[en] Oef stars are O-stars that display a double-peaked He II λ 4686 line in their optical spectra,
suggesting that the inner part of the stellar wind is co-rotating with the star. This hypothesis
is also often used to explain their ubiquitous spectral variability in the optical domain. In this
context, the fact that the high-resolution X-ray spectra of ζ Pup (O4Ief) meet the expectations
of the wind-embedded shock model, assuming a spherically symmetric wind came as a surprise. To understand what is going on, we have obtained a 300 ksec observation of λ Cephei, the second brightest Oef star. This observation not only allows to collect the RGS high-resolution spectrum of the star, but further enables us to search for X-ray variability. To correlate the potential X-ray variability with that of the optical spectrum of λ Cep, we monitored the optical spectrum simultaneously with the TIGRE telescope. We present here the first results of this campaign, both in terms of the line profiles in the RGS spectrum and the search for X-ray variability in correlation with the optical variations.
Research center :
LiSRI - Liège Space Research Institute - ULiège
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Rauw, Grégor ; Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Nazé, Yaël ; Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Gonzalez-Perez, Nicolas
Hempelmann, Alexander
Mittag, Marco
Schmitt, Jürgen
Schröder, Klaus-Peter
Hervé, Anthony
Eenens, Philippe
Gosset, Eric ; Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Language :
English
Title :
The X-ray properties of lambda Cep, a true twin of zeta Pup?