Proceedings of the Workshop
"The Magellanic Clouds and Other Dwarf Galaxies"
of the Bonn/Bochum-Graduiertenkolleg

UBVRI Photometry of Supergiants in Multiple Star Systems

and the OB Association LH 10

Th. Schmidt-Kaler1,2, J. Gochermann3, J. Middendorf1, and W.F. Wargau4

1Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
2Georg-Büchner-Str. 37, D-97276 Margetshöchheim, Germany, Fax 931-4675972
3Optikzentrum NRW, Universitätsstr. 142, D-44799 Bochum, Germany
4Department of Mathematics, Applied Mathematics and Astronomy, PO Box 392, 0001 Pretoria, South Africa; deceased November 6, 1996

Received 13th March 1998
Abstract. A number of CCD frames in UBVRI were taken with the 1 m telescope on SAAO fields and in cases where individual photoelectric diaphragm photometry was hopeless. The treatment was standard; the errors are ±0.04, ±0.03, ±0.04, ±0.05, ±0.06 for V, B-V, U-B, V-R, R-I for V < 14.5 and increase up to 0.13 for V = 15.7

1. Members in Multiple Systems

Here we report just a few interesting results of CCD photometry

Identifier MK Type MV (U-B)0 (B-V)0 (V-R)0 (R-I)0
HD 36402B WC5 -3.5 -0.36 -0.35 -0.66 0.27
HDE 268801A M2 Iab* -6.9   1.77 1.00 1.08
HDE 269927A WN9 -7.7 -0.90 -0.13    
R134B WN6 -5.8     0.07 -0.84
LH 10 star 43 M2 Iab* -6.0   1.84 1.01  
R 143 F7 Ia -7.6 -0.49 0.38 0.33  
* inferred from colours

2. The Association LH 10

With a diameter of almost 4' (corresponding to ≅ 50 pc) it lies in the NW corner of the LMC and contains three open clusters (NGC 1763, IC 2115 and IC 2116). The reddening was determined to be EB-V = 0.165; the galactic foreground contributes 0.08 to the total reddening (Oestreicher et al. 1995). The turnoff-point of the main sequence is at V0 = 14.0 with (B-V)0 = -0.32 corresponding to spectral type O6.5 with MV(ZAMS) = -4.6 or V0 - MV = 18.6. The turnoff-point corresponds to an age of 6·106 yr according to the evolutionary models of Schaller et al. (1992). The brightest stars have V ≅ 12.5 or MV ≅ -6.5 (B0 Iab), star 43 seems to be an M-supergiant member. The luminosity function is characterized by γ = 0.28 within V < 16.5, the IMF by x = -1.3±0.2.

References

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First version: 18thJune,1998
Last update: 30thAugust,1998
Jochen M. Braun   &   Tom Richtler
 (E-Mail: jbraun|richtler@astro.uni-bonn.de)