COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2966

                                                         Konkoly Observatory
                                                         Budapest
                                                         18 December 1986

                                                         HU ISSN 0374 - 0676


          FIRST EPHEMERIS FOR THE W UMa-TYPE STAR NSV 12040

NSV 12040 (CSV 8172, BV 313, BD+52d 2426) discovered by Strohmeier
and Knigge, (1960) is listed as a rapid variable star, with spectral type
F, in the New Catalogue of Suspected Variable Stars (Kukarkin et al., 1982).
Its coordinates are: alpha = 19h24m55s, delta = +52d20.8' (1950.0 ).
   Visual observations led to the possibility that the star was a close
binary system (Boninsegna, 1984: Wils, 1984). A first ephemeris has been 
computed using 85 visual times of minimum obtained by a dozen of GEOS observers
from 1983 to 1985. Both minima are of almost equal value in brightness.

    Min I or II = Hel. J.D. 24 45825.389 + 0d.342437 E                    (1)
                                     +-4        +-7

   To confirm the visual observations, NSV 12040 was monitored photoelectrically 
jointly with other stars of the GEOS and Hipparcos programme. The
Jungfraujoch Observatory's 76 cm telescope was used. The measurements were
made using the cooled photometer with BV filters of the Geneva Observatory.
23 BV measurements of NSV 12040 were obtained during 5 nights in 1985 and
1986 (see Table I) by the GEOS members H. Boithias, M. Dumont, E. Joffrin,
P. Louis, P. Rousselot and the author. Reductions of the observations were made
using the method described by Dumont (1983). Transformation of the B-V values
from the Geneva system into Johnson and Morgan's one was made using Meylan's
and Hauck's formulae (1981).
    A V and B-V light-curve is constructed using ephemeris (1) (see Fig.1).
No variation of the B-V index greater than 0.03 mag. appears. The V magnitude
at maximum is 10.65 and 11.10 at minimum. The mean B-V value, not corrected
for reddening, is +0.43. The period obtained using visual observations is
confirmed.
   Approximate times of minimum were computed from the composite lightcurve. 
These are listed in Table I along with the number of cycles and O-C's
according to ephemeris (1). It was not possible to discriminate the primary
minimum from the secondary one.


Table I: photoelectric measurements of NSV 12040

       H.J.D
      2446000+         V         B-V

      268.4371       10.71      0.42
      268.4628       10.85      0.42
      644.4163       10.65      0.43
      644.4413       10.74      0.43
      644.4701       10.89      0.44
      644.4917       11.06      0.45
      644.5101       11.08      0.46
      644.5437       10.82      0.47
      644.5913       10.66      0.43
      646.4754       10.60      0.40
      646.5122       10.76      0.43
      646.5281       10.86      0.43
      646.5427       11.00      0.42
      646.5608       11.11      0.44
      649.4052       10.74      0.43
      649.4306       10.95      0.41
      649.4545       11.09      0.43
      649.4702       11.10      0.43
      649.4872       10.98      0.44
      649.5129       10.81      0.43
      649.5469       10.66      0.42
      649.5858       10.66      0.41
      655.5733       10.65      0.42


Table II: Times of minimum of NSV 12040 using
          the composite V light-curve of fig. 1.

    Hel J.D.         E       O-C (d)

  2446644.503     2392      +0.005
  2446649.462     2406.5    -0.002



                        [FIGURE 1]

   Figure 1: V and B-V light curve of NSV 12040.
             Phase according to ephemeris of this paper.


   The quasi-constancy of the B-V index, along with the 0.34 day period
and the spectral type, allow us to catalogue NSV 12040 as a probable new
W UMa type variable, It is, however, noteworthy that NSV 12040 lies near the
upper boundary of the period-color diagram for contact binaries, described by
Eggen (1967), see also Giuricin et al, (1983). More observations are needed
for this particularly interesting object. A more accurate ephemeris will be
published (Boninsegna, 1987).


                      R. BONINSEGNA

                     Groupe Europeen.
                d'Observation Stellaire (GEOS)
                      12, rue Bezout
                      F-75014 Paris



References:

Boninsegna, R., 1984, GEOS NC 422
Boninsegna, R., 1987, GEOS Circular on Eclipsing Binaries (to be published)
Dumont, M., 1983, GEOS Circular on RR LYR type variables 7
Eggen, O.J., 1967, Mem. R. Astr. Soc., 70, 111 [BIBCODE 1967MmRAS..70..111E ]
Giuricin,G., Mardirossian, F., Mezzetti, M., 1983. Astron, Astrophys., 119, 218 [BIBCODE 1983A&A...119..218G ]
Kukarkin, B.V., Kholopov, P.N., Artiukhina, N.M., Fedorovich, V.P. Frolov, M.S.,
    Goranskij, N.P., Gorynya, N.A., Karitskaya, E.A., Kireeva, N.N.,
    Kukarkina, N.P., Kurochkin, N.E., Medvedeva, G.I., Perova, N.B.,
    Ponomareva, G.A., Samus, N.M., Shugarov, S.Yu, 1982, New Catalogue of
    Suspected Variable Stars ("Nauka", Moscow)
Meylan, G., Hauck, B., 1981, Astron. Astrophy. Suppl. Ser., 46, 281 [BIBCODE 1981A&AS...46..281M ]
Strohmeier, W., Knigge, K., 1960, Bamb. Ver., 5, No 5
Wils, P., 1984, Heelal, 29, 242