High-resolution imaging of Galactic massive stars with AstraLux*
I. 138 fields with δ > -
Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain e-mail: firstname.lastname@example.org
2 Ramón y Cajal Fellow
Accepted: 20 April 2010
Context. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties.
Aims. I study a sample of massive stars with high angular resolution to better characterize their multiplicity.
Methods. I observed 138 fields that include at least one massive star with AstraLux, a lucky imaging camera at the 2.2 m Calar Alto telescope. I also used observations of 3 of those fields with ACS/HRC on HST to obtain complementary information and to calibrate the AstraLux data. The results were compared with existing information from the Washington Double Star Catalog, Tycho-2, 2MASS, and other literature results.
Results. I discover 16 new optical companions of massive stars, the majority of which are likely to be physically bound to their primaries. I also improve the accuracy for the separation and magnitude difference of many previously known systems. In a few cases the orbital motion is detected when comparing the new data with existing ones and constraints on the orbits are provided.
Conclusions. The analysis indicate that the majority of the AstraLux detections are bound pairs. For a range of separations of 01–14´´ and magnitude differences lower than 8, I find that the multiplicity fraction for massive stars is close to 50%. When objects outside those ranges are included, the multiplicity fraction should be considerably higher.
Key words: techniques: high angular resolution / surveys / astrometry / binaries: visual / stars: early-type / stars: massive
Table 3 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/518/A1
Based on data obtained with the 2.2 m telescope at Calar Alto Observatory (CAHA). Also, some images from the NASA/ESA Hubble Space Telescope (HST) were used. The HST data were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
© ESO, 2010