Variable circumstellar activity of V351 Orionis

Abstract

Context. Emission and absorption line profiles which are formed in the interaction of pre-main sequence stars and their circumstellar environment are found to be variable at various timescales.

Aims. We investigate the patterns and timescales of temporal line profile variability in order to explore the dynamical circumstellar environment of the pre-main sequence Herbig Ae star V351 Ori.

Methods. We obtained 45 high-resolution (R ~ 28 000) spectra of V351 Ori at timescales of hours, days, and months. We analysed the Hα line profiles and also examined the Hβ, NaD1 and NaD2 line profiles to explore the nature of the spectroscopic variability.

Results. The Hα line profiles showed strong variations over all timescales. The shape of the profiles changed over timescales of a day. Single as well as simultaneous event(s) of blue-shifted and red-shifted transient absorption components, i.e. signatures of outflow and infall, were also observed in the Hα line profiles. The shortest period of variation in the transient absorption components was ≤1 hour. All transient absorption events were found to decelerate with a rate of a few to fractions of m s-2. The depth and width of the transient absorption components were also changing with time. The presence of elongated red-shifted components at some epochs supports the episodic nature of accretion.

Conclusions. Variable emission and absorption components detected in Hα line profiles show the dynamic nature of interaction between V351 Ori and its circumstellar environment. The Hα non-photospheric profiles of the star most probably originate in the disk wind. Episodic accretion of gaseous material at a slow rate and outflow of clumpy gaseous material are still occurring in V351 Ori at an age of ~6.5 Myr. Dynamic magnetospheric accretion and disk wind emerge as the most satisfactory model for interpreting the observed line profile variations of V351 Ori.