DV URSAE MAJORIS - UNDER THE KNIFE
DV UMa is an eclipsing dwarf nova, which staged superoutbursts in
April 1997 and December 1999, spotted by Timo Kinnunen and Tonny
Vanmunster. We obtained good CBA coverage of both (outbursts, that is).
In both cases the star flashed powerful superhumps with P=0.0887(1)
d, 3.3% longer than the known orbital period. The first figure below
shows sample nightly light curves from the 1997 eruption, illustrating the
superhumps and the deep eclipses. Interestingly, the out-of-eclipse
photometric wave on the first night (only) occurs on the orbital
period, not the superhump period.
The second figure shows the "cleaned" amplitude spectrum of the 10-day
light curve in superoutburst, with eclipse excluded. Significant
detections are flagged with arrows, and the inset is the mean superhump
waveform. Three of the signals (at 11.26, 22.51, and 44.98 c/d) are
merely harmonics of the basic superhump. The other three are more
interesting, occurring at 2w, 3w-2W, and 3w-W, where w is the orbital
frequency and W is the putative precession frequency. Interesting fodder
for theorists, disk modellers, people of that ilk.
The third figure is a folded light curve of DV UMa in quiescence. The
main shape is a combination of the double-humped waveform characteristic
of a distorted secondary, and the single hump characteristic of the bright
spot at disk's edge. The eclipse has sharp features when the small
structures (white dwarf and bright spot) are eclipsed, but this time
resolution (~80 s) is somewhat too coarse to show their true shapes.
(click figures for larger versions)
DV UMa Figure 1.
DV UMa Figure 2.
DV UMa Figure 3.