GRO J1744-28: An intermediate B-field pulsar in a low-mass X-ray binary

Marco Matranga, Carmela Galiano, Tiziana Di Salvo, Rosario Iaria, D'Aì, Riggio, Dauser, Bozzo, Pintore, Sanna, Matranga, Galiano, Robba, Burderi, García, Iaria, Di Salvo

Risultato della ricerca: Articlepeer review

20 Citazioni (Scopus)

Abstract

The bursting pulsar, GRO J1744-28, went again in outburst after ~18 yr of quiescence in 2014 mid-January. We studied the broad-band, persistent, X-ray spectrum using X-ray data from a XMM-Newton observation, performed almost at the peak of the outburst, and from a close INTEGRAL observation, performed 3 d later, thus covering the 1.3-70.0 keV band. The spectrum shows a complex continuum shape that cannot be modelled with standard high-mass X-ray pulsar models, nor by two-components models. We observe broad-band and peaked residuals from 4 to 15 keV, and we propose a self-consistent interpretation of these residuals, assuming they are produced by cyclotron absorption features and by a moderately smeared, highly ionized, reflection component. We identify the cyclotron fundamental at ~4.7 keV, with hints for two possible harmonics at ~10.4 and ~15.8 keV. The position of the cyclotron fundamental allows an estimate for the pulsar magnetic field of (5.27 ± 0.06) × 10<sup>11</sup> G, if the feature is produced at its surface. From the dynamical and relativistic smearing of the disc reflected component, we obtain a lower limit estimate for the truncated accretion disc inner radius (≳100 R<inf>g</inf>) and for the inclination angle (18°-48°). We also detect the presence of a softer thermal component that we associate with the emission from an accretion disc truncated at a distance from the pulsar of 50-115 R<inf>g</inf>. From these estimates,we derive the magnetospheric radius for disc accretion to be ~0.2 times the classical Alfvén radius for radial accretion.
Lingua originaleEnglish
pagine (da-a)4288-4303
Numero di pagine16
RivistaMonthly Notices of the Royal Astronomical Society
Volume449
Stato di pubblicazionePublished - 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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