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Astron. Astrophys. 327, 1070-1076 (1997)
The discovery of a new massive O-type close binary:
![[FORMULA]](../../../entities/ltau.gif)
CMa (HD 57061), based on Hipparcos and Walraven photometry
*
F. van Leeuwen 1 and
A.M. van Genderen 2
1 Royal Greenwich Observatory, Madingley Road, Cambridge
CB3 0EZ, UK
2 Leiden Observatory, Postbus 9513, 2300 RA Leiden, The
Netherlands
Received 9 June 1997 / Accepted 4 July 1997
Abstract
We present an interpretation of Hipparcos Hp and Walraven
VBLUW photometry of the brightest star in the open cluster
NGC 2362 (although not necessarily associated with this cluster),
HD 57061 (30
![[FORMULA]](img1.gif)
CMa, HR 2782, HIP 35415). In
this multiple system the central component consist of a visual double
star, two O-type stars separated by 0:00151, which is also known to be
a 154:d9 period single lined spectroscopic binary. It is now shown
that this system also contains a massive close binary with a period of
1:d282122, most probably as the main component of the spectroscopic
binary. This system therefore contains both the longest period
spectroscopic binary and the shortest period eclipsing binary known
for O-type stars. The shape of the light curve is characteristic for
heavily distorted double star components. An estimate has been made
for various physical parameters of the system. The system seems to be
typical for some binary interaction results obtained in N-body
simulations for open clusters. Improved ephemeris are provided for two
similar stars that were observed around the same time as
HD 57061: HD 57060 and HD 167971.
Key words: technique:
photometric 
stars: individual: HD 57061 = 30 o CMa = HR 2782 =
HIP 35415, HD 57060 = UW CMa = HIP 35412, HD167971 = MY Ser = HIP
89681
(stars) binaries: close
* Based on observations made with the ESA Hipparcos satellite, and on observations collected at the European Southern Observatory, La Silla, Chile
Send offprint requests to: F. van Leeuwen
Contents
- 1. Introduction
- 2. Previous work on
CMa
- 3. Observations and reductions
- 3.1. Hipparcos photometry
- 3.2. VBLUW photometry
- 4. The period determination
- 5. Physical parameter estimates
- 6. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 1997
Online publication: April 6, 1998
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