COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3036



                                        Konkoly Observatory
                                        Budapest
                                        22 June 1987

                                        HU ISSN 0374-0676


    INSTABILITIES IN THE LIGHT CURVE OF THE RR LYRAE STAR SS Leo

   As part of a long-term project to calculate Baade-Wesselink radii,
and hence absolute magnitudes, of RR Lyrae stars (Longmore et al. 1985,
Jameson et al. 1987) we obtained UBV photometry of SS Leo (P = 0.62634289 day)
on the night of 13/14 March 1987 using the 1m. telescope at the South
African Astronomical Observatory. During the ascending branch of the light
curve the star showed large fluctuations at all three wavelengths. The
comparison star HD 100269, which is less than half a degree distant, was
observed at 15 minute intervals and remained constant to within 0.02 mags
in each filter. The light curves of SS Leo are shown in the attached
figure.
   On the night of 9/10 April 1987 one of us reobserved the star. The
ascending branch on this occasion was quite normal.
   As far as we are aware, the behaviour of SS Leo on the night of 13/14
March 1987 is unique not just for this star but for any RR Lyrae (e.g. Lub
1977). We can find no reason to disbelieve our data; however, until these
observations have been independently reproduced there must be an obvious
question mark against their reality, and for this reason we feel further
analysis or comment is premature.


                            [FIGURE 1]




I. SKILLEN, Astronomy Dept., Leicester University, Leicester, England
J.A. FERNLEY, Physics and Astronomy Dept., University College London,
 London, England
D. KILKENNY, S. African Astronomical Observatory, Cape Town, S. Africa



References:

Jameson R.F., Fernley J.A. and Longmore A.J. 1987 M.N.R.A.S. Submitted
Longmore A.J., Fernley J.A., Jameson R.F., Sherrington M.R., and Frank J.
 1985 M.N.R.A.S. 216 873 [BIBCODE 1985MNRAS.216..873L ]
Lub J. 1977 Astr. Ap. Supp. 29 345 [BIBCODE 1977A&AS...29..345L ]