Monthly Notices of the Royal Astronomical Society
A radial velocity study of the Hα emission line of the cataclysmic variable HX Peg = PG 2337 + 123 shows that its orbital period is 0.2008 ± 0.0005 d (4.82 h). Magnitudes from Harvard College Observatory archive plates suggest that it is either a dwarf nova or a VY Scl star. The quiescent spectrum shows KIλλ 7665, 7699 Å in absorption, consistent with the presence of an unusual subdwarf-K mass-losing star.
At the beginning of the second night of the run, O Iλ 7773 Å was in absorption. Near midnight, the continuum rose rapidly into maximum, with time-resolved red spectra taken throughout. This is the second-ever example of time-resolved spectroscopy of a cataclysmic variable's rise from minimum to a high state (after that of Mansperger & Kaitchuck), and the first with red spectra.
Ringwald, F. A., "The Cataclysmic Variable HX Pegasi = PG 2337 + 123: Caught on the Rise to Maximum" (1994). Open Dartmouth: Faculty Open Access Articles. 3390.