Search Publications
CHARA Array Measurements of the Angular Diameters of Exoplanet Host Stars
Goldfinger, P. J.; McAlister, Harold A.; ten Brummelaar, Theo A. +5 more
We have measured the angular diameters for a sample of 24 exoplanet host stars using Georgia State University's CHARA Array interferometer. We use these improved angular diameters together with Hipparcos parallax measurements to derive linear radii and to estimate the stars' evolutionary states.
The Energy Flux of Internal Gravity Waves in the Lower Solar Atmosphere
McIntosh, Scott W.; Straus, Thomas; Fleck, Bernhard +5 more
Stably stratified fluids, such as stellar and planetary atmospheres, can support and propagate gravity waves. On Earth these waves, which can transport energy and momentum over large distances and can trigger convection, contribute to the formation of our weather and global climate. Gravity waves also play a pivotal role in planetary sciences and …
Radially Inflowing Molecular Gas in NGC 1275 Deposited by an X-Ray Cooling Flow in the Perseus Cluster
Lim, Jeremy; Dinh-V-Trung; Ao, YiPing
We have imaged in CO(2-1) the molecular gas in NGC 1275 (Perseus A), the cD galaxy at the center of the Perseus Cluster, at a spatial resolution of ~1 kpc over a central region of radius ~10 kpc. Per A is known to contain ~1.3 × 1010 M⊙ of molecular gas, which has been proposed to be captured from mergers with or ram pressure…
X-Ray Spectroscopy of the 2006 Outburst of RS Ophiuchi
Orio, Marina; Still, Martin; Nelson, Thomas +3 more
We present X-ray grating spectra of the recurrent nova RS Ophiuchi during its 2006 outburst, obtained with XMM-Newton and Chandra. For the first month after optical maximum, the X-ray spectrum was hard and dominated by emission lines of H-like and He-like ions. The X-ray luminosity was 2.4 × 1036 ergs s-1 in the 0.33-10 keV r…
Delving Deeper into the Tumultuous Lives of Galactic Dwarfs: Modeling Star Formation Histories
Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon A. +3 more
The paucity of observed dwarf galaxies in the Local Group relative to the abundance of predicted dark matter halos remains one of the greatest puzzles of the ΛCDM paradigm. Solving this puzzle now requires not only matching the numbers of objects but also understanding the details of their star formation histories. We present a summary of such his…
Cooling of the Crust in the Neutron Star Low-Mass X-Ray Binary MXB 1659-29
Miller, Jon M.; Cackett, Edward M.; Wijnands, Rudy +2 more
In quasi-persistent neutron star transients, long outbursts cause the neutron star crust to be heated out of thermal equilibrium with the rest of the star. During quiescence, the crust then cools back down. Such crustal cooling has been observed in two quasi-persistent sources: KS 1731-260 and MXB 1659-29. Here we present an additional Chandra obs…
Radio-Quiet Fast and Wide Coronal Mass Ejections
Kaiser, M. L.; Howard, R. A.; Gopalswamy, N. +5 more
We report on the properties of radio-quiet (RQ) and radio-loud (RL) coronal mass ejections (CMEs) that are fast and wide (FW). RQ CMEs lack type II radio bursts in the metric and decameter-hectometric (DH) wavelengths. RL CMEs are associated with metric or DH type II bursts. We found that ~40% of the FW CMEs from 1996 to 2005 were RQ. The RQ CMEs …
Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies Using X-Ray Emission: Results from the Chandra Deep Fields
Wolf, C.; Lehmer, B. D.; Hornschemeier, A. E. +11 more
We report on the X-ray evolution over the last ≈9 Gyr of cosmic history (i.e., since z = 1.4) of late-type galaxy populations in the Chandra Deep Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S, respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists of 2568 galaxies, which were identified using rest-fr…
The Baryon Content of Dark Matter Halos: Empirical Constraints from Mg II Absorbers
Chen, Hsiao-Wen; Tinker, Jeremy L.
We study the extent and covering fraction of cool baryons around galaxies of different luminosity and mass, based on a survey of Mg II λλ2796, 2803 absorption features near known galaxies. The initial sample consists of 13 galaxy and absorber pairs and 10 galaxies that do not produce Mg II absorption lines to within sensitive upper limits. The red…
Hinode Observations of Magnetic Elements in Internetwork Areas
Lites, B. W.; Ishikawa, R.; Tarbell, T. D. +3 more
We use sequences of images and magnetograms from Hinode to study magnetic elements in internetwork parts of the quiet solar photosphere. Visual inspection shows the existence of many long-lived (several hours) structures that interact frequently and may migrate over distances of ~7 Mm over a period of a few hours. About a fifth of the elements hav…