Search Publications
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 …
A Search for Discrete X-Ray Spectral Features in a Sample of Bright γ-Ray Burst Afterglows
Sako, Masao; Harrison, Fiona A.; Rutledge, Robert E.
We present uniform, detailed spectral analyses of γ-ray burst (GRB) X-ray afterglows observed with ASCA, BeppoSAX, Chandra, and XMM-Newton and critically evaluate the statistical significances of X-ray emission and absorption features in these spectra. The sample consists of 21 X-ray afterglow observations up to and including that of GRB 040106 wi…
UV Continuum Spectroscopy of a 6L* z = 5.5 Starburst Galaxy1,
Rosati, P.; Fazio, G. G.; van der Wel, A. +10 more
We have obtained a high S/N (22.3 hr integration) UV continuum VLT FORS2 spectrum of an extremely bright (z850=24.3) z = 5.515 +/- 0.003 star-forming galaxy (BD38) in the field of the z = 1.24 cluster RDCS 1252.9-2927. From HST Advanced Camera for Surveys imaging, this object was selected as a potential z ~ 6 Lyman break galaxy (LBG) ba…
XMM-Newton Spectroscopy of the Starburst-Dominated Ultraluminous Infrared Galaxy NGC 6240
Lutz, D.; Kaspi, Shai; Turner, T. J. +5 more
We present a new XMM-Newton observation of the ultraluminous infrared galaxy (ULIRG) NGC 6240. We analyze the reflecting grating spectrometer (RGS) data, as well as data from the other instruments, and find a starburst-dominated 0.5-3 keV spectrum with global properties resembling those observed in M82 but with a much higher luminosity. We show th…
The Look-back Time Evolution of Far-Ultraviolet Flux from Elliptical Galaxies: The Fornax Cluster and A2670
Rey, Soo-Chang; Heckman, Timothy M.; Madore, Barry F. +30 more
In order to investigate the origin of the far-UV (FUV) flux from the early-type galaxies, the Galaxy Evolution Explorer is collecting the UV data for the elliptical-rich clusters at moderate redshifts (z<0.2) where the dominant FUV source is predicted to be hot horizontal-branch (HB) stars and their post-HB progeny. Here we present our first re…