Discovery of Red-shifted He-like Iron Absorption Line from Luminous Accreting Neutron Star SMC X-1. (arXiv:1811.08140v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kubota_M/0/1/0/all/0/1">Megu Kubota</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Odaka_H/0/1/0/all/0/1">Hirokazu Odaka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tamagawa_T/0/1/0/all/0/1">Toru Tamagawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nakano_T/0/1/0/all/0/1">Toshio Nakano</a>
We have analyzed X-ray data of SMC X-1 obtained with textit{Suzaku}, and
discovered a combination of an absorption line and an underlying broadened
emission line centered at 6.4 keV in an observation performed on May 19, 2012.
This absorption line is centered at $6.61_{-0.03}^{+0.02}$~keV with an
absorption strength of $5.9_{-1.4}^{+1.7}$, naturally interpreted as an
He$_{alpha}$ resonance line of Fe at 6.7~keV that has a redshift of
$4000_{-1300}^{+1400};mathrm{km;s^{-1}}$. Although textit{Suzaku} observed
this system ten times during 11 months in 2011–2012, the absorption feature
has been seen only in a single observation when the NS was in a rising phase of
the super-orbital modulation, which can be regarded as an egress from
occultation by an extended accretion disk. We therefore attribute the line to a
low density, highly ionized absorber in an accretion disk corona arising from
the disk illuminated by the NS’s intense X-rays. This interpretation also
agrees with a discussion on the photoionization degree and the line depth.
We have analyzed X-ray data of SMC X-1 obtained with textit{Suzaku}, and
discovered a combination of an absorption line and an underlying broadened
emission line centered at 6.4 keV in an observation performed on May 19, 2012.
This absorption line is centered at $6.61_{-0.03}^{+0.02}$~keV with an
absorption strength of $5.9_{-1.4}^{+1.7}$, naturally interpreted as an
He$_{alpha}$ resonance line of Fe at 6.7~keV that has a redshift of
$4000_{-1300}^{+1400};mathrm{km;s^{-1}}$. Although textit{Suzaku} observed
this system ten times during 11 months in 2011–2012, the absorption feature
has been seen only in a single observation when the NS was in a rising phase of
the super-orbital modulation, which can be regarded as an egress from
occultation by an extended accretion disk. We therefore attribute the line to a
low density, highly ionized absorber in an accretion disk corona arising from
the disk illuminated by the NS’s intense X-rays. This interpretation also
agrees with a discussion on the photoionization degree and the line depth.
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