COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2107

                                Konkoly Observatory
                                Budapest
                                1982 March 12

                                HU ISSN 0374-0676





         1981 UBVR PHOTOMETRIC OBSERVATIONS OF ER Vul


ER Vul (BD+27d3952, HD 200391, SAO 089396),  first observed spectroscopically 
by Northcott and Bakos (1946) and subsequently by them photometrically (1955), 
is one of the RS CVn binaries currently being observed at the University 
of New Mexico's Capilla Peak observatory. The object, an eclipsing
binary at right ascension 21h00m16.4s and declination +27d36'33.4" (1950) was
observed from August through November of 1981 with the 61-cm telescope and its
single-channel photon-counting photometer. The photometer employs a liquid
cooled (-20dC) EMR 641A phototube and UBVR filters obtained from Kitt Peak;
its output is fed directly to a microcomputer enabling rapid data access and
reduction.
The data reduction method was standard: comparison star (BD+27d3946)
minus source (ER Vul) minus sky. The data were obtained with an accuracy of
+-.01 magnitude or less, checked in real time at the  telescope.
Phase calculations were accomplished using HJD=2440182.3212+0.62892990 E
(Al-Naimiy, 1978). Table 1 lists the dates of observations and phases covered.
Figure 1 through 4 summarize the results.
Previously reported light curves by Northcott and Bakos (1976), Al-Naimiy
(1978), Hrivnak (1982) and Kadouri (1981) show remarkable  similarities, the
most notable being the substantial difference in depth between primary and
secondary minima (0.1 magnitude) and, by contrast, the similarity of the
shoulders (no more than 0.02 magnitude difference).

                         [FIGURE 1]
                         [FIGURE 2]
                         [FIGURE 3]
                         [FIGURE 4]

                        ER Vul 1981 Phase Log
                              Table I
-------------------------------------------------------------------
Date    Phase         Date    Phase             Date      Phase
-------------------------------------------------------------------
8-21   0.14->0.59    10-10   0.27->0.40        10-26    0.16->0.22
9- 3   0.60->0.70    10-18   0.70->0.13        11-10    0.63->0.73
9-20   0.37->0.53    10-21   0.99->0.03        11-19    0.56->0.66
9-27   0.91->0.04                              11-25    0.13->0.29
-------------------------------------------------------------------




   Our data confirm these results. In addition, we note that (1) the Intrinsic 
scatter in the system seems larger outside of eclipses (~0.04 mag) than
during them, (2) variations in the light curve are noticeable over a time as
short as a week. Both effects were also noted by Hrivnak (1982) and Zeilik et
al. (1982).






 M. ZEILIK, R. ELSTON, G. HENSON, P. SCHMOLKE, P. SMITH
                Capilla Peak Observatory
           Department of Physics and Astronomy
               The University of New Mexico
                 Albuquerque, NM  87131
                         U.S.A.



References:

Al-Naimiy, H. M. 1978, IBVS # 1481.
Hrivnak, B. J., 159th meeting of the American Astronomical Society,
   Boulder, Colorado, 1982.
Kadouri, R. S., 1981, IBVS # 2057.
Northcott, R. S. and Bakos, G. A., 1956. Astron. Journal, 61, p. 1238. [BIBCODE 1956AJ.....61..188N ]
Northcott, R. S. and Bakos, G. A., 1967, Astron. Journal, 72, p. 1. [BIBCODE 1967AJ.....72...89N ]
Zeilik, M. Elston, R., Henson, G., Smith, P., Schmolke, P., 159th
   meeting of the American Astronomical Society, Boulder, Colorado, 1982.