Search Publications
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…
Ion Charge States in Halo Coronal Mass Ejections: What Can We Learn about the Explosion?
Laming, J. Martin; Rakowski, Cara E.; Lepri, Susan T.
We describe a new modeling approach to develop a more quantitative understanding of the charge state distributions of the ions of various elements detected in situ during halo coronal mass ejection (CME) events by the Advanced Composition Explorer (ACE) satellite. Using a model CME hydrodynamic evolution based on observations of CMEs propagating i…
Pismis 24-1: The Stellar Upper Mass Limit Preserved
Walborn, Nolan R.; Maíz Apellániz, J.; Morrell, N. I. +2 more
Is there a stellar upper mass limit? Recent statistical work seems to indicate that there is and that it is in the vicinity of 150 Msolar. In this paper we use HST and ground-based data to investigate the brightest members of the cluster Pismis 24, one of which (Pismis 24-1) was previously inferred to have a mass greater than 200 M…
An Investigation of the Origin of Soft X-Ray Excess Emission from Ark 564 and Mrk 1044
Rao, A. R.; Dewangan, G. C.; Griffiths, R. E. +1 more
We investigate the origin of the soft X-ray excess emission from Ark 564 and Mrk 1044. Based on a long XMM-Newton observation of Ark 564, we find clear evidence for time delays such that the variations in the 4-10 kev band lag behind that in the 0.2-0.5 kev band by 1768+/-122 s. The full-band power density spectrum (PDS) of Ark 564 has a break at …
A Time Delay for the Cluster-Lensed Quasar SDSS J1004+4112
Keeton, C. R.; Kochanek, C. S.; Maoz, D. +12 more
We present 426 epochs of optical monitoring data spanning 1000 days from 2003 December to 2006 June for the gravitationally lensed quasar SDSS J1004+4112. The time delay between the A and B images is ΔtBA=38.4+/-2.0 days (Δχ2=4) in the expected sense that B leads A and the overall time ordering is C-B-A-D-E. The measured dela…