Spectroscopic behaviour of the unusual Ae star HD 190073

¹ Pulkovo Observatory, Saint-Petersburg, 196140, Russia e-mail: pogodin@gao.spb.ru
² Isaac Newton Institute of Chile, Saint-Petersburg Branch, Russia
³ Departamento de Física – UFMG, Belo Horizonte, Brazil e-mail: franco@fisica.ufmg.br
⁴ Observatório Nacional, Rio de Janeiro, Brazil e-mail: dalton@on.br

Received: 5 September 2003
Accepted: 31 March 2005

Abstract

The results of high-resolution spectroscopy of the peculiar Ae star HD 190073 obtained within the framework of a cooperative observing programme in 1994–2002 are presented. The temporal behaviour of the Hα, Hβ, Hγ, Hδ, He i λ 5876 Å, Na i D and other circumstellar line profiles are investigated in detail. Special attention has been paid to the analysis of the deep multicomponent blueshifted Ca ii H and K absorption lines. It has been found that the fine structure of their profiles is variable on timescales from months to decades. The analysis of the circumstellar spectrum of HD 190073, rich in shell-like and emission lines with narrow absorption cores, allows us to conclude that all absorption lines and cores are likely to be of photospheric origin. The emission lines are variable in time and demonstrate signs of a stellar wind as well as a dense equatorial circumstellar disk. As a preliminary hypothesis, we propose that a global magnetic field of a specific topology can be responsible for the formation of stable latitudinal stratification of the outflowing gas resulting in appearance of the complex structure of the Ca ii H and K line profiles. We emphasise that a measurement of the stellar magnetic field and an investigation of its detailed configuration would be an important step in understanding the nature of HD 190073.