Search Publications
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…
Elemental abundances in the atmosphere of clump giants
Soubiran, C.; Korotin, S. A.; Bienaymé, O. +4 more
Aims.The aim of this paper is to provide the fundamental parameters and abundances for a large sample of local clump giants with a high accuracy. This study is a part of a big project, in which the vertical distribution of the stars in the Galactic disc and the chemical and dynamical evolution of the Galaxy are being investigated.
Methods: .Th…
The XMM-Newton/Chandra monitoring campaign of the Galactic center region. Description of the program and preliminary results
Wijnands, R.; Homan, J.; van der Klis, M. +10 more
We present the first results of our X-ray monitoring campaign on a 1.7 square degree region centered on Sgr A* using the satellites XMM-Newton and Chandra. The purpose of this campaign is to monitor the behavior (below 10 keV) of X-ray sources (both persistent and transient) which are too faint to be detected by monitoring instruments aboard other…
The Chandra view of the 3C/FR I sample of low luminosity radio-galaxies
Capetti, A.; Grandi, P.; Balmaverde, B.
We present results from Chandra observations of the 3C/FR I sample of low luminosity radio-galaxies. We detected a power-law nuclear component in 12 objects out of the 18 with available data. In 4 galaxies we detected nuclear X-ray absorption at a level of NH ∼ (0.2{-}6) × 1022 cm-2. X-ray absorbed sources are asso…
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,…
X-ray nature of the LINER nuclear sources
Guerrero, M. A.; González-Martín, O.; Márquez, I. +2 more
We report the results from a homogeneous analysis of the X-ray (Chandra ACIS) data available for a sample of 51 LINER galaxies selected from the catalogue by Carrillo et al. (1999, Rev. Mex. Astron. Astrofis., 35, 187) and representative of the population of bright LINER sources. The nuclear X-ray morphology has been classified by their nuclear co…
On the AU Microscopii debris disk. Density profiles, grain properties, and dust dynamics
Augereau, J. -C.; Beust, H.
Context: .
Dynamical mass estimates for two luminous star clusters in galactic merger remnants
Saglia, R. P.; Bastian, N.; Zoccali, M. +4 more
We present high-dispersion spectra of two extremely massive star clusters in galactic merger remnants, obtained using the UVES spectrograph mounted on the ESO Very Large Telescope. One cluster, W30, is located in the ~500 Myr old merger remnant NGC 7252 and has a velocity dispersion and effective radius of σ=27.5±2.5 km s-1 and Ref…
Reconstruction of solar irradiance variations in cycles 21-23 based on surface magnetic fields
Solanki, S. K.; Krivova, N. A.; Fröhlich, C. +1 more
Aims.We present a reconstruction of total solar irradiance (TSI) back to 1974, i.e. from the minimum of cycle 21 to the declining phase of cycle 23. We also present a cross-calibration between the magnetograms obtained by the 512 channel magnetograph and the spectromagnetograph at Kitt Peak.
Methods: .The TSI reconstruction is carried out usin…
Detection of Wolf-Rayet stars in host galaxies of gamma-ray bursts (GRBs): are GRBs produced by runaway massive stars ejected from high stellar density regions?
Le Floc'h, E.; Schaerer, D.; Dessauges-Zavadsky, M. +3 more
We have obtained deep spectroscopic observations of several nearby gamma-ray burst (GRB) host galaxies revealing for the first time the presence of Wolf-Rayet (WR) stars and numerous O stars located in rich and compact clusters or star forming regions. Surprisingly, high spatial resolution imaging shows that the GRBs and the associated supernovae …