arXiv subjects

B. Cordier

Publications and source records attributed to B. Cordier.

60 records · Page 4Linked to original sources

arXiv2003

Early SPI/INTEGRAL contraints on the morphology of the 511 keV line emission in the 4th galactic quadrant

We provide first constraints on the morphology of the 511 keV line emission from the galactic centre region on basis of data taken with the spectrometer SPI on the INTEGRAL gamma-ray observatory. The data suggest an azimuthally symmetric galactic bulge component with FWHM of ~9 deg with a 2 sigma uncertainty range covering 6-18 deg. The 511 keV line flux in the bulge component amounts to (9.9+4.7-2.1) 10e-4 ph cm-2 s-1. No evidence for a galactic disk component has been found so far; upper 2 sigma flux limits in the range (1.4-3.4) 10e-3 ph cm-2 s-1 have been obtained that depend on the assumed disk morphology. These limits correspond to lower limits on the bulge-to-disk ratio of 0.3-0.6.

astro-ph↗

arXiv2003

SIMBOL-X : a new generation hard X-ray telescope

SIMBOL-X is a hard X-ray mission, operating in the 0.5-70 keV range, which is proposed by a consortium of European laboratories for a launch around 2010. Relying on two spacecraft in a formation flying configuration, SIMBOL-X uses a 30 m focal length X-ray mirror to achieve an unprecedented angular resolution (30 arcsec HEW) and sensitivity (100 times better than INTEGRAL below 50 keV) in the hard X-ray range. SIMBOL-X will allow to elucidate fundamental questions in high energy astrophysics, such as the physics of accretion onto Black Holes, of acceleration in quasar jets and in supernovae remnants, or the nature of the hard X-ray diffuse emission. The scientific objectives and the baseline concepts of the mission and hardware design are presented.

astro-ph↗

arXiv2003

Simultaneous multi-wavelength observations of GRS 1915+105

We present the result of multi-wavelength observations of the microquasar GRS 1915+105 in a plateau state with a luminosity of ~7.5x10^{38) erg s-1 (~40% L_Edd), conducted simultaneously with the INTEGRAL and RXTE satellites, the ESO/NTT, the Ryle Telescope, the NRAO VLA and VLBA, in 2003 April 2-3. For the first time were observed concurrently in GRS 1915+105 all of the following properties: a strong steady optically thick radio emission corresponding to a powerful compact jet resolved with the VLBA, bright near-IR emission, a strong QPO at 2.5 Hz in the X-rays and a power law dominated spectrum without any cutoff in the 3-400 keV range.

astro-ph↗

arXiv2003

INTEGRAL/SPI ground calibration

Three calibration campaigns of the spectrometer SPI have been performed before launch in order to determine the instrument characteristics, such as the effective detection area, the spectral resolution and the angular resolution. Absolute determination of the effective area has been obtained from simulations and measurements. At 1 MeV, the effective area is 65 cm^2 for a point source on the optical axis, the spectral resolution ~2.3 keV. The angular resolution is better than 2.5 deg and the source separation capability about 1 deg. Some temperature dependant parameters will require permanent in-flight calibration.

astro-ph↗

arXiv2001

Observation of a Black-Hole X-ray Nova in Outburst with INTEGRAL

We simulate the observation of a bright Nova Musca-like X-ray nova during outburst with INTEGRAL, the next ESA gamma-ray space observatory. We will show how performances of the INTEGRAL instruments allow deep study of X-ray Novae and will evaluate the scientific output that INTEGRAL will provide on this class of transient gamma-ray sources, which are now believed to contain black holes in low mass binary systems. The variable high-energy feature around 511 keV observed from X-ray Nova Musca in 1991 by the SIGMA telescope would be detected by INTEGRAL at very high significance level. INTEGRAL data will permit to set important constraints on the models and allow to distinguish between electron-positron or nuclear de-excitation origin of the line. Characteristic spectral and timing features detected by INTEGRAL instruments over a very large energy band will also provide clues to understand physics of accretion in these black holes binaries and in particular to distinguish between thermal and non-thermal origin of radiation and to assess the role of bulk motion comptonization.

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arXiv1996

Two Distinct Modes In The Low (Hard) State Of Cyg X-1 And 1E1740-294

The entire dataset of the GRANAT/SIGMA observations of Cyg X-1 and 1E1740.7-294 in 1990-1994 was analyzed in order to search for correlations between primary observational characteristics of the hard X-ray emission - hard X-ray luminosity L_X, hardness of the spectrum (quantified in terms of the best fit thermal bremsstrahlung temperature kT) and the RMS of short term flux variations. Two distinct modes of the kT vs. L_X dependence were found for both sources. At low luminosity - below the level corresponding approximately to the gamma_1 state of Cyg X-1 - the kT increases as the L_X increases. Above the luminosity level of ~1.2L_gamma_1 the spectrum hardness is nearly constant (kT ~150 keV) and does not depend on the luminosity. In the case of Cyg X-1 the correlation of similar kind was found between the spectrum hardness and RMS of the short term flux variations. The increase of the kT, corresponding to the increasing branch on the kT vs. L_X diagram, is accompanied with increase of the RMS from few percent level to ~10-15%. Further increase of the RMS is not accompanied with change of the kT and does not correlate with changes in the luminosity.

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