COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2234 Konkoly Observatory Budapest 1982 November 25 HU ISSN 0374-0676 FOUR COLOUR PHOTOMETRY OF THE BRIGHT PRE-MAIN SEQUENCE SHELL STAR V856 Sco (HR 5999) The semi-regular variable V856 Sco (=HR 5999 = HD 144668) has recently aroused much interest as a bright probable pre-main sequence star (see, e.g. The and Tjin A Djie, 1978; Tjin A Djie et al., 1982). Its brightness undergoes irregular variations of a few tenths of a magnitude, interrupted on time scales of months by deep minima (~1.5 mag deep) lasting a few days or weeks. V856 Sco forms a visual binary system with HR 6000, a late B star with remarkable spectral peculiarities (Castelli et al., 1981). HR 6000 seems to be constant in light (The and Tjin A Djie, 1978) and radial velocity (Andersen and Nordstrom, unpublished). V856 Sco was monitored in the Stromgren uvby system from February 2 through 25, 1981, using the Danish 50 cm reflecting telescope on La Silla, Chile, and the 4-channel photometer and pulse-counting equipment described by Gronbech et al. (1976). HR 6000 was used as the comparison star and appears constant Table I: Magnitude differences V856 Sco - HR6000 H J D y b-y m1 c1 b v u 2444638.86657 0.112 0.211 0.049 0.494 0.322 0.583 1.336 2444639.87099 0.122 0.216 0.049 0.527 0.338 0.603 1.395 2444639.87343 0.118 0.216 0.051 0.523 0.334 0.602 1.392 2444640.84274 0.239 0.229 0.048 0.484 0.469 0.746 1.507 2444640.84704 0.242 0.231 0.045 0.486 0.473 0.750 1.513 2444640.87215 0.247 0.230 0.047 0.484 0.476 0.753 1.514 2444641.87063 0.254 0.234 0.044 0.505 0.488 0.767 1.551 2944642.89446 0.419 0.242 0.058 0.503 0.660 0.960 1.764 2444643.87916 0.296 0.238 0.046 0.483 0.534 0.819 1.586 2444644.86374 0.198 0.222 0.054 0.489 0.420 0.696 1.461 2444645.88509 0.157 0.218 0.047 0.495 0.376 0.641 1.402 2494648.85685 0.129 0.220 0.046 0.507 0.349 0.616 1.389 2444649.89295 0.130 0.209 0.059 0.485 0.340 0.608 1.361 2444650.89684 0.132 0.211 0.058 0.487 0.342 0.611 1.366 2444651.88671 0.119 0.211 0.056 0.501 0.330 0.597 1.364 2444653.84944 0.114 0.211 0.043 0.495 0.325 0.578 1.327 2444654.84873 0.134 0.212 0.054 0.512 0.346 0.612 1.390 2944555.88873 0.122 0.214 0.051 0.506 0.337 0.602 1.374 2444656.90070 0.142 0.210 0.053 0.540 0.352 0.615 1.419 2444658.88793 0.240 0.214 0.055 0.517 0.459 0.723 1.509 2444659.89806 0.291 0.232 0.053 0.530 0.524 0.809 1.624 also during our observations, extinction coefficients being available from other programme stars observed the same nights. During the same period, coude spectra were obtained with the ESO 1.5 m telescope to monitor the suspected radial velocity variations of V856 Sco. The spectroscopic results will be published later. Table I lists the observed magnitude differences in the sense V856 Sco - HR 6000 in the instrumental system. For transformation to the standard uvby system, use the coefficients given by Clausen et al. (1976) and the standard uvby indices for HR 6000 by Gronbech and Olsen (1976) - (note that HR 5999 and HR 6000 have been interchanged in this catalogue). During the period of our observations, the brightness of V856 Sco varied through a range of 0.3 mag, but no deep minimum occurred. We plan no further photometry of this star at present. This work was supported by the Danish Board for Astronomical Research and the Danish Natural Science Research Council. J. ANDERSEN, J.V. CLAUSEN B. NORDSTROM Copenhagen University Observatory Brorfelde, DK-9340 Tollose Denmark References: Castelli, F., Cornachin, M., Hack, M.: 1981, Proc.Liege Colloq. No. 23. Univ. de Liege, 199 [BIBCODE 1981LIACo..23..149C ] Clausen, J.V., Gyldenkerne, K., Gronbech, B.: 1976, Astron. Astrophys. Suppl. 23, 261 [BIBCODE 1976A&AS...23..261C ] Gronbech. H., Olsen, E.H.: 1976, Astron.Astrophys.Suppl. 25, 213 [BIBCODE 1976A&AS...25..213G ] Gronbech, B., Olsen, E.H., Stromgren, B.: 1976, Astron.Astrophys. Suppl. 26, 155 [BIBCODE 1976A&AS...26..155G ] The, P.S., Tjin A Djie, H.R.E.: 1978, Astron.Astrophys. 62, 439 [BIBCODE 1978A&A....62..439T ] Tjin A Djie, H.R.E., The, P.S., Hack, M., Selvelli, P.L. 1982, Astron. Astrophys. 106, 98 [BIBCODE 1982A&A...106...98T ]