Search Publications
An Accretion Model for the Anomalous X-Ray Pulsar 4U 0142+61
Zezas, A.; Dennerl, K.; Trümper, J. E. +2 more
We propose that the quiescent emission of anomalous X-ray pulsars/soft gamma-ray repeaters (AXPs/SGRs) is powered by accretion from a fallback disk, requiring magnetic dipole fields in the range 1012-1013 G, and that the luminous hard tails of their X-ray spectra are produced by bulk-motion Comptonization in the radiative sho…
Curved Walls: Grain Growth, Settling, and Composition Patterns in T Tauri Disk Dust Sublimation Fronts
Hernández, J.; Watson, D. M.; Sargent, B. +6 more
The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall prop…
Distribution of Plasmoids in Post-coronal Mass Ejection Current Sheets
Huang, Y. -M.; Guo, L. -J.; Bhattacharjee, A.
Recently, the fragmentation of a current sheet in the high-Lundquist-number regime caused by the plasmoid instability has been proposed as a possible mechanism for fast reconnection. In this work, we investigate this scenario by comparing the distribution of plasmoids obtained from Large Angle and Spectrometric Coronagraph (LASCO) observational da…
Testing Diagnostics of Nuclear Activity and Star Formation in Galaxies at z > 1
Barro, Guillermo; Pérez-González, Pablo G.; Kocevski, Dale D. +9 more
We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line …
The Coldest Brown Dwarf (or Free-floating Planet)?: The Y Dwarf WISE 1828+2650
Cushing, Michael C.; Kirkpatrick, J. Davy; Gelino, Christopher R. +4 more
We have monitored the position of the cool Y dwarf WISEPA J182831.08+265037.8 using a combination of ground- and space-based telescopes and have determined its distance to be 11.2+1.3 -1.0 pc. Its absolute H magnitude, MH = 22.21+0.25 -0.22 mag, suggests a mass in the range 0.5-20 M Jup
The Afterglow and ULIRG Host Galaxy of the Dark Short GRB 120804A
Menten, K. M.; Berger, E.; Chornock, R. +12 more
We present the optical discovery and subarcsecond optical and X-ray localization of the afterglow of the short GRB 120804A, as well as optical, near-IR, and radio detections of its host galaxy. X-ray observations with Swift/XRT, Chandra, and XMM-Newton extending to δt ≈ 19 days reveal a single power-law decline. The optical afterglow is faint, and…
Measuring X-Ray Variability in Faint/Sparsely Sampled Active Galactic Nuclei
Pinto, C.; Allevato, V.; Paolillo, M. +1 more
We study the statistical properties of the normalized excess variance of variability process characterized by a "red-noise" power spectral density (PSD), as in the case of active galactic nuclei (AGNs). We perform Monte Carlo simulations of light curves, assuming both a continuous and a sparse sampling pattern and various signal-to-noise ratios (S…
Regional Variations in the Dense Gas Heating and Cooling in M51 from Herschel Far-infrared Spectroscopy
Boquien, M.; Roussel, H.; Cooray, A. +13 more
We present Herschel PACS and SPIRE spectroscopy of the most important far-infrared cooling lines in M51, [C II](158 µm), [N II](122 and 205 µm), [O I](63 and 145 µm), and [O III](88 µm). We compare the observed flux of these lines with the predicted flux from a photon-dominated region model to determine characteristics of t…
Suzaku Observations of the Outskirts of A1835: Deviation from Hydrostatic Equilibrium
Zhang, Y. -Y.; Finoguenov, A.; Sato, Kosuke +12 more
We present results of four-pointing Suzaku X-ray observations (total ~200 ks) of the intracluster medium (ICM) in the A1835 galaxy cluster (kT ~ 8 keV, z = 0.253) out to the virial radius (r vir ~ 2.9 Mpc) and beyond. Faint X-ray emission from the ICM out to r vir is detected. The temperature gradually decreases with radius f…
Three-dimensional Magnetohydrodynamic Modeling of Propagating Disturbances in Fan-like Coronal Loops
Ofman, Leon; Davila, Joseph M.; Wang, Tongjiang
Quasi-periodic propagating intensity disturbances (PDs) have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. Motivated by the …