Search Publications
Light variations of massive stars (α Cyg variables). XIX. The late-type supergiants R 59, HDE 268822, HDE 269355, HDE 269612 and HDE 270025 in the LMC
Sterken, C.; van Genderen, A. M.; Jones, A. F.
We present and discuss VBLUW photometry (Walraven system) of five supergiants in the LMC. For one well-known variable, the hypergiant R 59 = HDE 268757 (G7 Ia+) also Hipparcos photometry and numerous visual observations are available. The second variable is HDE 269612 (F0 Ia), and a third one is HDE 268822 (F6 Ia). Two F6 Ia supergiants…
The first XMM-Newton study of two Narrow-Line Seyfert 1 galaxies discovered in the Sloan Digital Sky Survey
Ponti, G.; Grandi, P.; Foschini, L. +6 more
The Early Data Release of the Sloan Digital Sky Survey (SDSS) contains 150 Narrow-Line Seyfert 1 (NLS1) galaxies, most of them previously unknown. We present here the study of the X-ray emission from two of these active galaxies (SDSS J030639.57+000343.2 and SDSS J141519.50-003021.6), based upon XMM-Newton observations. The spectral and timing cha…
A new mass-ratio for the X-ray binary X2127+119 in M 15?
Charles, P. A.; Naylor, T.; Ioannou, Z. +1 more
The luminous low-mass X-ray binary X2127+119 in the core of the globular cluster M 15 (NGC 7078), which has an orbital period of 17 hours, has long been assumed to contain a donor star evolving off the main sequence, with a mass of 0.8 M⊙space (the main-sequence turn-off mass for M 15). We present orbital-phase-resolved spectroscopy of …
The circumstellar environment of the star V923 Aquilae
Ringuelet, A. E.; Arias, M. L.; Cidale, L. S.
BeppoSAX observations of the quasar Markarian 205
Petrucci, P. -O.; Courvoisier, T. J. -L.; Beckmann, V. +1 more
We present the first BeppoSAX observation (0.1 to 220 keV) of the quasar
A possible feature of thermal matter in relativistic jets of radio-loud quasars
Staubert, R.; Courvoisier, T. J. -L.; Wang, J. -M.
It has been suggested that relativistic jets in quasars may contain a considerable amount of thermal matter. In this paper, we explore the possibility that the Kα line from the thermal matter may appear at tens of keV due to a high Doppler blue-shift. In the jet comoving frame, the energy density of photons originally emitted by the accretion disk…
On the precision of X-ray source parameters estimated from ROSAT data
Boese, F. G.
The precision of the point source parameters, i.e. those for source position, source counts and source extension obtained via Maximum Likelihood Estimation from ROSAT data, is investigated. The various categories of error in X-ray observatories are identified. An analytic perturbation analysis is set forth. This means in the ROSAT case a perturbat…
The Compton trail of gamma-ray bursts: A long-after glow
Parizot, E.; Allard, D.
As they travel through the gas of the host galaxy, some of the gamma-rays emitted in a Gamma-Ray Burst (GRB) may experience Compton scattering and reach an observer even if he is not located in the direction of the primary photon beam. Such a process will last until the GRB photons have left their host galaxy, and the ambient electron density beco…
A synthetic view on structure and evolution of the Milky Way
Reylé, C.; Robin, A. C.; Derrière, S. +1 more
Since the Hipparcos mission and recent large scale surveys in the optical and the near-infrared, new constraints have been obtained on the structure and evolution history of the Milky Way. The population synthesis approach is a useful tool to interpret such data sets and to test scenarios of evolution of the Galaxy. We present here new constraints…
The INTEGRAL mission
Sunyaev, R.; Mas-Hesse, J. M.; Gehrels, N. +17 more
The ESA observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory) is dedicated to the fine spectroscopy (2.5 keV FWHM @ 1 MeV) and fine imaging (angular resolution: 12 arcmin FWHM) of celestial gamma-ray sources in the energy range 15 keV to 10 MeV with concurrent source monitoring in the X-ray (3-35 keV) and optical (V-band, 550 nm) …