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http://hdl.handle.net/20.500.12386/27740
Title: | A faint outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021 in NGC 6440 | Authors: | Pintore, Fabio Sanna, A. Riggio, A. Di Salvo, T. MEREGHETTI, Sandro Bozzo, E. Sánchez-Fernández, C. Burderi, L. Iaria, R. |
Issue Date: | 2018 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 479 | Issue: | 3 | First Page: | 4084 | Abstract: | SAX J1748.9-2021 is an accreting X-ray millisecond pulsar observed in outburst five times since its discovery in 1998. In early October 2017, the source started its sixth outburst, which lasted only ∼13 days, significantly shorter than the typical 30 days duration of the previous outbursts. It reached a 0.3-70 keV unabsorbed peak luminosity of ∼3 × 10<SUP>36</SUP> erg s<SUP>-1</SUP>. This is the weakest outburst ever reported for this source to date. We analysed almost simultaneous XMM-Newton, NuSTAR, and INTEGRAL observations taken during the decaying phase of its 2017 outburst. We found that the spectral properties of SAX J1748.9-2021 are consistent with an absorbed Comptonization plus a blackbody component. The former, characterized by an electron temperature of ∼20 keV, a photon index of ∼1.6-1.7 keV, and seed photon temperature of 0.44 keV, can be associated to a hot corona or the accretion column, while the latter is more likely originating from the neutron star surface (kT<SUB>bb</SUB> ∼ 0.6 keV, R<SUB>bb</SUB> ∼ 2.5 km). These findings suggest that SAX J1748.9-2021 was observed in a hard spectral state, as it is typically the case for accreting millisecond pulsars in outburst. | URI: | http://hdl.handle.net/20.500.12386/27740 | URL: | https://academic.oup.com/mnras/article/479/3/4084/5047317 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/sty1735 | Bibcode ADS: | 2018MNRAS.479.4084P | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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