Dynamics of the circumstellar gas in the Herbig Ae stars BF Orionis, SV Cephei, WW Vulpeculae and XY Persei

¹ Departamento de Física Teórica C-XI, Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain
² Visiting Scientist at ESA/ESTEC and Leiden University, The Netherlands
³ Osservatorio Astrofisico di Arcetri, Largo Fermi 5, 50125 Firenze, Italy
⁴ NOAO/STIS, Goddard Space Flight Center, Code 681, NASA/GSFC, Greenbelt, MD 20771, USA
⁵ TNO/TPD-Space Instrumentation, Stieltjesweg 1, PO Box 155, 2600 AD Delft, The Netherlands
⁶ Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh, UK
⁷ CNRS, Institute d'Astrophysique de Paris, 98bis Bd. Arago, 75014 Paris, France
⁸ DLR Department of Planetary Exploration, Rutherfordstrasse 2, 12489 Berlin, Germany
⁹ Instituto de Astrofísica de Andalucía, Apartado de Correos 3004, 18080 Granada, Spain
¹⁰ LAEFF, VILSPA, Apartado de Correos 50727, 28080 Madrid, Spain
¹¹ Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
¹² Department of Physics, Center for Astrophysics and Space Sciences, University of California San Diego, Mail Code 0424, La Jolla, CA 92093-0424, USA
¹³ Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, Scotland, UK
¹⁴ Instituto de Astrofísica de Canarias, La Laguna 38200 Tenerife, Spain
¹⁵ Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
¹⁶ Observatoire de Paris, 92195 Meudon, France
¹⁷ SRON, Universiteitscomplex “Zernike”, Landleven 12, PO Box 800, 9700 AV Groningen, The Netherlands

Corresponding author: A. Mora, alcione.mora@uam.es

Received: 3 June 2003
Accepted: 12 February 2004

Abstract

We present high resolution (λ/ = 49 000) échelle spectra of the intermediate mass, pre-main sequence stars BF Ori, SV Cep, WW Wul and XY Per. The spectra cover the range 3800-5900 Å and monitor the stars on time scales of months and days. All spectra show a large number of Balmer and metallic lines with variable blueshifted and redshifted absorption features superimposed to the photospheric stellar spectra. Synthetic Kurucz models are used to estimate rotational velocities, effective temperatures and gravities of the stars. The best photospheric models are subtracted from each observed spectrum to determine the variable absorption features due to the circumstellar gas; those features are characterized in terms of their velocity, v, dispersion velocity, , and residual absorption, R_max. The absorption components detected in each spectrum can be grouped by their similar radial velocities and are interpreted as the signature of the dynamical evolution of gaseous clumps with, in most cases, solar-like chemical composition. This infalling and outflowing gas has similar properties to the circumstellar gas observed in UX Ori, emphasizing the need for detailed theoretical models, probably in the framework of the magnetospheric accretion scenario, to understand the complex environment in Herbig Ae (HAe) stars. WW Vul is unusual because, in addition to infalling and outflowing gas with properties similar to those observed in the other stars, it shows also transient absorption features in metallic lines with no obvious counterparts in the hydrogen lines. This could, in principle, suggest the presence of CS gas clouds with enhanced metallicity around WW Vul. The existence of such a metal-rich gas component, however, needs to be confirmed by further observations and a more quantitative analysis.