COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      NUMBER 370


                                 Konkoly Observatory
                                 Budapest
                                 1969 August 13


  A COMPARISON SEQUENCE TO THE FLARE STAR EV LACERTAE


      Establishment of photoelectric comparison sequences
to a number of flare stars may be valuable for a quick 
determination of magnitudes of these stars made in the course
of visual, photographic or photoelectric flare monitoring.
On the other hand, the need exists to study possible slow
(secondary) light variations of flare stars. The sequence to
the star YZ CMi has been recently given (ref. 1) and now we
have obtained one for the star EV Lac. Magnitudes and colours
of both flare stars have been determined as well and these
may serve as initial points in the studies of secondary
variations.
      The present observations were made at the Crimean
Astrophysical Observatory on two nights. The 70 cm reflector
equipped with an E.M.I. 6256 photomultiplier and conventional
UBV filters was used. Twelve stars in the cluster IC 4665
and five in Selected Areas SA 18 and SA 66 served as the
standards for transformation of colour systems and extinction
determinations. Magnitudes and colours of these stars
were taken from papers of Johnson (ref. 2) and Priser
(ref. 3). The resulting accuracy of observation was about
+/-0.015m for V magnitudes and (B-V) colours and +/-0.03m for
(U-B) colours. No systematic differences were found in 
observations between two nights.


                                             Table I

Star                                 V         (B-V)    (U-B)
BD +43d4299                         9.21        +1.17    +1.00
   +43 4302                         8.45        +0.46    -0.03
   +43 4303                         9.92        +1.40    +1.31
   +43 4304                        10.79        +0.24    -0.21
EV Lac                             10.25        +1.58    +1.06

Optical companion, a few seconds
of arc to the west of EV Lac
(Hel. Ph. Cat. +43d22h45m No 115)  12.00        +0.74    +0.21
EV Lac + opt.companion             10.05        +1.37    +0.75



      Table I contains the mean data of two nights (July
7-8 and 8-9). The V magnitude and (B-V) colour for EV Lac
differ considerably from previous measurements of Mumford
(ref. 4) but if we compare his data with those contained in
the last line of Table I it seems highly likely that he
measured the total light of EV Lac and its optical companion.




REFERENCES

1) A. D. Andrews, I.B.V.S. No. 342 (1969)              
2) H. L. Johnson, Astrophys. Journ., 119, 181 (1954) [BIBCODE 1954ApJ...119..181J ]
3) J. B. Priser, Publ. Astron. Soc. of Pacific, 78, 474 (1966) [BIBCODE 1966PASP...78..474P ]
4) G. S. Mumford, Astron. Journ., 61, 213 (1956) [BIBCODE 1956AJ.....61..213M ]




           A. D. ANDREWS            P. F. CHUGAINOV
        Armagh Observatory        Crimean Astrophysical
                                       Observatory