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We analyse simultaneous UBVR quiescent light curves of the cataclysmic variable V2051 Oph using the Physical Parameter Eclipse Mapping (PPEM) method in order to map the gas temperature and surface density of the disc for the first time. The disc appears optically thick in the central regions, and gradually becomes optically thin towards the disc edge or shows a more and more dominating temperature inversion in the disc chromosphere. The gas temperatures in the disc range from about 13 500 K near the white dwarf to about 6000 K at the disc edge. The intermediate part of the disc has temperatures of 9000 to 6500 K. The quiescent disc (chromosphere) shows a prominent bright region with temperatures of 10 500 K around the impact region of the stream from the secondary with an extension towards smaller azimuths. The disc has a size of 0.53±0.03Rℒ1 and a mass accretion rate ℳ˙=1015 to 1017 g s−1. The light curves must include an uneclipsed component, a hot chromosphere and/or a disc wind. The PPEM method allows us to determine a new distance of 146±20 pc, compatible with previous rough estimates. For the white dwarf we then reconstruct a temperature of 19 600 K, if the lower hemisphere of the white dwarf is occulted by the disc. We suggest that the accretion disc is a sandwich of a cool, optically thick central disc with hot chromospheric layers on both sides, as was suggested for HT Cas. This chromosphere is the origin of the emission lines. We find that although V2051 Oph is very similar to the SU UMa‐type dwarf novae HT Cas, OY Car and Z Cha, there must be a substantial difference in order to explain its unique light curve. The reason for the difference could be a higher mass transfer rate caused by the more massive secondary, and/or a small but significant magnetic field of the white dwarf, just strong enough to disrupt the innermost disc.

We present an Eclipse Mapping analysis of ten eclipses taken during decline from superoutburst of the dwarf nova V2051 Oph. On decline from superoutburst the disc cools down considerably from nearly 50 000 K in the intermediate disc (∼0.2 R L1 ) near maximum to about 25 000 K at the end of our observing run, i.e. within four days. The average mass accretion rate through the disc drops in the same time from 10 18 g s −1 to below 10 17 g s −1 .While in some maps the brightness temperature follows the steady-state model, in others the temperature profile shows flattenings and/or an indication of an inward travelling cooling front with a speed of approximately −0.12 km s −1 , possibly a reflected heating front with a speed of +1.8 km s −1 and a newly reflected cooling front with the same speed as the first. Such a scenario has been predicted but has not been observed before. Furthermore, we see a prograde precession of the enlarged disc with a precession period of about 52.5 h in very good agreement with the independently determined superhump period observed by Kiyota and Kato. At the same time, the uneclipsed component -presumably a disc wind -decreases significantly in strength during decline from superoutburst.

ABSTRACT. We report the discovery of a pulsating field star with period 0.060 769 0(1) days, amplitude A y=0.57 mag, mean magnitude {m v )= 18.35, and late-A or early-F spectral type. These characteristics suggest that the star is an SX Phe variable, located approximately 11 kpc away in the Galactic halo. These Population II variables are believed to originate as blue stragglers, and only eight other such field stars, all located in the disk, are known to exist.