A new Wolf-Rayet star in Cygnus

Free access article

Issue		A&A Volume 396, Number 2, December III 2002


Page(s)		533 - 538
Section		Stellar clusters and associations
DOI		http://dx.doi.org/10.1051/0004-6361:20021373

A&A 396, 533-538 (2002)
DOI: 10.1051/0004-6361:20021373

A new Wolf-Rayet star in Cygnus

A. Pasquali¹, F. Comerón², R. Gredel³, J. Torra⁴ and F. Figueras⁴

¹ ESO/ST-ECF, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
² ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
    e-mail: fcomeron@eso.org
³ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: gredel@caha.es
⁴ Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
    e-mail: jordi@am.ub.es;cesca@am.ub.es

(Received 22 August 2002 / Accepted 19 September 2002 )

Abstract
We report the discovery of a new Wolf-Rayet star in the direction of Cygnus. The star is strongly reddened but quite bright in the infrared, with J = 9.22, H = 8.08 and K_S = 7.09 (2MASS). On the basis of its H + K spectrum, we have classified WR 142a a WC8 star. We have estimated its properties using as a reference those of other WC8 stars in the solar neighbourhood as well as those of WR 135, whose near-infrared spectrum is remarkably similar. We thus obtain a foreground reddening of $A_V \simeq 8.1$ mag, $M_J \simeq -4.3$ , $\log (L/L_\odot) \sim 5.0-5.2$ , $R = 0.8~R_\odot$ , $T \simeq 125\,000$ K, $M = 7.9-9.7~M_\odot$ , ${\dot M} = (1.4-2.3) \times 10^{-5}~M_\odot$ yr ^-1. The derived distance modulus, $DM = 11.2 \pm 0.7$ mag, places it in a region occupied by several OB associations in the Cygnus arm, and particularly in the outskirts of both Cygnus OB2 and Cygnus OB9. The position in the sky alone does not allow us to unambiguously assign the star to either association, but based on the much richer massive star content of Cygnus OB2 membership in this latter association appears to be more likely.

Key words: stars: emission line, Be -- stars: fundamental parameters -- stars: Wolf-Rayet -- Galaxy: open clusters and associations: general

Offprint request: A. Pasquali, apasqual@eso.org

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