Publication Date:
2016-02-06
Description:
We report the results of a long campaign of time series photometry on the nova-like variable UX Ursae Majoris during 2015. It spanned 150 nights, with ~ 1800 h of coverage on 121 separate nights. The star was in its normal ‘high state’ near magnitude V = 13, with slow waves in the light curve and eclipses every 4.72 h. Remarkably, the star also showed a nearly sinusoidal signal with a full amplitude of 0.44 mag and a period of 3.680 ± 0.007 d. We interpret this as the signature of a retrograde precession (wobble) of the accretion disc. The same period is manifest as a ±33 s wobble in the timings of mid-eclipse, indicating that the disc's centre of light moves with this period. The star also showed strong ‘negative superhumps’ at frequencies orb + N and 2 orb + N , where orb and N are, respectively, the orbital and precession frequencies. It is possible that these powerful signals have been present, unsuspected, throughout the more than 60 yr of previous photometric studies.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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