AAS 207th Meeting, 8-12 January 2006
Session 186 Eclipsing Binaries
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[186.03] New Ephemeris and Model for the Eclipsing Binary DE CVn

C.T. Flora (East Carolina U.; Maria Mitchell Obs.), O. Ezhkova, T. Khruzina (Sternberg Astron. Inst., Russia), N. N. Samus (Inst. of Astron., Russian Ac. Sci.; Sternberg Astron. Inst.; Maria Mitchell Obs.), R. E. Wilson (U. of Florida; Maria Mitchell Obs.)

Past photometric observations (1,2) of the eclipsing binary DE CVn have suggested that it is a white dwarf/red dwarf pair. The data show a deep (1 mag) primary minimum in the U band with a very steep ingress and egress, a much shallower (0.1 mag) primary minimum in R, and lack of a secondary minimum. In May 2005, we obtained more accurate CCD photometry in the U band with the 31" Lowell Observatory telescope. Photometric points on both branches of the eclipse and a well represented plateau at its bottom allowed for accurate determinations of the middles of the observed minima. By combining those with the times of minima from our previous observations in UBVR(2), from unpublished data of Robb & Greimel (priv. comm.), and from(1,3), we improved the ephemeris to HJD= 2450549.4697 + 0.36413865E. We used two independent programs (4,5) to model the binary. The physical and geometrical parameters obtained from the two models are similar and close to those proposed in (1), except for the position of a dark spot (or collection of small spots) needed to explain the asymmetry of the wave seen in V and R and the inequality of light in quadratures. The authors thank R.M. Robb and R. Greimel for permission to use their unpublished data. This project was supported by the NSF/REU grant AST-0354056 and the Nantucket Maria Mitchell Association. REW's participation was supported by the NSF as part of grant 0307561.

References: (1) Robb, R.M. & Greimel R. 1997, IBVS, No.4486. (2) Samus, N.N., Flora, C.T., Khruzina, T., Holms, S., Ezhkova, O. & Wilson, R.E. (in prep.). (3) Tas, G. et al. 2004, IBVS, No.5548. (4) Wilson R.E., Devinney E.J. 1971, ApJ, 166, 605. (5) Khruzina, T.S. 1998, Astronomy Reports, 42, 180; Khruzina, T.S. & Cherepashchuk, A.M. 1995, Astronomy Reports, 39, 178.

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