1,503 research outputs found
The Be/X-ray Transient V0332+53: Evidence for a tilt between the orbit and the equatorial plane?
We present optical and infrared observations of BQ Cam, the optical
counterpart to the Be/X-ray transient system V0332+53. BQ Cam is shown to be an
O8-9Ve star, which places V0332+53 at a distance of ~7 kpc. H-alpha
spectroscopy and infrared photometry are used to discuss the evolution of the
circumstellar envelope. Due to the low inclination of the system, parameters
are strongly constrained. We find strong evidence for a tilt of the orbital
plane with respect to the circumstellar disc (pressumably on the equatorial
plane). Even though the periastron distance is only ~ 10 R_*, during the
present quiescent state the circumstellar disc does not extend to the distance
of periastron passage. Under these conditions, X-ray emission is effectively
prevented by centrifugal inhibition of accretion. The circumstellar disc is
shown to be optically dense at optical and infrared wavelengths, which together
with its small size, is taken as an indication of tidal truncation.Comment: 9 pages, 3 figures, uses mn.sty and epsfig Accepted for publication
in MNRA
A 0535+26: Back in business
In May/June 2005, after 10 years of inactivity, the Be/X-ray binary system A
0535+26 underwent a major X-ray outburst. In this paper data are presented from
10 years of optical, IR and X-ray monitoring showing the behaviour of the
system during the quiescent epoch and the lead up to the new outburst. The
results show the system going through a period when the Be star in the system
had a minimal circumstellar disk and then a dramatic disk recovery leading,
presumably, to the latest flare up of X-ray emission. The data are interpreted
in terms of the state of the disk and its interaction with the neutron star
companion.Comment: Accepted for publication in MNRA
Long-term variability of high-mass X-ray binaries. I.Photometry
We present photometric observations of the field around the optical
counterparts of high-mass X-ray binaries. Our aim is to study the long-term
photometric variability in correlation with their X-ray activity and derive a
set of secondary standard stars that can be used for time series analysis. We
find that the donors in Be/X-ray binaries exhibit larger amplitude changes in
the magnitudes and colours than those hosting a supergiant companion. The
amplitude of variability increases with wavelength in Be/X-ray binaries and
remains fairly constant in supergiant systems. When time scales of years are
considered, a good correlation between the X-ray and optical variability is
observed. The X-rays cease when optical brightness decreases. These results
reflect the fact that the circumstellar disk in Be/X-ray binaries is the main
source of both optical and X-ray variability. We also derive the colour excess,
E(B-V), selecting data at times when the contribution of the circumstellar disk
was supposed to be at minimum, and we revisit the distance estimates
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