The circumstellar environments of EP Aqr and Y CVn probed by the H I emission at 21 cm

Thibaut Le Bertre (1) , Éric Gérard (2, 3)

1 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
2 GEPI - Galaxies, Etoiles, Physique, Instrumentation
3 Physique des Galaxies et Cosmologie

The H I line at 21 cm has been detected in the circumstellar shells of the two semi-regular variables, EP Aqr and Y CVn, with the Nançay Radio-Telescope (NRT). In both cases the line shape is composite and the emission is spatially extended compared to the NRT beam size (4 arcmin). The total H I masses of the two envelopes are respectively ˜0.047 M_&sun; and 0.044 M_&sun;. For EP Aqr, we find three components: a narrow one centered on the star and spatially unresolved, and two broad, Gaussian components, offset w.r.t. the star and spatially extended. The narrow component traces the present wind from EP Aqr whereas the two others seem to trace one or several mass-loss episodes of long duration. For Y CVn, we find two components: a narrow, spatially very extended, feature, and a broad one, less extended. We argue that the second component traces the outflow and the first one, its interaction with the ISM. These observations show that the H I emission can be used not only to probe the mass loss history of long-period variables, but also to investigate the interaction between stellar outflows and the surrounding ISM.

Domaines: Astrophysique [astro-ph]; Planète et Univers [physics]

Thibaut Le Bertre, Éric Gérard. The circumstellar environments of EP Aqr and Y CVn probed by the H I emission at 21 cm. Astronomy and Astrophysics - A&A, 2004, 419, pp.549-561. ⟨10.1051/0004-6361:20035797⟩. ⟨hal-03730567⟩