Search Publications
Signatures of synchrotron emission and of electron acceleration in the X-ray spectra of Mrk 421
Tramacere, A.; Massaro, F.; Cavaliere, A.
Context: BL Lac objects undergo strong flux variations involving considerable changes in their spectral shapes. We specifically investigate the X-ray spectral evolution of Mrk 421 over a time span of about nine years.
Aims: We aim at statistically describing and physically understanding the large spectral changes in X rays observed in Mrk 421 …
Hard X-ray emission from the Galactic ridge
Sunyaev, R.; Krivonos, R.; Revnivtsev, M. +3 more
We present results of a study of the Galactic ridge X-ray emission (GRXE) in hard X-rays performed with the IBIS telescope aboard INTEGRAL. The imaging capabilities of this coding aperture telescope make it possible to account for the flux from bright Galactic point sources whereas the wide field of view permits us to collect large flux from the u…
WEBT and XMM-Newton observations of 3C 454.3 during the post-outburst phase. Detection of the little and big blue bumps
Lee, C. -U.; Nishiyama, S.; Pian, E. +73 more
Context: The quasar-type blazar
Aims: In this paper we report on f…
The variable X-ray spectrum of Markarian 766. I. Principal components analysis
Turner, T. J.; Kraemer, S. B.; Reeves, J. N. +3 more
Aims:We analyse a long XMM-Newton observation of the narrow-line Seyfert 1 galaxy Mrk 766, using the marked spectral variability on timescales >20 ks to separate components in the X-ray spectrum.
Methods: Principal components analysis is used to identify distinct emission components in the X-ray spectrum, possible alternative physical model…
A study of Jupiter's aurorae with XMM-Newton
Branduardi-Raymont, G.; Soria, R.; Cravens, T. E. +6 more
We present a detailed analysis of Jupiter's X-ray (0.2-10 keV) auroral emissions as observed over two XMM-Newton revolutions in Nov. 2003 and compare it with that of an earlier observation in Apr. 2003. We discover the existence of an electron bremsstrahlung component in the aurorae, which accounts for essentially all the X-ray flux above 2 keV: i…
ACS imaging of star clusters in M 51. I. Identification and radius distribution
Bastian, N.; Larsen, S. S.; Gieles, M. +3 more
Context: Size measurements of young star clusters are valuable tools to put constraints on the formation and early dynamical evolution of star clusters.
Aims: We use HST/ACS observations of the spiral galaxy M 51 in F435W, F555W and F814W to select a large sample of star clusters with accurate effective radius measurements in an area covering …
A description of sources detected by INTEGRAL during the first 4 years of observations
Rodriguez, J.; Kuulkers, E.; Produit, N. +6 more
Context: In its first 4 years of observing the sky above 20 keV, INTEGRAL-ISGRI has detected 500 sources, around half of which are new or unknown at these energies. Follow-up observations at other wavelengths revealed that some of these sources feature unusually large column densities, long pulsations, and other interesting characteristics.
Ai…
X-ray precursors to flares and filament eruptions
Mason, H. E.; Dennis, B. R.; Tripathi, D. +1 more
Aims:To study preflare X-ray brightenings as diagnostics of the destabilisation of flare-associated erupting filaments/prominences.
Methods: We combine new observations from the Transition Region and Coronal Explorer (TRACE) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), as well as revisit events reported in the literat…
The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
Wijnands, R.; Mowlavi, N.; Kretschmar, P. +13 more
Aims:The Galactic bulge region is a rich host of variable high-energy point sources. Since 2005, February 17 we are monitoring the source activity in the Galactic bulge region regularly and frequently, i.e., about every three days, with the instruments onboard INTEGRAL. Thanks to the large field of view, the imaging capabilities and the sensitivit…
Lyα emission in high-redshift galaxies
Noll, S.; Heidt, J.; Appenzeller, I. +4 more
Context: A significant fraction of the high-redshift galaxies show strong Lyα emission lines. For redshifts z > 5, most known galaxies belong to this class. However, so far not much is known about the physical structure and nature of these objects.
Aims: Our aim is to analyse the Lyα emission in a sample of high-redshift UV-continuum select…