COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3179 Konkoly Observatory Budapest 25 April 1988 HU ISSN 0374-0676 VARIABILITY IN THE Be STAR SB 357 (=CD -37 316) Star number 357 in the survey of Slettebak & Brundage (1971) was classified 'B' type by them and B2 pec by Graham end Slettebak (1973) who also made observations in the Stromgren (uvby) system. Graham & Slettebak (1973) note that H-beta is not visible in their low dispersion spectrograms and that the star may have emission. This was confirmed by Heber & Langhans (1986) who found central reversal in all the Balmer hydrogen lines, HeI 4922, and possibly other helium lines. From uvby photometry and fitting the wings of H-gamma, they find Teff = 17900, log g = 4.0, V sin i = 130 km/sec, and a distance from the galactic plane of nearly 6 kpc, which is quite remarkable. SB 357 (=CD =37 316) has been observed with the SAAO 1m telescope in the 'faint blue' star programme (see e.g. Kilkenny 1987) and is clearly variable. Stromgren photometry from this programme is given in Table 1; the colours are typical of a B2-B3 star reddened by E(b-y) ~ 0.05, though there may also be variability in colour. Heber & Langhans (1986) give E(B-V) = 0.055 derived from Stromgren photometry. Some short sequences of almost continuous monitoring of SB 357 were made using Johnson B end V filters, also with the SAAO 1m telescope; these are listed in Table 2 and shown in Fig. 1. There is no evidence for any short period variability as big as 0.01 mag, on a timescale of less than 2-3 hours. The mean values given in Table 2 have standard deviations in the range 0.003 - 0.006 mag; I am grateful to Mr F. Marang who made the last two single observations with the SAAO 0.5m telescope. The observations on HJD 2447073 were tied to regular observations at the E-region standard E1/46 (Menzies, Banfield & Laing 1980) whilst those on HJD 2447119 and 7120 were corrected to the much nearer HD 5061 (= SB 352) which was classified A0Vn by Slettebak & Brundage (1971) and appears constant from SAAO observations tied to E-region standards (V = 8.640 +/- 0.004, B-V = +0.011 +/- 0.002; 17 observations on 3 nights). [FIGURE 1] Figure 1. V magnitudes from three short BV sequences of observations of SB 357 (= CPD -37 316). The Julian date of each run is noted and all observations are corrected to E1/46 or HD5061 (see text). Table 1. Stromgren photometry of SB 357 HJD V (b-y) m1 c1 Date 2446682.592 12.536 -0.063 +0.093 +0.251 8 Sep 86 6768.398 12.494 -0.043 +0.079 +0.193 3 Dec 86 6769.400 12.479 -0.030 +0.059 +0.202 4 Dec 86 6772.386 12.531 -0.071 +0.116 +0.208 7 Dec 86 7071.495 12.325 -0.017 +0.063 +0.210 2 Oct 87 7072.385 12.325 -0.017 +0.075 +0.186 3 Oct 87 .443 12.320 -0.017 +0.069 +0.197 .554 12.328 -0.027 +0.072 +0.187 7121.368 12.341 -0.020 +0.071 +0.177 21 Nov 87 .463 12.365 -0.042 +0.090 +0.192 ?122.365 12.362 -0.029 +0.066 +0.222 22 Nov 87 Table 2. BV photometry of SB 357 HJD V (B-V) n Date 2447073.44 to .58 12.331 -0.091 36 4 Oct 87 7119.34 to .43 12.382 -0.125 28 19 Nov 87 7120.36 to .44 12.367 -0.127 24 20 Nov 87 7123.39 to .40 12.351 -0.107 4 23 Nov 87 7127.344 12.382 -0.096 1 27 Nov 87 7128.337 12.377 -0.075 1 28 Nov 87 Considering all the date, there is weak evidence from the 1987 results around HJD 2447120-30 for variability on a time scale of >/~ 10 days and with amplitude >/~ 0.04 mag, but comparing 1986 and 1987 photometry indicates that variations of up to 0.2 mag are possible over a year or less. Given the unusual location of this apparently normal Be star, some 6 kpc from the Galactic plane, sustained monitoring would be worthwhile. DAVID KILKENNY S A Astronomical Observatory P O Box 9 Observatory 7935 South Africa References: Graham, J.A. & Slettebak, A., 1973. Astr. J., 78, 295. [BIBCODE 1973AJ.....78..295G ] Heber, U. & Langhans, G., 1986. 8 years of uv astronomy with the I.U.E. Satellite, ESA SP-263 p279, London. [BIBCODE 1986ESASP.263..279H ] Kilkenny, D., 1987. Mon. Not. R. astr. Soc., 228, 713. [BIBCODE 1987MNRAS.228..713K ] Menzies, J.W., Banfield, R.M. & Laing, J.D., 1980. SAAO Circular 5, 149. [BIBCODE 1980SAAOC...1..149M ] Slettebak, A. & Brundage, R.K., 1971. Astr. J., 76, 338. [BIBCODE 1971AJ.....76..338S ]