Search Publications
Magneto-thermal convection in solar prominences
Shibata, Kazunari; Testa, Paola; Boerner, Paul +6 more
Coronal cavities are large low-density regions formed by hemispheric-scale magnetic flux ropes suspended in the Sun's outer atmosphere. They evolve over time, eventually erupting as the dark cores of coronal mass ejections. Although coronal mass ejections are common and can significantly affect planetary magnetospheres, the mechanisms by which cav…
Distance Scale Zero Points from Galactic RR Lyrae Star Parallaxes
Kochukhov, Oleg; Nelan, Edmund P.; Freedman, Wendy L. +15 more
We present new absolute trigonometric parallaxes and proper motions for seven Population II variable stars—five RR Lyr variables: RZ Cep, XZ Cyg, SU Dra, RR Lyr, and UV Oct; and two type 2 Cepheids: VY Pyx and κ Pav. We obtained these results with astrometric data from Fine Guidance Sensors, white-light interferometers on Hubble Space Telescope. W…
X-ray absorption by broad-line region clouds in Mrk 766
Maiolino, R.; Elvis, M.; Fabbiano, G. +5 more
We present a new analysis of a 9-d long XMM-Newton monitoring of the narrow-line Seyfert 1 galaxy Mrk 766. We show that the strong changes in the spectral shape, which occurred during this observation, can be interpreted as due to broad-line region clouds crossing the line of sight to the X-ray source. Within the occultation scenario, the spectral…
Quenching of Carbon Monoxide and Methane in the Atmospheres of Cool Brown Dwarfs and Hot Jupiters
Moses, Julianne I.; Visscher, Channon
We explore CO\rightleftarrows CH_{4} quench kinetics in the atmospheres of substellar objects using updated timescale arguments, as suggested by a thermochemical kinetics and diffusion model that transitions from the thermochemical-equilibrium regime in the deep atmosphere to a quench-chemical regime at higher altitudes. More specifically, we exam…
Thin current sheets in collisionless plasma: Equilibrium structure, plasma instabilities, and particle acceleration
Malova, H. V.; Popov, V. Yu.; Petrukovich, A. A. +2 more
The review is devoted to plasma structures with an extremely small transverse size, namely, thin current sheets that have been discovered and investigated by spacecraft observations in the Earth's magnetotail in the last few decades. The formation of current sheets is attributed to complicated dynamic processes occurring in a collisionless space p…
Extended Schmidt Law: Role of Existing Stars in Current Star Formation
Papovich, Casey; Armus, Lee; Helou, George +4 more
We propose an "extended Schmidt law" with explicit dependence of the star formation efficiency (SFE = SFR/M gas) on the stellar mass surface density (Σstar). This relation has a power-law index of 0.48 ± 0.04 and a 1σ observed scatter on the SFE of 0.4 dex, which holds over five orders of magnitude in the stellar density for …
The XMM Deep survey in the CDF-S. I. First results on heavily obscured AGN
Silverman, J. D.; Bauer, F. E.; Brandt, W. N. +25 more
We present the first results of the spectroscopy of distant, obscured AGN as obtained with the ultra-deep (≈3.3 Ms) XMM-Newton survey in the Chandra deep field South. One of the primary goals of the project is to characterize the X-ray spectral properties of obscured and heavily obscured Compton-thick AGN over the range of redhifts and luminositie…
Establishing a Connection Between Active Region Outflows and the Solar Wind: Abundance Measurements with EIS/Hinode
Warren, Harry P.; Brooks, David H.
One of the most interesting discoveries from Hinode is the presence of persistent high-temperature high-speed outflows from the edges of active regions (ARs). EUV imaging spectrometer (EIS) measurements indicate that the outflows reach velocities of 50 km s-1 with spectral line asymmetries approaching 200 km s-1. It has been …
Star Clusters in M31. V. Internal Dynamical Trends: Some Troublesome, Some Reassuring
Caldwell, Nelson; Strader, Jay; Seth, Anil C.
We present internal velocity dispersions and precise radial velocities for 200 globular clusters (GCs) in M31 that are derived using new high-resolution spectra from MMT/Hectochelle. Of these, 163 also have King model structural parameters that allow us to estimate their mass-to-light ratios. This is, by far, the largest such data set available fo…
A Stochastic Model for the Luminosity Fluctuations of Accreting Black Holes
Siemiginowska, Aneta; Kelly, Brandon C.; Sobolewska, Małgorzata
In this work, we have developed a new stochastic model for the fluctuations in light curves of accreting black holes. The model is based on a linear combination of stochastic processes and is also the solution to the linear diffusion equation perturbed by a spatially correlated noise field. This allows flexible modeling of the power spectral densi…