Mora, A.; Natta, A.; Eiroa, C.; Grady, C. A.; de Winter, D.; Davies, J. K.; Ferlet, R.; Harris, A. W.; Montesinos, B.; Oudmaijer, R. D.; Palacios, J.; Quirrenbach, A.; Rauer, H.; Alberdi, A.; Collier Cameron, A.; Deeg, H. J.; Garzón, F.; Horne, K.; Merín, B.; Penny, A.; Schneider, J.; Solano, E.; Tsapras, Y.; Wesselius, P. R.
Referencia bibliográfica
Astronomy and Astrophysics, v.393, p.259-271 (2002)
Fecha de publicación:
10
2002
Revista
Número de citas
25
Número de citas referidas
24
Descripción
We present the results of a high spectral resolution (lambda / Delta
lambda = 49 000) study of the circumstellar (CS) gas around the
intermediate mass, pre-main sequence star UX Ori. The
results are based on a set of 10 échelle spectra covering the
spectral range 3800-5900 Å, monitoring the star on time scales of
months, days and hours. A large number of transient blueshifted and
redshifted absorption features are detected in the Balmer and in many
metallic lines. A multigaussian fit is applied to determine for each
transient absorption the velocity, v, dispersion velocity, Delta v, and
the parameter R, which provides a measure of the absorption strength of
the CS gas. The time evolution of those parameters is presented and
discussed. A comparison of intensity ratios among the transient
absorptions suggests a solar-like composition of the CS gas. This
confirms previous results and excludes a very metal-rich environment as
the cause of the transient features in UX Ori. The features can be
grouped by their similar velocities into 24 groups, of which 17 are
redshifted and 7 blueshifted. An analysis of the velocity of the groups
allows us to identify them as signatures of the dynamical evolution of 7
clumps of gas, of which 4 represent accretion events and 3 outflow
events. Most of the events decelerate at a rate of tenths of m
s-2, while 2 events accelerate at approximately the same
rate; one event is seen experiencing both an acceleration and a
deceleration phase and lasts for a period of few days. This time scale
seems to be the typical duration of outflowing and infalling events in
UX Ori. The dispersion velocity and the relative aborption strength of
the features do not show drastic changes during the lifetime of the
events, which suggests they are gaseous blobs preserving their
geometrical and physical identity. These data are a very useful tool for
constraining and validating theoretical models of the chemical and
physical conditions of CS gas around young stars; in particular, we
suggest that the simultaneous presence of infalling and outflowing gas
should be investigated in the context of detailed magnetospheric
accretion models, similar to those proposed for the lower mass T Tauri
stars.