First XMM-Newton observations of a cataclysmic variable I: Timing studies of OY Car

Abstract

Abstract. We present XMM-Newton observations of the eclipsing, disc accreting, cataclysmic variable OY Car which were obtained as part of the performance verification phase of the mission. The star was observed 4 days after an outburst and then again 5 weeks later when it was in a quiescent state. There is a quasi-stable modulation of the X-rays at ∼2240 s, which is most prominent at the lowest energies. We speculate that this may be related to the spin period of the white dwarf. The duration of the eclipse ingress and egress in X-rays is 20-30 s. This indicates that the bulk of the X-ray emission originates from the boundary layer which has a negligible height above the surface of the white dwarf. The eclipse profile implies a white dwarf of mass M1 = 0.9−1.1 M and a secondary star of M2 = 0.08−0.11 M .

XMM-Newton observations of OY Car III: OM light curve modelling, X-ray timing and spectral studies

“…The data were processed using the XMM-Newton Science Analysis System v5.3.3. Additional optical data in B band was obtained in August 2000 when it was at a similar brightness to the June observation (Ramsay et al 2001a). Ramsay et al (2001a) found evidence for a quasi-stable X-ray modulation on a period of ∼2240 s, which was strongest in soft X-rays.…”

“…Additional optical data in B band was obtained in August 2000 when it was at a similar brightness to the June observation (Ramsay et al 2001a). Ramsay et al (2001a) found evidence for a quasi-stable X-ray modulation on a period of ∼2240 s, which was strongest in soft X-rays. This modulation was observed for around 1/3 of the duration of the observation and it was speculated that this period was related to the spin period of the white dwarf.…”

“…Ramsay et al (2001a) found a prominent energy dependent modulation at a period of 2240 s: this modulation was only seen for ∼1/3 of the observation duration. In our new analysis, we examine this time interval in greater detail.…”

“…Recently, it has been observed at X-ray and optical/UV energies using XMM-Newton. Ramsay et al (2001a) found that there was a quasi-stable modulation of the X-rays at ∼2240 s, which was most prominent at lower energies. They speculated that this was the due to disc material orbiting above the binary orbital plane or due to the spin period of the white dwarf.…”

Simultaneous X-Ray and Ultraviolet Observations of the Sw Sextantis Star Dw Ursae Majoris

“…Because of the low count rate (and, hence, low signalto-noise ratio, S/N) and poor time sampling of the DW UMa X-ray light curve, it is difficult to make a meaningful comparison with the X-ray light curves of other CVs; for example, the flatbottomed total eclipses seen in the XMM-Newton observation of the dwarf novae HT Cas (Nucita et al 2009b) and OY Car (Ramsay et al 2001), or the partial X-ray eclipse observed with Suzaku in the dwarf nova V893 Sco (Mukai et al 2009). The best comparison might be made with the X-ray eclipse seen in XMMNewton observations of the longer-period (P orb = 4.72 hr) novalike CV UX UMa (Pratt et al 2004); however, we note that in the case of UX UMa, the eclipse is observed in only the hard X-ray light curve and not the soft, whereas the situation is reversed for DW UMa.…”