Abstract
We used six simultaneous XMM-Newton and Rossi X-ray Timing Explorer plus
five Suzaku observations to study the continuum spectrum and the iron
emission line in the neutron-star low-mass X-ray binary 4U 1636-53 as a
function of the position of the source in the colour-colour diagram. We
modelled the spectra with two thermal components, a multicolour disc
blackbody and a blackbody, that represent, respectively, the emission
from the accretion disc and the neutron-star surface plus boundary
layer, a Comptonised component to account for the hard part of the
spectrum produced by a corona of hot electrons, and either a Gaussian or
a relativistic line component to model an iron emission line at 6.5 keV.
For the relativistic line component we used either the diskline, laor or
kyrline model, the latter for three different values of the spin
parameter. The fitting results for the continuum are consistent with the
standard truncated disc scenario, in which the inner disc temperature,
the temperature at the surface of the neutron star (or boundary layer)
and the optical depth of the corona increase while the inner disc radius
and the temperature of the corona decrease as mass accretion rate onto
the neutron star increases. We also find that the flux and equivalent
width of the iron line first increases and then decreases as the flux of
the Comptonised component increases. This could be explained either by
changes in the ionisation state of the accretion disc where the line is
produced by reflection, or by light bending of the emission from the
Comptonised component if the height at which this component is produced
changes with mass accretion rate.
Original language | English |
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Pages | 1913 |
Publication status | Published - 2014 |
Event | 40th COSPAR Scientific Assembly - Moscow, Russian Federation Duration: 2-Aug-2014 → 10-Aug-2014 |
Conference
Conference | 40th COSPAR Scientific Assembly |
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Country/Territory | Russian Federation |
City | Moscow |
Period | 02/08/2014 → 10/08/2014 |