COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3031


                                       Konkoly Observatory
                                       Budapest
                                       5 June, 1987

                                       HU ISSN 0374-0676


                  SPOT OBSERVATIONS OF EV Lac

  Presented here are the preliminary results of our photometric observations 
of the spotted flare star, EV Lac. In particular, this paper discusses
the results of this last season of observation covering the period from August
1986 to December 1986 and its noted differences from that of previous observations.
We also suggest a more suitable second comparison star than the one in
standard use. The present observations were taken with the 41 cm telescope at
Table Mountain Observatory in four colors (UBVR) using a pulse counting
photometer. Carol Ambruster has also provided some data taken with the 36
inch reflector at Kitt Peak. A more detailed report of our results and
methods of analysis will be forthcoming in another publication.
   In 1983, EV Lac was found to vary with a total amplitude in V of 0.08
mag. and a period of 4.375 days (Pettersen et al. 1983). These data were
taken between June 1979 and December 1981. In 1985, we began our observations
and found no discernible variation of the star. This period of nonvariability
was later confirmed by other observers (Skiff, Brian, private communication)
(Melikan, N.D., Melkonian, A.C., private communication).
   In August of 1986, we started observing EV Lac again and found a new
variation of 0.13 mag. as opposed to Pettersen's (1983) 0.08 mag. Pettersen's
period of 4.375 days was assumed, and found to fit our data very well. There
was, however, a phase shift noted from Pettersen's (1983) ephemeris, as one
would expect if observing a new spot. The phase difference was measured to be
-0.236 phase or -1.033 days. We therefore propose a new ephemeris for maximum


                                [FIGURE 1]

 Fig. 1. (P-C1) V magnitude vs. phase for EV Lac. The starred points were
         taken at Table Mountain and the triangles at Kitt Peak.


spot visibility to be JD 2446499.18 + 4.375*E adjusted from Pettersen's (1983)
result for both the phase difference and the approximate appearance data of
the new spot. Figure 1 is a plot of the differential V magnitude in P-C1 vs.
phase using our new ephemeris. The starred points are the points taken at
Table Mountain, and the triangles are those from Carol Ambruster at Kitt Peak.
  Pettersen (1983) reported no noticeable variation in the V-R. Our new
results, however, do suggest a small but visible variation of 0.03 mag., again
suggesting a newer, larger spot than previously observed.
  We have long been suspicious of the comparison star, C2, proposed by
Pettersen (1980) and which has recently been confirmed to be variable
(Tsvetkov et al. 1986). The C2 we have employed is SAO 052337, an 8.9V, R2
star which has worked quite well. It is also close enough to EV Lac and the
standard C1 so that differential extinction is not usually a problem.
  We would be grateful for correspondence regarding any data you might have
that may help in defining this new variation or its connection to past
observations.



        SCOT J. KLEINMAN, WILLIAM H. SANDMANN   CAROL W. AMBRUSTER
        Department of Physics                   JILA
        Harvey Mudd College                     University of Colorado
        Claremont, CA 91711                     Boulder, CO 80309





References:

Pettersen, B.R., 1980, Astron. J. 85.7.871 [BIBCODE 1980AJ.....85..871P ]
Pettersen, B.R., Kern, G.A., Evans, D.S., 1983, Astron. and Astrophys.
  123.184 [BIBCODE 1983A&A...123..184P ]
Tsvetkov, M.K., Tsvetkov, K.P., Melikan, N.D., 1986, I.B.V.S. No. 2954