COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1301


                                 Konkoly Observatory
                                 Budapest
                                 1977 July 5




PHOTOMETRIC VARIABILITY OF THE NONRADIAL PULSATOR 53 PERSEI



    It has been shown recently (Smith 1977) that line profile
variations in many sharp-lined early to mid B-type stars (Petrie
and Pearce, 1962, Smith and Karp 1976) can be mimicked easily
and quantitatively by a traveling wave velocity field which is
characteristic of a nonradial pulsation. The photometric behaviour 
of these stars (see also Percy 1970) is of interest because
it gives information on the surface temperature variation during
the wave cycle. This note reports evidence for a small light 
variability in 53 Persei (HR 1350, B4.5V; Mv=4.88) which exhibits
large amplitude profile variations. Smith and McCall (1978)have
observed the star over several months and concluded that it 
exhibits a complex, time dependent period spectrum, with usually
one period present with a value of from 3.6 to 14.45 hours.
    Differential photometry in the Stromgren v-filter was carried 
out on the nights of December 23 and 24, 1976 on the 30-
inch telescope of McDonald Observatory. The Stromgren v-filter
was used as a compromise between the requirements of a larger
expected amplitude in the ultraviolet and the more stable 
extinction properties in the blue wavelength region. Each 
"observation" consists of an average of six ten-second star-sky 
integrations. The average r.m.s. error was computed by averaging
through the night the r.m.s. from the individual integrations
in an observation. For the three stars figures are +- 0.0023
(night 1) and +- 0.0011 (night 2). Observations were not 
continued past 1.6 air masses.

     Our standard observing sequence consists of a Standard 1,
Program Star, Standard 2 cycle. We chose as standards lambda Per


(HR 1261, B9V) and HR 1482 (A0V) two stars with no known history 
of variability and in a nonvariable region of the H-R Diagram.

    The results are depicted in Figure 1, displayed both in
terms of the difference between two standards (Figs. 1b and 1d)
and of the program star minus the average of the two standards
(Figs. 1a and 1c). From the first night one can conclude that
a decrease of 0.01 mag. occurs in about four hours. This result
is nearly identical to the July, 1976 results of Percy and Lane
(1977) for this star, which may be a coincidence since it is
not clear that the star exhibited the same period during both
times. The observations of the second night show smaller scatter,
but since the star was monitored for only two hours no variability 
is evident.                           
    In Figure 2 we have drawn in a curve by means of an assumed 
7.29 hour period (phase convention due to Osaki 1971) which
was determined a few nights later (December 28-31) by Smith and    
McCall spectroscopically. At this point one can say only that
our data are consistent with their period. It is also too early
to decide whether the light curve is sinusoidal or not.
    The unravelling of the complex period behavior in 53 Per
(which may be due to nonlinear coupling between physically driven 
nonradial modes (Smith and McCall 1978)) is a long-term 
observational problem with fruitful rewards. When the excited 
nonradial modes can be identified correctly in this and other B
stars it will be possible to isolate the region of the star
which excites the oscillations. It is to be wholeheartedly 
recommended that 53 Per be put on photometric variability 
programs, particularly since photometricists with easily accessible
small telescopes will be able to add vastly to the data pool
for this object. However, they should be advised, first, that
the periods for this class of objects appear to be about twice
that of the Beta Cepheids (Smith, unpublished) and, second, that
the photometric variations of the smaller amplitude line profile
variable B stars may well escape detection.

                     [FIGURE 1]

Fig. 1: Photometric results (Stromgren v-filter) for 53 Persei during
December 23 and 24, 1976. Panels (c) and (d) give the differences as a 
function of time of the apparent magnitudes between two standards,
HR 1261 and HR 1482 (zero level is arbitrary). Panels (c) and (d) give
the magnitude differences between 53 Persei and the average of the two 
standards; the zero level is determined from Figure 2.

                     [FIGURE 2]

Fig. 2: Composite observations for 53 Persei from Fig. 1. A period of 
7.29 hours has been assumed, based on a separate spectroscopic study.
The zero magnitude level is set at the average apparent magnitude.


                                        JOHN AFRICANO

                                        McDonald Observatory
                                        Fort Davis, Texas 79734

References:

Osaki, Y. 1971 Pub.A.S.J., 23, 485 [BIBCODE 1971PASJ...23..485O ]
Percy, J.R. 1970, A.J., 75, 818 [BIBCODE 1970AJ.....75..818P ]
Percy, J.R., and Lane, M.J. 1977, A.J. [BIBCODE 1977AJ.....82..353P ]
Petrie, R.M. and Pearce, J.A. 1962, Pub. D.A.O., 12, 1 [BIBCODE 1961PDAO...12....1P ]
Smith, M.A. and Karp, A.H. 1976, Los Alamos Conf. on Solar and Stellar Pulsation, Aug. 3-5th, p.289 [BIBCODE 1976ssp..conf..289S ]
Smith, M.A., and McCall, M.L. 1978, Ap.J., in press [BIBCODE 1978ApJ...223..221S ]
Smith, M.A. 1977, Ap.J., 215 [BIBCODE 1977ApJ...215..574S ]