Search Publications
Characterization of Intracluster Medium Temperature Distributions of 62 Galaxy Clusters with XMM-Newton
Fabian, A. C.; Sanders, J. S.; Peterson, J. R. +2 more
We measure the intracluster medium (ICM) temperature distributions for 62 galaxy clusters in the HIFLUGCS, an X-ray flux-limited sample, with available X-ray data from XMM-Newton. We search for correlations between the width of the temperature distributions and other cluster properties, including median cluster temperature, luminosity, size, prese…
An Archival Chandra and XMM-Newton Survey of Type 2 Quasars
Heckman, Timothy; Zakamska, Nadia L.; Ptak, Andrew +1 more
In order to investigate obscuration in high-luminosity type 2 active galactic nuclei (AGNs), we analyzed Chandra and XMM-Newton archival observations for 71 type 2 quasars detected at 0.05 < z < 0.73, which were selected based on their [O III] λ5007 emission lines. For 54 objects with good spectral fits, the observed hard X-ray luminosity ra…
The Cosmic Evolution of Faint Satellite Galaxies as a Test of Galaxy Formation and the Nature of Dark Matter
Wang, W.; Treu, T.; Lu, Y. +2 more
The standard cosmological model based on cold dark matter (CDM) predicts a large number of subhalos for each galaxy-size halo. Matching the subhalos to the observed properties of luminous satellites of galaxies in the local universe poses a significant challenge to our understanding of the astrophysics of galaxy formation. We show that the cosmic …
An extended main-sequence turn-off in the Small Magellanic Cloud star cluster NGC 411
Girardi, Léo; Chandar, Rupali; Marigo, Paola +8 more
Based on new observations with the Wide Field Camera 3 onboard the Hubble Space Telescope, we report the discovery of an extended main-sequence turn-off (eMSTO) in the intermediate-age star cluster NGC 411. This is the second case of an eMSTO being identified in a star cluster belonging to the Small Magellanic Cloud (SMC), after NGC 419. Despite t…
Rapid Gamma-Ray Flux Variability during the 2013 March Crab Nebula Flare
Cheung, C. C.; Grove, J. E.; Hays, E. +5 more
We report on a bright flare in the Crab Nebula detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The period of significantly increased luminosity occurred in 2013 March and lasted for approximately two weeks. During this period, we observed flux variability on timescales of approximately 5 hr. The combined ph…
Seasonal variations of temperature, acetylene and ethane in Saturn's atmosphere from 2005 to 2010, as observed by Cassini-CIRS
Fletcher, L. N.; Irwin, P. G. J.; Sinclair, J. A. +6 more
Acetylene (C2H2) and ethane (C2H6) are by-products of complex photochemistry in the stratosphere of Saturn. Both hydrocarbons are important to the thermal balance of Saturn's stratosphere and serve as tracers of vertical motion in the lower stratosphere. Earlier studies of Saturn's hydrocarbons using Cas…
Resonant scattering in the Perseus Cluster: spectral model for constraining gas motions with Astro-H
Simionescu, A.; Sunyaev, R.; Sazonov, S. +6 more
X-ray spectra from cores of galaxy clusters can be strongly distorted by resonant scattering of line photons, affecting metal abundance and gas velocity measurements. We introduce simulated spectral models that take into account the resonant scattering effect, radial variations of thermodynamic properties of the hot gas, projection effects and sma…
Activity of the Seyfert galaxy neighbours
Georgantopoulos, I.; Chavushyan, V.; Plionis, M. +4 more
We present a follow-up study of a series of papers concerning the role of close interactions as a possible triggering mechanism of AGN activity. We have already studied the close (≤100 h-1 kpc) and the large-scale (≤1 h-1 Mpc) environment of a local sample of Sy1, Sy2, and bright IRAS galaxies (BIRG) and of their respective c…
Propagation Characteristics of CMEs Associated with Magnetic Clouds and Ejecta
Cho, K. -S.; Moon, Y. -J.; Gopalswamy, N. +2 more
We have investigated the characteristics of magnetic cloud (MC) and ejecta (EJ) associated coronal mass ejections (CMEs) based on the assumption that all CMEs have a flux rope structure. For this, we used 54 CMEs and their interplanetary counterparts (interplanetary CMEs: ICMEs) that constitute the list of events used by the NASA/LWS Coordinated D…
Timing and Spectral Properties of Be/X-Ray Pulsar EXO 2030+375 during a Type I Outburst
Maitra, Chandreyee; Paul, Biswajit; Naik, Sachindra +1 more
We present results from a study of broadband timing and spectral properties of EXO 2030+375 using a Suzaku observation. Pulsations with a period of 41.41 s and strong energy-dependent pulse profiles were clearly detected up to 100 keV. Narrow dips are seen in the profiles up to ~70 keV. The presence of prominent dips at several phases in the profi…