COMMISSION 27 OF THE I. A. U.
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 3579

                                                         Konkoly Observatory
                                                         Budapest
                                                         15 March 1991

                                                         HU ISSN 0374 - 0676


         A NEW ECLIPSING VARIABLE IN THE BX PEGASI FIELD

A new eclipsing variable star has been discovered near BX Peg during a study of this
W UMa type star, DeYoung et al., (1991). The U. S. Naval Observatory
0.61-meter Cassegrain telescope at Washington, DC and a Metachrome-II coated
Thomson CSF THX31156 1Kx1K CCD was employed in a program to determine times of
minima of eclipsing variable stars. A "wide red" (H alpha-H beta-calcium)
filter was used for 701 images and "v" (GG495(2.6mm) + BG39(1.8mm)) was used
for 28 images.

The DAOPHOT photometry package, Stetson (1987), was used in synthetic aperture
mode for five of the brightest stars in the CCD field.  On the first night the
light curve of BX Peg was skewed. The brightest comparison star was determined
to be variable. A search of the General Catalogue of Variable Stars (1985),
The New Catalogue of Suspected Variable Stars (1982) and the various IBVS
issues published since 1985 revealed no object corresponding with the new
variable. Subsequent observations revealed variations that confirm an Algol
type eclipsing variation. Differential instrumental magnitude light curves
were constructed for each nights run. The method of Kwee and van Woerden
(1956) was used to determine the times of well observed minima (see Table 1).
Using the four well observed minima and four partially observed minima, an
estimate of the period yielded a value of 0.816 days. A period search using a
discrete Fourier transform method based on Scargle (1982) and a Jurkevich
search method based on Morris and DuPuy (1980) proved to be inconclusive, with
the 0.816 day period only weakly indicated. A trial of all other suggested
periods in the periodograms showed that no other period fit the data. A linear
least squares fit to the four well observed minima gives the following
preliminary ephemeris.


       JD Hel Min I = 2448158.5675 + 0.816384 * E                  (1)
                              +-11       +-19

The following data were found in the Space Telescope Guide Star Catalog (CD ROM
Version 1 issued on 1 June 1989) on the new eclipsing variable.


  Right Ascension (J2000.0)     Declination (J2000.0)        mv

        21h39m10.7s                +26d42'34"               12.07



                                Table 1.

   New observed epochs of primary and secondary minimum fit to Equation 1.


                            PRIMARY MINIMA

                            Mean Error                O-C
Filter            HJD         (Days)       Cycles    (Days)

"wide red"   2448158.5685    0.000358        0.0    -0.0010
'wide red"   2448225.5122    0.000276       82.0    -0.0012
             2448225.5099    0.000697       82.0     0.0012



                         SECONDARY MINIMUM

                            Mean Error                O-C
Filter            HJD         (Days)       Cycles    (Days)

"wide red"   2448160.6075    0.000409        3.5     0.0010


                              [FIGURE 1]
                              [FIGURE 2]


The magnitude at maximum is 12.1 in the "v" filter, determined by differential
measures with respect to BX Peg when both the new variable and BX Peg were at
maximum. Our maximum magnitude agrees well with the data from the Guide Star
Catalog. The observed instrumental amplitude of primary minimum is 0.31 in the
"v" filter. Figure 1 shows the instrumental differential "wide red", indicated
by small boxes, and "v" magnitudes, indicated by plus symbols, versus phase
computed using Equation 1. Figure 2 is a "wide red" image finder chart for
the new variable. Table 1 gives the times of primary and secondary minima found
in this study reduced to Equation 1.


                                           James A. DeYoung
                                           U. S. Naval Observatory
                                           34th & Mass. Ave. NW
                                           Washington DC 20392 USA



References:

DeYoung, J.A., Schmidt, R.E., and Gritz, L.I., 1991, (to appear in the
      Information Bulletin on Variable Stars). [IBVS 3578]
Kholopov, P.N., (ed.), 1982, New Catalogue of Suspected Variable Stars Nauka,
      Moscow. [BIBCODE 1982ncss.book.....K ]
Kholopov, P.N., (ed.), 1985, General Catalogue of Variable Stars, 4th ed.,
      Nauka, Moscow
Kwee, K.K. and van Woerden, H., 1956, Bull. Astron. Netherlands, 12, 327. [BIBCODE 1956BAN....12..327K ]
Morris, S. and DuPuy, D., 1980, Publ. Astron. Soc. Pacific, 92, 303. [BIBCODE 1980PASP...92..303M ]
Scargle J., 1982, Astrophys. J., 263, 835. [BIBCODE 1982ApJ...263..835S ]
Space Telescope Science Institute, 1989, Guide Star Catalog (CD ROM, Ver. 1),
      Baltimore.
Stetson, P. B., 1987, Publ. Astron. Soc. Pacific, 99, 191. [BIBCODE 1987PASP...99..191S ]