102 research outputs found
XMM-Newton observations of OY Car III: OM light curve modelling, X-ray timing and spectral studies
We revisit the XMM-Newton observations of the dwarf nova OY Car taken in July
2000 which occured shortly after an outburst. Ramsay et al (2001a) found a
prominent energy dependent modulation at a period of 2240 sec: this modulation
was only seen for app. 1/3 of the observation duration. In our new analysis, we
examine this time interval in greater detail. In addition to the 2240 sec
period we find evidence for other periods, the most prominent being near 3500
sec. Both these modulations are most likely due to changes in photoelectric
absorption over this period: this is supported by phase-resolved spectroscopy.
This may indicate the presence of matter above the accretion disc or a presence
of a magnetic accretion curtain. In this case the 2240 sec period could
represent a spin period of the white dwarf and the 3500 sec period a beat
period between the spin and orbital periods. We also model the B band and UV
eclipse profiles and light curves using a new technique to map the spatial
extent of the accretion disc. As a result we find that whilst the optical
emission is dominated by both the emission close to the accretion disc boundary
layer and the hot spot where the accretion stream hits the disc, the UV
emission is mainly dominated by the inner disc/boundary layer only.Comment: 10 pages, 12 figures, accepted for publication in A&
Red giant pulsations from the suspected symbiotic star StHA 169 detected in Kepler data
We present Kepler and Swift observations of StHa 169 which is currently
classified as a symbiotic binary. The Kepler light curve shows quasi periodic
behaviour with a mean period of 34 d and an amplitude of a few percent. Using
Swift data we find a relatively strong UV source at the position of StHa 169
but no X-ray counterpart. Using a simple two component blackbody fit to model
the combined Swift and 2MASS spectral energy distribution and an assessment of
the previously published optical spectrum, we find that the source has a hot
(~10,000K) component and a cooler (~3700K) component. The Kepler light is
dominated by the cool component and we attribute the variability to pulsations
in a red giant star. If we remove this approximate month long modulation from
the light curve, we find no evidence for additional variability in the light
curve. The hotter source is assigned to a late B or early A main sequence star.
We briefly discuss the implications of these findings and conclude that StHA
169 is a red giant plus main sequence binary.Comment: Accepted for publication in MNRA
- …