Catching Up on State Transitions in Cygnus X-1 (2008)
Boeck, Moritz, Hanke, Manfred, Wilms, Joern, Grinberg, Victoria, Pottschmidt, Katja, Markoff, Sera, ...
In 2005 February we observed Cygnus X-1 over a period of 10 days quasi-continuously with the Rossi X-ray Timing Explorer and the Ryle telescope. We present the results of the spectral and timing...
Multi-Satellite Observations of Cygnus X-1 to Study the Focused Wind and Absorption Dips (2008)
Hanke, Manfred, Wilms, Joern, Boeck, Moritz, Nowak, Michael A., Schulz, Norbert S., Pottschmidt, Katja, ...
High-mass X-ray binary systems are powered by the stellar wind of their donor stars. The X-ray state of Cygnus X-1 is correlated with the properties of the wind which defines the environment of mass...
High variability in Vela X-1: giant flares and off states (2008)
Kreykenbohm, Ingo, Wilms, Joern, Kretschmar, Peter, Torrejon, Jose Miguel, Pottschmidt, Katja, Hanke, Manfred, ...
We investigate the spectral and temporal behavior of the high mass X-ray binary Vela X-1 during a phase of high activity, with special focus on the observed giant flares and off states. INTEGRAL...
Reynolds, Christopher S., Nowak, Michael A., Markoff, Sera, Tueller, Jack, Wilms, Joern, Young, Andrew J.
[abridged] We present an X-ray study of the low-luminosity active galactic nucleus (AGN) in NGC4258 using data from Suzaku, XMM-Newton, and the Swift/BAT survey. We find that signatures of X-ray...
Nowak, Michael A., Juett, Adrienne, Homan, Jeroen, Yao, Yangsen, Wilms, Joern, Schulz, Norbert S., ...
We present simultaneous Chandra-HETG and RXTE observations of a moderate flux `soft state' of the black hole candidate 4U1957+11. These spectra, having a minimally discernible hard X-ray excess, are...
Hanke, Manfred, Wilms, Joern, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Lee, Julia C.
We present analyses of a 50 ks observation of the supergiant X-ray binary system Cygnus X-1/HDE 226868 taken with the Chandra High Energy Transmission Grating Spectrometer (HETGS). Cyg X-1 was in its...
Tracking the Orbital and Super-orbital Periods of SMC X-1 (2007)
Trowbridge, Sarah, Nowak, Michael A., Wilms, Joern
The High Mass X-ray Binary (HMXB) SMC X-1 demonstrates an orbital variation of 3.89 days and a super-orbital variation with an average length of 55 days. As we show here, however, the length of the...
Wilms, Joern, Pottschmidt, Katja, Pooley, Guy G., Markoff, Sera, Nowak, Michael A., Kreykenbohm, Ingo, ...
We report on the first detection of a quasi-simultaneous radio-X-ray flare of Cygnus X-1. The detection was made on 2005 April 16 with pointed observations by the Rossi X-ray Timing Explorer and the...
Accreting X-ray pulsars observed with Integral (2007)
Kreykenbohm, Ingo, Fritz, Sonja, Mowlavi, Nami, Wilms, Joern, Kretschmar, Peter, Staubert, Ruediger, ...
In this paper, we review the observational properties of two accreting X-ray pulsars, the persistent source 4U1907+09 and the transient V0332+53. Accreting X-ray pulsars are among the brightest...
INTEGRAL observation of the accreting pulsar GX 1+4 (2006)
Ferrigno, Carlo, Segreto, Alberto, Santangelo, Andrea, Wilms, Joern, Kreykenbohm, Ingo, Denis, Miroslav, ...
We present the results of the INTEGRAL monitoring campaign on the accreting low mass X-ray binary pulsar GX 1+4 performed during the Galactic plane scan of the INTEGRAL Core Programme. The source was...
INTEGRAL and RXTE Observations of Centaurus A (2005)
Rothschild, Richard E., Wilms, Joern, Tomsick, John, Staubert, Ruediger, Benlloch, Sara, Collmar, Werner, ...
INTEGRAL and RXTE performed three simultaneous observations of the nearby radio galaxy Cen A in 2003 March, 2004 January, and 2004 February with the goals of investigating the geometry and emission...
Is the `IR Coincidence' Just That? (2005)
Nowak, Michael, Wilms, Joern, Heinz, Sebastian, Pooley, Guy, Pottschmidt, Katja, Corbel, Stephane
(Abridged) Motch (1985) suggested that in the hard state of GX 339-4 the soft X-ray power-law extrapolated backward in energy agrees with the IR flux. Corbel & Fender (2002) showed that the hard...
The variable cyclotron line in GX 301-2 (2004)
Kreykenbohm, Ingo, Wilms, Joern, Coburn, Wayne, Kuster, Markus, Rothschild, Richard E., Heindl, William A., ...
We present pulse phase resolved spectra of the hypergiant high mass X-ray binary GX 301-2. We observed the source in 2001 October with RXTE continuously for a total on-source time of almost 200ksec....
Iron Line Spectroscopy of NGC4593 with XMM-Newton: Where is the Black Hole Accretion Disk? (2004)
Reynolds, Christopher S., Brenneman, Laura W., Wilms, Joern, Kaiser, Mary Elizabeth
We present an analysis of the 2-10keV XMM-Newton/EPIC-pn spectrum of the Seyfert-1 galaxy NGC4593. Apart from the presence of two narrow emission lines corresponding to the Kalpha lines of cold and...
Nowak, Michael A., Wilms, Joern, Dove, James B.
We present spectral fits and timing analysis of Rossi X-ray Timing Explorer observations of GX339-4. These observations were carried out over a span of more than two years and encompassed both the...
Wilms, Joern, Reynolds, Christopher S., Begelman, Mitchell C., Reeves, James, Molendi, Silvano, Stuabert, Ruediger, ...
We present XMM-Newton European Photon Imaging Camera (EPIC) observations of the bright Seyfert 1 galaxy MCG-6-30-15, focusing on the broad Fe K$\alpha$ line at ~6keV and the associated reflection...
Lehr, Dana E., Wagoner, Robert V., Wilms, Joern
We report the development of a new tool to determine the origin of quasi-periodic oscillations (QPOs) in accretion disk systems. The technique uses the source energy spectrum and the energy...
Wilms, Joern, Nowak, Michael, Dove, James B., Fender, Robert P., Di Matteo, Tiziana
We discuss a series of observations of the black hole candidate GX 339-4 in low luminosity, spectrally hard states. We present spectral analysis of three separate archival Advanced Satellite for...
On the enigmatic X-ray Source V1408 Aql (=4U 1957+11) (1999)
Nowak, Michael A., Wilms, Joern
Models for the characteristically soft X-ray spectrum of the compact X-ray source V1498 Aql (=4U 1957+11) have ranged from optically thick Comptonization to multicolor accretion disk models. We...
Low Luminosity States of the Black Hole Candidate GX~339--4. II. Timing Analysis (1998)
Nowak, Michael A., Wilms, Joern, Dove, James B.
Here we present timing analysis of a set of eight Rossi X-ray Timing Explorer (RXTE) observations of the black hole candidate GX 339-4 that were taken during its hard/low state. On long time scales,...
RXTE Observation of Cygnus X--1: III. Implications for Compton Corona and ADAF Models (1998)
Nowak, Michael A., Wilms, Joern, Vaughan, Brian A., Dove, James B., Begelman, Mitchell C.
We have recently shown that a `sphere+disk' geometry Compton corona model provides a good description of Rossi X-ray Timing Explorer (RXTE) observations of the hard/low state of Cygnus X--1....
RXTE Observation of Cygnus X-1: II. Timing Analysis (1998)
Nowak, Michael A., Vaughan, Brian A., Wilms, Joern, Dove, James B., Begelman, Mitchell C.
We present timing analysis for a Rossi X-ray Timing Explorer observation of Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg X-1 taken after it transited back to this...
Cygnus X-1: A Case for a Magnetic Accretion Disk? (1996)
Nowak, Michael A., Vaughan, Brian A., Dove, James, Wilms, Joern
With the advent of RXTE, which is capable of broad spectral coverage and fast timing, as well as other instruments which are increasingly being used in multi-wavelength campaigns (via both...