Search Publications
Spectral analysis of the Galactic e+e- annihilation emission
Knödlseder, J.; Marcowith, A.; Guessoum, N. +5 more
We present a spectral analysis of the e+e- annihilation emission from the Galactic Centre region based on the first year of measurements made with the spectrometer SPI of the INTEGRAL mission. We have found that the annihilation spectrum can be modelled by the sum of a narrow and a broad 511 keV line plus an ortho-positronium…
Origin of the Galactic ridge X-ray emission
Sunyaev, R.; Revnivtsev, M.; Sazonov, S. +2 more
We analyze a map of the Galactic ridge X-ray emission (GRXE) constructed in the 3-20 keV energy band from RXTE/PCA scan and slew observations. We show that the GRXE intensity follows the Galactic near-infrared surface brightness closely and thus traces the Galactic stellar mass distribution. The GRXE consists of two spatial components that can be …
The unprecedented optical outburst of the quasar 3C 454.3 . The WEBT campaign of 2004-2005
Lee, C. -U.; Lähteenmäki, A.; Umana, G. +85 more
Context: .The radio quasar
Aims: .In order to follow the emission behaviour of the …
XMM-Newton and INTEGRAL observations of new absorbed supergiant high-mass X-ray binaries
Parmar, A. N.; Walter, R.; Ubertini, P. +7 more
Context: .During the first year in operation, INTEGRAL, the European Space Agency's γ-ray observatory, has detected more than 28 new bright sources in the galactic plane which emit the bulk of their emission above 10 keV.
Aims: .To understand the nature of those sources we have obtained follow-up observations in the X-ray band with XMM-Newton.…
Unveiling the nature of INTEGRAL objects through optical spectroscopy. V. Identification and properties of 21 southern hard X-ray sources
Palazzi, E.; Minniti, D.; Masetti, N. +13 more
Optical spectroscopic identification of the nature of 21 unidentified southern hard X-ray objects is reported here in the framework of our campaign aimed at determining the nature of newly-discovered and/or unidentified sources detected by INTEGRAL. Our results show that 5 of these objects are magnetic Cataclysmic Variables (CVs), 4 are High-Mass …
Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14
Tiengo, A.; Götz, D.; Mereghetti, S. +1 more
Using 2.5 Ms of data obtained by the INTEGRAL satellite in 2003-2004, we discovered persistent hard X-ray emission from the soft gamma-ray repeater SGR 1900+14. Its 20-100 keV spectrum is well described by a steep power law with photon index Γ=3.1±0.5 and flux 1.5×10-11 erg cm-2 s-1. Contrary to SGR 1806-20, the on…
The sky distribution of positronium annihilation continuum emission measured with SPI/INTEGRAL
Knödlseder, J.; Shrader, C. R.; Schanne, S. +15 more
We present a measurement of the sky distribution of positronium (Ps) annihilation continuum emission obtained with the SPI spectrometer on board ESA's INTEGRAL observatory. The only sky region from which significant Ps continuum emission is detected is the Galactic bulge. The Ps continuum emission is circularly symmetric about the Galactic centre,…
IGR J17544-2619 : a new supergiant fast X-ray transient revealed by optical/infrared observations
Chaty, S.; Negueruela, I.; Pellizza, L. J.
One of the most recent discoveries of the INTEGRAL observatory is the existence of a previously unknown population of X-ray sources in the inner arms of the Galaxy.
Average hard X-ray emission from NS LMXBs: observational evidence of different spectral states in NS LMXBs
Titarchuk, L.; Frontera, F.; Goldoni, P. +9 more
Aims.We studied and compared the long-term average hard X-ray (>20 keV) spectra of a sample of twelve bright low-mass X-ray binaries hosting a neutron star (NS). Our sample comprises the six well studied Galactic Z sources and six Atoll sources, four of which are bright (“GX”) bulge sources while two are weaker ones in the 2-10 keV range (H 175…
INTEGRAL observations of the blazar 3C 454.3 in outburst
Maraschi, L.; Tagliaferri, G.; Ghisellini, G. +22 more
In Spring 2005, the blazar 3C 454.3 underwent a dramatic outburst at all wavelengths from mm to X-rays. This prompted INTEGRAL observations, accomplished in 15-18 May 2005. The source was detected by the INTEGRAL instruments from 3 to 200 keV in a bright state (∼ 5 × 10-10 erg s-1 cm-2), at least a factor of 2-3 hi…