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Furiously fast and red: sub-second optical flaring in V404 Cyg during the 2015 outburst peak
Altamirano, D.; Knigge, C.; Dhillon, V. S. +25 more
We present observations of rapid (sub-second) optical flux variability in V404 Cyg during its 2015 June outburst. Simultaneous three-band observations with the ULTRACAM fast imager on four nights show steep power spectra dominated by slow variations on ∼100-1000 s time-scales. Near the peak of the outburst on June 26, a dramatic change occurs and …
A comprehensive analysis of the hard X-ray spectra of bright Seyfert galaxies
Papadakis, I. E.; Paltani, S.; Walter, R. +7 more
Hard X-ray spectra of 28 bright Seyfert galaxies observed with INTEGRAL were analysed together with the X-ray spectra from XMM-Newton, Suzaku and RXTE. These broad-band data were fitted with a model assuming a thermal Comptonization as a primary continuum component. We tested several model options through a fitting of the Comptonized continuum acc…
Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021
Sanna, A.; Di Salvo, T.; Burderi, L. +6 more
We analysed a 115-ks XMM-Newton observation and the stacking of 8 d of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst …
High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst
Rodriguez, J.; Fender, R.; Dubus, G. +7 more
We report on Fermi/Large Area Telescope observations of the accreting black hole low-mass X-ray binary V404 Cygni during its outburst in 2015 June-July. Detailed analyses reveal a possible excess of γ-ray emission on 2015 26 June, with a very soft spectrum above 100 MeV, at a position consistent with the direction of V404 Cyg (within the 95 per ce…
Cyclic variations in O-C diagrams of field RR Lyrae stars as a result of LiTE
Zejda, M.; Skarka, M.; Liška, J. +2 more
This paper presents an extensive overview of known and proposed RR Lyrae stars in binaries. The aim is to revise and extend the list with new Galactic field systems. We utilized maxima timings for 11 RRab type stars with suspicious behaviour from the GEOS data base, and determined maxima timings from data of sky surveys and our own observations. T…
The first observation of an intermediate flare from SGR 1935+2154
Hurley, K.; Zhang, X. -L.; Israel, G. L. +8 more
We report on the bright burst detected by four Interplanetary network (IPN) spacecraft on 2015 April 12. The IPN localization of the source is consistent with the position of the recently discovered soft gamma-repeater SGR 1935+2154. From the Konus-Wind (KW) observation, we derive temporal and spectral parameters of the emission, and the burst ene…
Evidence for magnetic field compression in shocks within the jet of V404 Cyg
Covino, S.; Russell, D. M.; Fender, R. P. +3 more
We present optical and near-IR linear polarimetry of V404 Cyg during its 2015 outburst and in quiescence. We obtained time-resolved r'-band polarimetry when the source was in outburst, near-IR polarimetry when the source was near quiescence and multiple waveband optical polarimetry later in quiescence. The optical-to-near-IR linear pola…
SWIFT view of the 2015 outburst of GS 2023+338 (V404 Cyg): complex evolution of spectral and temporal characteristics
Nandi, A.; Mandal, S.; Agrawal, V. K. +1 more
We study the spectral and temporal characteristics of the source GS 2023+338 (V404 Cyg) during the initial phase of its 2015 June outburst, over the energy range of 0.5-150 keV. This is the first detailed study of the characteristics of this source based on SWIFT observations, being reported. Based on our analysis, we understand that the source ex…
Soft γ-ray selected radio galaxies: favouring giant size discovery
Venturi, T.; Dallacasa, D.; Ubertini, P. +5 more
Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of 64 confirmed plus three candidate radio galaxies selected in the soft gamma-ray band. The sample covers all optical classes and is dominated by objects showing a Fanaroff-Riley type II radio morphology; a large fraction (70 per cent) of the sample is made of `radiat…
The INTEGRAL/IBIS AGN catalogue: an update
Bird, A. J.; Ubertini, P.; Landi, R. +4 more
In the most recent IBIS survey based on observations performed during the first 1000 orbits of INTEGRAL, are listed 363 high-energy emitters firmly associated with AGN, 107 of which are reported here for the first time. We have used X-ray data to image the IBIS 90 per cent error circle of all the AGN in the sample of 107, in order to obtain the co…