COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1530

                                 Konkoly Observatory
                                 Budapest
                                 1979 January 8




            THE LIGHT VARIATIONS OF HR 9070


   It is sobering to realize that even among the stars in the Yale Catalogue
of Bright Stars (YCBS), there are probably several hundred variable stars
yet to be discovered, and several hundred more whose variability is not well.
understood. One example is HR 9070 (HD 224559, R.A. (1900) = 23h53m41s
Dec. (1900) = +45d51'). This star has been variously classified as B3 IV,
B3:nne and B4 V nnne; the B3 IV classification (which appears in the YCBS) is
not necessarily an indication that the emission is variable, but may simply
be due to the different plate material used. Recent plates taken with the
1.9 m reflector at the David Dunlap Observatory show emission at Hbeta quite
clearly (Fraquelli, private communication).
   The star is listed as VAR? in the YCBS, probably on the basis of the
extensive observations by Provin (1953), who used it as a comparison star for
HR 9080. Provin found variations of 0.03m in a few hours, when comparing HR
9070 with HR 1. The star was reobserved by Percy and Lane (1977), who also
found variations of about 0.03m in a few hours.
   Further photometric observations have now been made, using the 0.4 m
reflector at Kitt Peak National Observatory (Percy and Lane 1977) and, on one
night only, the 0.4 m reflector on the campus of the University of Toronto.
The observations are shown in Figure 1, which indicates the filters (Stromgren
b or y or Johnson B) and the comparison star used. A table of the observations 
can be obtained by writing to the author.
   On each night, the star varies with a quasi-period of about 6h and a
range of 0.02m to 0.06m. In this sense the star mimics the light variations
of a beta Cephei star exactly. Perhaps the star is a beta Cephei star; if so, it
would be the first beta Cephei star with Be star characteristics. The period

                              [FIGURE 1]

   Figure 1. Photometric observations of HR 9070 on six nights.
   The filter and comparison star are indicated.

(6h) is longer than would be expected for a beta Cephei star of this luminosity,
although the luminosity of HR 9070 is difficult to determine because of the
nature of the spectrum.
   On the other hand, it is well known that the Be stars tend to be variable 
in light, and it is becoming increasingly evident that the major light
variations of Be stars occur on a time scale of hours rather than a time scale
of days or weeks as previously believed (Percy and Lane 1977, Jakate 1979);
the cause of these short-period variations is not known. Yet another kind
of variable star has recently been discovered in this same part of the HR
diagram: the non-radial pulsators of which 53 Per is the prototype (Percy and
Lane 1977; Buta and Smith, preprint).
   Spectroscopic observations would obviously shed some further light on
the nature of HR 9070. The radial velocity is marginally variable according
to Petrie (1958) but probably constant according to Wilson and Joy (1950).
With such a difficult spectrum, small velocity variations due to pulsation
might well go unnoticed.
   The purpose of this paper, then, is to point out that (i) the identification 
of specific types of variables among the early B stars is no longer
simple, so that searches for beta Cephei stars (for instance) must be conducted
with great care and (ii) at least one Be star shows quasi-regular light
variations with a short period. There may in fact be some relationship
between the classical beta Cephei stars and the Be star variables.
   I am grateful to Dorothy A. Fraquelli for obtaining and examining the
spectrograms of HR 9070, to Alan H. Batten for providing the individual 
velocities obtained by Petrie (1958), and to Kitt Peak National Observatory for
providing observing time. This work was supported by an operating grant from
the National Research Council of Canada.


                         JOHN R. PERCY
                         Department of Astronomy  
                         University of Toronto
                         Toronto, Canada M5S 1A7



References:

Wilson, R.E. and Joy, A.H. 1950, Ap. J. 111, 99. [BIBCODE 1950ApJ...111..221W ]
Jakate, S.M. 1979, Ph.D. thesis, University of Toronto. [BIBCODE 1979PhDT........31J ]
Percy, J.R. and Lane, M.C. 1977, A.J. 82, 353. [BIBCODE 1977AJ.....82..353P ]
Petrie, R.M. 1958, M.N.R.A.S. 118, 80. [BIBCODE 1958MNRAS.118...80P ]
Provin, S.S. 1953, Ap.J. 118, 489. [BIBCODE 1953ApJ...118..489P ]