Search Publications
High-Energy Gamma Rays from the Massive Black Hole in the Galactic Center
Aharonian, F.; Neronov, A.
Accreting black holes (BHs) are believed to be sites of possible particle acceleration with conditions that are also favorable for effective gamma-ray production. However, because of photon-photon pair production, only low-energy (MeV) gamma rays can escape these compact objects with typically very large compactness parameters, κ=(L/LEdd
Discovery of the Accretion-powered Millisecond X-Ray Pulsar IGR J00291+5934
Chakrabarty, Deepto; Galloway, Duncan K.; Markwardt, Craig B. +2 more
We report on observations of the sixth accretion-powered millisecond pulsar, IGR J00291+5934, with the Rossi X-Ray Timing Explorer. The source is a faint recurrent X-ray transient initially identified by the International Gamma-Ray Astrophysics Laboratory. The 599 Hz (1.67 ms) pulsation had a fractional rms amplitude of 8% in the 2-20 keV range, a…
The First Giant Flare from SGR 1806-20: Observations Using the Anticoincidence Shield of the Spectrometer on INTEGRAL
Götz, D.; Mereghetti, S.; von Kienlin, A. +4 more
A giant flare from the soft gamma-ray repeater SGR 1806-20 has been discovered with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) on 2004 December 27 and detected by many other satellites. This tremendous outburst, the first one observed from this source, was a hundred times more powerful than the two giant flares previously obser…
An XMM-Newton View of the Soft Gamma Repeater SGR 1806-20: Long-Term Variability in the Pre-Giant Flare Epoch
Tiengo, A.; Götz, D.; Mereghetti, S. +7 more
The low-energy (<10 keV) X-ray emission of the soft gamma repeater SGR 1806-20 has been studied by means of four XMM-Newton observations carried out in the last two years, the latest performed in response to a strong sequence of hard X-ray bursts observed on 2004 October 5. The source was caught in different states of activity; over the 2003-20…
INTEGRAL IGR J18135-1751 = HESS J1813-178: A New Cosmic High-Energy Accelerator from keV to TeV Energies
Walter, R.; Bird, A. J.; Ubertini, P. +10 more
We report the discovery of a soft gamma-ray source, namely, IGR J18135-1751, detected with IBIS, the Imager on Board the INTEGRAL Satellite. The source is persistent and has a 20-100 keV luminosity of ~5.7× 1034 ergs s-1 (assuming a distance of 4 kpc). This source is coincident with one of the eight unidentified objects recen…
X-Ray Observations of the Black Hole Transient 4U 1630-47 during 2 Years of X-Ray Activity
Kaaret, Philip; Goldwurm, Andrea; Tomsick, John A. +1 more
The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for more than 2 years during its 2002-2004 outburst, which is one of the brightest and longest outbursts ever seen from this source. We use more than 300 observations made with the Rossi X-Ray Timing Explorer (RXTE) to study the source throughout …
INTEGRAL SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane
Hornstrup, A.; Parmar, A. N.; Güdel, M. +25 more
The center of our Galaxy is a known strong source of electron-positron 511 keV annihilation radiation. Thus far, however, there have been no reliable detections of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched in …
Extragalactic Source Counts in the 20-50 keV Energy Band from the Deep Observation of the Coma Region by INTEGRAL IBIS
Sunyaev, R.; Krivonos, R.; Churazov, E. +3 more
We present the analysis of serendipitous sources in a deep, 500 ks, hard X-ray observation of the Coma Cluster region with the IBIS instrument on board INTEGRAL. In addition to the Coma Cluster, the final 20-50 keV image contains 12 serendipitous sources with statistical significance >4 σ. We use these data (after correcting for expected number…
XTE J1550-564: INTEGRAL Observations of a Failed Outburst
Shrader, C. R.; Sturner, S. J.
The well-known black hole X-ray binary transient XTE J1550-564 underwent an outburst during the spring of 2003, which was substantially underluminous in comparison to previous periods of peak activity in that source. In addition, our analysis shows that it apparently remained in the hard spectral state over the duration of that outburst. This is a…
Theoretical Interpretation of the Luminosity and Spectral Properties of GRB 031203
Ruffini, Remo; Bernardini, Maria Grazia; Fraschetti, Federico +3 more
The X-ray and gamma-ray observations of the source GRB 031203 by INTEGRAL are interpreted within our theoretical model. In addition to a complete spacetime parameterization of the GRB, we specifically assume that the afterglow emission originates from a thermal spectrum in the comoving frame of the expanding baryonic matter shell. By determining t…