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The bright unidentifiedγ-ray source 1FGL J1227.9-4852: can it be associated with a low-mass X-ray binary?
Hill, A. B.; Camilo, F.; Dubois, R. +10 more
We present an analysis of high energy (HE; 0.1-300 GeV) γ-ray observations of 1FGL J1227.9-4852 with the Fermi Gamma-ray Space Telescope, follow-up radio observations with the Australia Telescope Compact Array, Giant Metrewave Radio Telescope and Parkes radio telescopes of the same field and follow-up optical observations with the ESO VLT. We also…
Positron annihilation spectrum from the Galactic Centre region observed by SPI/INTEGRAL revisited: annihilation in a cooling ISM?
Sunyaev, R.; Tsygankov, S.; Sazonov, S. +2 more
We analyse SPI/INTEGRAL data on the 511-keV line from the Galactic Centre, accumulated over ∼6 yr of observations. We decompose the X-ray and soft gamma-ray emission of the central part of the Milky Way into relatively compact 'bulge' and more extended 'disc' components and report their spectral properties. The bulge component shows a prominent 51…
Narrow-line Seyfert 1 galaxies at hard X-rays
de Rosa, A.; Miniutti, G.; Ubertini, P. +7 more
Narrow-line Seyfert 1 (NLSy1) galaxies are a peculiar class of type 1 active galactic nuclei (broad-line Seyfert 1 galaxies, hereinafter BLSy1). The X-ray properties of individual objects belonging to this class are often extreme and associated with accretion at high Eddington ratios. Here, we present a study on a sample of 14 NLSy1 galaxies selec…
A faint optical flash in dust-obscured GRB 080603A: implications for GRB prompt emission mechanisms
Melandri, A.; Bloom, J. S.; Frail, D. A. +23 more
We report the detection of a faint optical flash by the 2-m Faulkes Telescope North simultaneously with the second of two prompt γ-ray pulses in INTEGRAL gamma-ray burst (GRB) 080603A, beginning at trest= 37 s after the onset of the GRB. This optical flash appears to be distinct from the subsequent emerging afterglow emission, for which…
Cepheid investigations using the Kepler space telescope
Smolec, R.; Szabados, L.; Handler, G. +35 more
We report results of initial work done on selected candidate Cepheids to be observed with the Kepler space telescope. Prior to the launch, 40 candidates were selected from previous surveys and data bases. The analysis of the first 322 d of Kepler photometry, and recent ground-based follow-up multicolour photometry and spectroscopy allowed us to co…
IGR J17354-3255 as a candidate intermediate supergiant fast X-ray transient possibly associated with the transient MeV AGL J1734-3310
Bird, A. J.; Ubertini, P.; Landi, R. +3 more
We present spectral and temporal results from INTEGRAL long-term monitoring of the unidentified X-ray source IGR J17354-3255. We show that it is a weak persistent hard X-ray source spending a major fraction of the time in an out-of-outburst state with an average of 18-60 keV X-ray flux of ∼1.1 milliCrab, occasionally interspersed with fast X-ray f…
Spectral states evolution of 4U 1728-34 observed by INTEGRAL and RXTE: non-thermal component detection
Belloni, T.; Ubertini, P.; Bazzano, A. +2 more
We report results of a one-year monitoring of the low-mass X-ray binary (LMXB) source (atoll type) 4U 1728-34 with INTEGRAL and RXTE. Three time intervals were covered by INTEGRAL, during which the source showed strong spectral evolution. We studied the broad-band X-ray spectra in detail by fitting several models in the different sections of the h…
A detailed spectral study of GRB 041219A and its host galaxy
Covino, S.; Götz, D.; Esposito, P. +4 more
GRB 041219A is one of the longest and brightest gamma-ray bursts (GRBs) ever observed. It was discovered by the INTEGRAL satellite, and thanks to a precursor happening about 300 s before the bulk of the burst, ground-based telescopes were able to catch the rarely observed prompt emission in the optical and in the near-infrared bands.
Here we …Inner disc rearrangement revealed by dramatic brightness variations in the young star PV Cep
Apai, D.; Pál, A.; Ábrahám, P. +11 more
Young Sun-like stars at the beginning of the pre-main-sequence (PMS) evolution are surrounded by accretion discs and remnant protostellar envelopes. Photometric and spectroscopic variations of these stars are driven by interactions of the star with the disc. Time-scales and wavelength dependence of the variability carry information on the physical…
The high-energy view of the broad-line radio galaxy 3C 111
Ballo, L.; Tombesi, F.; Reeves, J. N. +2 more
We present the analysis of Suzaku and XMM-Newton observations of the broad-line radio galaxy (BLRG) 3C 111. Its high-energy emission shows variability, a harder continuum with respect to the radio-quiet active galactic nucleus population, and weak reflection features. Suzaku found the source in a minimum flux level; a comparison with the XMM-Newto…