A5029210401- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Spectroscopy and Chemometric Analyses
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Neutrino Physics Research
- Adaptive optics and wavefront sensing
- Mechanics and Biomechanics Studies
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Ionosphere and magnetosphere dynamics
- Particle Detector Development and Performance
- High-pressure geophysics and materials
- Nuclear Physics and Applications
- Radio Astronomy Observations and Technology
- Laser-Plasma Interactions and Diagnostics
University of California, Santa Cruz
2016-2025
University of California System
2025
University of Copenhagen
2015-2023
University of California, Berkeley
2022
ARC Centre of Excellence for All-sky Astrophysics
2020
ASTRO-3D
2020
Center for Astrophysics Harvard & Smithsonian
2016
Institute for Advanced Study
2004-2015
Harvard University
2015
Marshall Space Flight Center
2005-2010
The distribution of elements in galaxies provides a wealth information about their production sites and subsequent mixing into the interstellar medium. Here we investigate within stars IllustrisTNG simulations. In particular, analyze abundance ratios magnesium europium Milky Way-like from TNG100 simulation (stellar masses ${\log} (M_\star / {\rm M}_\odot) \sim 9.7 - 11.2$). As abundances for individual Way are observed across variety spatial locations metallicities, comparison with stellar...
We present new observations of the early X-ray afterglows first 27 gamma-ray bursts (GRBs) well observed by Swift X-Ray Telescope (XRT). The show a canonical behavior, where light curve broadly consists three distinct power-law segments: (1) an initial very steep decay (∝t-α with 3 ≲ α1 5), followed (2) shallow (0.5 α2 1.0), and finally (3) somewhat steeper (1 α3 1.5). These segments are separated two corresponding break times, tbreak,1 500 s 103 tbreak,2 104 s. On top this many events have...
On 2017 August 17, gravitational waves were detected from a binary neutron star merger, GW170817, along with coincident short gamma-ray burst, GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, and infrared light curves SSS17a extending 10.9 hours to 18 days post-merger. constrain radioactively-powered resulting ejection neutron-rich material. The fast rise curves, subsequent...
On 2017 August 17, the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo interferometer detected gravitational waves emanating from a binary neutron star merger, GW170817. Nearly simultaneously, Fermi INTEGRAL telescopes gamma-ray transient, GRB 170817A. 10.9 hours after wave trigger, we discovered transient fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with SSS17a is located in NGC 4993, an S0 galaxy at distance of 40 megaparsecs. The precise...
With its rapid-response capability and multiwavelength complement of instruments, the Swift satellite has transformed our physical understanding gamma-ray bursts (GRBs). Providing high-quality observations hundreds bursts, facilitating a wide range follow-up within seconds each event, revealed an unforeseen richness in observed burst properties, shed light on nature short-duration helped realize promise GRBs as probes processes environments star formation out to earliest cosmic epochs. These...
While gas accretion onto some massive black holes (MBHs) at the centers of galaxies actively powers luminous emission, vast majority MBHs are considered dormant. Occasionally, a star passing too near MBH is torn apart by gravitational forces, leading to bright panchromatic tidal disruption flare (TDF). high-energy transient Swift J164449.3+573451 ("Sw 1644+57") initially displayed none theoretically anticipated (nor previously observed) TDF characteristics, we show that observations (Levan...
The disruption of stars by supermassive black holes has been linked to more than a dozen flares in the cores galaxies out redshift z ∼ 0.4. Modeling these properly requires prediction rate mass return hole after disruption. Through hydrodynamical simulation, we show that aside from full solar star at exact limit where is destroyed, common assumptions used estimate , hole, are largely invalid. While analytical approximation tidal predicts least-centrally concentrated and deepest encounters...
On 2017 August 17, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of binary neutron star gravitational wave event GW170817. We report time-series spectroscopy SSS17a from 11.75 hours until 8.5 days after merger. Over first hour observations ejecta rapidly expanded and cooled. Applying blackbody fits to spectra, we measure photosphere cooling $11,000^{+3400}_{-900}$ K $9300^{+300}_{-300}$ K, determine a photospheric velocity roughly 30% speed light. The...
We present the initial-final mass relation (IFMR) based on self-consistent analysis of Sirius B and 79 white dwarfs from 13 star clusters. have also acquired additional signal eight previously analyzed in NGC 2099 cluster field, four which are consistent with membership. These reobserved masses ranging 0.72 to 0.97 M$_\odot$, initial 3.0 3.65 where IFMR has an important change slope that these new data help observationally confirm. In total, this directly measured small scatter ($\sigma$ =...
In the past few years wide-field optical and UV transient surveys as well X-ray telescopes have allowed us to identify a dozen candidate tidal disruption events (TDEs). While in theory physical processes TDEs are expected be ubiquitous, distinct classes of been observed. Some radiate mainly NUV/optical while others produce prominent X-rays. Moreover, relativistic jets observed only handful TDEs. This diversity might related details super-Eddington accretion emission physics relevant TDE...
When a star comes within critical distance to supermassive black hole (SMBH), immense tidal forces disrupt the star, resulting in stream of debris that falls back onto SMBH and powers luminous flare. In this paper, we perform hydrodynamical simulations disruption main-sequence by characterize evolution after disruption. We demonstrate is confined self-gravity two directions perpendicular original direction star's travel, as consequence has negligible surface area makes almost no contribution...
Photons from a gravitational wave event Two neutron stars merging together generate signal and have also been predicted to emit electromagnetic radiation. When the GW170817 was detected, astronomers rushed search for source using conventional telescopes (see Introduction by Smith). Coulter et al. describe how One-Meter Two-Hemispheres (1M2H) collaboration first locate source. Drout present 1M2H measurements of its optical infrared brightness, Shappee report their spectroscopy event, which is...
Abstract While once rare, observations of stars being tidally disrupted by supermassive black holes are quickly becoming commonplace. To continue to learn from these events, it is necessary robustly and systematically compare our growing number with theory. We present a tidal disruption module for the Modular Open Source Fitter Transients ( MOSFiT ) results fitting 14 events (TDEs). Our model uses FLASH simulations TDEs generate bolometric luminosities passes through viscosity reprocessing...
Observations of luminous flares resulting from the possible tidal disruption stars by supermassive black holes have raised a number puzzles. Outstanding questions include origin optical and ultraviolet (UV) flux, weakness hydrogen lines in spectrum, occasional simultaneous observation x-rays. Here we study emission events (TDEs) produced as radiation hole accretion propagates through an extended, optically thick envelope formed stellar debris. We analytically describe key physics controlling...
Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < −18), blue transients. While commonly attributed the breakout a supernova shock into dense wind, great distances transients this class found so far hampered detailed investigation their properties. We present photometry and spectroscopy from comprehensive worldwide campaign observe AT 2018cow (ATLAS 18qqn), first fast-luminous transient be in real time at low redshift. Our spectra (<2 days...
Abstract We present preexplosion optical and infrared (IR) imaging at the site of type II supernova (SN II) 2023ixf in Messier 101 6.9 Mpc. astrometrically registered a ground-based image SN to archival Hubble Space Telescope (HST), Spitzer (Spitzer), near-IR images. A single point source is detected position consistent with wavelengths ranging from HST R band 4.5 μ m. Fitting blackbody red supergiant (RSG) spectral energy distributions (SEDs), we find that anomalously cool significant...
Abstract Stars grazing supermassive black holes on bound orbits may produce periodic flares over many passages, known as repeating partial tidal disruption events (TDEs). Here, we present 3D hydrodynamic simulations of Sun-like stars multiple encounters. The star is significantly restructured and becomes less concentrated a result mass loss heating. vulnerability to depends sensitively the stellar density structure, strong correlation between fractional Δ M / * ratio central average...
Abstract We present the discovery of a second radio flare from tidal disruption event (TDE) AT2020vwl via long-term monitoring observations. Late-time flares TDEs are being discovered more commonly, with many showing emission thousands days after stellar disruption, but mechanism that powers these late-time is uncertain. Here, we spectral observations first and observed TDE AT2020vwl. Through detailed monitoring, find evidence for two distinct outflow ejection episodes or period renewed...
According to the collapsar model, γ-ray bursts are thought be produced in shocks that occur after relativistic jet has broken free from stellar envelope. If mass density of collimated outflow is less than envelope, will then surrounded by a cocoon plasma. This material would itself able escape along direction least resistance, which likely rotation axis progenitor, and accelerate approximately same way as an impulsive fireball. We discuss how properties envelope have decisive effect on...
We present a possible Cepheid-like luminosity estimator for the long gamma-ray bursts based on variability of their light curves. To construct estimator, we use CGRO/BATSE data 13 bursts, Wind/Konus five Ulysses/GRB one burst, and NEAR/XGRS burst. Spectroscopic redshifts, peak fluxes, high-resolution curves are available 11 these bursts; partial information is remaining nine bursts. find that isotropic equivalent luminosities L positively correlate with rigorously constructed measure V fit...