Search Publications
X-Ray-Emitting Stars Identified from the ROSAT All-Sky Survey and the Sloan Digital Sky Survey
Anderson, Scott F.; Hawley, Suzanne L.; Szkody, Paula +7 more
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. Combining the RASS Bright and Faint Source Catalogs yields an average of about three X-ray sources per square degree. However, while X-ray source counterparts are known to range from distant quasars to nearby M dwarfs, the RASS data alone are often insufficient t…
Propagating transverse waves in soft X-ray coronal jets
Nakariakov, V. M.; Verwichte, E.; Van Doorsselaere, T. +1 more
Aims: The theoretical model for magnetohydrodynamic (MHD) modes guided by a field-aligned plasma cylinder with a steady flow is adapted to interpret transverse waves observed in solar coronal hot jets, discovered with Hinode/XRT in terms of fast magnetoacoustic kink modes.
Methods: Dispersion relations for linear magnetoacoustic perturbations …
Feedback through multiple outbursts in the cluster 2A 0335+096
Fabian, A. C.; Sanders, J. S.; Taylor, G. B.
We examine the core of the X-ray bright galaxy cluster 2A 0335+096 using deep Chandra X-ray imaging and spatially resolved spectroscopy, and include new radio observations. The set of around eight X-ray bright blobs in the core of the cluster, appearing like eggs in a bird's nest, contains multiphase gas from ~0.5 to 2 keV. The morphology of the c…
The Ultraviolet Spectrum and Physical Properties of the Mass Donor Star in HD 226868 = Cygnus X-1
Kaper, L.; Herrero, A.; Bolton, C. T. +8 more
We present an examination of high-resolution, ultraviolet (UV) spectroscopy from Hubble Space Telescope of the photospheric spectrum of the O-supergiant in the massive X-ray binary HD 226868 = Cyg X-1. We analyzed this and ground-based optical spectra to determine the effective temperature and gravity of the O9.7 Iab supergiant. Using non-LTE, lin…
Cassini RADAR images at Hotei Arcus and western Xanadu, Titan: Evidence for geologically recent cryovolcanic activity
Lorenz, R. D.; Janssen, M. A.; Lunine, J. I. +14 more
Images obtained by the Cassini Titan Radar Mapper (RADAR) reveal lobate, flowlike features in the Hotei Arcus region that embay and cover surrounding terrains and channels. We conclude that they are cryovolcanic lava flows younger than surrounding terrain, although we cannot reject the sedimentary alternative. Their appearance is grossly similar t…
Sizes of LYα-emitting Galaxies and Their Rest-frame Ultraviolet Components at z = 3.1
Schawinski, Kevin; Gronwall, Caryl; Gawiser, Eric +3 more
We present a rest-frame ultraviolet analysis of ~120 z ~ 3.1 Lyman Alpha Emitters (LAEs) in the Extended Chandra Deep Field South. Using Hubble Space Telescope (HST) images taken as part of the Galaxy Evolution From Morphology and SEDS (GEMS) survey, Great Observatories Origins Deep Survey (GOODS), and Hubble Ultradeep Field surveys, we analyze th…
Suzaku Observations of Tycho's Supernova Remnant
Kunieda, Hideyo; Szymkowiak, Andrew; Kokubun, Motohide +19 more
Tycho's supernova remnant was observed by the XIS and HXD instruments onboard the Suzaku satellite on 2006 June 26--29 for 92ks. The spectrum up to 30keV was well fitted with a two-component model, consisting of a power-law with a photon index of 2.7 and a thermal bremsstrahlung model with a temperature of 4.7keV. The former component can alternat…
The ACS Nearby Galaxy Survey Treasury. II. Young Stars and their Relation to Hα and UV Emission Timescales in the M81 Outer Disk
de Jong, Roelof S.; Williams, Benjamin F.; Dolphin, Andrew +11 more
We have obtained resolved stellar photometry from Hubble Space Telescope Advanced Camera for Surveys observations of a field in the outer disk of M81 as part of ANGST. Motivated by the recent discovery of extended UV disks around many nearby spiral galaxies, we use the observed stellar population to derive the recent star formation histories of fi…
IGR J17544-2619 in Depth With Suzaku: Direct Evidence for Clumpy Winds in a Supergiant Fast X-ray Transient
Smith, David M.; Negueruela, Ignacio; Rampy, Rachel A.
We present direct evidence for dense clumps of matter in the companion wind in a Supergiant Fast X-ray Transient (SFXT) binary. This is seen as a brief period of enhanced absorption during one of the bright, fast flares that distinguish these systems. The object under study was IGR J17544-2619, and a total of 236 ks of data were accumulated with t…
Modelling the Longitudinal Asymmetry in Sunspot Emergence: The Role of the Wilson Depression
Watson, F.; Fletcher, L.; Dalla, S. +1 more
The distributions of sunspot longitude at first appearance and at disappearance display an east-west asymmetry that results from a reduction in visibility as one moves from disk centre to the limb. To first order, this is explicable in terms of simple geometrical foreshortening. However, the centre-to-limb visibility variation is much larger than …