COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1986

                                    Konkoly Observatory
                                    Budapest
                                    1981 July 6

                                    HU ISSN 0374-0676


          RAPID OSCILLATIONS IN RR PICTORIS *


Novae are very rare among the cataclysmic variables which
show ultra short light variations with periods around 30s
and Q = 1/|dP/dt| ~10^4 - 10^5. The oscillations in dwarf
novae seem to be strongly correlated to eruptions. Two nova
like objects UX UMa and V3885 Sgr presumably in continuous
outburst stage, are also known to show rapid oscillations,
and there was RR Pic already mentioned by Warner (1976, 1981)
who found periods between 20 and 40s.
Simultaneous photometric and spectroscopic observations have
been performed during two nights in Dec., 1980. Table I gives
a summary of the photometric observations and results.

                  Table I.

Start           Stop    Oscillation       dP/dt * 10^5
HJD-2444500             Period P(s)
                        at Start

76.70976   76.84133      31.54               1.2
77.69081   77.77000      31.31               0
77.77000   77.84014      31.42               0

Telescope: 1.5m Time resolution: 1s   Filter: B


While in the first night a single slowly increasing period of
initially 31.5s prevailed, two different quasiconstant periods
of 31.3s and 41.4s existed separately with a sudden changeover
about in the middle of run 2. Figures 1a, b, c and 2a, b, c
show light curve, relative amplitude and phase variation of the

* Based on observations collected at the European Southern
Observatory, Veroffentlichungen der Sternwarte Munchen, Bd. 7
Nr. 33


                       [FIGURE 1]

 Fig. 1a,b,c Run 1. Light curve of RR Pic, relative amplitude
             of oscillation and phase variation of oscillation
             versus orbital phase.
 Fig. 1d     Run 1. Autocorrelation function (slow intensity
             variations subtracted, value of zero delay omitted)
 Fig. 1e     Run 1. Periodogram. Relative amplitude versus
             periods per day.

                       [FIGURE 2]

 Fig. 2a-e   Run 2. Same as Fig. 1a-e


oscillation versus orbital phase for the two nights respectively. 
The orbital phase is according to Vogt (1975) who defined
 phi = 0 for the main brightness maximum: HJD (MAX) = 2438815.379
+ .1450255*E. Primary eclipse occurs at phi = .75 (Haefner et al,
1981). The oscillation amplitude in both nights is small around
orbital phase .6 before primary eclipse. However no strong
phase shift of the oscillation during eclipse occurs, as was
found by Nather (1974) for UX UMa and Patterson (1979) for
HT Cas. The oscillations maintained phase stability as long as
they were detectable, with a phase-jitter of approx. +-50d
for a fitted sine track of 40 periods. From the autocorrelation 
functions (Fig. 1d, 2d) Q was determined to Q >~ 10^5(run 1)
and Q ~ 10^4(run 2). These values coincide quite well with those
known for dwarf novae. In run 2 during phase .2 +- .1 a broad
minimum of the oscillation amplitude is seen and both runs
show a steep increase to maximum (phi ~ .85) just after eclipse.
Fig. 1e and 2e show a periodogram in the range of 25-50s 
demonstrating the signal to noise ratio. The double peak of Fig. 2e
is produced by the two oscillation periods. The fact that no
phase shift during eclipse is observed (Fig. 1c, 2c) may be
interpreted by a partial eclipse which does not affect the
oscillating source. The orbital inclination of RR Pic according 
to Haefner et al. (1981) is 65d and they claim that only
the outer rim of the disc is eclipsed by the secondary. This
confirms the central location of the oscillation source. The
low oscillation amplitude around orbital phase .2 (run 2)
and .6 (run 1, 2) could be due to veiling of the centre by
the disc itself which may have an increased z-dimension at
such areas which are between primary and observer during the
relevant phases. In the model of Haefner et al. these areas
coincide with the normal hot spot and a hot area on the outer
disc.

                        R. SCHOEMBS, B. STOLZ
                    Universitats-Sternwarte Munchen
                           Scheinerstr. 1
                         D-8000 Munchen 80

References:
Haefner, R., Metz, K. 1981, submitted to Astron. Astrophys. [BIBCODE 1982A&A...109..171H ]
Nather, E.R., Robinson, E.L. 1974, APJ 190, 637 [BIBCODE 1974ApJ...190..637N ]
Patterson, J. 1979, Ph. D. Dissert.,The Univ. of Texas, Austin [BIBCODE 1979PhDT.........5P ]
Vogt, N. 1975, Astron. Astrophys., 41, 15 [BIBCODE 1975A&A....41...15V ]
Warner, B. 1981, Mon. Not. R. Astr. Soc. 195, 101 [BIBCODE 1981MNRAS.195..101W ]