Proposal #14

Is PG 1230+226 a VY Scl star?

PG 1230+226 has 2000 coordinates of 12h 32m 55.1s +22Âd 22m€™ 10s€. Finding charts are available from SIMBAD and SkyView. PG 1230+226 was discovered and misclassified as a hot subdwarf by the Palomar-Green survey (Green, Schmidt, & Liebert 1986, ApJS, 61, 305). It was recognized as a cataclysmic variable by the Sloan Digital Sky Survey (Szkody et al. 2011, AJ, 142, 181), who show a spectrum characteristic of a nova-like variable, with Balmer and He I lines in weak emission and absorption, on a strong, blue continuum.

Little is known of PG 1230+226. The SIMBAD database shows only the two previous papers and another spectroscopic misclassification as a hot subdwarf (Kilkenny et al. 1988, SAAOC, 12, 1). Time-resolved photometry that I have carried out confirms that it is a cataclysmic variable, since it flickers erratically. It does not show eclipses: I plan to do a radial velocity study in the next year to measure its orbital period

Since the Palomar-Green survey was an ultraviolet-excess sample, it discovered many nova-like variables. This is because unreddened cataclysmic variables almost always have U -“ B < -€“0.4, the inclusion criterion of the PG catalog. Aside from these extreme colors, nova-like variables otherwise don't call attention to themselves: they don't have the outbursts of dwarf novae or classical novae. The systematic survey of nova-likes in the PG survey led to recognition of a new class, the SW Sextantis stars, noteworthy because they do not fit the canonical model of accretion disks in cataclysmic variables well (Thorstensen et al. 1991, AJ, 102, 272, which so far has had 136 citations). PG1230+255 is among the last cataclysmic variables found in the complete sample of the Palomar-Green survey: knowing whether it has outburst or other variability would be essential for population studies.

The Palomar-Green survey lists PG 1230+226 as having B = 15.19. The SDSS shows u = 17.593, g = 17.696, and r = 17.822. This discrepancy seems too large to be from the differences in the filters used. It might be due to variability shown by a class of nova-like variables known as VY Scl stars. VY Scl stars are also called anti-dwarf novae, since they do the opposite of what dwarf novae do. Most of the time VY Scl stars are bright, with spectra showing weak emission and absorption lines on a bright blue continuum, but they fade erratically by 2-5 magnitudes, with spectra showing strong emission lines (Robinson et al. 1981, 251, 611). The low states are thought not to be caused by the disk instability cycle of dwarf novae, despite VY Scl stars being called "€œanti-dwarf novae."€ Pringle and Livio (1994, ApJ, 427, 956) attribute the low states to the mass transfer being choked off by starspots on the mass-losing star. Ritter (2008, New Astronomy Reviews, 51, 869) argues that the low states are caused by irradiation of the mass-losing star.

I propose for either the APASS North or SRO50 telescopes to do once-per-night monitoring of PG 1230+226 for a year, to find out whether it has the erratic low states of a VY Scl star. This would require obtaining differential photometry within 0.05 magnitudes through a V filter once per night, during as many nights as possible throughout a year. Since the field is not crowded, I will measure the differential photometry of PG 1230+226 with comparison and check stars in the field with the aperture photometry tools of AIP4WIN (in The Handbook of Astronomical Image Processing, by Richard Berry and James Burnell). These observations can be done in bright time or in dark time, and don't require good seeing. I will publish these observations in a refereed journal: I may first give them to a student to measure.

The AAVSOnet photometry of the dwarf nova V425 Cas we got from the Wright 28-cm (W28) automated telescope at Astrokolkhoz Observatory, managed onsite by Tom Krajci and approved by Arne Henden, did help to show that V425 Cas is indeed a Z Cam star. My current M.S. student, Dillon Trelawny, showed this photometry off in a poster at the recent American Astronomical Society meeting (Trelawny, D., Ringwald, F. A. 2013, Bulletin of the American Astronomical Society, volume 221, 148.03, ``The Outbursts of the Cataclysmic Variable V425 Cassiopeiae''). We have written a paper that we intend to submit for publication in a refereed journal (``The Outbursts of the Cataclysmic Variable V425 Cassiopeiae,'' by Dillon T. Trelawny, F. A. Ringwald, R. K. Honeycutt, and A. Henden), as soon as one of our collaborators (Kent Honeycutt) finishes analyzing data he contributed.