Epoch-dependent absorption line profile variability in λ Cep

 

J.M. Uuh-Sonda,¹ G. Rauw,² P. Eenens,¹ L. Mahy,² M. Palate,² E. Gosset,^2,3 and C.A. Flores¹

 

¹ Departamento de Astronomía, Universidad de Guanajuato, Apartado 144, 36000 Guanajuato, Guanajuato, Mexico.

² Groupe d'Astrophysique des Hautes Energies, Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, 4000 Liège, Belgium (gosset@astro.ulg.ac.be, mahy@astro.ulg.ac.be, palate@astro.ulg.ac.be, rauw@astro.ulg.ac.be).

³ Senior Research Associate F.R.S.-FNRS.

 

Received 2013 September 30.
Accepted 2013 December 2.

 

RESUMEN

Reportamos el análisis de una campaña de monitoreo espectroscópico multiépoca de la estrella O6 Ief λ Cep. Observaciones previas habían reportado la existencia de dos modos de pulsaciones no-radiales en esta estrella. Nuestros datos revelan una situación considerablemente más compleja. Las frequencias contenidas en el espectro de potencia cambian considerablemente de una época a otra. No encontramos ninguna frecuencia estable que pueda ser atribuida inequívocamente a pulsaciones. La dependencia temporal de las frequencias y los patrones devariabilidad son similares a los observados en las líneas de emisión del viento en esta y otras estrellas Oef, lo cual sugiere que ambos fenómenos tienen probablemente el mismo origen, aunque éste siga todavía sin conocerse.

 

ABSTRACT

We present the analysis of a multi-epoch spectroscopic monitoring campaign of the O6Iefstar λ Cep. Previous observations reported the existence of two modes of non-radial pulsations in this star. Our data reveal a much more complex situation. The frequency content of the power spectrum considerably changes from one epoch to the other. We find no stable frequency that can unambiguously be attributed to pulsations. The epoch-dependence of the frequencies and variability patterns are similar to what is seen in the wind emission lines of this and other Oef stars, suggesting that both phenomena likely have the same, currently still unknown, origin.

Key Words: stars: early-type — stars: individual (λ Cep) — stars: oscillations — stars: variables: general.

 

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ACKNOWLEDGMENTS

This research is supported by a bilateral convention between Conacyt (Mexico) and F.R.S.-FNRS (Belgium), and an ARC grant for Concerted Research Actions, financed by the Federation Wallonia-Brussels. The Liège team further acknowledges additional support by the Communauté Française de Belgique for the OHP observing campaigns, as well as by Belspo through an XMM/INTEG RALPRODEX contract.

 

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