A5001277336- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Career Development and Diversity
- Astro and Planetary Science
- Geological and Geochemical Analysis
- Spectroscopy and Laser Applications
- Pulsars and Gravitational Waves Research
- Diversity and Career in Medicine
- Twentieth Century Scientific Developments
- Atmospheric Ozone and Climate
- Statistical and numerical algorithms
- High-pressure geophysics and materials
- Cosmology and Gravitation Theories
- Planetary Science and Exploration
- History and Developments in Astronomy
- Astronomical and nuclear sciences
- Scientific Research and Discoveries
- Research in Cotton Cultivation
University of Washington
2022-2023
University of Michigan
2020-2023
NASA Astrobiology Institute
2023
Joint Institute for Nuclear Astrophysics
2016-2022
University of Notre Dame
2016-2021
National Superconducting Cyclotron Laboratory
2018
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...
ABSTRACT We investigate anew the distribution of absolute carbon abundance, A (C) = log ϵ (C), for carbon-enhanced metal-poor (CEMP) stars in halo Milky Way, based on high-resolution spectroscopic data a total sample 305 CEMP stars. The includes 147 CEMP- s (and r / ) stars, 127 CEMP-no and 31 that are unclassified, currently employed [Ba/Fe] criterion. confirm previous claims is (at least) bimodal, with newly determined peaks centered 7.96 (the high-C region) 6.28 low-C region). very high...
This compilation is the fourth data release from R-Process Alliance (RPA) search for r-process-enhanced stars and second based on "snapshot" high-resolution (R ∼ 30,000) spectra collected with du Pont 2.5 m Telescope. In this release, we propose a new delineation between r-I r-II stellar classes at , instead of empirically chosen level previously in use, statistical tests complete set RPA released to date. We also statistically justify minimum [Eu/Fe] definition stars, > +0.3. Redefining...
Abstract Within the next decade, atmospheric O 2 on Earth-like M-dwarf planets may be accessible with visible–near-infrared (NIR), high-spectral-resolution, ground-based extremely large telescope (ELT) instruments. However, prospects for using ELTs to detect environmental properties that provide context have not been thoroughly explored. Additional molecules help indicate planetary habitability, rule out abiotically generated , or reveal alternative biosignatures. To understand accessibility...
Abstract We present results from a medium-resolution ( R ∼ 2000) spectroscopic follow-up campaign of 1694 bright V < 13.5), very metal-poor star candidates the RAdial Velocity Experiment (RAVE). Initial selection low-metallicity targets was based on stellar parameters published in RAVE Data Releases 4 and 5. Follow up accomplished with Gemini-N Gemini-S, ESO/NTT, KPNO/Mayall, SOAR telescopes. The wavelength coverage for most observed spectra allows determination carbon α -element...
We present results from an observing campaign to identify low-metallicity stars in the Best & Brightest Survey. From medium-resolution (R ~ 1, 200 - 2, 000) spectroscopy of 857 candidates, we estimate stellar atmospheric parameters (Teff, log g, and [Fe/H]), as well carbon alpha-element abundances. find that 69% observed have [Fe/H] <= -1.0, 39% -2.0, 2% -3.0. There are also 133 carbon-enhanced metal-poor (CEMP) this sample, with 97 CEMP Group I 36 II identified A(C) versus diagram. A subset...
Abstract Close-in lava planets represent an extreme example of terrestrial worlds, but their high temperatures may allow us to probe a diversity crustal compositions. The brightest and most well-studied these objects is 55 Cancri e, nearby super-Earth with remarkably short 17 hr orbit. However, despite numerous studies, debate remains about the existence composition its atmosphere. We present upper limits on atmospheric pressure Cnc e derived from high-resolution time-series spectra taken...
Extensive progress has been recently made into our understanding of heavy element production via the $r$-process in Universe, specifically with first observed neutron star binary merger (NSBM) event associated gravitational wave signal detected by LIGO, GW170817. The chemical abundance patterns metal-poor $r$-process-enhanced stars provides key evidence dominant site(s) $r$-process, and whether NSBMs are sufficiently frequent or prolific sources to be responsible for majority material...
Abstract Spectroscopic studies of planets outside our own solar system provide some the most crucial information about their formation, evolution, and atmospheric properties. In ground-based spectroscopy, process extracting signal from stellar telluric has proven to be difficult barrier accurate information. However, with novel normalization smoothing methods, this can minimized detection significance dramatically increased over existing methods. paper, we take two examples CRIRES emission...
Gender equity is one of the biggest issues facing field astrophysics, and there broad interest in addressing gender disparities within astronomy. Many studies these topics have been performed by professional astronomers who are relatively unfamiliar with research fields such as sociology. As a result, they adopt normative view binary choice 'male' or 'female', leaving whose genders do not fit that model out entirely. Reductive frameworks an overemphasis on quantification indicator gendered...
Abstract We present results from high-resolution ( R ∼ 40,000) spectroscopic observations of over 200 metal-poor stars, mostly selected the RAVE survey, using Southern African Large Telescope. were able to derive stellar parameters for a total 108 stars; an additional sample 50 stars this same effort was previously reported on by Rasmussen et al. Among our newly observations, we identify 84 very (VMP; [Fe/H] < −2.0, 53 identified) and three extremely (EMP; −3.0, one stars. The elemental...
Abstract We derive dynamical parameters for a large sample of 446 r -process-enhanced (RPE) metal-poor stars in the halo and disk systems Milky Way, based on data releases from R -Process Alliance, supplemented by additional literature samples. This represents more than 10-fold increase size relative to that previously considered Roederer et al. and, design, covers larger range -process-element enrichment levels. test number clustering analysis methods derived orbital energies other this...
We present 18 years of OGLE photometry together with spectra obtained over 12 years, revealing that the early Oe star AzV 493 shows strong photometric (Delta I < 1.2 mag) and spectroscopic variability a dominant, 14.6-year pattern ~40-day oscillations. estimate stellar parameters T_eff = 42000 K, log L/L_sun 5.83 +/- 0.15, M/M_sun 50 9, vsini 370 40 km/s. Direct evidence episodes both gas ejection infall. There is no X-ray detection, it likely runaway star. may have an unseen companion on...
Gender inequity is one of the biggest challenges facing STEM workforce. While there are many studies that look into gender disparities within and academia, majority these have been designed executed by those unfamiliar with research in sociology studies. They adopt a normative view as binary choice 'male' or 'female,' leaving individuals whose genders do not fit model out such entirely. This especially impacts experiencing multiple axes marginalization, race, disability, socioeconomic...
Abstract We present the first release of a large-scale study relatively bright ( V < 13.5) metal-poor stars observed with Southern African Large Telescope (SALT), based on high-resolution spectra 50 resolving power R ∼ 40,000 and S/N 20 per pixel at 4300 Å. The elemental abundances C, Sr, Ba, Eu are reported, as well several α -elements (Mg, Ca, Sc, Ti, V) iron-peak elements (Mn, Co, Ni, Zn). find diverse array abundance patterns, including consistent signatures carbon-enhanced CEMP- i r...
Within the next decade, atmospheric O$_2$ on Earth-like M dwarf planets may be accessible with visible--near-infrared, high spectral resolution extremely large ground-based telescope (ELT) instruments. However, prospects for using ELTs to detect environmental properties that provide context have not been thoroughly explored. Additional molecules help indicate planetary habitability, rule out abiotically generated O$_2$, or reveal alternative biosignatures. To understand accessibility of ELT...
We present chemical abundances and velocities of five stars between 0.3 kpc to 1.1 from the center Tucana II ultra-faint dwarf galaxy (UFD) high-resolution Magellan/MIKE spectroscopy. find that every star is deficient in metals (-3.6 < [Fe/H] -1.9) neutron-capture elements as characteristic UFD stars, unambiguously confirming their association with II. Other (e.g., C, iron-peak) largely follow trends suggest faint core-collapse supernovae (SNe) dominated early evolution see a downturn...
Close-in lava planets represent an extreme example of terrestrial worlds, but their high temperatures may allow us to probe a diversity crustal compositions. The brightest and most well-studied these objects is 55 Cancri e, nearby super-Earth with remarkably short 17-hour orbit. However, despite numerous studies, debate remains about the existence composition its atmosphere. We present upper limits on atmospheric pressure Cnc e derived from high-resolution time-series spectra taken...
Abstract The study of extremely metal-poor (EMP; [Fe/H] &lt;−3.0) and ultra (UMP; &lt;−4.0) stars is crucial for better understanding first-star nucleosynthesis constraining the initial mass function in early Universe. However, UMP discovered past 25 years only number ~25. A few recent theoretical studies have pointed out that there likely to exist large numbers EMP periphery Galactic halo, at distances exceeding 30-50 kpc. We present identifications several new EMP/UMP introduce a...
Abstract The RAVE survey obtains moderate-resolution (R ~ 7500) spectroscopy of relatively bright stars in the region Ca triplet, and derives estimates stellar atmospheric parameters (Teff, log g, [Fe/H]) abundance for a limited number elements. sample is selected on apparent magnitude, effectively removing biases typically associated with searches metal-poor such as metallicity, evolutionary status, or Galactic population membership. For past several years, we have been obtaining...