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TIZIANA DI SALVO

Spectral and timing properties of IGR J00291+5934 during its 2015 outburst

  • Autori: Sanna, A.; Pintore, F.; Bozzo, E.; Ferrigno, C.; Papitto, A.; Riggio, A.; Di Salvo, T.; Iaria, R.; D'Aì, A.; Egron, E.; Burderi, L.
  • Anno di pubblicazione: 2017
  • Tipologia: Articolo in rivista (Articolo in rivista)
  • OA Link: http://hdl.handle.net/10447/228375

Abstract

We report on the spectral and timing properties of the accreting millisecond X-ray pulsar IGR J00291+5934 observed by XMM-Newton and NuSTAR during its 2015 outburst. The source is in a hard state dominated at high energies by a Comptonization of soft photons (~0.9 keV) by an electron population with kTe ~30 keV, and at lower energies by a blackbody component with kT ~ 0.5 keV. A moderately broad, neutral Fe emission line and four narrow absorption lines are also found. By investigating the pulse phase evolution, we derived the best-fitting orbital solution for the 2015 outburst. Comparing the updated ephemeris with those of the previous outbursts, we set a 3σ confidence level interval -6.6 × 10-13 s s-1 < P˙ orb < 6.5 × 10-13 s s-1 on the orbital period derivative. Moreover, we investigated the pulse profile dependence on energy finding a peculiar behaviour of the pulse fractional amplitude and lags as a function of energy.We performed a phase-resolved spectroscopy showing that the blackbody component tracks remarkably well the pulse profile, indicating that this component resides at the neutron star surface (hotspot).