Search Publications
The Absorption Signature of Six Mg II-selected Systems over 0.5 <= z <= 0.9
Charlton, Jane C.; Churchill, Christopher W.; Ding, Jie
We present the results of photoionization modeling of six Mg II-selected absorption systems, at redshift 0.5<=z<=0.9, along lines of sight toward three quasars: PG 1241+176, PG 1248+401, and PG 1317+274. These are part of a larger sample of ~20 Mg II absorbers at intermediate redshift, which facilitates a survey of the properties of, and pro…
Large-Scale CO and [C I] Emission in the ρ Ophiuchi Molecular Cloud
Kulesa, Craig A.; Hungerford, Aimee L.; Walker, Christopher K. +2 more
We present a comprehensive study of the ρ Ophiuchi molecular cloud that addresses aspects of the physical structure and condition of the molecular cloud and its photodissociation region (PDR) by combining far-infrared and submillimeter-wave observations with a wide range of angular scale and resolution. We present 1600 arcmin2 maps (2.3…
X-Ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years
Filippenko, Alexei V.; Greenhill, Lincoln J.; Fruscione, Antonella +3 more
We report monitoring of the 0.3-10 keV spectrum of NGC 4258 with the XMM-Newton Observatory at five epochs over 1.5 yr. We also report reprocessing of an overlapping four-epoch series of archival Chandra observations (0.5-10 keV). By including earlier ASCA and BeppoSAX observations, we present a new, 9 year time series of models fitted to the X-ra…
The 10 µm Feature of M-Type Stars in the Large Magellanic Cloud and the Dust Condensation Sequence
Abraham, P.; Speck, A. K.; Dijkstra, C. +1 more
We present 7-14 µm Infrared Space Observatory (ISO) spectroscopy of 12 M-type evolved stars in the Large Magellanic Cloud (LMC), in order to study the dust mineralogy and condensation process around these stars. The sample stars show a broad dust feature in the 7-14 µm region, which is seen in either emission or (self-) absorption. The…
The Model Dependence of Solar Energetic Particle Mean Free Paths under Weak Scattering
Mason, G. M.; Zhang, M.; Qin, G. +2 more
The mean free path is widely used to measure the level of solar energetic particles' diffusive transport. We model a solar energetic particle event observed by Wind STEP at 0.31-0.62 MeV nucleon-1, by solving the focused transport equation using the Markov stochastic process theory. With different functions of the pitch angle diffusion …
Comparison of Interplanetary Disturbances at the NEAR Spacecraft with Coronal Mass Ejections at the Sun
Russell, C. T.; Andrews, M. D.; Mulligan, T. +4 more
We examined interplanetary (IP) magnetic field disturbances recorded by the Near Earth Asteroid Rendezvous-Shoemaker spacecraft (NEAR) when it was above either the east or west solar limb as seen from Earth; we then identified the associated coronal mass ejections (CMEs) detected above the limbs by the SOHO LASCO coronagraph. We found 10 cases in …
Luminous X-Ray Flares from Low-Mass X-Ray Binary Candidates in the Early-Type Galaxy NGC 4697
Sarazin, Craig L.; Jordán, Andrés; Sivakoff, Gregory R.
We report results of the first search specifically targeting short-timescale X-ray flares from low-mass X-ray binaries in an early-type galaxy. A new method for flare detection is presented. In NGC 4697, the nearest, optically luminous, X-ray-faint elliptical galaxy, three out of 157 sources are found to display flares at >99.95% probability, a…
Variation in the Scattering Shroud Surrounding Markarian 231
Brandt, W. N.; Chartas, G.; Gallagher, S. C. +5 more
We present a detailed study of the nuclear structure of the highly polarized broad absorption line quasar, Mrk 231, through a multiwavelength campaign of Chandra observations, optical spectroscopy, optical spectropolarimetry, and imaging polarimetry. This campaign was designed to extend the 40 ks Chandra study of Gallagher and coworkers and the op…
Chandra Study of X-Ray Point Sources in the Early-Type Galaxy NGC 4552 (M89)
Kundu, Arunav; Xu, Haiguang; Zhang, Zhongli +3 more
We present a Chandra ACIS study of the early-type galaxy NGC 4552. We detect 47 X-ray point sources, most of which are likely low-mass X-ray binaries (LMXBs), within four effective radii (Re). The brightest X-ray source coincides with the optical, UV, and radio center of the galaxy and shows variability on >1 hr timescales, indicatin…
Submillimeter Array Observations of Disks in the SR 24 Multiple Star System
Andrews, Sean M.; Williams, Jonathan P.
We present high-resolution aperture synthesis images from the Submillimeter Array of the 225 GHz (1.3 mm) continuum and 12CO J=2-1 line emission from the disks around components of the hierarchical triple system SR 24, located in the Ophiuchus star-forming region. The most widely separated component, SR 24 S (with a projected semimajor …