A5043335996- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- CCD and CMOS Imaging Sensors
- Ocular and Laser Science Research
- Solar and Space Plasma Dynamics
- Spacecraft and Cryogenic Technologies
- Advanced Mathematical Theories
- Distributed and Parallel Computing Systems
- Career Development and Diversity
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Infrared Target Detection Methodologies
- Advanced NMR Techniques and Applications
- Superconducting Materials and Applications
University of Washington
2015-2024
Université Laval
2019
Boston Medical Center
2018
University of Colorado Boulder
2010-2015
Laboratory for Atmospheric and Space Physics
2011-2014
Einstein Institute of Science
2011-2013
University of Hawaiʻi at Mānoa
2007-2011
University of Hawaii System
2007-2011
Smithsonian Astrophysical Observatory
2009-2011
Center for Astrophysics Harvard & Smithsonian
2009-2010
We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine effective temperatures of 74 Galactic red supergiants (RSGs). The stars are mostly members OB associations or clusters with known distances, allowing a critical comparison modern evolutionary tracks. find we can achieve excellent matches between observations reddened model fluxes molecular transitions, although atomic lines Ca I λ4226 II H K found be unrealistically strong in models....
We present a new set of synthesis models for stellar populations obtained with Starburst99, which are based on evolutionary tracks rotation. discuss zero rotation velocity and velocities 40% the break-up zero-age main-sequence. These values expected to bracket realistic distributions in populations. The rotating massive stars more luminous hotter due larger convective core enhanced surface abundances. This results pronounced changes integrated spectral energy distribution population...
We used a recent grid of stellar models computed with and without rotation to make predictions concerning the WR populations frequency different types core-collapse SNe. Current rotating were checked provide good fits following features: solar luminosity radius at age, main-sequence width, red-giant red-supergiant (RSG) positions in HRD, surface abundances, rotational velocities. Rotating predict that about half observed stars least type Ibc SNe may be produced through single-star evolution...
The double explosion of SN 2009ip in 2012 raises questions about our understanding the late stages massive star evolution. Here we present a comprehensive study during its remarkable rebrightenings. High-cadence photometric and spectroscopic observations from GeV to radio band obtained variety ground-based space facilities (including Very Large Array, Swift, Fermi, Hubble Space Telescope, XMM) constrain be low energy (E ∼ 1050 erg for an ejecta mass ∼0.5 M☉) asymmetric complex medium shaped...
We use the MARCS stellar atmosphere to derive physical properties of 36 red supergiants (RSGs) in LMC, and 39 RSGs SMC using moderate-resolution optical spectrophotometry (4000-9000A) broad-band colors (V-R, V-K). The results from dereddened V-R are good agreement with those derived spectrophotometry, but V-K give temperatures that 3-4% warmer for data, LMC Milky Way showing a smaller similar effect. conclude this discrepancy is due limitations 1D models. Our newly effective bolometric...
We use the first data release from SINGG H-alpha survey of HI-selected galaxies to study quantitative behavior diffuse, warm ionized medium (WIM) across range properties represented by these 109 galaxies. The mean fraction f_WIM diffuse gas in this sample is 0.59+/- 0.19, slightly higher than found previous samples. Since lower surface-brightness tend have f_WIM, we believe that most difference due selection effects favoring large, optically-bright, nearby with high star-formation rates. As...
We present a statistically robust mass-metallicity (M-Z) relation for long-duration gamma-ray burst (LGRB) host galaxies at z < 1. By comparing the LGRB M-Z to samples representative of general star-forming galaxy population, we conclude that LGRBs occur in with lower metallicities than and this trend extends ~ 1, an average offset -0.42 +/- 0.18 from galaxies. Our sample work includes new spectroscopic data 6 obtained Keck Magellan telescopes, as well 2 literature. Combined our previous...
Despite both being outbursts of luminous blue variables (LBVs), SN 2009ip and UGC 2773 OT2009-1 have very different progenitors, spectra, circumstellar environments, possibly physical mechanisms that generated the outbursts. From pre-eruption HST images, we determine initial masses >60 >25 M_sun, respectively. Optical spectroscopy shows at peak had a 10,000 K photosphere its spectrum was dominated by narrow H Balmer emission, similar to classical LBV giant outbursts, also known as "supernova...
We present spectroscopic observations of the host galaxy and explosion site long-duration gamma-ray burst GRB 020819. determine a metallicity for this environment log(O/H) + 12 = 9.0 ± 0.1, by far highest determined (LGRB) to date. compare other properties 020819 existing LGRB galaxies consider implications that has our understanding progenitor scenarios. also how unusually high may relate status as "dark" burst, with no detected optical afterglow.
We report the discovery and detailed monitoring of X-ray emission associated with Type IIb SN 2011dh using data from Swift Chandra satellites, placing it among best-studied supernovae (SNe) to date. further present millimeter radio obtained Submillimeter Array, Combined Array for Research in Millimeter-wave Astronomy, Expanded Very Large during first three weeks after explosion. Combining these observations early optical photometry, we show that panchromatic set is well described by...
We present a sample of synthetic massive stellar populations created using the Starburst99 evolutionary synthesis code and new sets tracks, including one set that adopts detailed treatment rotation. Using outputs code, we compare populations' integrated properties, ionizing radiation fields, bolometric luminosities, colors. With these comparisons are able to probe specific effects rotation on properties population. find population rotating stars produces much harder field higher luminosity,...
Abstract We present numerical simulations investigating the interaction of active galactic nucleus jets with galaxy clusters, for first time taking into account dynamic nature cluster gas and detailed physics. The successfully reproduce observed morphologies radio sources in clusters. find that inhomogeneities large-scale flows have a significant impact on morphology source cannot be ignored priori when dynamics. Morphological comparison suggests centres clusters like Virgo Abell 4059 shows...
Ultraviolet, optical, and near-infrared photometry optical spectroscopy of the broad-lined Type Ic supernova (SN) 2009bb are presented, following flux evolution from −10 to +285 days past B-band maximum. Thanks very early discovery, it is possible place tight constraints on SN explosion epoch. The expansion velocities measured near maximum spectra found be only slightly smaller than those prototype 1998bw associated with GRB 980425. Fitting an analytical model pseudobolometric light curve...
We have obtained limited photometric and spectroscopic data for supernova (SN) 2008bk in NGC 7793, primarily at ≳ 150 days after explosion. find that it is a Type II-Plateau (II-P) SN most closely resembles the low-luminosity 1999br 4900. Given overall similarity between observed light curves colors of SNe 1999br, we infer total visual extinction to (AV = 0.065 mag) must be almost entirely due Galactic foreground, similar what has been assumed 1999br. confirm identification putative red...
We present the discovery of an absorption-line redshift z = 2.609 for GRB 090426, establishing first firm lower limit to a gamma-ray burst with observed duration <2 s. With rest-frame T_90z 0.35 s and detailed examination peak energy event, we suggest that this is likely (at >90% confidence) member short/hard phenomenological class GRBs. From analysis optical-afterglow spectrum find originated along very low HI column density sightline, N_HI < 3.2 x 10^19 cm^-2. Our 090426 afterglow also...
We present the first observations from a large-scale survey of nearby (z < 1) long-duration gamma-ray burst (LGRB) host galaxies, which consist eight rest-frame optical spectra obtained at Keck and Magellan. Along with two galaxy literature, we use emission-line diagnostics to determine metallicities, ionization parameters, young stellar population ages, star formation rates. compare LGRB environments variety local intermediate-redshift populations, as well newest grid synthesis...
The post main-sequence evolution of massive stars is very sensitive to many parameters the stellar models. Key are mixing processes, metallicity, mass-loss rate and effect a close companion. We study how red supergiant lifetimes, tracks in Hertzsprung-Russel diagram (HRD), positions this pre-supernova progenitor as well structure at that time change for various rates during phase (RSG), two different initial rotation velocities. surface abundances RSGs much more than phase. A RSG has strong...
We present the first spectroscopic study of host environments Type Ibc supernovae (SNe Ibc) discovered exclusively by untargeted SN searches. Past studies have been biased toward high-mass, high-metallicity galaxies focusing on SNe in galaxy-targeted Our new observations more than double total number stellar population age and metallicity measurements published for environments. For 12 Ib 21 Ic our sample, we find median metallicities 0.62 Z☉ 0.83 Z☉, respectively, but determine that...
Abstract We present an ongoing, five-year systematic search for extragalactic infrared transients, dubbed SPIRITS—SPitzer InfraRed Intensive Transients Survey. In the first year, using Spitzer /IRAC, we searched 190 nearby galaxies with cadence baselines of one month and six months. discovered over 1958 variables 43 transients. Here, describe survey design highlight 14 unusual transients no optical counterparts to deep limits, which refer as SPRITEs (eSPecially Red Intermediate-luminosity...
We present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one least luminous SNe IIb or Ib observed to date. Our begin with a discovery within 1 day explosion span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly are replaced by Ib-like He-rich features on timescale week. High-cadence monitoring this transition suggests absorption attributable high velocity (>...
Deriving the physical properties of red supergiants (RSGs) depends upon accurate corrections for reddening by dust. We use our recent modeling optical spectra RSGs to address this topic. find: (1) Previous broad-band studies have underestimated correction extinction in visible, and hence luminousities, if derived from V. (2) A significant fraction Galactic OB associations clusters show up several magnitudes excess visual compared stars same regions; we argue that is likely due circumstellar...
The recent long-duration GRB 100316D, associated with supernova SN 2010bh and detected by Swift, is one of the nearest gamma-ray burst (GRB)–supernovae (SNe) ever observed (z = 0.059). This provides us a unique opportunity to study explosion environment on ∼kpc scale in relation host galaxy complex. Here we present spatially resolved spectrophotometry galaxy, focusing both site brightest star-forming regions. Using these data, extract spatial profiles relevant emission features (Hα, Hβ, [O...
Thorne-Zytkow objects (TZOs) are a theoretical class of star in which compact neutron is surrounded by large, diffuse envelope. Supergiant TZOs predicted to be almost identical appearance red supergiants (RSGs). The best features that can used at present distinguish from the general RSG population unusually strong heavy-element and Li lines their spectra, products star's fully convective envelope linking photosphere with extraordinarily hot burning region vicinity core. Here we our discovery...