COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2173

                                  Konkoly Observatory
                                  Budapest
                                  1982 July 2

                                  HU ISSN 0374-0676





       VBLUW MEASUREMENTS OF THE SHELL STAR PLEIONE


Measurements in the Walraven VBLUW system were performed of Pleione,
the well known shell star in the Pleiades cluster (HD23862, m_v= 5.20.
Sp. type B8Vn + shell according to Abt and Levato (1978)). The measures
were made in the periods 1977 November and December, 1979 November,
1980 November and 1981 October and November, with the Walraven VBLUW
photometer on the Dutch 91cm telescope at the ESO site on La Silla,
Chile (see Lub (1979) for further references). The observations of 1977
were performed before the telescope and photometer were moved from the
Leiden Southern Station on the SAAO annex near the Hartbeespoortdam
in South Africa to the ESO site.
Golay and Mauron (1982) presented data for Pleione on the Geneva system,
obtained between 1962 and 1979 December. The data presented here can be
seen as an extension to these measurements up to 1981 November and are
therefore presented in a similar way. Table I gives the data and their
estimated mean errors (in units of 0.001 magn) as differences in magnitudes
between Pleione and Maia (HD 23408, m_v = 3.88 Sp.type B8 IV sn).
The 1981 measurements are split into three groups. All data are shown in
Fig. 1.



                                 Table I
Date            DeltaV m.e. DeltaB m.e. DeltaL m.e. DeltaU m.e. DeltaW m.e.   n

1977 Nov.-Dec.    1.343 2    1.390 3      1.438 4       1.593 6      1.686  10    2
1979 Nov.         1.348 1    1.375 1      1.440 2       1.770 3      2.055   5    3
1980 Nov.         1.350 1    1.380 1      1.470 2       1.873 3      2.185   4    1
1981 Oct.18-23    1.340 0    1.378 0      1.463 1       1.900 1      2.273   2   11
1981 Oct. Nov.6   1.340 0    1.378 0      1.465 1       1.898 1      2.265   2   19
1981 Nov.17       1.340 1    1.375 1      1.460 2       1.910 3      2.250   4    2

                           [FIGURE 1]

Figure 1. Differences in magnitude between Pleione and Maia for the five
Walraven channels as measured during the years 1977 till 1981.

The Ultra Violet blocking by the Hydrogen shell clearly increased during
1980 and 1981, but the increase goes less rapidly than in the years 1977
to 1979. The blocking is prominent in the Balmer continuum and does not
influence the B V and L channels. The slope becomes less steep towards
the W channel, which is in agreement with IUE observations during 1978-1979
(see Golay and Mauron), which show a maximum absorption at about 2500 A.
The 1981 measurements may indicate some shorter time scale variations in
U and W. On November 17 the U flux had decreased by 0.012 magnitudes,
while the W flux had increased by 0.015 magnitudes with respect to the
October measurements.




F. VAN LEEUWEN                J.J.M. MEYS   and P. ALPHENAAR
Royal Greenwich Observatory   Sterrewacht te Leiden
Herstmonceux Castle           Postbus 9513
Hailsham, East Sussex         2300 RA Leiden
BN27 1RP                      Netherlands
Great Britain





References;

Abt, H. A. and Levato H., 1978: Publ. Astron. Soc. Pacific 90, 201-203 [BIBCODE 1978PASP...90..201A ]
Golay, M. and Mauron, N., 1982: Astron. Astroph. Suppl. Ser. 47, 547-559 [BIBCODE 1982A&AS...47..547G ]
Lub, J., 1979: ESO Messenger 19. [BIBCODE 1979Msngr..19....1L ]