the final event in the lives of massive stars, core collapse and the resultant supernovae (or failed explosions) are important probes of stellar evolution with broad implications for many areas of astrophysics. With the combination of its wide field-of-view, exquisite resolution, and near-infrared sensitivity, the Nancy Grace Roman Space Telescope will be a powerful tool in revealing the array of core-collapse outcomes both locally and at high redshift. In this talk, I will focus on some of these areas where the unique capabilities of Roman will have the potential for large impacts including: uncovering the obscured core-collapse supernovae in the densest regions of highly star-forming galaxies, and probing the population of disappearing massive stars undergoing direct collapse to black holes as failed supernovae.
Contributed Talk: Predictions of the Roman Galactic Bulge Time Domain Survey: Constraints on the Frequenct of Earth-Analogs
By: Samson Johnson
Abstract: The frequency of Earth-like planets in the habitable zone of Sun-like stars (eta-Earth) is a fundamental input in estimating the occurrence rate of life resembling that on Earth, and therefore an important parameter for designing future direct imaging missions. eta-Earth is currently best estimated by the Kepler transit survey, but Earth-analog systems with long periods and shallow transits are on the edge of the survey’s sensitivity. The Roman Galactic Bulge Time Doman Survey will be able to detect Earth-analog systems through microlensing, but similarly they will be on the boundary of its sensitivity due to low-mass ratios and small projected separations. We perform simulations of the Roman Galactic Bulge Time Domain Survey to estimate its ability to measure eta-Earth. We incorporate the Galactic Model presented by Koshimoto et al. (2021) in these simulations and we investigate the impact of observational cadence on Roman's sensitivity to these systems. Roman’s ability to estimate eta-Earth will hinge on the extrapolation from systems with larger mass-ratios and wider projected separations.
Co-Authors: Matthew T. Penny, B. Scott Gaudi, Naoki Koshimoto, et al.
Invited Talk: Using the Roman Space Telescope Supernova Survey to Unravel Cosmic Controversies
By: David Jones
Abstract: The Roman Space Telescope supernova survey offers a unique chance to measure the properties of dark energy but requires significant preparation from the SN Ia community to take advantage of these data. I will discuss projected constraints on dark energy properties from Roman along with ongoing efforts to prepare for Roman Space Telescope data by building new SN anchor samples from Pan-STARRS, rebuilding the model for measuring SN distances, and understanding SN Ia behavior in the NIR. I will also discuss new measurements of the Hubble constant and their potential implications for the LCDM model and cosmology with Roman.
Contributed Talk: NIR searches for electromagnetic counterparts of gravitational waves with WINTER and Roman
By: Viraj Karambelkar
Abstract: Most searches for electromagnetic counterparts of gravitational waves (EMGW) to date have been at optical wavelengths. However, kilonova emission is predicted to be longer lived, and depending on the opacity, can be significantly brighter at infrared wavelengths than the optical. In this talk, I will use the upcoming infrared surveyor WINTER as a case study to describe the potential of near-infrared searches in discovering kilonovae. WINTER is a 1-meter, 1 sq. deg field-of-view Y, J and H-band telescope at Palomar Observatory that will come online in March 2022. WINTER will conduct a time-domain survey of the northern sky to a depth of J = 21 mag, making it ideal for followup of gravitational wave triggers during LIGO O4. We have carried out an end-to-end simulation of a one-year follow-up campaign of binary neutron star GW triggers during O4 with WINTER. We simulated BNS mergers based on the existing rate estimates; calculated the localisation skymaps for those that will be detected by LVK; and calculated the expected electromagnetic emission from these using different kilonova models. We then simulated realistic WINTER followup for these GW alerts using optimal tiling strategies for each skymap. We predict that for realistic BNS merger rates, a NIR search with WINTER can independently discover up to five kilonovae during O4. Using a larger grid of kilonova lightcurve models, we identify the BNS phase space where an infrared search performs better than an optical. WINTER will be a pathfinder for more sensitive EMGW followup with the Nancy Grace Roman Space Telescope. Extending insights from our WINTER simulation, I will outline optimal strategies for EMGW observations with Roman during future LIGO observing runs.
Co-Authors: Sylvia Biscoveanu, Danielle Frostig, , Geoffrey Mo, Tito Dal Canton, Hsin-Yu Chen, Mansi Kasliwal, Erik Katsavounidis, Nathan Lourie, Robert Simcoe, Salvatore Vitale
Poster: Parameterizing Type Ia Supernovae for Roman Space Telescope Cosmology Using Neural Networks and Twins Embedding
By: Mitchell Karmen
Abstract: The Twins Embedding (Boone 2021a) is a nonlinear parameterization of the spectral diversity of Type Ia Supernovae (SNe Ia), and a powerful tool for their standardization (Boone 2021b). Using neural networks trained on the twins embedding, we create an empirical generative model of the population diversity of SN Ia spectral time series. This model can be used for forward modeling to fit spectral time series from the Roman Space Telescope prism, as well as photometry from the Wide Field Instrument. Furthermore, the model can be used to correct systematic errors in SN Ia brightness estimates from Roman spectroscopy or photometry in order to achieve high-precision distance estimates. We can also use the generative model alongside Kernel Density Estimates of the distributions of twins embedding parameters for survey simulations that include the full spectral diversity of SNe Ia.
Co-Authors: The Nearby Supernova Factory
Contributed Talk: Hunting for isolated black holes with gravitational microlensing
By: Casey Lam
Abstract: There are expected to be 100 million black holes (BHs) in the Milky Way, although mass measurements exist for only two dozen in X-ray binary systems. A substantial fraction of the Milky Way's BHs are expected to be isolated. This leaves large uncertainty in the number, masses, velocities, and formation channels of the Galactic BH population. Detection of isolated BHs would enable the comparison of the single vs. binary/merger BH mass functions, which in turn would enable improved understand of BH formation channels.
We present the analysis of five isolated BH hole candidates identified from MOA and OGLE between 2009-2011. Archival HST astrometric data from 2009-2017 is jointly analyzed with the MOA and OGLE lightcurves in order to measure the masses of the lens. One of the five targets is likely a low-mass BH. We also compare the full sample of 5 candidates to theoretical expectations on the number and masses of BHs in the Milky Way detectable via microlensing. Due to the small size as well as sample selection issues, the resulting constraints are weak; however, they are consistent with the theoretical expectation of 2 hundred million BHs in the Milky Way. Roman's Galactic Bulge Time Domain Survey will be able to detect and measure the masses of hundreds to thousands of BHs using the techniques developed with this method, and definitively constrain the number of BHs.
Co-Authors: Lu, J. R. (Berkeley), Hosek Jr., M. W. (UCLA), Dawson, W. A. (LLNL), Golovich, N. R. (LLNL), Udalski, A. (Warsaw), Bond, I. (Massey), Bennett, D. P. (NASA Goddard), Sumi, T. (Osaka), Szyma{\'n}ski, M. K. (Warsaw), Skowron, J. (Warsaw), Poleski, R. (Warsaw), Mr{\'o}z, P. (Warsaw), Koz{\l}owski, S. (Warsaw), Pietrukowicz, P. (Warsaw), Soszy{\'n}ski, I. (Warsaw), Ulaczyk, K. (Warsaw), Wyrzykowski, {\L}. (Warsaw), Miyazaki, S. (Osaka), Suzuki, D. (Osaka), Koshimoto, K. (NASA Goddard), Rattenbury, N (Auckland).
Poster: FUV Variable Stars in M31
By: Denis Leahy
Abstract: The AstroSAT/UVIT survey of M31 has observed the central part of M31 in FUV at different epochs, allowing a search for FUV variables. Here we report the detection of >100 variables (at >5-sigma confidence) and >1000 variables (at >3-sigma confidence). Counterparts are found for most of the >5-sigma variables. Most of the counterparts are young massive stars or stellar clusters. Results on the nature of the counterparts will be presented.
Co-Authors: D.A. Leahy, M. Buick, J.E. Postma
Invited Talk: Archival data retrieval and analysis in the time domain: speak, friend, and enter
By: Adrian B Lucy
Abstract: There are many different ways to retrieve data from archives. Time domain science often pushes us towards more complicated solutions—even when we're not trying to do time-domain science, like when cool giant pulsations erase the information in color catalogs. Choosing the right data retrieval technique for a given science case can sometimes feel like solving an intractable riddle. Focusing on a few real and hypothetical examples drawn from my research into symbiotic star accretion disks and my functional work at the Mikulski Archive for Space Telescopes, I will discuss how the technical requirements of your science case can constrain your options for data retrieval. From querying SkyMapper in TOPCAT to mining Roman data in the cloud, I'll review some existing and future archival interfaces, and describe how I try to think in productive directions when facing a technical challenge. In the end, however, the answer to the riddle is this: remember that it's good to ask for help.
Contributed Talk: An Updated Reference Time-Domain Survey and Cosmology Forecast with the Roman Space Telescope
By: Phillip Joseph Macias
Abstract: The Nancy Grace Roman Space Telescope (NGRST) was the top-ranked large space mission in the 2010 Astronomy and Astrophysics Decadal Survey and promises to revolutionize astrophysics after its launch in the mid 2020s. The Roman High Latitude Time Domain Survey (HLTDS) is unique in its combined large field of view, IR sensitivity, and spectroscopic capabilities, and will discover 2,000-15,000 Type Ia Supernovae (SNe) to be used for cosmology (as well as comparable numbers of non-Ia transients). I will present an updated reference HLTDS designed to meet Roman Dark Energy Science Requirements, but which will also be transformational for a variety of transient science. I will describe recent progress in simulating this survey using the Supernova Analysis Package (SNANA) and Pippin, a pipeline for supernova cosmology analysis. Because of the large numbers of SNe we expect Roman to detect, cosmological inferences are likely to be dominated by systematics, underscoring the need for a better understanding of both SN physics and potential biases related to their environments. I will discuss ongoing efforts toward improving our simulations to maximize Roman’s benefit to cosmology and transient science broadly.
Co-Authors: Ryan Foley
Poster: What can we learn about transients from 21 cm line emission in their environments?
By: Michał Jerzy Michałowski
Abstract: I will present the result of an observational campaign to map the 21 cm atomic hydrogen line in host galaxies of supernovae (SN), long gamma-ray bursts (GRB), and fast radio bursts (FRBs). For all analysed hosts of type Ic-BL SNe and GRBs we found off-centre gas concentrations close to the GRB/SN positions and irregular velocity fields. This suggests a recent gas inflow. This is consistent with GRB/SN progenitors being born when a galaxy accretes metal-poor gas from the intergalactic medium, and opens a possibility to use GRB/SN hosts to study gas accretion. This supports a very massive model for their progenitors. Similarly, the host galaxies of FRBs exhibit very asymmetric 21 cm lines, suggesting a connection between the birth of FRB progenitors and galaxy interactions. On the other hand, the host galaxy of the unusual transient AT 2018cow (the first fast blue optical transient, FBOT) does not exhibit such features, which suggests that its progenitor may not have been a massive star.
Poster: The Astronomical Event Observatory Network (AEON) and Time Domain Follow-up from the Ground and Space
By: Bryan Whitfield Miller
Abstract: As emphasized in the 2020 Decadal Survey report Pathways to Discovery, time domain and multi-messenger astrophysics from both the ground and space is a tremendous challenge and opportunity in the coming decade. The era of large transient surveys (e.g. Catalina, Pan-STARRS, ZTF, Rubin/LSST, Roman) provides many exciting opportunities for new discoveries and understanding of the variable sky. However, the volume of alerts make software automation imperative for object classification, prioritization, scheduling, and data reduction so that the community can get the most science from the new discoveries. Therefore, the NSF's National OIR Astronomy Research Laboratory (NOIRLab: Rubin, Gemini, SOAR, CTIO, KPNO, and the Community Science and Data Center) is teaming up with the Las Cumbres Observatory to develop tools for automating transient follow-up and to incorporate the participating telescopes into the Astronomical Event Observatory Network (AEON). SOAR now has an "AEON", or queue, mode that makes use of the Las Cumbres scheduler and Gemini is working on significant software and instrumentation upgrades. Within the next 10 years we hope to incorporate other facilities including the CTIO 4m/DECam and the US-ELTs. This poster will describe this project, future plans, and ideas for cooperation and synergies between ground and space-based facilities.
Co-Authors: Rachel Street, Cesar Briceno, Andy Adamson, Janice Lee, Lisa Storrie-Lombardi, Monika Soraisam, Joanna Thomas-Osip, Jay Elias, Steve Heathcote, Adam Bolton, Arturo Nunez
Poster: The Transient UV Object (TUVO) Project
By: David Modiano
Abstract: With the recent advances in time-domain astronomy, transient searches have become prevalent through a range of facilities at most electromagnetic wavelengths. However, the ultraviolet (UV) is a notable exception, in that despite being used often for follow-up studies of transients, it has been significantly under-utilised for serendipitous transient discoveries. This presents a considerable obstacle to a complete multi-wavelength understanding of transient phenomena in the Universe, and could also mean that we are foregoing potential discoveries of completely unknown types of transients. To explore this gap, we have developed the Transient UV Objects (TUVO) project. We make use of a pipeline we constructed which processes all data from Swift’s UV telescope (UVOT) in order to search for serendipitous UV transients using difference image analysis, in near real-time. From 2020-09-15 we have to date processed over 80,000 individual UVOT images, and currently we detect an average rate of ~100 transient candidates per day. The types of sources we find include variable stars, flares, dwarf novae, novae, outbursts from X-ray binaries, tidal disruption events, variable active galactic nuclei, and supernovae. Although most sources we detect are already known, a few represent previously unreported new transients, or undiscovered outbursts of previously known sources. This subset of discoveries are our prime targets for further study, for which we have undertaken photometric and spectroscopic follow-up campaigns with optical ground-based observatories. Due to the significant potential scientific gains of finding and studying transients across different wavelengths, this systematic UV transient search can be used to complement transient surveys carried out by various facilities, such as the Nancy Grace Roman Space Telescope in the infrared. This multi-wavelength approach could lead to extensive insight into the physics underlying various types of transient phenomena, much of which remains to be understood in detail. In this talk I will give an overview of the TUVO project, the operation of the pipeline, and initial results.
Co-Authors: Rudy Wijnands
Contributed Talk: Discovering Supernovae at Epoch of Reionization with Nancy Grace Roman Space Telescope
By: Takashi Moriya
Abstract: Some massive stars explode as superluminous supernovae (SLSNe) or pair-instability supernovae (PISNe) that are luminous enough to observe even at z>6 and allow for the direct characterization of massive star properties at the reionization epoch. In addition, hypothetical long-sought-after PISNe are expected to be present preferentially at high redshifts, and their discovery will have a tremendous impact on our understanding of massive star evolution and the formation of stellar mass black holes. The near-infrared Wide Field Instrument on Nancy Grace Roman Space Telescope will excel at discovering such rare high-redshift supernovae. In this work, we investigate the best survey strategy to discover and identify SLSNe and PISNe at z>6 with Roman. We show that the combination of the F158 and F213 filters can clearly separate both SLSNe and PISNe at z>6 from nearby supernovae through their colors and magnitudes. The limiting magnitudes are required to be at least 27.0 mag and 26.5 mag in the F158 and F213 filters, respectively, to identify supernovae at z>6. If we conduct a 10 deg2 transient survey with these limiting magnitudes for 5 years with a cadence of one year, we expect to discover ~ 20 PISNe and ~ 3 SLSNe at z>6, depending on the cosmic star-formation history. Such a supernova survey requires the total observational time of approximately 525 hours in 5 years.
Co-Authors: Robert Quimby, Brant Robertson
Contributed Talk: Roman's potential impact on the census of evolved massive stars in transtion
By: Pat Morris
Abstract: Stars born massive enough to end their lives in core collapse supernovae or collapse directly to black holes experience brief phases of extreme instability on their approach to the Eddington Limit as they evolve from the Main Sequence. The known population of rare massive stars in transition is significantly smaller than predicted, however, while methods using broad-band colors and near-infrared spectroscopy we developed to address this discrepancy have lead to the discovery of over 100 massive stars near the end points of their evolution. We discuss how observations with Roman, starting with the proposed Galactic Plane survey, in conjunction with other facilities such as LSST will yield a much more robust level of completeness in the evolved massive star census, focusing specifically on the luminous blue variable (LBV) phase and a spectroscopically variable population of blue supergiants with extreme stellar winds bordering on those of the known LBVs.
Co-Authors: Schuyler van Dyk (Caltech/IPAC), Anthony Marston (ESA), John Mauerhan (Aerospace Corp.), Giuseppe Morello (IAC)
Invited Talk: Transient alerts and brokers, a perspective from Fink broker
By: Anais Möller
Abstract: In the upcoming years, new facilities will explore the transient sky like never before obtaining large data volumes over different wavelengths and messengers. In this talk I will discuss the use of transient alerts from the biggest optical survey in the world at the Vera C. Rubin Observatory, together with other multi-messenger and wavelength data such as the one from Nancy Grace Roman Telescope.
Given the large data volumes of Rubin, it will be crucial to make use of brokers to ingest, enrich and filter transient data in real-time. I will discuss our experience with the Fink broker developed on high-end technology and designed for fast and real-time processing of big data streams. Fink enables the selection of promising transients using machine learning and combining information from catalogues and surveys at all-wavelengths and messengers. We are already deployed using ZTF data and have ongoing collaborations in a wide range of science. I will discuss the potential breakthroughs in time-domain including supernovae and multi-wavelength/messenger events as kilonovae and Gamma Ray Burst afterglows.
Poster: The SALVATION Project: A Red Nova in M31 and Other Highlights
By: Rafael Nunez
Abstract: The SALVATION (Spectroscopic Analysis of Luminous Variables and Transients in our Neighbor) project, which started in the fall of 2019, uses Lick Observatory’s Shane 3-m telescope and Kast double spectrograph in cadence and target-of-opportunity modes to carry out visible (~4000–9000 Angstrom) spectroscopic follow up of variable stars and transients identified by the ANTARES community alert broker from the real-time data stream of the Zwicky Transient Factory. Most of these sources are in the Andromeda galaxy (M31) or along the line-of-sight to it; during times of the night when M31 is inaccessible, we obtain spectra of transients along other lines of sight. We are carrying out routine spectroscopic monitoring of ~50 luminous variable stars, and have obtained spectra of several tens of transients to date, many of which have been reported in rapid response via Astronomer’s Telegrams.
In fall of 2021, we spectroscopically classified a transient, AT2021tdu, identified from the community alert broker ANTARES as a red nova in M31. Red novae and their luminous counterparts are thought to be the result of stellar mergers and occupy a particularly sparse portion of the transient gap (the gap between classical novae and supernovae) with only a few published examples, three of which are recorded in M31, making this the discovery of a rare object. A large subset of the observed variables are unclassified and the collected spectra were used to classify them and identify the atmospheric parameters: stellar effective temperature (T_eff), surface gravity [log(g)], and metallicity [Fe/H]. The spectral continuum shape is used for a zeroth-order estimate of T_eff via a blackbody curve comparison. This is improved with template fitting using popular empirical spectral libraries such as MILES. This process has been used to classify 12 new variable stars in M31, and has helped trace and identify atmospheric parameter changes with spectral and photometric changes over time.
Co-Authors: Stephanie Figuereo, Monika Soraisam, Kevin McKinnon, Puragra Guhathakurta, Stefan Kimura, Chien-Hsiu Lee, Patrick Aleo
Contributed Talk: SALT3-NIR: Taking the Type Ia Supernova Cosmology Workhorse to Longer Wavelengths
By: Justin Pierel
Abstract: In the next decade, a series of transient surveys from upcoming missions such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) and Nancy Grace Roman Space Telescope will attempt to revolutionize our understanding of Dark Energy using observations of Type Ia supernovae (SNe Ia). Roman observations will be made primarily in the near-infrared (NIR), at wavelengths beyond the reach of the current standard model for SNIa cosmology, SALT3 (~0.2-1.1 micron), at z<0.5. Such a gap will force the Roman SN survey to optimize to a higher redshift range, therefore probing rest-frame optical wavelengths where SNeIa are thought to be less standardizeable, while relying on ground-based surveys to fill in low-z optical observations of SNe Ia. We can reduce future systematic uncertainties related both to calibration and light curve standardization by training SALT3 at NIR wavelengths. We therefore present the SALT3-NIR model, which is trained with all presently available rest-frame NIR photometry and spectra in the open-source SALTShaker framework. The training process is flexible and ready to accommodate new observations into the future. Even with limited data, SALT3-NIR significantly reduces the Hubble scatter of low-z SNe Ia and enables further optimization of the Roman SN cosmology survey into the rest-frame NIR.
Co-Authors: David Jones, D'Arcy Kenworthy, Richard Kessler, Mi Dai, Saurabh Jha, Russell Ryan, Armin Rest, Ryan Foley
Poster: Primordial Black Hole Microlensing Predictions for Roman
By: Kerianne Pruett
Abstract: Primordial black holes (PBHs), theorized to have originated in the early universe, are speculated to be a viable source of dark matter in our universe, and should be detectable via gravitational microlensing signals from local stars in the Milky Way. The Population Synthesis Code for Compact Object Microlensing Events (PopSyCLE) allows users to simulate microlensing surveys with both photometric and astrometric microlensing effects, making it a powerful tool for gaining insight into future PBH detection estimates. We first detail our addition of a PBH population model into PopSyCLE and compare our simulations with OGLE-IV results as a proof of concept. Then, we compare the resulting PBH parameter distributions to those of stellar evolved black holes, and estimate the order of detectable PBH microlensing events we expect from the planned Nancy Grace Roman Space Telescope microlensing survey.
Co-Authors: Michael Medford, William Dawson, Casey Lam, Nathan Golovich, Jessica Lu, George Chapline
Contributed Talk: Photometric Supernova Classification in the Roman Era
By: Helen Qu
Abstract: The Roman Space Telescope offers a unique opportunity to make major strides in the quantity and quality of our type Ia supernovae (SNe Ia) dataset. Building a robust dataset of SNe Ia across a wide range of redshifts will allow for the construction of an accurate Hubble diagram that will enrich our understanding of the expansion history of the universe as well as place constraints on the dark energy equation of state. As long as logistical challenges prevent the spectroscopic follow-up of most detected SNe, a reliable photometric SN classification algorithm will allow us to tap into the vast potential of the photometric dataset. SCONE (Supernova Classification with a Convolutional Neural Network) is a novel application of deep learning to the early and full lightcurve photometric SN classification problem with applications in spectroscopic targeting as well as development of photometric SNe Ia samples for cosmology. SCONE is a convolutional neural network (CNN), an architecture prized in the deep learning community for its state-of-the-art image recognition capabilities. Our model requires raw photometric data only, precluding the necessity for accurate redshift approximations. The dataset is preprocessed using a lightcurve modeling technique via Gaussian processes, which alleviates the issue of irregular sampling between filters but also allows the CNN to learn from information in all filters simultaneously. The model also has relatively low computational and dataset size requirements without compromising on performance – the model is fully trained on our ∼10^4 sample dataset in around 15 minutes on a GPU. Using a dataset of simulated Roman SN lightcurves, SCONE achieved 98.5% training accuracy and 98.9% test accuracy performing binary (SNe Ia vs. core collapse SNe) classification. We will also use the photometric SNe Ia samples from SCONE to study the effect on cosmology resulting from different Roman survey strategies.
Co-Authors: Masao Sako
Contributed Talk: Informed Kilonova Searches Following Short GRBs with the Roman Space Telescope
By: Jillian Rastinejad
Abstract: The discovery of GW170817 and GRB170817A in tandem with AT2017gfo cemented the connection between neutron star mergers, short gamma-ray bursts (GRBs), and kilonovae. In this talk, I will present our comprehensive catalog of past optical and near-IR observations of 85 short GRBs discovered in the last 15 years. I will discuss how this catalog reveals diversity in kilonovae uniformly observed from a pole-on viewing angle. With Hubble-like slew times and depths that extend well into the near-IR, the Nancy Grace Roman Space Telescope is uniquely poised to observe lanthanide-rich kilonovae following short GRBs out to cosmological distances. The Roman Space Telescope will continue what Hubble started with exciting, deep, multi-band follow-up to short GRBs, and, with its broad near-IR coverage, has the potential to reveal unprecedented kilonova diversity.
Co-Authors: W. Fong, C. D. Kilpatrick, K. Paterson, N. R. Tanvir, A. J. Levan, B. D. Metzger, E. Berger, R. Chornock, B. E. Cobb, T. Laskar, P. Milne, A. E. Nugent, N. Smith
Contributed Talk: Energetic nuclear transients in luminous infrared galaxies
By: Thomas Michael Reynolds
Abstract: There have been a number of observations of infrared (IR) echoes associated with tidal disruption events (TDEs). These arise as a result of re-radiation of the TDE’s UV/optical photons by dust in the nuclear environment. Furthermore, there have been multiple fortuitous discoveries of IR echoes in the nuclei of luminous infrared galaxies (LIRGs) over the last few years, which have been identified as TDE candidates. LIRGs are dusty systems often resulting from galaxy mergers and hosting both a powerful starburst and an active galactic nucleus (AGN). TDE candidates in the dusty nuclei of LIRGs are challenging to identify and can often be out of the reach of optical or X-ray observations due to the large column densities of gas and dust obscuring them. Therefore, IR observations are required to characterise them, and can provide important information on the population of TDEs and their rates in these dust obscured nuclear environments. Additionally, IR echoes can be used to probe the total radiated energies from TDEs in cases where a significant fraction of the radiated energy was re-processed by dust to IR wavelengths.
Here we present our search for nuclear transients within local LIRGs using mid-IR observations performed by the WISE satellite, which are almost unaffected by dust extinction. In this search we found multiple new TDE candidates through detection of luminous and slowly evolving mid-IR outbursts. We characterise the nature of these objects through modelling of the spectral energy distributions of their host galaxies and measurements of their luminosities and resulting energetics as well as by comparison of these properties with those of previously published TDEs and TDE candidates. Combining previous discoveries with the new transients detected as part of this search, we set a new lower limit for dust obscured TDEs occurring within LIRGs. We show that even low cadence Roman observations could provide a large number of such events with light curve information useful for their characterisation.
Co-Authors: Seppo Mattila
Invited Talk: Better than the Sum of its Parts: Synergistic Observations for Roman Extragalactic Transient Science
By: Benjamin Rose
Abstract: By itself, the Roman Extragalactic Time-Domain Survey will be an outstanding data set for many transient science cases. However, coordinating with other facilities will greatly increase the overall science return, especially the constraints on dark energy. In this talk, I will discuss synergistic observations and data processing between Roman and other facilities leading to improvements in both statistical and systematic precision. I will discuss how coordinated efforts in field-selection and survey operations, photometric calibration, spectroscopic follow-up, pixel-level processing and computing can lead to improved calibration, classification, redshift measurements and the understanding of survey characteristics. The most impactful synergies will be contemporaneous observations, but there is still a lot of work to do that can and needs to be done now. These efforts will benefit not only science with Type Ia supernovae but all time-domain studies including multi-messenger astrophysics.
Contributed Talk: Evaluating and Optimizing the Roman Prism for the SN Survey
By: David Rubin
Abstract: I present a set of studies from the SN SITs evaluating a low-dispersion slitless prism on Roman, primarily for supernova and host-galaxy spectroscopy. These studies show SN spectral energy distributions provided by a prism carry more information than imaging alone, improving redshift measurements and subtyping of SNe. Observing a random sample of photometric SNe with the prism can thus limit systematic errors in the cosmological measurements provided by Type Ia SNe. The prism can simultaneously observe ~ 10 supernovae as well as multiple hosts (the multiplexing of hosts is greater as they are always present). The prism thus significantly enhances scientific opportunities for the mission, and is particularly important for the Roman supernova cosmology program to provide the systematics controlled measurement that is the focus of the Roman dark energy mission.
Co-Authors: SN SITs
Contributed Talk: Astrometric microlensing with Roman Space Telescope and Gaia
By: Krzysztof Adam Rybicki
Abstract: Observing campaigns focused on detecting microlensing events have been running for almost 30 years and contributed significantly to our knowledge about the Galaxy, specifically in the fields related to the Milky Way structure and extrasolar planets. During that time, the whole microlensing industry has been dynamically evolving, especially from the observational point of view.
Till recently we have been only discovering the photometric events and we learned a lot from them. In 2017 the first detection of astrometric microlensing has been made, and the second detection followed a year after that, both using HST astrometric measurements for very special events where the nearby lens was resolved from the source. Now that we are entering a new era of advanced astrometric, space-based missions, it will be possible to detect the positional part of microlensing events more often. The Gaia satellite will provide astrometric data accurate enough to measure centroid shifts in microlensing events, which we have already tested on Gaia16aye event (https://www.cosmos.esa.int/web/gaia/iow_20210924). While spaced-based observatories (like HST, Gaia, Spitzer etc.) have been already widely used in microlensing studies, Roman Space Telescope will be the first mission with a dedicated time allocated for microlensing survey, which might be a real game-changer, as it will no longer be limited to special cases, but will allow for astrometric microlensing detections even for relatively "standard" events.
I will present the predictions for the observations, detection feasibility and modelling of both photometric and astrometric microlensing from the perspective of Roman Space Telescope and comparison to Gaia mission, for which similar studies were conducted. I will focus particularly on Roman’s revolutionary capabilities in terms of deriving masses of lenses for large populations of stars and identifying dark stellar remnants, like neutron stars and stellar mass black holes.
Co-Authors: Yossi Shvartzvald, Sebastiano Calchi Novati, Łukasz Wyrzykowski
Poster: Novel polarimetric technique to constrain the magnetic field structure and strength of Gamma-ray burst jets
By: Manisha Shrestha
Abstract: Gamma-ray bursts (GRBs) are extremely energetic events of cosmological origin. Observed GRBs have high luminosity and rapid variability that requires ultra-relativistic motion in the production mechanism which drive the synchrotron radiation associated with the relativistic jets and their shocked interactions with the local ambient medium. They are broadly divided into two types based on the gamma-ray duration; long GRBs (>2 seconds), and short GRBs (<2 seconds). Long GRBs are thought to be originated from explosions of very massive stars and short GRBs are thought to be produced by the merger of compact binaries. Several key open questions about our understanding of GRB physics remain: What is the driving mechanism of GRB jets? What is the origin and role of magnetic fields in driving the explosion? Since these events happen at cosmological distances, they can not be resolved using traditional astronomical techniques. However, polarimetric observations of GRBs have allowed us to start the exploration of the structure and magnetic field configurations of their relativistic jets. Generally, polarization is measured via the ratio of fluxes by taking consecutive exposures, however for rapidly varying objects such as GRBs, it is not an effective way to observe polarization. Liverpool Telescope (LT) has utilized rapidly rotating polaroids to overcome this problem and created a series of polarimeters that have successfully detected early-time optical polarimetry of various GRBs. I will present photometric and polarimetric results of various GRBs observed by RINGO3. 10 GRBs were bright enough to perform analysis and we were able to perform polarimetric analysis for 7 GRBs. I will discuss how polarimetric detection for a long GRB 191016A along with photometric data constraint the energy injection mechanism for the central engine. In addition, I will present how polarization depends on various properties of GRBs such as photometric decay index, isotropic energy of GRBs, redshift etc.
Co-Authors: I. A. Steele, S. Kobayashi, R. Smith, C. Guidorzi, N. Jordana-Mitjans, H. Jermak, D. Arnold, C. G. Mundell, A. Gomboc
Contributed Talk: "Super-Kilonovae" from Massive Collapsars as Signatures of Black-Hole Birth in the Pair-instability Mass Gap
By: Daniel Siegel
Abstract: The core collapse of rapidly rotating massive ~10 M⊙ stars ("collapsars"), and resulting formation of hyper-accreting black holes, are a leading model for the central engines of long-duration gamma-ray bursts (GRBs) and promising sources of r-process nucleosynthesis. Here, we explore the signatures of collapsars from progenitors with extremely massive helium cores >130 M⊙ above the pair-instability mass gap. While rapid collapse to a black hole likely precludes a prompt explosion in these systems, we demonstrate that disk outflows can generate a large quantity (up to >50 M⊙) of ejecta, comprised of 5−10 M⊙ in r-process elements and ~0.1−1 M⊙ of 56Ni, expanding at velocities ~0.1 c. Radioactive heating of the disk-wind ejecta powers an optical/infrared transient, with a characteristic luminosity ~10^42 erg/s and spectral peak in the near-infrared (due to the high optical/UV opacities of lanthanide elements) similar to kilonovae from neutron star mergers, but with longer durations ~1 month. These "super-kilonovae" (superKNe) herald the birth of massive black holes >60 M⊙, which—as a result of disk wind mass-loss—can populate the pair-instability mass gap 'from above' and could potentially create the binary components of GW190521. SuperKNe could be discovered via wide-field surveys such as those planned with the Roman Space Telescope or via late-time infrared follow-up observations of extremely energetic GRBs. Gravitational waves of frequency ~0.1−50 Hz from non-axisymmetric instabilities in self-gravitating massive collapsar disks are potentially detectable by proposed third-generation intermediate and high-frequency observatories at distances up to hundreds of Mpc; in contrast to the "chirp" from binary mergers, the collapsar gravitational-wave signal decreases in frequency as the disk radius grows ("sad trombone").
Co-Authors: Aman Agarwal, Jennifer Barnes, Brian D. Metzger, Mathieu Renzo, V. Ashley Villar
Poster: PGIR 20eid (SN2020qmp): A Type IIP Supernova at 15.6 Mpc discovered by the Palomar Gattini-IR survey
By: Gokul Prem Srinivasaragavan
Abstract: We present a detailed analysis of SN 2020qmp, a nearby Type IIP core-collapse supernova (CCSN), discovered by the Palomar Gattini-IR (PGIR) survey in the galaxy UGC07125 (distance of ≈ 15.6 ± 4 Mpc). SN 2020qmp displays characteristic hydrogen lines in its optical spectra, as well as a plateau in its optical LC, hallmarks of a Type IIP SN. We analyze data from observations in various bands: radio, NIR, optical and X-rays. We do not detect linear polarization during the plateau phase, with a 3σ upper limit of 0.78%. Through hydrodynamical LC modeling and an analysis of its nebular spectra, we estimate a progenitor mass of around 12 solar masses, and an explosion energy of around 0.5e51 erg. We find that the spectral energy distribution cannot be explained by a simple CSM interaction model, assuming a constant shock velocity and steady mass-loss rate. In particular, the excess X-ray luminosity compared with the synchrotron radio luminosity suggests deviations from equipartition. Finally, we simulate a sample of CCSNe with plausible distributions of brightness and extinction, within 40 Mpc, and test what fraction of the sample is detectable at peak light by NIR surveys versus optical surveys. Our simulations show that the Wide-Field Infrared Transient Explorer will detect about 14 more CCSNe out of 75 expected in its footprint within 40 Mpc, over five years than an optical survey equivalent to the Zwicky Transient Facility would detect. We have determined or constrained the main properties of SN 2020qmp and of its progenitor, highlighting the value of multiwavelength follow-up observations of nearby CCSNe, as well as demonstrated the advantages of NIR surveys over optical surveys for the detection of dust-obscured CCSNe in the local universe.
Co-Authors: Itai Sfaradi, Jacob Jencson, Kishalay De, Assaf Horesh, Mansi Kasliwal, Samaporn Tinaynont, Matthew Hankins, Steve Schulze, Michael Ashley, Matthew Graham, Viraj Karambelkar, Ryan Lau, Ashish Mahabal, Anna Moore, Eran Ofek, Yasvhi Sharma, Jesper Sollerman, Jamie Soon, Roberto Soria, Tony Travouillon, Richard Walters
Poster: Modeling the Diversity of Transient Light Curves through PCA (principal component analysis)
By: Nao Suzuki
Abstract: The diversity of light curves and spectra can be summarized by a small number of components through PCA (Principal Component Analysis). We discuss applications to supernova: SNIa, SNIbc, SNII, and kilonova. PCA can be used for simulations and works well with machine learning techniques. For Roman data, we can apply PCA for classifications and will play an important role to make decisions on triggering spectroscopic follow-ups. We demonstrate simulated light curves and assess the accuracy of classifications.
Contributed Talk: A Ubiquitous Unifying Degeneracy in 2-body Microlensing Systems
By: Keming Zhang
Abstract: While gravitational microlensing by planetary systems can provide unique vistas on the properties of exoplanets, observations of such 2-body microlensing events can often be explained with multiple and distinct physical configurations, so-called model degeneracies. An understanding of the intrinsic and exogenous origins of different classes of degeneracy provides a foundation for phenomenological interpretation. Here, leveraging a fast deep-learning based inference framework developed for Roman that allows for microlensing real-time inference, we present the discovery of a new regime of degeneracy--the offset degeneracy--which unifies the previously known close-wide and inner-outer degeneracies, generalises to resonant caustics, and upon reanalysis, is ubiquitous in previously published planetary events with 2-fold degenerate solutions. Importantly, our discovery suggests that the commonly reported close-wide degeneracy essentially never arises in actual events and should, instead, be more suitably viewed as a transition point of the offset degeneracy. While previous studies of microlensing degeneracies are largely studies of degenerate caustics, our discovery demonstrates that degenerate caustics do not necessarily result in degenerate events, which for the latter it is more relevant to study magnifications at the location of the source. This discovery fundamentally changes the way in which degeneracies in planetary microlensing events should be interpreted, suggests a deeper symmetry in the mathematics of 2-body lenses than has previously been recognised, and will increasingly manifest itself in data from new generations of microlensing surveys, particularly Roman.
Co-Authors: Scott Gaudi, Joshua Bloom
Contributed Talk: Discovering and characterising kilonovae with untriggered Roman searches
By: Jielai Zhang
Abstract: Kilonovae are unique laboratories for fundamental physics, element creation, cosmology and multi-messenger astrophysics. Kilonovae, resulting from neutron star merger events, are a unique means to determine the equation of state of dense matter and are theorised to produce more than half the elements heavier than iron in the Universe. Kilonovae can be used as standard candles for an independent measurement on the expansion rate of the Universe, which is currently under debate. Finally, neutron star merger events produce short gamma-ray bursts, and kilonovae can help discover much sought after off-axis gamma ray bursts and orphan afterglows. Despite immense interest and effort, only one kilonova has been spectroscopically confirmed by astronomers to date (AT2017gfo) resulting from follow-up of a gravitational wave event GW170817. Kilonovae are evading detection because they are rare and have to-date had poor localization. The way forward is to build a population of kilonovae via blind optical and infrared searches without gravitational wave triggers. I will discuss how Roman can contribute to this effort and synergies with upcoming surveys such as the Rubin LSST Very Deep and Fast time domain survey. I will also share lessons learned from past optical untriggered kilonovae searches such as via the Deeper Wider Faster Program and the Zwicky Transient Facility.
Co-Authors: Cooke, Jeff
Invited Talk: Tidal Disruption Events in the Rubin/Roman era: a multi-messenger feast
By: Sjoert van Velzen
Abstract: The tidal disruption of a star by a massive black hole results in a luminous outburst. This spectacle has been detected across (almost) the entire electromagnetic spectrum, from radio to gamma-rays. Recently, neutrinos have been added to the list of messengers that are used to study tidal disruption events (TDEs). In this talk, I will review this recent progress and explain how TDE observations can yield important inferences, such as the mass and spin of the black hole that disrupted the star. By the time the Nancy Grace Roman Space Telescope starts operations, the detection of TDE in large numbers (100s to 1000s) will be commonplace, with the majority harvested from the data stream of the Vera Rubin Observatory. In this near-future of data abundance in transient astronomy, observations with the Roman telescope will contribute in two unique ways. First of all, Roman data can be used to detect high-redshift TDEs. Because for z~5, the peak of the TDE SED shifts to near-IR wavelengths. Second, for lower redshift, the sensitive photometry of Roman observations can be used to discover dust echoes following black hole accretion flares. These echoes are extremely valuable for two reasons: (1) they provide a means to measure the bolometric luminosity of the flare; (2) optical flares with large dust echoes show a strong connection with neutrino emission. As such, we can expect Roman data will provide a rich contribution to the burgeoning fields of TDEs and multi-messenger astronomy.
