On the nature of the Herbig Be star V 380 Orionis

Up: Abstract

Astron. Astrophys. Suppl. Ser. 136, 95-105

On the nature of the Herbig Be star V 380 Orionis

C. Rossi¹ - L. Errico² - M. Friedjung³ - F. Giovannelli⁴ - G. Muratorio⁵ - R. Viotti⁴ - A. Vittone²

Send offprint request: C. Rossi, rossic@uniroma1.it

1 - Istituto Astronomico, Università La Sapienza, Via G.M. Lancisi 29, 00161 Roma, Italy
2 - Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italia
3 - Institut d'Astrophysique, CNRS, 98bis Boulevard Arago, 75014 Paris, France
4 - Istituto di Astrofisica Spaziale, CNR, Area di Ricerca Tor Vergata, Via del Fosso del Cavaliere, 00133 Roma, Italy
5 - Observatoire de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 04, France

Received August 11, 1997; accepted December 16, 1998

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 different epochs the wavelength range from 1200 Å to 5 $\mu$ m. The coordinated JHKLM and CVF infrared observations and optical spectroscopy made at ESO of March 1985 confirm the presence of a strong IR excess due to emission from hot cicumstellar dust. The comparison with IR photometry from the literature suggests the presence of oscillations, without secular variations. The optical spectrum of V 380 Ori, observed at ESO during 1983-1985, and at OHP in January 1995, remained substatially stable, and was all the time characterized by a large number of broad ( $FWHM~\sim~150$ km s^-1) permitted emission lines, probably formed in a rotating optically thick disk. The strongest Fe II lines have complex profile with a principal 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 Å line, which is present in all our spectra as a broad emission, while in other times it was absent or in absorption. The ultraviolet (IUE) spectrum shows a short wavelength cut off at $\sim 1300$ Å typical of a B9-A0 star, with a rich absorption spectrum, which is thought to be produced in an optically thick stellar envelope or wind. The 2175 Å interstellar band strength is consistent with a mean galactic-type extinction law with an $E_{B-V}=0.20\,\pm\,0.05$ , much smaller than that derived from the visual ( $\sim$ 0.5), which suggests an anomalous local UV extinction. The comparison of the archive IUE data shows that during 1978-1989 there was no significant flux variation, with the possible exception of the UV Mg II emission line.

Key words: stars: emission-line, Be -- stars: individual: V 380 Ori -- stars: pre-main sequence -- infrared: stars -- Ultraviolet: stars