Orbital periods of recurrent novae
The class of recurrent novae (RN) with thermonuclear runaways contains only three systems (T Pyx, U Sco, and V394 CrA) for which no orbital periods were known. I report on a series of photometric observations where the orbital periods for all three systems were discovered. T Pyx is found to have a sinusoidal modulation with an amplitude of 0.08 mag and a period of 2.3783 hr (with a possible alias of 2.6403 hr). This result is startling because the orbital period is in the middle of the period gap. U Sco is found to be an eclipsing system with an eclipse amplitude of roughly 1.5 mag and an orbital period of 1.2344 days. Both the high inclination and the orbital period are also startling because of the narrow He line in the spectrum and the high inferred accretion rate. V394 CrA is found to have a sinusoidal modulation with an amplitude of 0.5 mag and a period of 0.7577 days. So two out of three RN with thermonuclear runaways (or five out of six for all RN) have evolved companions.
Publication Source (Journal or Book title)
Schaefer, B. (1990). Orbital periods of recurrent novae. Astrophysical Journal, 355 (2 PART 2) https://doi.org/10.1086/185733