ICATE   21876
INSTITUTO DE CIENCIAS ASTRONOMICAS, DE LA TIERRA Y DEL ESPACIO
Unidad Ejecutora - UE
artículos
Título:
Two O2 If*/WN6 stars possibly ejected from the massive young Galactic cluster Westerlund 2
Autor/es:
ROMAN LOPES, A; BARBA, R.; MORRELL, N.
Revista:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2011 vol. 416 p. 501 - 508
ISSN:
0035-8711
Resumen:
In this paper we report the identification of two new Galactic O2
If*/WN6 stars (WR20aa and WR20c), on the outskirts of the massive young
stellar cluster Westerlund 2. The morphological similarity between the
near-infrared spectra of the new stars with that of WR20a and WR21a (two
of the most massive binaries known to date) is remarkable, indicating
that probably they are also very massive stars. New optical
spectroscopic observations of WR20aa suggest an intermediate O2 If*/WN6
spectral type. Based on a mosaic made from the 3.6 μm Spitzer IRAC
images of the region including part of the RCW49 complex, we studied the
spatial location of the new emission line stars, finding that WR20aa and
WR20c are well displaced from the centre of Westerlund 2, being placed
at ≈36 pc (15.7 arcmin) and ≈58 pc (25.0 arcmin), respectively,
for an assumed heliocentric distance of 8 kpc. Also, very remarkably, a
radius vector connecting the two stars would intercept the Westerlund 2
cluster exactly at the place where its stellar density reaches a
maximum. We consequently postulate a scenario in which WR20aa and WR20c
had a common origin somewhere in the cluster core, being ejected from
their birthplace by dynamical interaction with some other very massive
objects, perhaps during some earlier stage of the cluster evolution.