S. van Amerongen

A Comparison of H2252-035/AO PSC and 4U1849-31/V1223 SGR

From five-colour photometry of the triple-periodic systems H2252-035 and V1223 Sgr, which have very similar orbital and pulsation periods, we find a significant difference in the wavelength dependence of their short period pulsations. Our results indicate that in H2252-035 this pulse originates in a hot region, probably on the white dwarf (Motch and Pakull, 1981), whereas in V1223 Sgr both pulses are the result of reprocessing of X-rays (in the far side of the accretion disk, and in the companion star, respectively), as suggested by Warner (1985).

Time-Resolved Optical Spectroscopy of AM Her X-Ray Sources

We present high-time resolution spectroscopy of two AM Her sources E1405−451 and E1013−477. For E1405−451, the Balmer emission lines profiles can be divided into a narrow component and a broad one. The amplitudes of the radial velocity curves of these components are respectively 265±30 km/s and 390±50 km/s. The orientation of the column determined from polarimetry is not compatible with the broad component being formed in the lowest parts of the column. Photometric and spectroscopic results on E1013−477 do not confirm the previous reported 103 min. period. Rapid variability ( 3.3h) is present in these data.

Long-term optical photometry of the dwarf nova VW Hyi

Long-term five-colour photometry of the dwarf nova VW Hyi shows no evidence for a secular change of the flux during the quiescent interval between normal outbursts (3σ upper limits between 0.16 and 0.20 mag in the five passbands). However, the amplitudes in the orbital B-U and U-W colour curves change during quiescence. A delay in the progress of normal outbursts toward higher frequencies confirms the delay, seen with IUE, in the onset of a normal outburst towart higher frequencies. Just after outburst, the system is substantially bluer than later in quiescence.