Data of Westerlund 2 were obtained from the HST proposal 13038: A. Nota (ESA/STScI), E. Sabbi and C. Christian (STScI), E. Grebel and P. Zeidler (Astronomisches Rechen-Institut Heidelberg), M. Tosi (INAF, Osservatorio Astronomico di Bologna), A. Bonanos (National Observatory of Athens, Astronomical Institute), and S.E. de Mink (University of Amsterdam)
Fabian Schneider (former PhD student in Bonn, now postdoctoral fellow in Oxford) simulated the evolution of the stellar mass function of coeval populations, such as star clusters. He finds that mass loss and binary interaction reshapes the high end of … Read More »
The bright star VFTS 399 turned out to be more interesting than its not-so-catchy name suggests. While classified as “apparent single star”, it stood out by its rapid rotation and, as turned out when inspecting data from the Chandra Satellite, by its exceptionally bright in X-rays. In this paper lead by Simon Clark, we conclude this VFTS399 is most likely the secondary star in a binary system. It is about 20 times more massive than the sun, rapidly rotating and probably shedding material from its equator by the centrifugal effect. Its companion star is now gone and left a neutron star when it exploded as a supernova. The neutron star appears to be the second pulsar in this region. The other neutron star is about 200 light years away.
The VLT-FLAMES Tarantula survey XX. The nature of the X-ray bright emission line star VFTS 399, Clark et al. 2015, accepted for publication in Astronomy and Astrophysics, http://arxiv.org/abs/1503.00930
Evans et al. investigated the nearly 300 B-type stars in the Tarantula nebula measuring their velocities toward and away from us using the Doppler effect. Nine stars have extreme velocities and are candidate runaway stars.
They appear to have strange rotation rates: either they spin very very fast or very slow. The most extreme case is star VFTS 358, which is moving at 100 km/s. It is a very rapid rotator and shows peculiar surface chemistry. This is very suggestive of the so-called “binary ejection scenario”. Likely, the star was member of a close binary where it was enriched and spun up by its companion star. When the companion died (in a supernova explosion), star VFTS 358 was ejected, now flying through space all by it self.
The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars, C. J. Evans, et al. A&A, 574, A13, 2015 http://adsabs.harvard.edu/abs/2015A%26A…574A..13E
Very good news, the European Commission decided to support part of our research for the next two years through a Marie Skłodowska-Curie Research Fellowship.
Massive stars are instrumental to many areas of astrophysics, both in the local universe and at high redshift. The last decade has seen growing evidence of extreme multiplicity rates and a for a large fraction of massive stars to interact … Read More »