CBA Center for Backyard Astrophysics



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 1.

DV UMa Figure 2.
DV UMa Figure 2.

DV UMa Figure 3.
DV UMa Figure 3.

Joseph Patterson, CBA New York
Tonny Vanmunster, CBA Belgium
David Skillman, CBA East
Lasse Jensen, CBA Denmark
John Stull, CBA Alfred
Brian Martin, CBA Alberta
Lewis Cook, CBA California
Jonathan Kemp, CBA Oracle