Search Publications
On the Lack of a Soft X-Ray Excess from Clusters of Galaxies
Bregman, Joel N.; Lloyd-Davies, Edward J.
A soft X-ray excess has been claimed to exist in and around a number of galaxy clusters, and this emission has been attributed to the warm-hot intergalactic medium that may constitute most of the baryons in the local universe. We have reexamined a study of the XMM-Newton observations on this topic by Kaastra and coworkers and find that the X-ray e…
Carbon Monoxide in Comet 9P/Tempel 1 before and after the Deep Impact Encounter
Weaver, Harold A.; Feldman, Paul D.; A'Hearn, Michael F. +4 more
One of the goals of the Hubble Space Telescope program to observe periodic comet 9P/Tempel 1 in conjunction with NASA's Deep Impact mission was to study the generation and evolution of the gaseous coma resulting from the impact. For this purpose, the Solar Blind Channel of the Advanced Camera for Surveys was used with the F140LP filter, which is s…
Solar Energetic Particles and Radio-silent Fast Coronal Mass Ejections
Klein, K. -L.; Posner, A.; Marqué, C.
Both solar flares and shock waves driven by fast coronal mass ejections (CMEs) can accelerate charged particles in the solar corona and create transient enhancements of solar energetic particle fluxes in interplanetary space (SEP events). Fast CMEs and flares often occur together, which makes it difficult to directly identify the actual source of …
Physical Conditions in the Interstellar Medium toward HD 185418
Abel, N. P.; Ferland, G. J.; Srianand, R. +1 more
We have developed a complete model of the hydrogen molecule as part of the spectral simulation code Cloudy. Our goal is to apply this to spectra of high-redshift star-forming regions where H2 absorption is seen, but where few other details are known, to understand its implication for star formation. The microphysics of H2 is …
A Study of the Orientation of Interplanetary Magnetic Clouds and Solar Filaments
Wang, Yuming; Wang, Jingxiu; Wang, S. +2 more
As a kind of eruptive phenomenon associated with coronal mass ejections (CMEs), solar eruptive filaments are thought to be parallel to the axis of surrounding arcade coronal magnetic fields that erupt and develop into interplanetary magnetic clouds (MCs). By investigating three events from 2000 August, 2003 October, and 2003 November, we estimate …
XMM-Newton Observation of Diffuse Gas and Low-Mass X-Ray Binaries in the Elliptical Galaxy NGC 4649 (M60)
Sarazin, Craig L.; Irwin, Jimmy A.; Randall, Scott W.
We present an XMM-Newton X-ray observation of the X-ray-bright E2 elliptical galaxy NGC 4649. In addition to bright diffuse emission, we resolve 158 discrete sources, ~50 of which are likely to be LMXBs associated with NGC 4649. We find evidence for variability in three sources between this observation and a previous Chandra observation. Additiona…
Spectral States of the X-Ray Binary IGR J17091-3624 Observed by INTEGRAL and RXTE
Capitanio, F.; Bird, A. J.; Ubertini, P. +6 more
IGR J17091-3624 was discovered in 2003 April by IBIS, the gamma-ray imager on board the INTEGRAL satellite, during its Galactic Center Deep Exposure program. The source was initially detectable only in the 40-100 keV range but after 2 days was also detected in the 15-40 keV range. Its flux had by then increased to 40 and 25 mcrab in the 15-40 and …
Ultracompact Blue Dwarf Galaxies: Hubble Space Telescope Imaging and Stellar Population Analysis
Somerville, Rachel S.; Windhorst, Rogier A.; Vacca, William D. +3 more
We present deep Hubble Space Telescope (HST) Advanced Camera for Surveys/High Resolution Channel U-, narrow-V-, and I-band images of nine ``ultracompact'' blue dwarf galaxies (UCBDs) selected from the Sloan Digital Sky Survey (SDSS). We define UCBDs as local (z<0.01) star-forming galaxies having angular diameters less than 6" and physical diame…
High-Resolution Infrared Imaging of Herschel 36 SE: A Showcase for the Influence of Massive Stars in Cluster Environments
Pascucci, I.; Stecklum, B.; Henning, Th. +4 more
We present high-resolution infrared imaging of the massive star-forming region around the O star Herschel 36. Special emphasis is given to a compact infrared source at 0.25" southeast of the star. The infrared source, hereafter Her 36 SE, is extended in the broadband images but features spatially unresolved Brγ line emission. The line-emission sou…
The Binary Nucleus in VCC 128: A Candidate Supermassive Black Hole in a Dwarf Elliptical Galaxy
Pasquali, Anna; Seth, Anil; Debattista, Victor P. +3 more
Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) images of the Virgo Cluster dwarf elliptical galaxy VCC 128 reveal an apparently double nucleus. The two components, which are separated by ~32 pc in projection, have the same magnitude and color. We present a spectrum of this double nucleus and show that it is inconsistent with on…