COMMISSIONS 27 AND 42 OF THE IAU 
             INFORMATION BULLETIN ON VARIABLE STARS 
                          Number 3765 
 
                                          Konkoly Observatory 
                                          Budapest 
                                          8 September 1992 

                                          HU ISSN 0374 - 0676 
 
           PHOTOMETRY OF TWO BRIGHT EARLY-TYPE BINARIES: 
                     HD 101205 and HD 152248^1 
 
 1) Based on observations collected at the European Southern 
Observatory, La Silla, Chile 
 
 During observing periods with the 50 cm telescope at La Silla in 
February/March and May 1992, several early-type eclipsing binaries 
were measured in the UBV system. Here the results on two of them are 
reported. Both are listed in the New Catalogue of Suspected Variable 
Stars (Kholopov 1982), are members of open clusters and are brighter 
than 6.5m, though not listed in the Bright Star Catalogue. 
 
 HD 101205:  A member of the open cluster IC 2944; NSV 5277, spectral 
type is O7 III n((f)) according to Walborn (1973). Recently Balona 
(1992) discovered that this star is an eclipsing binary with a period 
of 2.084d (in this paper HD 101205 was erroneously designated as HD 
101191). Our new light curve is plotted in Fig. 1. The comparison 
star was HD 101298, the check star HD 101131. A normal minimum time 
of JDhel. 2448684.737 +/- 0.004d was derived from the light curve. 
Unfortunately the period is not known accurately enough to fix the 
number of cycles between our new minimum and Balona's determination 
unambiguously; among the possible alias periods, the value closest to 
the period given by Balona is 2.0842d. The amplitude in both minima 
is about 0.08m, in agreement with Balona's measurements. According 
to Thackeray and Wesselink (1965) as well as to Ardeberg and Maurice 
(1977), the star has variable radial velocity (SB1 type). 
 
 HD 152248:  This is a member of the well-studied open cluster NGC 
6231; NSV 8022, spectral type is 07 Ib:(n)(f)p according to Walborn 
(1972). Perry et al. (1991) classified the star as EB - but no 
period or light curve has been published. As known from spectroscopy 
by Struve (1944), Hill et al. (1974) and Levato and Morrell (1983), 
the star is of SB2 type with a period close to 6 days (two radial 
velocities reported by Hayford (1932) also do not contradict this 
period). From our Feb/March photometry the period should be:  about 
5.85d +/- 0.05d. The May data, compared with this photometry, are 
shifted by 63.95d +/- 0.04d; this shift must equal to 11 cycles, 
yielding an improved period of 5.814d +/- 0.004d. Further information 
on the period should follow from the spectroscopic conjunction phases. 
However, the present accuracy of the period is not sufficient to rule 
out all aliases when considering the complete sample of all individual 
observations. The radial velocity curves are affected by such a large 
scatter that they cannot help in resolving the ambiguity. Due to the 
same reason, the eccentricity determined from spectroscopy (Hill et 
al.:  e = 0; Levato and Morrell:  e = 0.18) is of low weight. It 
however seems, that a non-zero eccentricity is supported by 
photometry, since the secondary minimum phase is 0.525 +/- 0.010. 
Definite values of the period and eccentricity can hopefully be 
determined from future photometry scheduled for 1993. Our V light 
curve is plotted in Fig. 2. HD 152147 and 152314 served as comparison 
and check stars and were always measured with the variable, and no 
sign of variability was detected. 


                            [FIGURE 1]

 Fig. 1. Light curve in V color of the eclipsing binary HD 101205.
         Differences of magnitudes HD 101205 minus HD 101298 are
         given.

                            [FIGURE 2]

 Fig. 2. Light curve in V colour of the eclipsing binary HD 152248.
         Differences of magnitudes HD 152248 minus HD 152147 are
         given, ephemeris is Pri.Min. = JDhel. 2448688.77 + 5.814d E.
         Points - data from JD 2448682 to 2448691, crosses - data from
         JD 2448749, 2448752, 2448753 and 2448755.

 
 The time of the primary minimum is JDhel. 2448688.77 and amplitudes 
of minima are 0.24m (primary) and 0.13m (secondary) in all colours. 
HD 152248 is one of the earliest eclipsing binaries known. Its 
further study can help to improve our limited knowledge of accurate 
parameters and the temperature scale of hot stars. 
 
 
 
                                    Pavel Mayer 
                                    Astronomical Institute 
                                    Charles University 
                                    Svedska 8, 150 00 Praha 5 
                                    Czechoslovakia 
 
                                    Reinald Lorenz and Horst Drechsel 
                                    Dr. Remeis Observatory 
                                    University Nuerenberg-Erlangen 
                                    Sternwartstrasse 7 
                                    D-8600 Bamberg, Germany 
 
 
References: 
 
Ardeberg A., Maurice E.:  1977, A&A Suppl. 28, 153  [BIBCODE 1977A&AS...28..153A ]
 
Balona L. A.:  1992, MNRAS 254, 404  [BIBCODE 1992MNRAS.254..404B ]
 
Hayford P.:  1932, Lick Obs. Bull.16, 53  [BIBCODE 1932LicOB..16...53H ]
 
Hill G., Crawford D. L., Barnes J. V.:  1974, AJ 79, 1271  [BIBCODE 1974AJ.....79.1271H ]
 
Kholopov P. N.:  1982, New Catalogue of Suspected Variable Stars, 
  Moscow  [BIBCODE 1982ncss.book.....K ]
 
Levato H., Morrell N.:  1983, Astroph. Letters 23, 183  [BIBCODE 1983ApL....23..183L ]
 
Perry C. L., Hill G., Christodoulou D. M.:  1991, A&A Suppl. 90, 195  [BIBCODE 1991A&AS...90..195P ]
 
Struve O.:  1944, ApJ 100, 189  [BIBCODE 1944ApJ...100..189S ]
 
Thackeray A. D., Wesselink A. J.:  1965, MNRAS 131, 121  [BIBCODE 1965MNRAS.131..121T ]
 
Walborn N. R.:  1972, AJ 77, 312  [BIBCODE 1972AJ.....77..312W ]
 
Walborn N. R.:  1973, AJ 78, 1067  [BIBCODE 1973AJ.....78.1067W ]