Search Publications
A Chandra/LETGS Survey of Main-sequence Stars
Warren, Harry P.; Wood, Brian E.; Poppenhaeger, Katja +1 more
We analyze the X-ray spectra of 19 main-sequence stars observed by Chandra using its LETGS configuration. Emission measure (EM) distributions are computed based on emission line measurements, an analysis that also yields evaluations of coronal abundances. The use of newer atomic physics data results in significant changes compared to past publishe…
SMASHing the LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk
Bell, Eric F.; Monachesi, Antonela; Choi, Yumi +18 more
We explore the stellar structure of the Large Magellanic Cloud (LMC) disk using data from the Survey of the MAgellanic Stellar History and the Dark Energy Survey. We detect a ring-like stellar overdensity in the red clump star count map at a radius of ∼6° (∼5.2 kpc at the LMC distance) that is continuous over ∼270° in position angle and is only li…
Temperature structure in the Perseus cluster core observed with Hitomi
Done, Chris; Safi-Harb, Samar; Hamaguchi, Kenji +192 more
The present paper explains the temperature structure of X-ray emitting plasma in the core of the Perseus cluster based on 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) on board the Hitomi Observatory. A series of four observations was carried out, with a total effective exposure time of 338 ks that covered a central region of ∼…
X-Ray Census of Millisecond Pulsars in the Galactic Field
Cheng, K. S.; Takata, J.; Kong, A. K. H. +3 more
We have conducted a systematic survey for the X-ray properties of millisecond pulsars (MSPs). Currently, there are 47 MSPs with confirmed X-ray detections. We have also placed the upper limits for the X-ray emission from the other 36 MSPs by using the archival data. We have normalized their X-ray luminosities L x and their effective p…
A New Catalog of Radial Velocity Standard Stars from the APOGEE Data
Huang, Y.; Chen, B. -Q.; Wang, C. +5 more
We present a new catalog of 18080 radial velocity (RV) standard stars selected from the APOGEE data. These RV standard stars are observed at least three times and have a median stability (3σ RV) around 240 m s-1 over a time baseline longer than 200 days. They are largely distributed in the northern sky and could be extended t…
New Young Stars and Brown Dwarfs in the Upper Scorpius Association
Luhman, K. L.; Esplin, T. L.; Mamajek, E. E. +2 more
To improve the census of the Upper Sco association (∼11 Myr, ∼145 pc), we have identified candidate members using parallaxes, proper motions, and color-magnitude diagrams from several wide-field imaging surveys and have obtained optical and infrared spectra of several hundred candidates to measure their spectral types and assess their membership. …
A WISE Survey of Circumstellar Disks in the Upper Scorpius Association
Luhman, K. L.; Esplin, T. L.; Mamajek, E. E. +1 more
We have performed a survey for new members of the Upper Sco association that have circumstellar disks using mid-infrared photometry from the Wide-field Infrared Survey Explorer (WISE). Through optical and near-infrared spectroscopy, we have confirmed 185 candidates as likely members of Upper Sco with spectral types ranging from mid-K to M9. They c…
The SFR-M * Correlation Extends to Low Mass at High Redshift
Finkelstein, Steven L.; Koekemoer, Anton M.; Somerville, Rachel S. +8 more
To achieve a fuller understanding of galaxy evolution, SED fitting can be used to recover quantities beyond stellar masses (M *) and star formation rates (SFRs). We use star formation histories (SFHs) reconstructed via the Dense Basis method of Iyer & Gawiser for a sample of 17,873 galaxies at 0.5 < z < 6 in the Cosmic Assembl…
The Properties of GRB 120923A at a Spectroscopic Redshift of z ≈ 7.8
Cenko, S. B.; Covino, S.; Sánchez-Ramírez, R. +37 more
Gamma-ray bursts (GRBs) are powerful probes of early stars and galaxies, during and potentially even before the era of reionization. Although the number of GRBs identified at z ≳ 6 remains small, they provide a unique window on typical star-forming galaxies at that time, and thus are complementary to deep field observations. We report the identifi…
In situ measurements of Saturn’s ionosphere show that it is dynamic and interacts with the rings
Gurnett, D. A.; Persoon, A. M.; Kurth, W. S. +10 more
The ionized upper layer of Saturn’s atmosphere, its ionosphere, provides a closure of currents mediated by the magnetic field to other electrically charged regions (for example, rings) and hosts ion-molecule chemistry. In 2017, the Cassini spacecraft passed inside the planet’s rings, allowing in situ measurements of the ionosphere. The Radio and P…