Search Publications
The Archetypal Ultra-diffuse Galaxy, Dragonfly 44, Is not a Dark Milky Way
Bogdán, Ákos
Due to the peculiar properties of ultra-diffuse galaxies (UDGs), understanding their origin presents a major challenge. Previous X-ray studies demonstrated that the bulk of UDGs lack substantial X-ray emission, implying that they reside in low-mass dark matter halos. This result, in concert with other observational and theoretical studies, pointed…
The Large-scale Behavior in the Disk of δ Scorpii from 2000 to 2018
Carciofi, A. C.; Mota, B. C.; Tycner, C. +4 more
We model the circumstellar disk of δ Sco using the three-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large-scale changes in the disk through the years 2000-2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models throug…
Multiwavelength Study of an X-Ray Tidal Disruption Event Candidate in NGC 5092
Komossa, S.; Jin, Chichuan; Saxton, R. D. +7 more
We present multiwavelength studies of a transient X-ray source, XMMSL1 J131952.3+225958, associated with the galaxy NGC 5092 at z = 0.023 detected in the XMM-Newton SLew survey (XMMSL). The source brightened in the 0.2-2 keV band by a factor of > 20 in 2005 as compared with previous flux limits and then faded by a factor of >200 as observed …
Evidence for a Rotational Component in the Circumgalactic Medium of Nearby Galaxies
Wakker, Bart P.; French, David M.
We present results of a study comparing the relative velocity of Lyα absorbers to the rotation velocity of nearby galaxy disks in the local universe (z ≤ 0.03). We have obtained rotation curves via long-slit spectroscopy of eight galaxies with the Southern African Large Telescope, and combine this data set with an additional 16 galaxies with data …
Chemically Peculiar A and F Stars with Enhanced s-process and Iron-peak Elements: Stellar Radiative Acceleration at Work
Ting, Yuan-Sen; Rix, Hans-Walter; Zhang, Meng +6 more
We present ≳15,000 metal-rich ([Fe/H] > -0.2 dex) A and F stars whose surface abundances deviate strongly from solar abundance ratios and cannot plausibly reflect their birth material composition. These stars are identified by their high [Ba/Fe] abundance ratios ([Ba/Fe] > 1.0 dex) in the LAMOST DR5 spectra analyzed by Xiang et al. They are …
Chandra Monitoring of the J1809-1917 Pulsar Wind Nebula and Its Field
Pavlov, George G.; Kargaltsev, Oleg; Klingler, Noel +3 more
PSR J1809-1917 is a young (τ = 51 kyr) and energetic ( $\dot{E}=1.8\times {10}^{36}$ erg s-1) radio pulsar powering an X-ray pulsar wind nebula (PWN) that exhibits morphological variability. We report on the results of a new monitoring campaign by the Chandra X-ray Observatory (Chandra), carried out across six epochs with a ∼7 week cade…
A Rapidly Varying Red Supergiant X-Ray Binary in the Galactic Center
Gottlieb, Amy M.; Ackley, Kendall; DeWitt, Curtis +2 more
We analyzed multiwavelength observations of the previously identified Galactic center X-ray binary CXO 174528.79-290942.8 (XID 6592) and determine that the near-infrared counterpart is a red supergiant based on its spectrum and luminosity. Scutum X-1 is the only previously known X-ray binary with a red supergiant donor star and closely resembles X…
The Detection of Dust Gap-ring Structure in the Outer Region of the CR Cha Protoplanetary Disk
Dong, Ruobing; Kataoka, Akimasa; Sitko, Michael +13 more
We observe the dust continuum at 225 GHz and CO isotopologue (12CO, 13CO, and C18O) J = 2-1 emission lines toward the CR Cha protoplanetary disk using the Atacama Large Millimeter/submillimeter Array. The dust continuum image shows a dust gap-ring structure in the outer region of the dust disk. A faint dust ring is…
A Model-insensitive Baryon Acoustic Oscillation Feature in the 21 cm Signal from Reionization
Trac, Hy; Cain, Christopher; D'Aloisio, Anson +2 more
We examine the impact of baryon-dark matter relative velocities on intergalactic small-scale structure and the 21 cm signal during reionization. Streaming velocities reduced clumping in the intergalactic medium on mass scales of ∼104-108 M⊙. This effect produced a distinct baryon acoustic oscillation (BAO) feature …
Magnetohydrodynamic Turbulent Evolution of a Magnetic Cloud in the Outer Heliosphere
Telloni, Daniele; Zank, Gary P.; Adhikari, Laxman +8 more
This Letter exploits joint observations of the same interplanetary coronal mass ejection by widely separated spacecraft to study, for the first time, the turbulent evolution of the magnetohydrodynamic (MHD) properties of the embedded magnetic cloud, during its propagation throughout interplanetary space. Specifically, the event was observed by Win…