1 Introduction

V 380 Ori belongs to the class of the Herbig Ae/Be stars, defined by Herbig (1960). Such stars have an early spectral type with emission lines, lie in an obscured region and illuminate fairly bright nebulosity in their immediate vicinity. They generally lie above the zero age main sequence in the Hertsprung-Russel diagram and are thought to be in an early pre-main sequence evolutionary stage (e.g. Finkenzeller & Mundt 1984). According to Böhm & Catala (1995) Herbig Ae/Be stars should be in the radiative phase of pre-main sequence contraction. These stars have in addition infrared excesses. Basically two types of model have been invoked to explain the properties of Herbig Ae/Be stars; one involves the presence of an accretion disk and the other that of an active "chromosphere" plus wind, associated with a magnetic field.

From infrared photometry Strom et al. (1989) suggested that V 380 Ori belongs to the group of what they called "Class II" sources with a flux which decreased towards long wavelengths more slowly than that of a black body. These authors considered such sources to have a central object plus a disk. Hamann & Persson (1992a) from the comparison of the Ca II infrared triplet and the IR excess concluded that the line emitting envelopes are somehow related to the presence of disks.

A disk model with a central hole was supported by Hillenbrand et al. (1992) for most of the stars studied by them in order to better explain the infrared energy distribution. On the other hand Hartmann et al. (1993) show that this explanation raises serious problems of physical consistency, high accretion rates being necessary to produce the excess of emission. These authors suggest that, at least in some cases, it may rather be due to small grains of a dusty circumstellar nebula, transiently heated by stellar ultraviolet photons.

Böhm & Catala (1995) explain their results on activity tracers with chromosphere plus wind models and give reasons for supposing that the presence of a disk is not necessary to sustain the observed activity.

The disk and/or the nebula need not be the only reason for the infrared excess; actually Leinert et al. (1997) find evidence for binarity for this and other Herbig Ae/Be stars from speckle interferometry. They also fit the infrared energy distribution with two stars plus infrared excess distributions.

In this uncertain situation, where it may be dangerous to generalize a given physical model to all stars belonging to the same "class", detailed studies of individual objects are required. It is in this context that we have studied V 380 Ori.

The star has a very rich emission line spectrum in the optical including, besides the Balmer lines, many metallic lines, of which those of Fe II are the most numerous followed by those of Ti II. This star is associated with at least 3 Herbig-Haro objects, an extended H II region (NGC 1999), a bright crescent like reflection nebula around a dense globule, and sources of molecular emission (e.g. Shevchenko 1997). In this way it satisfies the conditions for belonging to the Herbig Ae/Be class. According to Böhm & Catala (1995) its mass is 3.3 $M_{\odot}$, and the effective temperature 9500 K; they were unable however to find a rotation velocity due to the highly non-photospheric spectrum. Hillenbrand et al. (1992) derive slightly different parameters; the mass is 3.6 $M_{\odot}$, while their effective temperature is 10700 K, and corresponds to a spectral class of B9. In the frame of a model involving circumstellar accretion disk, in order to explain the strong infrared excess observed in the spectrum of V 380 Ori, Hillenbrand et al. (1992) determine a corresponding improbably high mass accretion rate of 5 10^-6 $M_{\odot}$ y^-1. We finally recall that V 380 Ori is also an X-ray source (see Strom et al. 1990, and references therein). In the radio a bipolar outflow is present with only red shifted components (e.g. Levreault 1988).

In spite of the many investigations, the nature of V 380 Ori and that of the Herbig AeBe stars in general, still is matter of controversy. In order to improve our knowledge on some aspects of this star, such as the strength and profile of the optical lines, the peculiar UV spectrum, and the star's activity and the wind tracers, we have collected new and archive observations of V 380 Ori which are here discussed. In particular, we obtained optical spectrograms with a resolution of $\sim\!10^4$ which can also be a suitable basis for future more detailed studies of the process of formation of the heavy metal emission lines.

In Sects. 2 and 3 we present and discuss the observational data on V 380 Ori, which includes the long term spectroscopic monitoring at ESO and OHP, and the March 1985 coordinated program of simultaneous optical-infrared spectroscopy and IR photometry at ESO. In addition, we analyse the archive IUE data, and study the energy distribution and the interstellar extinction. In Sect. 4 we discuss the main results of our work and compare with current models.