Search Publications
The High-Energy Emission of GRO J1655-40 As Revealed with INTEGRAL Spectroscopy of the 2005 Outburst
Díaz Trigo, M.; Wijnands, R.; Mas-Hesse, J. M. +10 more
We present broadband (3-500 keV) INTEGRAL X-ray spectra and X-ray/optical light curves of the luminous black hole X-ray transient and relativistic jet source GRO J1655-40. Our analysis covers four Target of Opportunity observations of the outburst that started in 2005 February. We find that the high-energy emission of GRO J1655-40 can be modeled w…
A Deep Chandra Look at the Low-LB Elliptical NGC 821: X-Ray Binaries, a Galactic Wind, and Emission at the Nucleus
Elvis, M.; Pellegrini, S.; Baldi, A. +4 more
The relatively nearby (distance = 24.1 Mpc) elliptical galaxy NGC 821, hosting a central massive black hole but inactive at all wavelengths, was observed with Chandra for a total exposure time of 230 ks in order to search for nuclear emission and gas available for accretion. Within its optical image, 41 sources were detected, with spectral propert…
First Detection of Phase-dependent Colliding Wind X-Ray Emission outside the Milky Way
Corcoran, Michael F.; Moffat, Anthony F. J.; Nazé, Yaël +1 more
After having reported the detection of X-rays emitted by the peculiar system HD 5980, we assess here the origin of this high-energy emission from additional X-ray observations obtained with XMM-Newton. This research provides the first detection of apparently periodic X-ray emission from hot gas produced by the collision of winds in an evolved mass…
A Comparative Study of Optical and Ultraviolet Effective Temperatures for DA White Dwarfs from the IUE Archive
Bergeron, P.; Lajoie, C. -P.
We present a comparative study of effective temperatures determined from the hydrogen Balmer lines and from the UV energy distribution for 140 DA white dwarfs drawn from the International Ultraviolet Explorer (IUE) archive. Our results indicate that the optical and UV temperatures of the majority of stars below Teff~40,000 K and within …
Monitoring the Variable Interstellar Absorption toward HD 219188 with Hubble Space Telescope STIS
Welty, Daniel E.
We discuss the results of continued optical and UV spectroscopic monitoring of the variable intermediate-velocity (IV) absorption at vsolar=-38 km s-1 toward HD 219188. After reaching maxima in mid-2000, the column densities of both Na I and Ca II in that IV component declined by factors >~2 by the end of 2006. Comparisons…
The Field of the TeV Source HESS J1804-216 in X-Rays and Other Wavelengths
Garmire, G. P.; Pavlov, G. G.; Kargaltsev, O.
The field of the extended TeV source HESS J1804-216 was serendipitously observed with the Chandra ACIS detector on 2005 May 4. The data reveal several X-ray sources within the bright part of HESS J1804-216. The brightest of these objects, CXOU J180432.4-214009, which has been also detected with Swift (2005 November 3) and Suzaku (2006 April 6), is…
The Globular Cluster System in NGC 5866: Optical Observations from Hubble Space Telescope Advanced Camera for Surveys
Blakeslee, John P.; Cantiello, Michele; Raimondo, Gabriella
We perform a detailed study of the globular cluster (GC) system in the galaxy NGC 5866 based on F435W, F555W, and F625W (~B, V, and R) Hubble Space Telescope Advanced Camera for Surveys images. Adopting color, size, and shape selection criteria, the final list of GC candidates comprises 109 objects, with small estimated contamination from backgrou…
Evidence for the Importance of Resonance Scattering in X-Ray Emission Line Profiles of the O Star ζ Puppis
Leutenegger, Maurice A.; Kahn, Steven M.; Owocki, Stanley P. +1 more
We fit the Doppler profiles of the He-like triplet complexes of O VII and N VI in the X-ray spectrum of the O star ζ Pup, using XMM-Newton RGS data collected over ~400 ks of exposure. We find that they cannot be well fit if the resonance and intercombination lines are constrained to have the same profile shape. However, a significantly better fit …
Optical Spectroscopy of the Environment of a ULX in NGC 7331
Tennant, Allyn F.; Swartz, Douglas A.; Ghosh, Kajal K. +3 more
Optical photometric and spectroscopic data are presented that show an association of an ultraluminous X-ray source in NGC 7331 with a young star cluster of mass M=(1.1+/-0.2)×105 Msolar and age tc=4.25+/-0.25 Myr. If the ULX is part of the bright stellar cluster, then the mass of the progenitor of the compact accre…
The Dynamical Distinction between Elliptical and Lenticular Galaxies in Distant Clusters: Further Evidence for the Recent Origin of S0 Galaxies
Treu, Tommaso; Ellis, Richard S.; Moran, Sean M. +3 more
We examine resolved spectroscopic data obtained with the Keck II telescope for 44 spheroidal galaxies in the fields of two rich clusters, Cl 0024+16 (z=0.40) and MS 0451-03 (z=0.54) and contrast this with similar data for 23 galaxies within the redshift interval 0.3<z<0.65 in the GOODS northern field. For each galaxy we examine the case for …