Browsing by Subject "X-rays: binaries"
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- ItemOpen AccessAccurate classification of 29 objects detected in the 39 month Palermo Swift /BAT hard X-ray catalogue(2012) Parisi, P; Masetti, N; Jiménez-Bailón, E; Chavushyan, V; Palazzi, E; Landi, R; Malizia, A; Bassani, L; Bazzano, A; Bird, A J; Charles, P A; Galaz, G; Mason, E; McBride, V A; Minniti, D; Morelli, L; Schiavone, F; Ubertini, PThrough an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we have obtained optical spectroscopy for 29 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 39 months Palermo catalogue. All these objects have also observations taken with Swift/XRT or XMM-EPIC which not only allow us to pinpoint their optical counterpart, but also to study their X-ray spectral properties (column density, power law photon index and F2-10 keV flux). We find that 28 sources in our sample are AGN; 7 are classified as type 1 while 21 are of type 2; the remaining object is a galactic cataclysmic variable. Among our type 1 AGN, we find 5 objects of intermediate Seyfert type (1.2-1.9) and one Narrow Line Seyfert 1 galaxy; for 4 out of 7 sources, we have been able to estimate the central black hole mass. Three of the type 2 AGN of our sample display optical features typical of the LINER class and one is a likely Compton thick AGN. All galaxies classified in this work are relatively nearby objects since their redshifts lie in the range 0.008-0.075; the only galactic object found lies at an estimated distance of 90 pc. We have also investigated the optical versus X-ray emission ratio of the galaxies of our sample to test the AGN unified model. For them, we have also compared the X-ray absorption (due to gas) with the optical reddening (due to dust): we find that for most of our sources, specifically those of type 1.9-2.0 the former is higher than the latter confirming early results by Maiolino et al. (2001); this is possibly due to the properties of dust in the circumnuclear obscuring torus of the AGN.
- ItemOpen AccessLong-term evolution of the neutron-star spin period of SXP 1062(2013) Sturm, R; Haberl, F; Oskinova, L M; Schurch, M P E; Hénault-Brunet, V; Gallagher, J S; Udalski, AContext. The Be/X-ray binary SXP 1062 is of especial interest owing to the large spin period of the neutron star, its large spin-down rate, and the association with a supernova remnant constraining its age. This makes the source an important probe for accretion physics.
- ItemOpen AccessLong-term optical and X-ray variability of the Be/X-ray binary H 1145-619: Discovery of an ongoing retrograde density wave(2017) Alfonso-Garzón, J; Fabregat, J; Reig, P; Kajava, J J E; Sánchez-Fernández, C; Townsend, L J; Mas-Hesse, J M; Crawford, S M; Kretschmar, P; Coe, M JContext. Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity.
- ItemOpen AccessObscuration effects in super-soft-source X-ray spectra(2013) Ness, J-U; Osborne, J P; Henze, M; Dobrotka, A; Drake, J J; Ribeiro, V A R M; Starrfield, S; Kuulkers, E; Behar, E; Hernanz, M; Schwarz, G; Page, K L; Beardmore, A P; Bode, M FContext. Super-soft-source (SSS) X-ray spectra are blackbody-like spectra with effective temperatures ~3−7 × 105 K and luminosities of 1035−38 erg s-1. Grating spectra of SSS and novae in outburst that show SSS type spectra display atmospheric absorption lines. Radiation transport atmosphere models can be used to derive physical parameters. Blue-shifted absorption lines suggest that hydrostatic equilibrium is an insufficient assumption, and more sophisticated models are required.
- ItemOpen AccessPhase-resolved optical and X-ray spectroscopy of low-mass X-ray binary X1822–371(2012) Somero, A; Hakala, P; Muhli, P; Charles, P; Vilhu, OContext. X1822–371 is the prototypical accretion disc corona X-ray source, a low-mass X-ray binary viewed at very high inclination, thereby allowing the disc structure and extended disc coronal regions to be visible. As the brightest (closest) such source, X1822–371 is ideal for studying the shape and edge structure of an accretion disc, and comparing with detailed models.
- ItemOpen AccessSXP 7.92: a recently rediscovered be/x-ray binary in the small magellanic cloud, viewed edge on(2017) Bartlett, E S; Coe, M J; Israel, G L; Clark, J S; Esposito, P; D’Elia, V; Udalski, AWe present a detailed optical and X-ray study of the 2013 outburst of the Small Magellanic Cloud Be/X-ray binary SXP 7.92, as well as an overview of the last 18 years of observations from OGLE (Optical Gravitational Lensing Experiment), RXTE, Chandra and XMM-Newton. We revise the position of this source to RA(J2000) = 00:57:58.4, Dec(J2000) = −72:22:29.5 with a 1σ uncertainty of 1.5 arcsec, correcting the previously reported position by Coe et al. by more than 20 arcmin. We identify and spectrally classify the correct counterpart as a B1Ve star. The optical spectrum is distinguished by an uncharacteristically deep narrow Balmer series, with the Hα line in particular having a distinctive shell profile, i.e. a deep absorption core embedded in an emission line. We interpret this as evidence that we are viewing the system edge on and are seeing self-obscuration of the circumstellar disc. We derive an optical period for the system of 40.0 ± 0.3 d, which we interpret as the orbital period, and present several mechanisms to describe the X-ray/optical behaviour in the recent outburst, in particular the ‘flares'and ‘dips’ seen in the optical light curve, including a transient accretion disc and an elongated precessing disc.
- ItemOpen AccessThe nature of 50 Palermo Swift -BAT hard X-ray objects through optical spectroscopy(2017) Rojas, A F; Masetti, N; Minniti, D; Jiménez-Bailón, E; Chavushyan, V; Hau, G; McBride, V A; Bassani, L; Bazzano, A; Bird, A J; Galaz, G; Gavignaud, I; Landi, R; Malizia, A; Morelli, L; Palazzi, E; Patiño-Álvarez, V; Stephen, J B; Ubertini, PWe present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with the Burst Alert Telescope (BAT) instrument onboard the Swift satellite and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star.
- ItemOpen AccessUnveiling the nature of INTEGRAL objects through optical spectroscopy: III. Observations of seven southern sources(2006) Masetti, N; Pretorius, M L; Palazzi, E; Bassani, L; Bazzano, A; Bird, A J; Charles, P A; Dean, A J; Malizia, A; Nkundabakura, P; Stephen, J B; Ubertini, P. The detection, thanks to the
- ItemOpen AccessUnveiling the nature of INTEGRAL objects through optical spectroscopy: X. A new multi-year, multi-observatory campaign(2013) Masetti, N; Parisi, P; Palazzi, E; Jiménez-Bailón, E; Chavushyan, V; McBride, V; Rojas, A F; Steward, L; Bassani, L; Bazzano, A; Bird, A J; Charles, P A; Galaz, G; Landi, R; Malizia, A; Mason, E; Minniti, D; Morelli, L; Schiavone, F; Stephen, J B; Ubertini, PWithin the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the use of six telescopes of different sizes and from one on-line archive. The results indicate that the majority of these objects (23 out of 33) are active galactic nuclei (AGNs), whereas 10 are sources in the local Universe with eight of which in the Galaxy and two in the Small Magellanic Cloud (SMC). Among the identified AGNs, 13 are of Type 1 (i.e., with broad emission lines), eight are of Type 2 (with narrow emissions only), and two are X-ray bright, optically normal galaxies with no apparent nuclear activity in the optical. Six of these AGNs lie at high redshift (z > 0.5). Concerning local objects, we found that five of them are Galactic cataclysmic variables, three are high-mass X-ray binaries (two of which lying in the SMC), one is a low-mass X-ray binary, and one is classified as a flare star that is likely of RS CVn type. The main optical properties and inferred physical characteristics of these sources are presented and discussed.
- ItemOpen AccessX-ray pulsations from the region of the supergiant fast X-ray transient IGR J17544−2619(2012) Drave, S P; Bird, A J; Townsend, L J; Hill, A B; McBride, V A; Sguera, V; Bazzano, A; Clark, D JPhase-targeted RXTE observations have allowed us to detect a transient 71.49 pm 0.02 s signal that is most likely to be originating from the supergiant fast X-ray transient IGR J17544-2619. The phase-folded light curve shows a possible double-peaked structure with a pulsed flux of ~4.8*10-12 erg cm-2 s-1 (3-10 keV). Assuming the signal to indicate the spin period of the neutron star in the system, the provisional location of IGR J17544-2619 on the Corbet diagram places the system within the classical wind-fed supergiant XRB region. Such a result illustrates the growing trend of supergiant fast X-ray transients to span across both of the original classes of HMXB in Porb - Pspin space.