COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2829

                                  Konkoly Observatory
                                  Budapest
                                  3 December 1985

                                  HU ISSN 0374 - 0676


             A NEW PERIOD FOR AP SERPENTIS



  The variable AP Ser, discovered by Hoffmeister (1935), is
an RR Lyrae star of type c, with a short period. The first
known reference on the determination of the period is to
Solovyev (1940). This is made in the first edition of the
General Catalogue of Variable Stars by Kukarkin & Parenago
(1948). They mention a period of 0.254464 days; subsequent
editions give only minor corrections. No recent attempts
seem to have been made to verify this period, although the
available lightcurves are clearly irregular, even for an RRc
type variable suffering from the Blazhko effect. See for
example Varsavsky (1960) or even Lub (1977).


                    [FIGURE 1]
                    [FIGURE 2]


  142 new measurements, made in the VBLUW-system by A.M.
van Genderen in 1975 as part of a programme to study lightcurve 
variations (as yet unpublished), were analyzed with the
aid of a computer programme based on the method described by
Stellingwerf (1978), which seeks to minimize the dispersion 
at constant phase. From this analysis a new period of 
0.341320 days has been derived. The theta-transform of the
data shows several major dips, which are identified in
Figure 1. It is clear that the formerly assumed period is an
alias of the correct one with the sidereal day. The B-lightcurve, 
shown in Figure 2, is now typical for a c-type
RR Lyrae star.


                            J.W. DE BRUIJN

                                and

                              J. LUB


                            Sterrewacht Leiden
                            Wassenaarseweg 78
                            Leiden, Holland


 References :


 Hoffmeister, C. (1935), Astronomische Nachrichten 255, 401. [BIBCODE 1935AN....255..401H ]
 Kukarkin, B.V., Parenago, P.P. (1948), Obshchy Katalog
                            Peremennykh Zvyozd.
 Lub, J. (1977), Astronomy & Astrophysics Suppl. 29, 345. [BIBCODE 1977A&AS...29..345L ]
 Solovyev, A.V. (1940), Astronomichesky Tsirkulyar 2.
 Stellingwerf, R.F. (1978), Astrophysical Journal 224, 953. [BIBCODE 1978ApJ...224..953S ]
 Varsavsky, C.M. (1960), Astrophysical Journal 131, 623. [BIBCODE 1960ApJ...131..623V ]