Bibcode
Armas Padilla, M.; Ponti, G.; De Marco, B.; Muñoz-Darias, T.; Haberl, F.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 473, Issue 3, p.3789-3795
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1
2018
Citations
8
Refereed citations
8
Description
We report on a detailed study of the spectral and temporal properties of
the neutron star low-mass X-ray binary SLX 1737-282, which is located
only ∼1° away from Sgr A*. The system is expected to have a
short orbital period, even within the ultracompact regime, given its
persistent nature at low X-ray luminosities and the long duration
thermonuclear burst that it has displayed. We have analysed a Suzaku (18
ks) observation and an XMM-Newton (39 ks) observation taken 7 yr apart.
We infer (0.5-10 keV) X-ray luminosities in the range of 3-6 ×
1035ergs-1, in agreement with previous findings.
The spectra are well described by a relatively cool (kTbb =
0.5 keV) blackbody component plus a Comptonized emission component with
Γ ∼ 1.5-1.7. These values are consistent with the source being
in a faint hard state, as confirmed by the ∼20 per cent fractional
root-mean-square amplitude of the fast variability (0.1-7 Hz) inferred
from the XMM-Newton data. The electron temperature of the corona is
≳7 keV for the Suzaku observation, but it is measured to be as low
as ∼2 keV in the XMM-Newton data at higher flux. The latter is
significantly lower than expected for systems in the hard state. We
searched for X-ray pulsations and imposed an upper limit to their
semi-amplitude of 2 per cent (0.001-7 Hz). Finally, we investigated the
origin of the low-frequency variability emission present in the
XMM-Newton data and ruled out an absorption dip origin. This constraint
the orbital inclination of the system to ≲65° unless the
orbital period is longer than 11 h (i.e. the length of the XMM-Newton
observation).
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Accreting black-holes and neutron stars in X-ray binaries provide an ideal laboratory for exploring the physics of compact objects, yielding not only confirmation of the existence of stellar mass black holes via dynamical mass measurements, but also the best opportunity for probing high-gravity environments and the physics of accretion; the most
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Armas Padilla