COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2221

                                  Konkoly Observatory
                                  Budapest
                                  1982 November 4

                                  HU ISSN 0374-0676





              1982 PHOTOMETRY OF ER VUL


   We have completed a light curve for ER Vul (BD+27deg3952, HD 200391, SAO
089396) within a one week period in October 1982 to minimize the effects of
short-term, intrinsic variations. We carried out the observations at the
Capilla Peak Observatory of the University of New Mexico. Our 61-cm Boller
and Chivens telescope has a single-channel, photon-counting photometer with
a cooled EMR 641A phototube and a Kitt Peak UBVR filter set. A microcomputer
controls the photometer (Elston and Zeilik, 1982); its on-line data reduction
assures that observations obtain a statistical error of no more than +/-0.01 mag.
   As for our 1981 observations (Zeilik et. al., 1982), we used BD+27deg3946
as our comparison star. Observations of this star over a wide range of air
masses resulted in a good determination of the UBVR extinction coefficients.
Phases were calculated from HJD=2440182.3212 + 0.62892990E (Al-Naimiy, 1978).
Dates (UT) and phases covered were: 3 Oct., 0.17 to 0.50; 6 Oct., 0.47 to 0.73;
7 Oct., 0.82 to 0.19; and 9 Oct., 0.69 to 0.89. Figures 1 through 4 summarize
the results in instrumental magnitudes; actual observational points are shown
not normal points. Note that our data is comparison minus source, the opposite
of the usual convention, so the y-axis lacks a minus sign.
   We can compare these observations to those in 1981 by ourselves and Kadouri
(1981), who used the same comparison star. First, the overall system brightness



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



has decreased by 0.05 mag. at U, 0.04 mag. at B, 0.05 mag. at V, and 0.03 mag.
at R. Second, the shoulder at phase 0.25 is still depressed and more symmetrical
than that at 0.75. Third, the primary eclipse is still deeper than the secondary,
but the difference has decreased a little -- by about 0.01 mag. at UBV. Fourth,
both limbs appear flatter than before.
   As noted by Kadouri (1982), the ephemeris from Al-Naimiy (1978) no longer
gives consistent results; both the primary and secondary eclipses have shifted
~+0.05 phase with respect to that predicted from the earlier ephemeris.
   We are planning to continue observations of this system at least once a
year to track its variations.





       M. ZEILIK, B. BACA, D. BATUSKI, S. BURKE, R. ELSTON, and P. SMITH

                    Capilla Peak Observatory
               Department of Physics and Astronomy
                  The University of New Mexico
                     Albuquerque, NM 87137.
                            U.S.A.





 References:


 Al-Naimiy, H. M., 1978, IBVS # 1481.
 Elston, R. and Zeilik, M., 1982, Pub. Astron. Soc. Pacific, Vol. 94, p. 729. [BIBCODE 1982PASP...94..729E ]
 Kadouri, T. H., 1981, IBVS # 2057.
 Zeilik, M., Elston, R., Henson, G., Schmolke, P., and Smith, P., 1982,
    IBVS # 2107.