COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2950

                                                        Konkoly Observatory
                                                        Budapest
                                                        4 November 1986

                                                        HU ISSN 0374 - 0676


                          VARIABILITY OF Be STARS

Around 30 Be stars were monitored through red and near infra-red
photometry during the observing season 1982-83 and we had noticed that the
stars, HR 1508, HR 1789, HR 2538, HR 2996, HR 5193 and HD 45677 showed 
significant brightness fluctuations when compared with the earlier published
data.
   All programme stars including standard stars were observed with the standard 
RI passbands of the Johnson's system with a 20-seconds of arc diaphragm
for 4 nights. A photoelectric photometer attached to the 1.2 meter reflecting 
telescope of the Japal-Rangapur Observatory, Hyderabad, India was used
for the observations. A dry-ice cooled EMI 9558B photomultiplier tube was
used as the detector and the photocurrent was recorded by means of a GR
1230A - DC amplifier and a Honey-Well Brown chart recorder.
   The extinction coefficients for R and (R-I) were determined from the
observation of standard stars, taken from the list given by Johnson (1966),
and also from the observations of an early and a late spectral type star on
each night and all the observations were corrected for atmospheric extinction. 
The instrumental magnitudes of a programme star were transformed to the
standard system through normal procedure. Table I lists the observations
of the above mentioned six stars and the columns are self-explanatory. The
mean internal probable error of a single measurement in R and (R-I) is
+-0.02m and +-0.03m respectively.
   A few of the programme stars were observed earlier by Johnson (1965,
1966), Mendoza (1958) and Feinstein and Marraco (1979) on the standard RI
system. The variable nature of HR 1508, HR 1789, HR 2538, HR 2996, HR 5193
and HD 45677 is shown in the figure. A detailed version of this paper will
be published elsewhere.

   Figure 1 - 4  Variability of Be Stars. Red magnitudes (Filled Circles),
   Infra-Red Magnitudes (Filled Triangles).

                          [FIGURE 1]
                          [FIGURE 2]
                          [FIGURE 3]
                          [FIGURE 4]


HR 1508: This star suddenly became fainter by about 0.5m in both R, I
    passbands even though it had maintained constant level of brightness since
    1965 to early 1982.
HR 1789: Present observations show that this star is brighter in both R, I
    passbands but the brightness increase is much more predominant
    in I passband.
HR 2538: The present data indicates that the star is brighter by almost
    0.7m in both R, I compared to that of 1963 observations.
    Dachs et al. (1986) showed that the star brightened by almost
    0.5m in V passband and its color index (B-V) increased from
    -0.23 to -0.09 during the period 1965-83.
HR 2996: This star became fainter in both R, I passbands in the early
    part of 1983 even though it had maintained constant level of
    brightness from 1964 until late 1982.


                        Table I

Star        Sp.type         Heliocentric Date    R        (R-I)
                              of observation
                             (J.D. 2440000+ )

56 Eri      B2Ve            5315.1876           6.19      -0.13
HR 1508                     5315.1883           6.17      -0.11
                            5324.3049           6.10      -0.13
                            5324.3056           6.11      -0.13
                            5356.2545           6.13      -0.16
                            5356.2552           6.13      -0.16

25 Ori      B1VPe           5315.2984           4.81      -0.03
HR 1789                     5315.2991           4.81      -0.03
HD 35439                    5324.3155           4.88      -0.09
                            5324.3160           4.88      -0.08

Kappa CMa   B1.5 IVne       5324.4195           3.44      +0.02
HR 2538                     5324.4202           3.44      +0.02
HD 50013

3 Pup       A3q             5324.4262           3.68      +0.08
HR 2996                     5324.4269           3.68      +0.09
HD 62623                    5356.3815           3.92      -0.11
                            5356.3820           3.92      -0.11

mu Cen      B2 IV-Ve        5437.3450           3.63      -0.22
HR 5193                     5437.3455           3.63      -0.22
HD 120324

FS CMa      B3q             5356.3264           7.33      +0.08
HD 45677                    5356.3270           7.34      +0.07


HR 5193: Both R, I magnitudes are fainter than that of early 1965
         observations by about 0.3m.

HD 45677: The present observations show an increase in brightness by
          about 0.8m in both R, I passbands when compared with 1975
          observations.


                            G.C. KILAMBI
                         R. VIVEKANANDA RAO
                            M.B.K. SARMA

                 Centre of Advanced Study in Astronomy,
                        Osmania University
                         Hyderabad (India)


References:

Dachs, J., Hanuschik, R., Kaiser, D., Ballereau D., Bouchet, D., Kiehling, R.,
   Kozak,J., Rudolph, R., Schlosser, W., 1986 Astron. Astrophys., Suppl. Ser.
   63, 87. [BIBCODE 1986A&AS...63...87D ]
Feinstein, A. and Marraco, R.G., 1979, Astro. J. 84, 1713. [BIBCODE 1979AJ.....84.1713F ]
Johnson, H.L., 1965, Astrophy. J. 141, 923. [BIBCODE 1965ApJ...141..923J ]
Johnson, H.L., 1966. Comm. Lunar Planetary Labs. 4, 99. [BIBCODE 1966CoLPL...4...99J ]
Mendoza, V.E.E. 1958, Astrophy. J. 128, 207. [BIBCODE 1958ApJ...128..207M ]