Reference : The nature of the high Galactic latitude O-star HD 93521: new results from X-ray and ...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/131986
The nature of the high Galactic latitude O-star HD 93521: new results from X-ray and optical spectroscopy
English
Rauw, Grégor mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales >]
Morel, Thierry mailto [Université de Liège - ULg > > GAPHE : Astrophysique observationnelle (sol et espace) >]
Palate, Matthieu mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales >]
1-Oct-2012
Astronomy and Astrophysics
EDP Sciences
546
77
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] stars: early-type ; stars: fundamental parameters ; stars: abundances ; stars: massive ; stars: individual: HD 93521 ; X-rays: stars
[en] Context. Owing to its unusual location and its isolation, the nature of the high Galactic latitude O9.5 Vp object HD 93521 is still uncertain. <BR /> Aims: We have collected X-ray and optical observations to characterize the star and its surroundings. <BR /> Methods: X-ray images and spectra are analysed to search for traces of a recent star formation event around HD 93521 and to search for the signature of a possible compact companion. Optical echelle spectra are analysed with plane-parallel model atmosphere codes, assuming either a spherical star or a gravity darkened rotationally flattened star, to infer the effective temperature and surface gravity, and to derive the He, C, N and O abundances of HD 93521. <BR /> Results: The X-ray images reveal no traces of a population of young low-mass stars coeval with HD 93521. The X-ray spectrum of HD 93521 is consistent with a normal late O-type star although with subsolar metallicity. No trace of a compact companion is found in the X-ray data. In the optical spectrum, He and N are found to be overabundant, in line with the effect of rotational mixing in this very fast rotator, whilst C and O are subsolar. A critical comparison with the properties of subdwarf OB stars, indicates that, despite some apparent similarities, HD 93521 does not belong to this category. <BR /> Conclusions: Despite some ambiguities on the runaway status of the star, the most likely explanation is that HD 93521 is a Population I massive O-type star that was ejected from the Galactic plane either through dynamical interactions or a result of a supernova event in a binary system. Based on observations collected at the Observatoire de Haute Provence (France) and with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA).Hα images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/A77">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/A77</A>
http://hdl.handle.net/2268/131986
10.1051/0004-6361/201219865
http://adsabs.harvard.edu/abs/2012A%26A...546A..77R
http://de.arxiv.org/abs/1209.2606

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