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Time-Resolved Photometry of the Suspected Polar CSS 111127:033357+332152

ATel #8368; Colin Littlefield (Wesleyan), Enrique de Miguel (Universidad de Huelva; Center for Backyard Astrophysics, Huelva), Lew Cook (Center for Backyard Astrophysics, Concord)
on 5 Dec 2015; 06:47 UT
Credential Certification: Colin Littlefield (clittlefield@wesleyan.edu)

Subjects: Optical, Cataclysmic Variable, Transient, Variables

CSS 111127:033357+332152 (hereinafter "CSS 1111") was detected in 2011 by the Catalina Real-Time Transient Survey (Drake et al. 2009, ApJ, 696, 870) as a cataclysmic variable of unknown subtype. On 2015 November 30, a photometric time series showed it to be a likely AM Her-type object with a period of ~1.8 hours (C. Littlefield, vsnet-alert 19305). We report additional photometry of CSS 1111 and provide an ephemeris for its high-amplitude (~3 mag) photometric modulation.

We obtained unfiltered, time-resolved photometry of CSS 1111 with CCD-equipped 35-cm, 50-cm, 60-cm, and 74-cm telescopes on five nights between 2015 November 28-December 4. Typical integration times with these telescopes were 135 sec, 120 sec, 30 sec, and 30 sec, respectively. All timestamps were converted to HJD. We used a V zeropoint when performing aperture photometry, so we report inferred V magnitudes as opposed to true V magnitudes.

In our data, CSS 1111 undergoes extreme variation across its 1.8-hour period, peaking near V~18.0 and dropping to V~20.7. The most striking aspect of the light curve is a strong dip which lasts for 40% of the photometric period. Near the middle of the dip, CSS 1111 falls below V~20.0 for approximately 20 minutes. This is below the limiting magnitude of our individual images, but by coadding sets of consecutive images obtained during the dip, we achieved marginal detections (SNR~4) of CSS 1111 at V~20.7. The duration of the dip and the lack of abrupt ingress and egress features imply that the dip is not an eclipse of the white dwarf by the donor star.

Outside of the dip, the light curve intermittently shows double-humped structure which is highly variable from cycle-to-cycle, with the two humps being unequal by ~0.5 mag. Using the brighter of the two humps as the fiducial point in the light curve, we offer an ephemeris of T_max[HJD] = 2457355.3631(7) + 0.07676(2)E.

A phase plot consisting of the data from the 35-cm telescope is available at http://filico.dfa.uhu.es/ciecem/css0333+33.png . Light curves from the 74-cm and 60-cm telescopes are available at http://lewcook.com/CSS%20111127=033357+332152.jpg and https://drive.google.com/file/d/0B96c7_bXGorzaG9ub2tDWFNmLWs, respectively; they show the double-humped morphology of the light curve and its imperfect repetition across consecutive cycles.

The fast, high-amplitude photometric variation is consistent with CSS 1111 being an AM Her-type cataclysmic variable. The CRTS photometry, which shows evidence of multi-year high and low states, supports this interpretation. However, spectroscopic and/or polarimetric observations are necessary before CSS 1111 can be definitively classified as a polar.