Chemical composition in fast rotators main sequence stars

C. R. Fierro and L. Georgiev

Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70–264, 04510 México, D. F., (crfierro@astroscu.unam.mx, georgiev@astroscu.unam.mx)

Received 2007 July 23
Accepted 2008 February 6

RESUMEN

Usando datos públicos del Ultraviolet and Visual Echelle Spectrograph Paranal Observatory Project (UVES POP), y con el método de la transformada de Fourier, se obtuvieron las velocidades de rotación proyectadas, v sin i, para 16 estrellas en el campo del cúmulo galáctico IC 2391 (o Vel Cluster). Se encontró que sólo 12 de dichos objetos son miembros del cúmulo y al separarlos en dos grupos (estrellas de secuencia principal y estrellas evolucionadas) se encontró una correlación entre la velocidad de rotación y la temperatura efectiva, lo que indica que las estrellas dentro del cúmulo tienen aproximadamente la misma orientación del eje de rotación. Los cocientes N/C y O/C obtenidos para las estrellas de secuencia principal se incrementan con v sin i, mostrando evidencias de mezclado inducido por rotación.

ABSTRACT

Using public data of the Ultraviolet and Visual Echelle Spectrograph Paranal Observatory Project (UVES POP) the projected rotational velocities, v sin i, for 16 stars in the field of the galactic cluster IC 2391 (o Vel Cluster) were obtained using the method of the Fourier transform (FT). We found that only 12 of these objects are cluster members and separating them in two sets (main sequence stars and evolved stars) a correlation of the rotation velocity with the effective temperature was found, indicating a nearly equal orientation of the rotation axis for the member stars. The ratios N/C and O/C obtained for the main sequence stars increase with v sin i and show evidence of mixing induced by rotation.

Key Words: stars: early–type — stars: abundances — stars: rotation

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Acknowledgements

We express our deep thanks to Fiorella Castelli for her help to generate synthetic spectra with AT–LAS12 and SYNTHE under Linux, to the UVES Paranal Observatory Project for the access to the data on wich this investigation is based, to Jana Benda for her revision of this paper and to Alfredo Diaz for his computational support.

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