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The Orbital Period of the Classical Nova V368 Aquilae

ATEL # 1614; A. W. Shafter, E. Marin (SDSU), S. R. Warren (U. Minn)
on 14 Jul 2008; 0:01 UT
Password Certification: Allen W. Shafter (

Subjects: Optical, Cataclysmic Variables, Nova

The Orbital Period of the Classical Nova V368 Aquilae

A. W. Shafter, E. Marin (SDSU), and S. R. Warren (U. Minn)

Diaz & Bruch (1994, IBVS, 4079) reported the discovery of eclipses in the light curve of V368 Aql (Nova Aquilae 1936 No. 2), and concluded that the orbital period of the nova was 0.34521 d (8.285 hr).

As part of a program to study the light curves of eclipsing novae, we obtained time-resolved CCD photometry of V368 Aql on the nights of 2005 September 3, 4, and 5 UT using the Mount Laguna Observatory 1-m reflector. Although these observations revealed just a single eclipse (Tmin = HJD 2,453.617.760), the coverage on adjacent nights was sufficient to show that the putative orbital period reported by Diaz & Bruch (1994) could not be correct.

Follow-up observations of V368 Aql obtained on the nights of 2008 June 29 and 30 UT, and on 2008 July 1, 2, 5, and 7 UT resulted in the detection of four additional eclipses. Only one of these eclipses resulted in an accurate timing (Tmin = HJD 2,454.654.905), with two of the remaining eclipses occurring at twilight (and only partially covered) and a third obtained through heavy cloud cover. Despite these limitations, the coverage of our data was sufficient to allow us to resolve the cycle count ambiguity and establish the orbital period. Combining our two complete eclipse timings with the two timings given in Diaz & Bruch (1994) shows that the orbital period is actually 16.572 hr (i.e., twice their value), and results in the following eclipse ephemeris for V368 Aql:

Tmin = HJD 2,449,189.5230(7) + 0.69050942(14) E.

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