Study of the X-ray Pulsar XTE J1946+274 with NuSTAR. (arXiv:2110.05337v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gorban_A/0/1/0/all/0/1">A. S. Gorban</a> (1, 2), <a href="http://arxiv.org/find/astro-ph/1/au:+Molkov_S/0/1/0/all/0/1">S. V. Molkov</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Tsygankov_S/0/1/0/all/0/1">S. S. Tsygankov</a> (3, 1), <a href="http://arxiv.org/find/astro-ph/1/au:+Lutovinov_A/0/1/0/all/0/1">A. A. Lutovinov</a> (1,2) ((1) Space Research Institute, Russian Academy of Sciences, Moscow, Russia, (2) Higher School of Economics, National Research University, Moscow, Russia, (3) Tuorla Observatory, University of Turku, Turku, Finland)
We present the results of our spectral and timing analysis of the emission
from the transient X-ray pulsar XTE J1946+274 based on the simultaneous NuSTAR
and Swift/XRT observations in the broad energy range 0.3-79 keV carried out in
June 2018 during a bright outburst. Our spectral analysis has confirmed the
presence of a cyclotron absorption line at an energy $sim38$ keV in both
averaged and phase-resolved spectra of the source. Phase-resolved spectroscopy
has also allowed the variation in spectral parameters with neutron star
rotation phase, whose period is $simeq15.755$ s, to be studied. The energy of
the cyclotron line is shown to change significantly (from $simeq34$ to
$simeq39$ keV) on the scale of a pulse, with the line width and optical depth
also exhibiting variability. The observed behavior of the cyclotron line
parameters can be interpreted in terms of the model of the reflection of
emission from a small accretion column (the source’s luminosity at the time of
its observations was $sim 3 times 10^{37}$ erg s$^{-1}$) off the neutron star
surface. The equivalent width of the iron line has been found to also change
significantly with pulse phase. The time delay between the pulse and equivalent
width profiles can be explained by the reflection of neutron star emission from
the outer accretion disk regions.
We present the results of our spectral and timing analysis of the emission
from the transient X-ray pulsar XTE J1946+274 based on the simultaneous NuSTAR
and Swift/XRT observations in the broad energy range 0.3-79 keV carried out in
June 2018 during a bright outburst. Our spectral analysis has confirmed the
presence of a cyclotron absorption line at an energy $sim38$ keV in both
averaged and phase-resolved spectra of the source. Phase-resolved spectroscopy
has also allowed the variation in spectral parameters with neutron star
rotation phase, whose period is $simeq15.755$ s, to be studied. The energy of
the cyclotron line is shown to change significantly (from $simeq34$ to
$simeq39$ keV) on the scale of a pulse, with the line width and optical depth
also exhibiting variability. The observed behavior of the cyclotron line
parameters can be interpreted in terms of the model of the reflection of
emission from a small accretion column (the source’s luminosity at the time of
its observations was $sim 3 times 10^{37}$ erg s$^{-1}$) off the neutron star
surface. The equivalent width of the iron line has been found to also change
significantly with pulse phase. The time delay between the pulse and equivalent
width profiles can be explained by the reflection of neutron star emission from
the outer accretion disk regions.
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