EDP Sciences
Free access
Issue A&A
Volume 469, Number 1, July I 2007
Page(s) L31 - L34
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20077677



A&A 469, L31-L34 (2007)
DOI: 10.1051/0004-6361:20077677

Letter

On the optical counterpart of NGC 300 X-1 and the global Wolf-Rayet content of NGC 300

P. A. Crowther1, S. Carpano2, L. J. Hadfield1, and A. M. T. Pollock2

1  Department of Physics & Astronomy, University of Sheffield, Hicks Building, Hounsfield Rd, Sheffield, S3 7RH, UK
    e-mail: Paul.Crowther@sheffield.ac.uk
2  XMM-Newton Science Operations Center, ESAC, 28080 Madrid, Spain

(Received 19 April 2007 / Accepted 9 May 2007)

Abstract
Context.Surveys of Wolf-Rayet (WR) populations in nearby galaxies provide tests of evolutionary models plus type Ib/c supernova progenitors. This spectroscopic study complements the recent imaging survey of the spiral galaxy NGC 300 by Schild et al.
Aims.Revisions to the known WR content of NGC 300 are presented. We investigate the WR nature of candidate #41 from Schild et al. which is spatially coincident with the bright X-ray point source NGC 300 X-1.
Methods.VLT/FORS2 multi-object spectroscopy of WR candidates in NGC 300 is obtained.
Results.We establish an early-type WN nature of #41, i.e. similar to the optical counterpart of IC 10 X-1, which closely resembles NGC 300 X-1. We confirm 9 new WR stars, bringing the current WR census of the inner disk to 31, with N(WC)/N(WN) ~ 0.9.
Conclusions.If #41 is the optical counterpart for NGC 300 X-1, we estimate a WR mass of 38 $M_{\odot}$ based upon ground-based photometry, from which a black hole mass of $\geq$10 $M_{\odot}$ results from the 32.8 h period of the system and WR wind velocity of 1250 km s-1. We estimate an 95% completeness among WC stars and 70% among WN stars, such that the total WR content is ~40, with N(WC)/N(WN) ~ 0.7. From the H$\alpha$-derived star formation rate of the inner galaxy, we infer N(WR)/N(O) ~ 0.04.


Key words: galaxies: individual: NGC 300 -- stars: Wolf-Rayet -- X-rays: binaries -- X-rays: individuals: NGC 300 X-1



© ESO 2007

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)