On the nature of the Herbig Be star V 380 Orionis

Abstract

We discuss new and archive spectroscopic and photometric observations of the Herbig Ae star V 380 Ori obtained between 1978 and 1995 and covering at dier- ent epochs the wavelength range from 1200 At o 5m. The coordinated JHKLM and CVF infrared observations and optical spectroscopy made at ESO of March 1985 conrm the presence of a strong IR excess due to emis- sion from hot cicumstellar dust. The comparison with IR photometry from the literature suggests the presence of oscillations, without secular variations. The optical spec- trum of V 380 Ori, observed at ESO during 1983{1985, and at OHP in January 1995, remained substatially sta- ble, and was all the time characterized by a large number of broad (FWHM 150 km s 1 ) permitted emission lines, probably formed in a rotating optically thick disk. The strongest Fe ii lines have complex prole with a prin- cipal central emission and a blue{shifted ( 140 km s 1 ) wind component, the redward component probably being occulted by the disk. The multiplet 42 lines have P Cygni absorption components shifted by 250 km s 1 which should be associated with a teneous cool wind. We remark the secular behaviour of the stellar activity probe He i 5876 A line, which is present in all our spectra as a broad emission, while in other times it was absent or in absorp- tion. The ultraviolet (IUE) spectrum shows a short wave- length cut o at 1300 A typical of a B9{A0 star, with a rich absorption spectrum, which is thought to be pro- duced in an optically thick stellar envelope or wind. The 2175 A interstellar band strength is consistent with a mean Send oprint requests to: C. Rossi, rossic@uniroma1.it ? Based on observations made with the International Ultraviolet Explorer collected at the Villafranca Satellite Tracking Station of ESA, on archive IUE data, and on ob- servations collected at the European Southern Observatory, at the Observatoire de Haute Provence. ?? Table 3 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html galactic{type extinction law with anEB V =0 :20 0:05, much smaller than that derived from the visual (0.5), which suggests an anomalous local UV extinction. The comparison of the archive IUE data shows that during 1978{1989 there was no signicant flux variation, with the possible exception of the UV Mg ii emission line.