One of the most massive stars in the Galaxy may have formed in isolation
L. M. Oskinova, M. Steinke, W.-R. Hamann, A. Sander, H. Todt, A. Liermann
Very massive stars, 100 times heavier than the sun, are rare. It is not
yet known whether such stars can form in isolation or only in star
clusters. The answer to this question is of fundamental importance. The
central region of our Galaxy is ideal for investigating very massive
stars and clusters located in the same environment. We used archival
infrared images to investigate the surroundings of apparently isolated
massive stars presently known in the Galactic Center. We find that two
such isolated massive stars display bow shocks and hence may be
"runaways" from their birthplace. Thus, some isolated massive stars in
the Galactic Center region might have been born in star clusters known
in this region. However, no bow shock is detected around the isolated
star WR102ka (Peony nebula star), which is one of the most massive and
luminous stars in the Galaxy. This star is located at the center of an
associated dusty circumstellar nebula. To study whether a star cluster
may be "hidden" in the surroundings of WR102ka, to obtain new and better
spectra of this star, and to measure its radial velocity, we obtained
observations with the integral-field spectrograph SINFONI at the ESO's
Very Large Telescope (VLT). Our observations confirm that WR102ka is one
of the most massive stars in the Galaxy and reveal that this star is not
associated with a star cluster. We suggest that WR102ka has been born in
relative isolation, outside of any massive star cluster.
Fetch Pdf-File (peony-isolated.pdf, 0.5MB)