Search Publications
Revealing the Interaction between the X-Ray Gas of Starburst Galaxy UGC 6697 and the Hot Intracluster Medium of A1367
Vikhlinin, A.; Sun, M.
We present the result from a Chandra observation of an X-ray-luminous starburst galaxy, UGC 6697, which is embedded in the northwest hot region of A1367 (5-6 keV). A very sharp X-ray edge (~13-fold surface brightness jump) at the southeast and a long tail (at least 60 kpc from the nucleus) at the northwest of the galaxy are detected, as expected i…
The Acoustic Showerglass. I. Seismic Diagnostics of Photospheric Magnetic Fields
Braun, D. C.; Lindsey, Charles
A problem of major interest in the helioseismology of active regions is the acoustics of magnetic photospheres and shallow subphotospheres. Magnetic fields suppress the photospheric signatures of acoustic waves impinging onto them from the underlying solar interior and shift their phases. The phase shifts function as a sort of acoustic showerglass…
On the Origin of Exponential Disks at High Redshift
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Vollbach, David R. +2 more
The major-axis and ellipse-fit intensity profiles of spiral galaxies larger than 0.3" in the Hubble Space Telescope Ultra Deep Field (UDF) are generally exponential, whereas the major-axis profiles in irregular disk galaxies, called clump clusters in our previous studies, are clearly not. Here we show that the deprojected positions of star-forming…
The Age and Progenitor Mass of Sirius B
Holberg, J. B.; Liebert, James; Williams, Kurtis A. +2 more
The Sirius AB binary system has masses that are well determined from many decades of astrometric measurements. Because of the well-measured radius and luminosity of Sirius A, we employed the TYCHO stellar evolution code to determine the age of the Sirius AB binary system accurately, at 225-250 Myr. Note that this fit requires the assumption of sol…
XMM-Newton Detection of Pulsations and a Spectral Feature in the X-Ray Emission of the Isolated Neutron Star 1RXS J214303.7+065419/RBS 1774
Treves, A.; Cropper, M.; Zane, S. +4 more
We report on the results of a deep XMM-Newton observation of RBS 1774, the most recent dim isolated neutron star candidate found in the ROSAT archive data. Spectral and timing analysis of the high-quality pn and MOS data confirm the association of this source with an isolated neutron star. The spectrum is thermal and blackbody-like, and there is e…
Mass Segregation and the Initial Mass Function of Super Star Cluster M82-F
Graham, James R.; McCrady, Nate; Vacca, William D.
We investigate the initial mass function and mass segregation in super star cluster M82-F with high-resolution Keck NIRSPEC echelle spectroscopy. Cross-correlation with template supergiant spectra provides the velocity dispersion of the cluster, enabling measurement of the kinematic (virial) mass of the cluster when combined with sizes from NICMOS…
INTEGRAL IGR J18135-1751 = HESS J1813-178: A New Cosmic High-Energy Accelerator from keV to TeV Energies
Walter, R.; Bird, A. J.; Ubertini, P. +10 more
We report the discovery of a soft gamma-ray source, namely, IGR J18135-1751, detected with IBIS, the Imager on Board the INTEGRAL Satellite. The source is persistent and has a 20-100 keV luminosity of ~5.7× 1034 ergs s-1 (assuming a distance of 4 kpc). This source is coincident with one of the eight unidentified objects recen…
System Parameters of the Transiting Extrasolar Planet HD 209458b
Henry, Gregory W.; Butler, R. P.; Wittenmyer, Robert A. +10 more
We derive improved system parameters for the HD 209458 system using a model that simultaneously fits both photometric transit and radial velocity observations. The photometry consists of previous Hubble Space Telescope STIS and FGS observations, 12 I-band transits observed between 2001 and 2003 with the Mount Laguna Observatory 1 m telescope, and …
A New Variety of Coronal Mass Ejection: Streamer Puffs from Compact Ejective Flares
Bemporad, A.; Poletto, G.; Moore, Ronald L. +1 more
We report on SOHO UVCS, LASCO, EIT, and MDI observations of a series of narrow ejections that occurred at the solar limb. These ejections originated from homologous compact flares whose source was an island of included polarity located just inside the base of a coronal streamer. Some of these ejections result in narrow CMEs (``streamer puffs'') th…
FUSE Measurements of Far-Ultraviolet Extinction. II. Magellanic Cloud Sight Lines
Martin, P. G.; Gordon, Karl D.; Sofia, Ulysses J. +8 more
We present an extinction analysis of nine reddened/comparison star pairs in the Large and Small Magellanic Clouds (LMC and SMC) based on Far-Ultraviolet Spectroscopic Explorer (FUSE) FUV observations. To date, just two LMC sight lines have probed dust grain composition and size distributions in the Magellanic Clouds using spectral data for wavelen…