The X-Ray Pulsar XTE J1858+034 Observed with NuSTAR and Fermi/GBM: Spectral and Timing Characterization plus a Cyclotron Line

: Malacaria C, Kretschmar P, Madsen KK, Wilson-Hodge CA, Coley Joel B., Jenke P, Lutovinov Alexander A., Pottschmidt K, Tsygankov Sergey S., Wilms J

Publisher: IOP PUBLISHING LTD

: 2021

: Astrophysical Journal

: ASTROPHYSICAL JOURNAL

: ASTROPHYS J

: ARTN 153

: 909

: 2

: 7

: 0004-637X

: 1538-4357

DOI: https://doi.org/10.3847/1538-4357/abddbc

: https://iopscience.iop.org/article/10.3847/1538-4357/abddbc

: https://research.utu.fi/converis/portal/detail/Publication/53689473

Accreting X-ray pulsars (XRPs) undergo luminous X-ray outbursts during
which the spectral and timing behavior of the neutron star can be
studied in detail. We analyze a NuSTAR observation of the XRP XTE
J1858+034 during its outburst in 2019. The spectrum is fit with a
phenomenological, a semiempirical, and a physical spectral model. A
candidate cyclotron line is found at 48 keV, implying a magnetic field
of 5.4 × 10¹² G at the site of emission. This is also
supported by the physical best-fit model. We propose an orbital period
of about 81 days based on the visual inspection of the X-ray outburst
recurrence time. Based on Fermi/GBM data, the standard disk
accretion-torque theory allowed us to infer a distance of 10.9 ± 1.0
kpc. Pulse profiles are single-peaked and show a pulsed fraction that is
strongly energy-dependent at least up to 40 keV.

2101.07020.pdf