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An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?
Baum, Stefi A.; O'Dea, Christopher P.; Sarazin, Craig L. +12 more
Quillen et al. presented an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray-luminous clusters. They found that at least half of these sources have signs of excess IR emission. Here we discuss the nature of the IR emission and its implications for cool core cl…
The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei
Maiolino, Roberto; Brandt, W. N.; Kaspi, Shai +2 more
We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3-3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/LEdd) and the hard X-ray photon index (Γ) for 35 moderate- to high-lum…
A Spitzer View of Protoplanetary Disks in the γ Velorum Cluster
Jeffries, R. D.; Gutermuth, R.; Stauffer, J. +4 more
We present new Spitzer Space Telescope observations of stars in the young (~5 Myr) γ Velorum stellar cluster. Combining optical and 2MASS photometry, we have selected 579 stars as candidate members of the cluster. With the addition of the Spitzer mid-infrared data, we have identified five debris disks around A-type stars and five to six debris dis…
The Coincidence of Nuclear Star Clusters and Active Galactic Nuclei
Seth, Anil; Basu-Zych, Antara; Agüeros, Marcel +1 more
We study galaxies that host both nuclear star clusters and AGNs, implying the presence of a massive black hole. We select a sample of 176 galaxies with previously detected nuclear star clusters that range from ellipticals to late-type spirals. We search for AGNs in this sample using optical spectroscopy and archival radio and X-ray data. We find g…
Resonant Cyclotron Scattering in Magnetars' Emission
Götz, D.; Rea, N.; Lyutikov, M. +2 more
We present a systematic fit of a model of resonant cyclotron scattering (RCS) to the X-ray data of 10 magnetars, including canonical and transient anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs). In this scenario, nonthermal magnetar spectra in the soft X-rays (i.e., below ~10 keV) result from resonant cyclotron scattering of the th…
The X-Ray Spectral Evolution in X-Ray Binaries and Its Application to Constrain the Black Hole Mass of Ultraluminous X-Ray Sources
Wu, Qingwen; Gu, Minfeng
We investigate the relationship between the hard X-ray photon index Γ and the Eddington ratio [ξ = LX(0.5-25 keV)/LEdd] in six X-ray binaries (XRBs) with well-constrained black hole masses and distances. We find that different XRBs follow different anticorrelations between Γ and ξ when ξ is less than a critical value, while Γ…
Extrasolar Giant Planets and X-Ray Activity
Drake, Jeremy J.; Kashyap, Vinay L.; Saar, Steven H.
We have carried out a survey of X-ray emission from stars with giant planets, combining both archival and targeted surveys. Over 230 stars have been currently identified as possessing planets, and roughly one-third of these have been detected in X-rays. We carry out detailed statistical analysis on a volume-limited sample of main-sequence star sys…
Precise Measurement of the Spin Parameter of the Stellar-Mass Black Hole M33 X-7
McClintock, Jeffrey E.; Liu, Jifeng; Davis, Shane W. +2 more
In prior work, Chandra and Gemini-North observations of the eclipsing X-ray binary M33 X-7 have yielded measurements of the mass of its black hole primary and the system's orbital inclination angle of unprecedented accuracy. Likewise, the distance to the binary is known to a few percent. In an analysis based on these precise results, 15 Chandra an…
Are Optically Selected Quasars Universally X-Ray Luminous? X-Ray-UV Relations in Sloan Digital Sky Survey Quasars
Brandt, W. N.; Schneider, Donald P.; Gibson, Robert R.
We analyze archived Chandra and XMM-Newton X-ray observations of 536 Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) quasars (QSOs) at 1.7 <= z<= 2.7 in order to characterize the relative UV and X-ray spectral properties of QSOs that do not have broad UV absorption lines (BALs). We constrain the fraction of X-ray-weak, non-BAL QSOs and …
X-Ray Properties of an Unbiased Hard X-Ray-detected Sample of Active Galactic Nuclei
Mushotzky, Richard F.; Tueller, Jack; Markwardt, Craig +1 more
The Swift gamma-ray observatory's Burst Alert Telescope (BAT) has detected a sample of AGNs based solely on their hard X-ray flux (14-195 keV). In this paper we present for the first time XMM-Newton X-ray spectra for 22 BAT AGNs with no previously analyzed X-ray spectra. If our sources are a representative sample of the BAT AGNs, as we claim, our …