Astron. Astrophys. 345, 505-513 (1999)

4. Eclipsing binaries

Three eclipsing binaries were discovered in the field. Their phase diagrams are shown in Fig. 8. The first one, Oo 1021 = NSV 779, was found to be probably variable by Oosterhoff (1937). Four well-defined minima were observed for this star. The corresponding times of minimum are given in Table 3. The most probable value of the orbital period is 13.7136 d. The primary minimum is only slightly deeper than the secondary and therefore there is a small possibility that the real orbital period is half the value given above. This, however, would imply a very shallow, i.e., practically unobservable secondary minimum and a very small mass ratio in the system. This is rather unlikely. Although barely visible in Fig. 8, the end of the egress was also observed on HJD 2 450 709 in the band (phase 0.76). There were, however, too few points falling into the eclipse to derive reliably the time of minimum for this night. The times of minimum light given in Table 3 define the following ephemeris:

For Oo 1147, the other EA-type eclipsing binary, only one primary and one secondary minimum (see Table 3) both in and bands were observed. They are not sufficient to derive the period unambiguously. Assuming a circular orbit we found two possible orbital periods: 31.804 0.008 and 6.361 0.002 d. If the latter is real, a few points at the beginning of HJD 2 450 008 fall into the secondary eclipse. Despite the lower quality of this night, a small decrease of brightness at that time is indeed observed. If small ellipticity is allowed, more periods, including some around 10.58 d, become possible. The eclipses are partial and the depths of the primary and secondary eclipses in the band amount to about 0.53 and 0.21 mag, respectively.

Fig. 8. Phase diagrams for three eclipsing binaries discovered in h Persei. Upper panel: light curves of Oo 1021 folded with period 13.7136 d; middle panel: light curve of Oo 1147 folded with period 6.361 d; lower panel: V light curve of W 49 folded with period 0.439727 d. For all stars phase 0.0 corresponds to HJD 2 449 606.28. Ordinate ticks are separated by 0.2 mag.

Table 3. Heliocentric times of minimum light for three eclipsing variables in the central region of h Persei.

Another eclipsing variable was detected only in the V-filter data and it appeared to be a W UMa-type eclipsing binary with well-marked minima of uneven depth. The star has no Oosterhoff (1937) number. It is designated as star number 49 by Wildey (1964) and 47005 by Moffat & Vogt (1974). Taking into account the star's brightness and colours, it could be an early G-type star belonging to h Persei. The eclipse is probably partial. All times of minimum given in Table 3 define the following ephemeris:

© European Southern Observatory (ESO) 1999

Online publication: April 19, 1999
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