COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2760

                                       Konkoly Observatory
                                       Budapest
                                       12 July 1985

                                       HU ISSN 0374 - 0676


       VBLUW PHOTOMETRY OF THE NEW BRIGHT O TYPE ECLIPSING
                  BINARY HD 167971 IN NGC 6604



  During a photometric program of high luminous OB type stars for the 
investigations of optical micro variations; the star HD 167971 in NGC 6604 of
spectral type O7.5 IF (Cruz-Gonzalez et al. 1974) attracted attention because
of the relative large light amplitude amounting to ~ 0.3mag.
The observations were made with the 90-cm Dutch telescope at the ESO, equipped
with the WBLUW photometer of Walraven during several occasions in 1981 by
M.D.P. van der Bij and in 1984 by E. Damen.

  The variability was also noticed by Leitherer et al. (1984) on account of
photometric observations made in 1983 and later on Forbes (1984) obtained
new observations, but the type of variability was still unknown.
Additional observations by Stahl et al. (1985) proved that the star is a
short-period eclipsing binary with two possible periods viz. 1.6607d and
3.3212d.

 The table lists our observations VJ (the V of the UBV system), which were
transformed from the V of the VBLUW system with the aid of a formula given
by Pel (1983). Each observation is an average of a series of-eight measurements
of the variable relative to the nearby comparison star HD 170719 (B9). The
mean error of the average of such a series amounts to <= +/-0.004mag.
 Combining our observations with those of Leitherer et al., Forbes and
Stahl et al. and by using the second period of Stahl et al., but slightly
revised, we obtained the light curve as shown in the figure (upper panel).
Phases were derived with the aid of the formula:

     phi=(J.D.- 2445555.0)/3.3215


in which the zero point is taken from Stahl et al.. The estimated error in
the period amounts to +/-0.0005d. The bracketed observation is from Forbes and
has a larger uncertainty than his other observations, viz. +0.1mag (Forbes,
priv. comm.).


                 Table I

    The visual magnitudes of HD 167971 in the UBV system.

       J.D.-      VJ   J.D.-       VJ

      4774.875  7.418  5971.524  7.435
      4779.847  7.430  5972.538  7.375
      4786.785  7.380  5973.528  7.660
      4795.792  7.513  5974.556  7.393
      5955.615  7.448  5978.559  7.595
      5964.566  7.393  5979.542  7.393
      5965.542  7.443  5981.566  7.468
      5970.514  7.463


                             [FIGURE 1]




  The primary and secondary minima have depths of~0.30mag and 0.25mag, respectively.
The other panels shows in log intensity scale the relative colour variations
with respect to the comparison star. The mean errors are usually <=+/-0.0005.
The primary minimum is deeper in V-B (equivalent to (B-V)J) and perhaps also
in B-U than the secondary one. The depths are roughly 0.012mag and 0.004mag,
respectively.
  Although the number of observations is actually still too low to draw
definite conclusions, the B-U curve appears to show the largest scatter. Other
hot luminous stars also show a relative large scatter in the B-U index (the
U band contains the Balmer limit) (van Genderen et al. 1985, van Genderen
1985). This fact suggests the presence of short time scale temperature -
and/or density variations in the outer parts of these stars. Further 
observations are planned to enlarge the number of data.
  HD 167971 is obviously a member of the small group of early type massive
interacting systems to which also HD 57060 = UW CMa in NGC 2362 belongs (cf.
Parthasarathy 1978; Herczeg et al. 1981).

  Acknowledgements

  I like to thank Drs Szabados, Leitherer and Forbes for their correspondence.




                          A.M. van GENDEREN
                          Leiden Observatory
                          Postbus 9513,
                          2300 RA Leiden
                          The Netherlands



References:

Cruz-Gonzalez, C., Recillas-Cruz, E., Costero, R., Peimbert, M., Torres-Peimbert, S.:
        1974, Rev.Mexicana Astron.Astrof. 1, 211. [BIBCODE 1974RMxAA...1..211C ]
Forbes, D.: 1984, Inf.Bull.Var.Stars No. 2605.
van Genderen, A.M., Alpenaar, P., van der Bij, M.D.P., Deul, E.R., van Driel, W.,
        van Heerde, G.M., de Lange, L., van Leeuwen, F., Meys, J.J.M.,
        Oppe, J., The, P.S., Wiertz, M.J.J.: 1985, Astron.Astrophys.
        Suppl. (in press). [BIBCODE 1985A&AS...61..213V ]
van Genderen, A.M.: 1985, Astron.Astrophys. (in press). [BIBCODE 1985A&A...151..349V ]
Herczeg, T., Drechsel, H., Rahe, J.: 1981, Astron.Astrophys. 104, 256. [BIBCODE 1981A&A...104..256H ]
Leitherer, C., Stahl, O., Zickgraf, F.-J., Klare, G., Wolf, B.,: 1984, 
	Inf.Bull.Var.Stars No. 2539.
Parthasarathy, M.: 1978, Monthly Not.Roy.Astron.Soc. 185, 485. [BIBCODE 1978MNRAS.185..485P ]
Pel, J.W.: 1983, Internal report.
Stahl, O., Forbes, D., Klare, G. Leitherer, C., Wolf, B., Zickgraf, F.-J.: 1985,
        Inf.Bull.Var.Stars No. 2726.