COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3033


                                        Konkoly Observatory
                                        Budapest
                                        10 June, 1987

                                        HU ISSN 0374-0676


           B, V, R, I LIGHT CURVES OF AD CANCRI

   The very short period eclipsing binary system AD Cnc (SVS 1277) was
discovered by Kurochkin (1960). He classified it as an RR Lyrae type
variable with a period of 0.146373 d. Efremov et al. (1964) correctly
identified AD Cnc as a W Ursae Majoris type system. The system's
spectral type is K0 (G. Herbig, 1961). Millis (1972) determined 19 B,V
standard magnitudes on the system covering about 60x of one complete
cycle. The General Catalog of Variable Stars (1968 and 1985), citing
unpublished manuscripts of Kurochkin, list two ephemerides,

   JD Hel Min. I = 2441363.8063 + 0.2771724dE

in the third edition and

   JD Hel Min. I = 2443192.430 + 0.28273824dE

in the fourth edition. Although the second ephemeris gives better
results, both produce large residuals (O-Cs) when applied to the present
observations.
   The present observations were made on the nights of January 28 -
February 1, 1987, inclusive. The 36" #2 reflector at Kitt Peak National
Observatory was used with standard B,V,R,I filters in the Cousins system
(Bessell 1976) with a dry-ice-cooled RCA 31034a Ga-As photomultiplier
tube. The coordinates of the check (BD +10 1866), comparison and
variable star are given in Table I. The comparison star has no
catalogue identification. Approximately 700 observations were obtained
at each effective wavelength.


                            [FIGURE 1]

 Fig. 1 - Light curves of AD Cnc defined by the individual observations.


                   Table I


Star         R.A.       Dec.
             (1950)     (1950)

AD Cnc       8h43m38s   10 31'02"
Comparison   8h43m15s   10 29'44"
Check        8h42m54s   10 30'01"

The five epochs of minimum light listed in Table II were determined from
the observations made during three primary and two secondary eclipses.
An iterative technique based on the Hertzsprung method (1928) was used.


             Table II
   JD Hel.
   2440000+    Minimum    Cycles       (O-C)
   
   46823.7661   I         -11.0       -0.0005
   46823.9082   II        -10.5        0.0002
   46826.8769   I           0.0        0.0001
   46827.7244   I           3.0       -0.0006
   46827.8670   II          3.5        0.0007

These times of minimum light along with Kurochkin's recent epoch (GCVS
1985) were introduced into a least squares solution to obtain the
following ephemeris:

   JD Hel Min. I = 2446826.8767 + 0.28273731dE

This ephemeris was used to calculate the O-Cs in Table II and the phases
of the present observations.
   The B, V, R and I light curves of AD Cnc defined by the individual
observations are shown in Figure 1 as Delta m versus phase. The analysis of
the observations is underway.


                                     *
                     RONALD G. SAMEC

                     BEVERLY B. BOOKMYER
                     Dept. of Physics & Astronomy
                     Clemson University
                     Clemson, SC 29634-1911 USA

*
Visiting Astronomer, Kitt Peak National Observatory, National Optical
Astronomy Observatories operated by AURA, Inc. under contract with the
National Science Foundation.


References:

Bessell, M. S. 1976, Pub. Astron. Soc. Pac. 88, 557. [BIBCODE 1976PASP...88..557B ]
Efremov, Y. N., Kholopov, P. N., Kukarkin, B V. and Sharov, A. S. 1964,
   I.B.V.S. No. 75.
GCVS 1968, 3(2).
GCVS 1985, 4(1).
Herbig, G. 1961, private communication to Moscow Var. Star Bureau.
Hertzsprung, E. 1928, Bull. Astron. Inst. Neth. 4, 179. [BIBCODE 1928BAN.....4..178H ]
Kurochkin, N. E. 1960, Astron. Circ. USSR 210, 25. [BIBCODE 1960ATsir.210...25K ]
Millis, R. L. 1972, I.B.V.S. No. 649.