COMMISSIONS 27 AND 42 OF THE IAU 
          INFORMATION BULLETIN ON VARIABLE STARS 
                      Number 3708
 
                                   Konkoly Observatory 
                                   Budapest 
                                   13 April 1992 
 
                                   HU ISSN 0374 - 0676 
 
 
  1991 V-Band Photometry of an Eclipsing Binary: 1E 1919+0427 
 
 
 
    As part of our long-term observing program of 
chromospherically-active binary stars, we have observed a 
photometric light curve of the RS CVn candidate 1E 1919+0427 at 
V-band. The light curve shows that it is an eclipsing system 
with evidence of a distortion wave. 
    1E 1919+0427 was discovered to be an x-ray source in 1986 
(Takalo, 1986). Takalo and Nousek (1988) investigated the source 
spectroscopically. They found that it is a double-lined binary 
system with observed spectral classes G5 V and K0 III - IV, as 
are typical for an RS CVn. Based on radial velocity 
measurements, they arrived at an orbital period of 0.8 days. 
   We observed 1E 1919+0427 on September 25 and 26 and October 
4 and 17 of 1991 with the 61-cm telescope at Capilla Peak 
Observatory equipped with a Photometrics CCD camera (Laubscher et 
al., 1988). We used this system as a multichannel photometer to 
sample sky, variable, and the comparison star simultaneously. 
Our filter set (Beckert and Newberry, 1989) is matched to Johnson 
at V. Typical exposures were 40 - 50 seconds at V. We used star 
"B" in figure 1 as a comparison star. Star "C" was used as a 
check star. 
    From our photometry, we were able to get precise times for 
primary and secondary eclipse. With this information we applied 
a Lafler-Kinman period search to find the period elements of 1E 
1919+0427: 
 
 
   JD_max = 2448533.71141 + 0.83414E 
 
 
 
   The V light curve is plotted at the 0.83414 day period in 
figure 2. This figure shows delta magnitudes in the instrumental 
system. The statistical error in the observations is about 0.01 
mag. 
   We noted that the star's magnitude as it enters primary 
eclipse is higher than as it comes out of eclipse -- evidence of 
a dark, spotted region. This region is modeled using an 
information limit optimization analysis (Budding and Zeilik, 
1987). We have taken T_1 = 5780 K, T_2 = 5260 K, and i = 85.29d 
to make this fit with a black (T = 0K) spotted region. The 
derived starspot parameters were: longitude = 168.49d +/- 14.32, 
latitude = 87.25d +/- 0.42 and radius = 38.42d +/- 0.31. Because we 
only sample the star in V-band we do not have enough information 
to find a blackbody spot temperature. Clearly, we need complete 
light curves at two colors in consecutive observing seasons to 
track the magnetic activity of this system. 


                          [FIGURE 1]

 FIGURE 1: Finding chart for 1E1919+0427 with Comparison Stars
           labeled.

                         [FIGURE 2]
                         [FIGURE 3]


    This research was supported in part by National Science 
Foundation Grant AST - 8903174 to MZ. 
 
 
 
 
 
                        D.L. SUMMERS, M. ZEILIK, E. JADERLUND, 
                        G. HOEPPE, and A. COLLINS 
                        Capilla Peak Observatory 
                        Institute for Astrophysics 
                        The University of New Mexico 
                        Albuquerque, NM 87131 
                        U.S.A. 
 
 
 
 
 
References: 
Beckert, D.C. and Newberry, M.V., (1989) Pub. Astron. Soc. Pac., 
  101, 849.  [BIBCODE 1989PASP..101..849B ]
Budding, E., and Zeilik, M., (1987) Astrophys. J., 319, 827.  [BIBCODE 1987ApJ...319..827B ]
Laubscher, B.E., Gregory, S., Bauer, T.J., Zeilik, M. and Burns, 
  J.O., (1988) Pub. Astron. Soc. Pac., 110, 131.  [BIBCODE 1988PASP..100..131L ]
Takalo, L.O. (1986) Ph.D. Thesis. Pennsylvania State 
   University.  [BIBCODE 1986PhDT.........4T ]
Takalo, L.O., and Nousek, J.A. (1988) Ap. J., 326, 779-90. [BIBCODE 1988ApJ...326..779T ]