Engineering topics

Thomas, Gino

Publications and source records attributed to Thomas, Gino.

3 records

NASA NTRS1993

Superhumps in cataclysmic variables: I. T. Leonis

We report photometry of the dwarf nova T Leonis during its 1993 supermaximum. The principle outburst lasted approximately 20 days, during which large-amplitude superhumps were consistently seen in the light curve. The mean period was 86.7 + or - 0.1 min, about 2.4% longer than the orbital period determined from radial-velocity measurements. Analysis of data obtained during the 1987 supermaximum implies that the superhump period decreased slowly, with dP/dt = - 6 x 10(exp -5), or dP/dm = -0.6 min. mag. These are typical values for SU Ursae Majoris-type dwarf novae. At the end of the outburst, the star suddenly brightened again to magnitude 13, from which it declined on a time scale of about 1 day and without superhumps. It is possible that this event was a normal outburst. This suggests that superoutbursts can trigger normal outbursts, and may explain the 'bump' frequently found in the light curves of SU UMa stars very late in a superoutburst.

Lemm, Kristi↗

NASA NTRS1993

The 1991 V603 Aquilae campaign - Superhumps and P-dots

The results are reported of an extensive 1991 campaign to determine an accurate value of the period of the old nova V603 Aquilae, free from aliasing, in at least one season. Phase drift of +/- 0.3 cycles around the mean period is present on a time scale of about six months. The period is shown to be unstable. There is an interesting resemblance of the 0.146 day photometric signal to the 'superhumps' of dwarf novae. However, the light variations are irregular and not similar to those of dwarf novae. The relationship between observed orbital and superhump period is studied, and it is predicted that V603 Aql is the first of many noneruptive cataclysmic variables which will be recognized as showing superhumps.

Patterson, Joseph↗

NASA NTRS1993

Rapid oscillations in cataclysmic variables. IX - BG Canis Minoris (=3A 0729+103)

Results of a 10-yr photometric program on BG Canis Minoris, a novalike variable distinguished by the presence of a strictly coherent 913-s wave in its light curve, are presented. Long-term ephemerides for the orbital clock, which manifests itself through a 3.2-h light modulation, and the 913-s clock, are presented. The light curve exhibits a persistent 0.3 mag modulation at a period consistent with the 3.2-h spectroscopic period. Well-distributed timings of the orbital minima prove that the period is 0.1347486 day. It is inferred from the shape of the waveform and from the existence of X-ray dips with a sharp energy dependence that the modulation is caused by absorption. Power spectra of the nightly light curves show variable secondary features, in addition to the regular 913-s pulse. The 913-s period, presumably the first harmonic of the true white-dwarf spin period, is decreasing by 0.0022 s/yr.

Patterson, Joseph↗