Search Publications
Cosmological Effects of Powerful AGN Outbursts in Galaxy Clusters: Insights from an XMM-Newton Observation of MS 0735+7421
McNamara, B. R.; Nulsen, P. E. J.; Gitti, M. +1 more
We report on the results of an analysis of XMM-Newton observations of MS 0735+7421, the galaxy cluster that hosts the most energetic AGN outburst currently known. The previous Chandra image shows twin giant X-ray cavities (~200 kpc diameter) filled with radio emission and surrounded by a weak shock front. XMM data are consistent with these finding…
Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf
Luhman, K. L.; McLeod, Kim K.; Hartmann, Lee +7 more
We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 µm spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosp…
Constraints on the Cosmic Near-Infrared Background Excess from NICMOS Deep Field Observations
Fan, Xiaohui; Kennicutt, Robert C.; Rieke, Marcia +2 more
NICMOS observations of the resolved object fluxes in the Hubble Deep Field-North and the Hubble Ultra Deep Field are significantly below the fluxes attributed to a 1.4-1.8 µm near-infrared background excess (NIRBE) from previous low spatial resolution NIRS measurements. Tests placing sources in the NICMOS image with fluxes sufficient to acco…
The Distance to the Isolated Neutron Star RX J0720.4-3125
van Kerkwijk, M. H.; Anderson, J.; Kaplan, D. L.
We have used a set of dedicated astrometric data from the Hubble Space Telescope to measure the parallax and proper motion of the nearby neutron star RX J0720.4-3125. At each of eight epochs over 2 years, we used the High Resolution Camera of the Advanced Camera for Surveys to measure the position of the B=26.6 target to a precision of ~2 mas (~0.…
Power Spectra of Black Holes and Neutron Stars as a Probe of Hydrodynamic Structure of the Source: Diffusion Theory and Its Application to Cygnus X-1 and Cygnus X-2 X-Ray Observations
Titarchuk, Lev; Shaposhnikov, Nikolai; Arefiev, Vadim
We present a model of Fourier power density spectrum (PDS) formation in accretion-powered X-ray binary systems derived from diffusion theory. Timing properties of X-ray emission are considered a result of diffusive propagation of the driving perturbations in a bounded medium. We prove that the integrated power Px of the resulting PDS is…
Type Ia and II Supernovae Contributions to Metal Enrichment in the Intracluster Medium Observed with Suzaku
Ishida, Manabu; Sato, Kosuke; Ohashi, Takaya +4 more
We studied the properties of the intracluster medium (ICM) in two clusters of galaxies (AWM 7 and Abell 1060) and two groups (HCG 62 and NGC 507) with the X-ray observatory Suzaku. Based on spatially resolved energy spectra, we measured for the first time precise cumulative ICM metal masses within 0.1 and ~0.3r180. Comparing our results…
The Relaxation of Sheared Magnetic Fields: A Contracting Process
Wang, Haimin; Ji, Haisheng; Huang, Guangli
In recent years, several authors have reported a contracting motion for solar flaring loops. That is, during the rising phase of solar flares, hard X-ray (HXR) loop-top sources or radio/extreme-ultraviolet (EUV) flaring loops have a descending motion and, at the same time, Hα ribbons or HXR footpoints (FPs) are converging. The usual expansion moti…
In/Out Pairs and the Detachment of Coronal Streamers
Sheeley, N. R., Jr.; Wang, Y. -M.
We previously described coronal events that originate in the 2-6 Rsolar field of view of the LASCO white-light coronagraph and involve the simultaneous ejection of material inward toward the Sun and outward away from it. Now, in a study of more than 160 in/out pairs, we have found that these features are density enhancements at the lead…
Energy Release Rates along Hα Flare Ribbons and the Location of Hard X-Ray Sources
Temmer, M.; Veronig, A. M.; Vršnak, B. +1 more
Local reconnection and energy release rates for an X3.8 flare that occurred on 2005 January 17 are derived. In particular, we distinguish between Hα flare ribbon segments that were accompanied by RHESSI hard X-ray (HXR) footpoints and those without HXRs. We find that the reconnection and energy release rates are not uniform along the flare ribbons…
XMM-Newton Observations of the Diffuse X-Ray Background
Covey, K.; Gupta, A.; Galeazzi, M. +1 more
We analyze two XMM-Newton observations toward the high-density, high-latitude, neutral hydrogen cloud MBM 20 and a nearby low-density region that we call the Eridanus hole. MBM 20 lies at a distance between 100 and 200 pc from the Sun, and its density is sufficient to shield about 75% of the foreground emission in the 3/4 keV energy band. The comb…