Search Publications
Star Cluster Survival in Star Cluster Complexes under Extreme Residual Gas Expulsion
Kroupa, P.; Fellhauer, M.
After the stars of a new, embedded star cluster have formed, they blow the remaining gas out of the cluster. Especially winds of massive stars and definitely the onset of the first supernovae can remove the residual gas from a cluster. This leads to a very violent mass loss and leaves the cluster out of dynamical equilibrium. Standard models predi…
The Spectral Evolution of Transient Anomalous X-Ray Pulsar XTE J1810-197
Gotthelf, E. V.; Halpern, J. P.
We present a multiepoch spectral study of the transient anomalous X-ray pulsar XTE J1810-197 obtained with the X-Ray Multi-Mirror Mission (XMM-Newton). Four observations taken over the course of a year reveal strong spectral evolution as the source fades from outburst. The origin of this is traced to the individual decay rates of the pulsar's spec…
The Core of NGC 6240 from Keck Adaptive Optics and Hubble Space Telescope NICMOS Observations
Antonucci, R.; Schneider, G.; Canalizo, G. +4 more
We present results of near-infrared imaging of the disk-galaxy merger NGC 6240 using adaptive optics on the Keck II telescope and reprocessed archival data from NICMOS on the Hubble Space Telescope. Both the northern and southern nuclei of NGC 6240 are clearly elongated, with considerable substructure within each nucleus. In K' band there are at l…
A Near-Solar Metallicity, Nitrogen-deficient Lyman Limit Absorber Associated with Two S0 Galaxies
Bowen, David V.; Tripp, Todd M.; Jenkins, Edward B. +1 more
The UV spectrum of the bright quasar PHL 1811 at zem=0.192 reveals a foreground gas system at z=0.080923 with logN(HI)=17.98+/-0.05. We have determined the abundances of various atomic species in this system from a spectrum covering the wavelength range 1160-1730 Å recorded at 7 km s-1 resolution by the E140M grating of the S…
Hubble Space Telescope STIS Observations of the Accreting White Dwarfs in BW Sculptoris, BC Ursae Majoris, and SW Ursae Majoris
Szkody, Paula; Howell, Steve B.; Sion, Edward M. +1 more
We have observed the short-period dwarf novae BW Scl, BC UMa, and SW UMa using the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS). In all three systems, the white dwarf is the dominant source of far-ultraviolet flux, even though in BC UMa and SW UMa an additional continuum component contributes ~10% and ~20% of the 1400 Å flux,…
Changes in the Subsurface Stratification of the Sun with the 11-Year Activity Cycle
Kosovichev, A. G.; Lefebvre, S.
We report on changes in the Sun's subsurface stratification inferred from helioseismology data. Using data from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) for the last 9 years and, more precisely, the temporal variation of f-mode frequencies, we have computed the variation in the radius of subsurface layers of the…
New Geoeffective Parameters of Very Fast Halo Coronal Mass Ejections
Cho, K. -S.; Kim, Y. -H.; Moon, Y. -J. +4 more
We have examined the physical characteristics of very fast coronal mass ejections (CMEs) and their geoeffective parameters. For this we consider SOHO LASCO CMEs whose speeds are larger than 1300 km s-1. By examining all SOHO EIT and SOHO LASCO images of the CMEs, we selected 38 front-side very fast CMEs and then examined their associati…
The Optical Counterpart of M101 ULX-1
Chu, You-Hua; Kuntz, K. D.; Gruendl, Robert A. +4 more
We have identified the optical counterpart of the ultraluminous X-ray source M101 ULX-1 (CXOKM101 J140332.37+542102), by comparing Hubble Space Telescope Advanced Camera for Surveys images with Chandra ACIS-S images. The optical counterpart has V=23.75 and colors consistent with those for a mid-B supergiant. Archival Wide Field Planetary Camera 2 …
Detection of a Hot Binary Companion of η Carinae
Hillier, D. John; Gull, Theodore R.; Sonneborn, George +2 more
We report the detection of a hot companion of η Carinae using high-resolution spectra (905-1180 Å) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024 day orbit: 2003 June, during ingress to the 2003.5 X-ray eclipse, and 2004 April, several months after egress. These data …
X-Ray Cluster Associated with the z = 1.063 CSS Quasar 3C 186: The Jet is Not Frustrated
Elvis, Martin; Cheung, C. C.; Bechtold, Jill +5 more
We report the Chandra discovery of an X-ray cluster at redshift z=1.063 associated with the compact steep spectrum (CSS) radio-loud quasar 3C 186 (Q0740+380). Diffuse X-ray emission is detected out to ~120 kpc from the quasar and contains 741+/-40 net counts. The X-ray spectrum of the extended emission shows strong Fe-line emission (EW=412 eV) at …