COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2755

                                        Konkoly Observatory
                                        Budapest
                                        3 July 1985

                                        HU ISSN 0374 - 0676


        PERIOD AND LIGHT CURVE OF THE W UMa-TYPE STAR NSV 4070

  NSV 4070 (= CSV 1297 = SVS 510), a star in the constellation of Cancer
with coordinates 1950.0: alpha= 8h23m24s delta= +21deg02'.7, spectral type F0, is listed
as a possible eclipsing binary in the New Catalogue of Suspected Variable Stars
(Kukarkin et al., 1982).
It was proved to be a variable star by Kulikovski in 1934. Shakhovski (1955)
confirmed the variability (photographic range: 11.5 to 12.4 mag) but not
Kulikovki's period of 1.68 day. He suggested a shorter period and a possible
W UMa type for the star. From 133 visual estimates made from 1983 February
to April, yielding 6 times of minima, Figer (1983) came to the same conclusion.

  To ascertain the period and obtain BV light curves we monitored NSV 4070
photoelectrically during 5 nights, from 1983 December 4 to 11, in alternance
with FZ Orionis, another under-studied EW star (see Le Borgne et al., 1984).
Both stars are part of the visual observing programme of the European group
GEOS.

  121 BV measurements of NSV 4070 were obtained at the 1 meter telescope of
Pic du Midi Observatory using a photoelectric photometer and computerized data
acquisition.
The measurements of several standard stars allowed the transformation to the
Johnson and Morgan BV system every night; as a rule the achieved accuracy
of the whole reduction procedure is about 0.03 mag.

  The 0.418 day-period can be derived straightaway from the nightly curves
of the variable. The mean V light curve in Figure 1 shows that most of the
variation cycle was covered, a cloudy interval beginning at about 3 h U.T. on
December 8 having unfortunately prevented us from observing what may have been
a primary eclipse : as a consequence there still remains a doubt in the
discrimination of both minima.

  The magnitude at maximum is 11.73 in V band and 12.26 in B, the range of
variation being near 0.7 magnitude in both colours. There seems to be a
slight B-V variation throughout the cycle with a somewhat bluer secondary
minimum (see Figure 1). If real, this effect could amount to 0.05 mag.


                              [FIGURE 1]

 Figure 1: V and B-V light-curve of NSV 4070. Phase according to 
 ephemeris (1).


 A first ephemeris has been computed using 35 visual times of minimum
obtained by several GEOS observers from 1983 to 1985 (Figer, 1985):

   (1) Min I? = Hel.J.D. 2 445 768.624  + 0.418 034d E
                               +/-.003 +/-0. 000 004

 Table I shows the photoelectric O-C's referring to this ephemeris.
The agreement is fairly good.




                  Table I

  Date        Filter    Hel.J.D.            O-C    Mag. Type of minimum
                                                          (tentative)
 1983 Dec 4     V     2 445 672.6838     -0.0012   12.40     II
                B              .6827     -0.0023   12.94     II
 1983 Dec 7     V           675.6123     +0.0011   12.43     II
                B              .6127     +0.0015   12.92     II
 1983 Dec 8     V           676.6545 (*) -0.0018   12.47??   I
                B              .6538 (*) -0.0025   13.03??   I

 (*) using the partial descending branch observed on 1983 Dec 8 and the
   ascending one on 1983 Dec 11.

 With its typical BV light curves, its 0.418-day period, its spectral type
and quasi-constant B-V index, NSV 4070 can be definitely catalogued as a new
W UMa-type variable.
The mean B-V index is equal to 0.53 mag. Considering that no correction for
interstellar reddening was made, this value remains consistent with Eggen's
period-colour relation for contact binaries (1961, 1967).





A. FIGER                 J.F. LE BORGNE              M. DUMONT
Groupe Europeen          Groupe Europeen             Observatoire du Pic
d'Observation Stellaire  d'Observation Stellaire     di Midi et de Toulouse
(GEOS)                   (GEOS)                      14 avenue Edouard Belin
12 rue Bezout            12 rue Bezout               F-31400 Toulouse (France)
F-75014 Paris (France)   F-75014 Paris (France)

                         Observatoire du Pic
                         du Midi et de Toulouse
                         14 avenue Edouard Belin
                         F-31400 Toulouse (France)




References :

Eggen, O.J., 1961, R.Obs.Bull., 31, 101 [BIBCODE 1961RGOB...31..101E ]
Eggen, O.J., 1967, Mem.R.Astr.Soc., 70, 111 [BIBCODE 1967MmRAS..70..111E ]
Figer, A., 1983, GEOS NC 367
Figer, A., 1985, GEOS Circ. EB 16 (to be published)
Kukarkin, B.V., Kholopov, P.N., Artiukhina, N.M., Fedorovich, V.P., Frolov, M.S.,
Goranskij, V.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.N.,
Shugarov, S.Yu., 1982, New Catalogue of Suspected Variable Stars (Moscow "Nauka")
Kulikovski, P.G., 1934, Variable Stars, 4, 294
Le Borgne, J.F., Figer, A., Dumont, M., 1984, IBVS 2566
Shakhovski, N.M., 1955, Astr.Tsirk. 165, 14.



                         [From IBVS 2795]


                              ERRATUM



  In IBVS 2755, there is an error in M. Dumont's adress. Instead of
"Observatoire du Pic di Midi et de Toulouse, 14 avenue Edouard Belin, F-31400
Toulouse", M. Dumont's address is "Groupe Europeen d'Observation Stellaire
(GEOS), 12 rue Bezout, F-75014 Paris (France).