Probing clumpy wind accretion in IGR J18027-2016 with XMM-Newton. (arXiv:1908.03582v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pradhan_P/0/1/0/all/0/1">Pragati Pradhan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bozzo_E/0/1/0/all/0/1">Enrico Bozzo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paul_B/0/1/0/all/0/1">Biswajit Paul</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Manousakis_A/0/1/0/all/0/1">Antonis Manousakis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferrigno_C/0/1/0/all/0/1">Carlo Ferrigno</a>
Supergiant X-ray binaries usually comprise a neutron star accreting from the
wind of a OB supergiant companion. They are classified as classical systems and
the supergiant fast X-ray transients (SFXTs). The different behavior of these
sub-classes of sources in X-rays, with SFXTs displaying much more pronounced
variability, is usually (at least) partly ascribed to different physical
properties of the massive star clumpy stellar wind. In case of SFXTs, a
systematic investigation of the effects of clumps on flares/outbursts of these
sources has been reported by Bozzo et al. (2017) exploiting the capabilities of
the instruments on-board XMM-Newton to perform a hardness-resolved spectral
analysis on timescales as short as a few hundreds of seconds. In this paper, we
use six XMM-Newton observations of IGR J18027-2016 to extend the above study to
a classical supergiant X-ray binary and compare the findings with those derived
in the case of SFXTs. As these observations of IGR J18027-2016 span different
orbital phases, we also study its X-ray spectral variability on longer
timescales and compare our results with previous publications. Although
obtaining measurements of the clump physical properties from X-ray observations
of accreting supergiant X-ray binaries was already proven to be challenging,
our study shows that similar imprints of clumps are found in the X-ray
observations of the supergiant fast X-ray transients and at least one classical
system, i.e. IGR J18027-2016. This provides interesting perspectives to further
extend this study to many XMM-Newton observations already performed in the
direction of other classical supergiant X-ray binaries.
Supergiant X-ray binaries usually comprise a neutron star accreting from the
wind of a OB supergiant companion. They are classified as classical systems and
the supergiant fast X-ray transients (SFXTs). The different behavior of these
sub-classes of sources in X-rays, with SFXTs displaying much more pronounced
variability, is usually (at least) partly ascribed to different physical
properties of the massive star clumpy stellar wind. In case of SFXTs, a
systematic investigation of the effects of clumps on flares/outbursts of these
sources has been reported by Bozzo et al. (2017) exploiting the capabilities of
the instruments on-board XMM-Newton to perform a hardness-resolved spectral
analysis on timescales as short as a few hundreds of seconds. In this paper, we
use six XMM-Newton observations of IGR J18027-2016 to extend the above study to
a classical supergiant X-ray binary and compare the findings with those derived
in the case of SFXTs. As these observations of IGR J18027-2016 span different
orbital phases, we also study its X-ray spectral variability on longer
timescales and compare our results with previous publications. Although
obtaining measurements of the clump physical properties from X-ray observations
of accreting supergiant X-ray binaries was already proven to be challenging,
our study shows that similar imprints of clumps are found in the X-ray
observations of the supergiant fast X-ray transients and at least one classical
system, i.e. IGR J18027-2016. This provides interesting perspectives to further
extend this study to many XMM-Newton observations already performed in the
direction of other classical supergiant X-ray binaries.
http://arxiv.org/icons/sfx.gif
