On the nature of variations in the T Tauri star WY Arietis (LkHα 264)

¹ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, Porto 4150, Portugal
² Departamento de Matemática Aplicada, Faculdade de Ciências da Universidade do Porto, Portugal
³ Departamento de Matemática, Instituto Superior de Engenharia do Porto, Portugal

Corresponding author: J. F. Gameiro, jgameiro@astro.up.pt

Received: 12 December 2001
Accepted: 11 March 2002

Abstract

We report optical spectroscopic and photometric results from our long-term study of the T Tauri star WY Arietis (LkHα 264). The data gathered show different types of variability: variations in the continuum level, in the emission line fluxes and line profiles. The timescales associated with these variations appear quite diverse. The correlation found between the variations observed in the veiling and in the continuum flux strongly suggest that an extra continuum source veiling the stellar photospheric spectrum is the cause driving the continuum variability. The present work also unveils the presence of an accretion flow onto the star, as revealed by the O I  Å and  Å line profiles, which is the first unambiguous model-independent detection of such an event in this star. Our photometric data allowed us to find a period of 3.04 days for this star, somewhat in tune with Fernandez & Eiroa ([CITE]). However, due to the poor time sampling our finding should be taken as tentative. A detailed analysis of the broad and narrow components of the He I line profiles indicates the presence of a hot wind during the November 1993 observation while in October 1999 a wind is only revealed by the blue wing asymmetry of the observed Balmer and CaII infrared triplet line profiles. The correlation between the strength of the hot wind and the amount of flux in the emission lines led also to the conclusion that this type of wind provides a significant contribution to the hydrogen and metal emission lines. We have also witnessed an exceptional activity during one of the nights which may be attributed to an increase in LkHα 264's accretion rate or to a flare-like event. Although it is not possible to clearly distinguish between these possibilities, the available data set points towards variable accretion as being responsible for the observed event.