VV Vul is also an EA-type eclipsing binary with orbital period (GCVS, 1985). Halbedel (1984) determined its spectral type to be A2/3V. Up to now, the system is neglected for photometric and spectroscopic studies and no absolute parameter has been published. Whitney (1959) gave 5 visual minima and obtained an ephemeris:

(20) |

After Whitney's (1959) work, 9 times of light minimum published in BBSAG Bulletin have been collected at Eclipsing Minimum Database. With the ephemeris given in the fourth edition of the GCVS,

(21) |

The O-C values of the 14 timings are calculated and are listed in the fourth column of Table 7. The corresponding O-C diagram is plotted in Fig. 10.

As shown in Fig. 10, the orbital period of this star is
variable. Since no observatins is between *E*=-2533 and *E*=-90,
the character of the variation is not clear. Considering a
continuous variation in the change of the orbital period,
a least square solution leads to the following quadratic
ephemeris:

(22) |

and to a continuous period increase rate: days/cycle days/year which is equivalent to a period increase of 29.6 s/century. This ephemeris can be used for the estimation of future times of light minimum.

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