NuSTAR observation of the Supergiant Fast X-ray Transient IGR J11215-5952 during its 2017 outburst
| Autor: | Sidoli, L., Postnov, K., Tiengo, A., Esposito, P., Sguera, V., Paizis, A., Castillo, G. A. Rodrıguez |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | A&A 638, A71 (2020) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/202038078 |
| Popis: | We report on the results of a NuSTAR observation of the Supergiant Fast X-ray Transient pulsar IGRJ11215-5952 during the peak of its outburst in June 2017. IGRJ11215-5952 is the only SFXT undergoing strictly periodic outbursts, every 165 days. NuSTAR caught several X-ray flares, spanning a dynamic range of 100, and detected X-ray pulsations at 187.0 s, consistent with previous measurements. The spectrum from the whole observation is well described by an absorbed power-law (with a photon index of 1.4) modified, above 7 keV, by a cutoff with an e-folding energy of 24 keV. A weak emission line is present at 6.4 keV, consistent with Kalpha emission from cold iron in the supergiant wind. The time-averaged flux is 1.5E-10 erg/cm2/s (3-78 keV, corrected for the absorption), translating into an average luminosity of about 9E35 erg/s (1-100 keV, assuming a distance of 6.5 kpc). The NuSTAR observation allowed us to perform the most sensitive search for cyclotron resonant scattering features in the hard X-ray spectrum, resulting in no significant detection in any of the different spectral extractions adopted (time-averaged, temporally-selected, spin-phase-resolved and intensity-selected spectra). The pulse profile showed an evolution with both the energy (3-12 keV energy range compared with 12-78 keV band) and the X-ray flux: a double peaked profile was evident at higher fluxes (and in both energy bands), while a single peaked, sinusoidal profile was present at the lowest intensity state achieved within the NuSTAR observations (in both energy bands). The intensity-selected analysis allowed us to observe an anti-correlation of the pulsed fraction with the X-ray luminosity. The pulse profile evolution can be explained by X-ray photon scattering in the accreting matter above magnetic poles of a neutron star at the quasi-spherical settling accretion stage. Comment: Accepted for publication in Astronomy & Astrophysics (Received 3 April 2020 / Accepted 17 April 2020). 14 pages, 5 Tables, 9 Figures |
| Databáze: | arXiv |
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