G. Montes,1,2 A. Alberdi,2 M. A. Pérez-Torres,2 and R. F. González 3
1 Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA. (gmontes@ucsc.edu).
2 Instituto de Astrofísica de Andalucía (IAA), CSIC, Glorieta de la Astronomía s/n, E-18008, Granada, Spain.
3 Centro de Radioastronomía y Astrofísica, UNAM, México.
Received September 2 2014. ]]> Accepted June 5 2015.
RESUMEN
El espectro centimétrico de binarias Wolf-Rayet (WR) muestra a menudo la contribución de una región de colisión de vientos (WCR). En sistemas de periodo corto (≲1 año), se espera que este componente sea absorbido por los vientos no chocados, perdiendo el efecto de su condición binaria. Estudios teóricos y observacionales sugieren que en estos sistemas, la WCR puede contribuir a la emisión tanto en la región centimétrica como milimétrica. Analizamos observaciones centimétricas y milimétricas de 17 estrellas WR (incluyendo nueve binarias de periodo corto). Encontramos que para distinguir entre los posibles escenarios son necesarias más observaciones. Enfatizamos la importancia de analizar el espectro utilizando observaciones cuasi-simultáneas en un amplio intervalo de frecuencias para así poder caracterizar y distinguir cualquier posible contribución extra a la emisión.
ABSTRACT
The centimeter spectra of Wolf-Rayet (WR) binaries often show a contribution from a wind-wind collision region (WCR) between the stars. In short period systems (≲ 1 yr), such a component is expected to be absorbed by the unshocked winds, losing any effect from its binarity. Recent studies suggest that the WCR in these systems may also contribute to the emission at both centimeter and millimeter wavelengths. We analyzed and compared centimeter and millimeter observations of a total sample of 17 WR stars (including nine confirmed short-period systems) to detect any possible WCR contribution. More detailed observations are required in order to distinguish between different scenarios. We highlight the importance of analyzing the spectrum from quasi-simultaneous observations in a wide range of frequencies in order to properly characterize and distinguish any possible extra contribution.
Key Words: binaries: close — radio continuum: stars — stars: winds, outflows — stars: Wolf-Rayet.
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]]>ACKNOWLEDGMENT
G.M. acknowledges financial support from the CSIC JAE-PREDOC and AAUW Postdoctoral Fellowships, as well as Carlos E. Carrasco-González for a critical reading of this paper. This research was partially supported by the Spanish MICINN through grant AYA2009-13036-CO2-01, co-funded with FEDER funds. RFG acknowledges support from Grant PAPIIT IN100511 and PAPIIT IN112014, UNAM, México.
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