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Astron. Astrophys. 359, 299-305 (2000)

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1. Introduction

HD 200775 (MWC 361, B2-B3 V e, V=7.4 mag.) is a bright northern Herbig Be star associated with the extended reflection nebula NGC 7023 (Herbig 1960). The star is situated in the centre of a compact region of star formation, which contains a number of low luminosity pre-main-sequence objects (Lepine & Rieu 1974). The strong emission in the H[FORMULA] and H[FORMULA] lines in the star's spectrum displays a complex multicomponent variability, which has been studied by many authors (see Beskrovnaya et al. 1994and references therein). The most frequently observed profiles of these lines are double-peaked with a slightly redshifted (or undisplaced) central absorption. However, during active periods, when the line emission becomes stronger, their structure becomes much more complicated. Miroshnichenko et al. (1998) collected and analyzed the bulk of the data for the H[FORMULA] line during the last twenty years and suggested that the appearance of the active states may have a cyclic character with a period of 1345 days (3.68 years).

The main goal of this paper is to present new high-resolution spectroscopic data obtained during the period 1994-1999. Included is a spectacular activity phase in the middle of 1997, which featured an enhanced emission equivalent width in H[FORMULA] (Miroshnichenko et al. 1998). Our analysis of the behaviour of H[FORMULA], H[FORMULA], and HeI [FORMULA] 5876 Å, which originate in different layers of the circumstellar (CS) envelope, allows us to discuss possible interpretations of the observed phenomena in the framework of current models, while in previous studies only rough suggestions were possible. At the same time, a clear understanding of the emission-line behaviour in HD 200775 is not achieved yet and requires further high-quality observational data.

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© European Southern Observatory (ESO) 2000

Online publication: June 30, 2000