Deep hard X-ray survey of the Large Magellanic Cloud

Abstract

Results of the deep survey of the Large Magellanic Cloud (LMC), performed with the INTEGRAL observatory, are presented. The long exposure (∼ 7 Ms) allowed us to detect twenty one sources in this sky region: ten belonging to the LMC itself (7 HMXBs, 2 PSRs, 1 LMXB), six of extragalactic origin and three belonging to other galaxies from the Local Group -the Milky Way (2 sources) and Small Magellanic Cloud (1 source). Four new hard X-ray sources of these 21 ones were discovered during the survey in addition to IGR J05414-6858 reported earlier; two of them were identified with extragalactic objects. We report also for the first time the detection of a hard Xray emission from the Crab-like pulsar PSR J0537-6910 and identification of the hard X-ray source IGR J05305-6559 with the high-mass X-ray binary EXO 053109-6609.

INTEGRAL/IBIS deep extragalactic survey: M81, LMC and 3C 273/Coma fields

“…Nevertheless, taking into account a peculiar property of LMC X-4 (the source periodically goes to the "off"-state) and using the corresponding subset of revolutions, Grebenev et al (2013) showed that the persistent hard X-ray emission actually originates from the sky region coinciding with the position of another X-ray pulsar, EXO 053109-6609.2. This conclusion was supported by an independent detection of this source in the standard X-ray energy band by the INTEGRAL/JEM-X telescope, which allowed Grebenev et al (2013) to reconstruct the source spectrum in a broad energy band and demonstrate that it is typical for accreting X-ray pulsars. Based on the extended data set obtained with INTEGRAL and using the current ephemerides for LMC X-4 (Molkov et al 2015), we have repeated such an analysis and verified the result of Grebenev et al (2013).…”

Unveiling the nature of INTEGRAL objects through optical spectroscopy

“…Using the same approach as in our previous Papers I-IX, we considered the IBIS surveys of , Krivonos et al (2010Krivonos et al ( , 2012, Coe et al (2010), Grebenev et al (2013), and the Swift/INTEGRAL ("SIX") joint catalogue of Bottacini et al (2012). Among them, we selected unidentified or unclassified hard X-ray sources containing a single bright soft X-ray object within the IBIS 90% confidence level error box.…”

“…For the source naming in Table 1, we directly adopted the names as they appear in the relevant works Bottacini et al 2012;Ricci et al 2012;Coe et al 2010;Grebenev et al 2013;Krivonos et al 2010Krivonos et al , 2012, and the IGR alias when available. However, we remark that we chose not to use the ROSAT name as reported in the fourth IBIS Survey ) for one of the selected objects (1RXS J090320.0+533022), because the soft X-ray emission detected with Swift/XRT within the corresponding 90% IBIS error circle is not positionally consistent with the one reported in the ROSAT Faint Catalogue (actually, no detectable emission appears to be associated with this ROSAT object from Table 1).…”

“…In these tables, X-ray luminosities were computed from the fluxes reported in McDowell (1994), Voges et al (1999Voges et al ( , 2000, ROSAT Team (2000), Saxton et al (2008), Rodriguez et al (2009, Cusumano et al (2010), Landi et al (2010Landi et al ( , 2012b, Maiorano et al (2010), Malizia et al ( , 2012a, Bottacini et al (2012), Krivonos et al (2012), Molina et al (2012a,b), Ricci et al (2012), Tomsick et al (2012), Baumgartner et al (2013), and Grebenev et al (2013).…”

“…The optical spectra of the firm or likely counterparts of 30 unidentified, unclassified, or poorly studied sources belonging to one or more IBIS surveys Coe et al 2010;Krivonos et al 2010Krivonos et al , 2012Bottacini et al 2012;Grebenev et al 2013) are shown in this paper. We moreover added to our sample the spectra of two INTEGRAL sources reported in Ricci et al (2012) and one in Townsend et al (2011), thus reaching a total of 33 objects hereby explored.…”