Astron. Nachr. / AN 327, No. 9, 912 – 916 (2006) / DOI 10.1002/asna.200510656 First ground-based photometry and light-curve analysis of the eccentric eclipsing binary V744 Cas ˙ I. Bulut 1 ,⋆ , C. C ¸ ic ¸ek 1 , A. Erdem 1 , V. Bakis 1 , O. Demircan 1 , and ¨ O.L. De ˘ girmenci 2 1 C ¸ anakkale Onsekiz Mart University Observatory, TR-17100 Terzio˘ glu Kamp¨ us¨ u, C ¸ anakkale, Turkey 2 Ege University Observatory, TR-35100, Bornova, ˙ Izmir, Turkey Received 2005 Dec 20, accepted 2006 May 16 Published online 2006 Oct 16 Key words stars: binaries: eclipsing – stars: individual: V744 Cas The first ground-based BVR photometric observations of the recently discovered eclipsing binary V744 Cas are presented. From these measurements, timings for two primary and one secondary minima have been calculated. The light curves of the system were analyzed by using the Wilson-Devinney program. The analysis shows that the system is detached with two similar components of spectral type A2V, and the orbit is eccentric (e = 0.0662 ± 0.0005). The longitude of the periastron (ω) was found significantly different for two different light curves (ours and that of Hipparcos), which is strongly suggestive of an apsidal motion with a period of about 425 ± 68 yr. This makes V744 Cas an important candidate for studies of apsidal motions. The first estimate of the absolute dimensions place the system close to the terminal age of the main sequence (TAMS) in the HR diagram. The distance from the spectroscopic parallax (d = 740 ± 10 pc) was found to be slightly larger than the Hipparcos distance of d = 610 ± 400 pc. c  2006 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim 1 Introduction The system V744 Cassiopeae = BD +52 ◦ 51 = HIP 1735 = HD 1744 (R.A. = 00 h 21 m 56. s 69, DEC = +53 ◦ 28 ′ 51. ′′ 1 at 2000.0) is among the variables discovered by the Hipparcos project (ESA 1997). The photometric observations of this system by Hipparcos show a light curve of the Algol type. The depth of the primary minimum is ∼0.26 in V, the to- tal light curve variation is between ∼8.44 and 8.70, and the mean colour indices (B-V ) and (V -I ) are 0.09 and 0.10, respectively. The mean orbital period and the epoch derived by the best light curve fitting of the Hipparcos data were 4. d 78180 and JD 2448501.7240 (ESA 1997). The spectral type of the system was given as B9 (ESA 1997). The par- allax measured by Hipparcos is 1.65 ± 1.10 mas, for a dis- tance of 610 ± 400 pc. Bulut & Demircan (2002) analyzed the Hipparcos pho- tometric data of the system by using the EBOP code (Et- zel 1981) which is based on the Nelson-Davis-Etzel model (Popper & Etzel 1981). They found an eccentricity of e = 0.056 ± 0.004 and a longitude of the periastron of ω = 23. ◦ 91 ± 2.31. In this study, the first ground-based photometric obser- vations of V744 Cas were analysed and the results were compared to earlier solutions. From the new observations, we obtained three new times of minimum, and estimated the apsidal motion period of the system. ⋆ Corresponding author: ibulut@comu.edu.tr 2 Observations Ground-based photometric observations of V744 Cas were made over 29 nights at C ¸ anakkale Onsekiz Mart University Observatory (C ¸ OMUO) in 2003–2004 by using the 40-cm Schmidt-Cassegrain type equipped with a single-channel photometer, uncooled Hamamatsu R 6358 photomultiplier and standard BVR filters of the Johnson system. The comparison star was BD +53 ◦ 67 (TYC 3653-204- 1, HD 2033; A0, V = 8.55) and the star BD +52 ◦ 54 (HIP 1786, HD 232168; A0, V = 9.11) was used as a check star. In total 1196, 1219 and 1094 observational points were ob- tained in the B, V, and R filters, respectively, during 2003– 2004. Differential measurements were made in the sequence comparison-sky-variable-sky-variable-comparison-sky. To- tal integration time in each filter was 10 s. All differen- tial magnitudes, in the sense of variable minus comparison, corrected for atmospheric extinction with Hardie’s method (Hardie 1962), using an extinction coefficient derived from nightly observations of the comparison star, and HJD were computed. The instrumental magnitudes were transformed to a standard system. Standard system coefficients were de- rived by Bakis et al. (2005). The probable error of a sin- gle observation was estimated to be ± 0.030, ±0.020 and ±0.025 for the B, V, and R filters, respectively. The large scatter of the observations in Fig. 1 and noted large proba- ble errors are more than was expected for such a bright star like V744 Cas observed with a 40-cm telescope. We there- fore consider the possibility of low amplitude variability of either the variable or comparison star. c  2006 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim