Search Publications
Chandra X-Ray Observatory Observations of the Globular Cluster M28 and Its Millisecond Pulsar PSR B1821-24
Pavlov, George G.; Weisskopf, Martin C.; Tennant, Allyn F. +8 more
We report here the results of the first Chandra X-Ray Observatory observations of the globular cluster M28 (NGC 6626). We detect 46 X-ray sources, of which 12 lie within 1 core radius of the center. We show that the apparently extended X-ray core emission seen with the ROSAT HRI is due to the superposition of multiple discrete sources, for which w…
The Black Hole Masses and Host Galaxies of BL Lacertae Objects
Ho, Luis C.; Barth, Aaron J.; Sargent, Wallace L. W.
We have measured the central stellar velocity dispersion in the host galaxies of 11 BL Lac objects with redshifts z<=0.125. The range of velocity dispersions, ~170-370 km s-1, is similar to that of nearby radio galaxies. Using the correlation between stellar velocity dispersion and black hole mass defined for nearby galaxies, we deri…
Source regions and storm effectiveness of frontside full halo coronal mass ejections
Webb, D. F.; Zhao, X. P.
Full halo coronal mass ejections (CMEs) erupting from the side of the Sun facing Earth, i.e., frontside full halo CMEs, are considered to be a likely cause of major, transient geomagnetic storms. However, this hypothesis has not been tested over a full solar cycle. We compare all frontside full halo CMEs observed during the first half of solar cyc…
ISO spectroscopy of star formation and active nuclei in the luminous infrared galaxy NGC 6240
Lutz, D.; Genzel, R.; Sturm, E. +4 more
We present Infrared Space Observatory mid- and far-infrared spectroscopy of the merging galaxy
A study of coronal abundances in RS CVn binaries%
Raassen, A. J. J.; Mewe, R.; Audard, M. +2 more
We present XMM-Newton data of several RS CVn binary systems. High-resolution X-ray spectra obtained with the Reflection Grating Spectrometers have been interpreted simultaneously with the European Photon Imaging Camera spectra. Highly active stars show a depletion of elements with a low first ionization potential (FIP) relative to high-FIP element…
Geminga's Tails: A Pulsar Bow Shock Probing the Interstellar Medium
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +5 more
We report the X-ray Multimirror Mission-Newton European Photon Imaging Camera observation of two elongated parallel x-ray tails trailing the pulsar Geminga. They are aligned with the object's supersonic motion, extend for ~2', and have a nonthermal spectrum produced by electron-synchrotron emission in the bow shock between the pulsar wind and the …
Star Formation at z~6: i-Dropouts in the Advanced Camera for Surveys Guaranteed Time Observation Fields
Ford, H. C.; Infante, L.; Zheng, W. +33 more
Using an i-z dropout criterion, we determine the space density of z~6 galaxies from two deep ACS GTO fields with deep optical-IR imaging. A total of 23 objects are found over 46 arcmin2, or ~0.5+/-0.1 objects arcmin-2 down to zAB~27.3 (6 σ), or a completeness-corrected ~0.5+/-0.2 objects arcmin-2 down to…
Addendum: Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling [Astron. J. 124, 3270 (2002)]
Gerssen, Joris; van der Marel, Roeland P.; Gebhardt, Karl +3 more
In Paper II, we reported the existence of a dark and compact mass component near the center of M15, based on an analysis of new data from the Hubble Space Telescope. Possible explanations for this mass component include (1) a single, intermediate-mass black hole (BH) and (2) a collection of dark remnants (e.g., neutron stars) that have sunk to the…
A self-consistent treatment of radiation in coronal loop modelling
Mason, H. E.; Bradshaw, S. J.
We perform a hydrodynamic simulation of a cooling coronal loop and calculate the time-dependent ion populations of the most abundant elements of the solar atmosphere at each time-step. We couple the time-dependent ion balance equations to the hydrodynamic equations in order to treat the energy loss through radiation in a self-consistent way by all…
Entropy scaling in galaxy clusters: Insights from an XMM-Newton observation of the poor cluster A1983
Arnaud, M.; Pratt, G. W.
An XMM-Newton observation of the cool (kT =2.1 keV ) cluster A1983, at z=0.044, is presented. Gas density and temperature profiles are calculated over the radial range up to 500 h50-1 kpc, corresponding to ~ 0.35 rv . The outer regions of the surface brightness profile are well described with a beta -model with beta =0.74, bu…