4Cmora.pdf

KINEMATICS OF THE CIRCUMSTELLAR GAS AROUND
UXOR STARS
Alcione Mora,1 Carlos Eiroa,1 Antonella Natta,2 and EXPORT3∗
1 Departamento de Fisica Teorica C-XI
Universidad Autonoma de Madrid
Cantoblanco 28049 Madrid, Spain
[email protected],[email protected]
2 Osservatorio Astrofisico di Arcetri
Largo Fermi 5
I-50125 Firenze, Italy
[email protected]
3 EXPORT Collaboration web page:
http://laeff.esa.es/EXPORT/
Abstract
This thesis presents the results of a high spectral resolution (λ/∆λ = 49000)
study of the circumstellar (CS) gas around the intermediate mass, pre-main sequence UXOR stars BF Ori, SV Cep, UX Ori, WW Vul and XY Per. The results
are based on a set of 38 echelle spectra covering the spectral range 3800-5900 A,
monitoring the stars on time scales of months, days and hours.
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, via multigaussian fitting, in terms of their velocity, v, dispersion velocity,
∆v, and residual absorption, Rmax .
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. Most of the events undergo accelerations/decelerations at a rate of tenths of m s−2 . The typical timescale for the
∗ EXo
Planetary Observational Research Team: A. Alberdi, A. C. Cameron, J. K. Davies, H. J. Deeg,
C. Eiroa, R. Ferlet, F. Garzon, C. A. Grady, A. W. Harris, K. Horne, L. F. Miranda, B. Merin, B. Montesinos,
A. Mora, R. D. Oudmaijer, J. Palacios, A. Penny, A. Quirrenbach, H. Rauer, J. Schneider, E. Solano,
Y. Tsapras, P. R. Wesselius, and D. de Winter
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duration of the events is a few days. The dispersion velocity and the relative
absorption strength of the features do not show drastic changes during the lifetime of the events, which suggests that they are gaseous blobs preserving their
geometrical and physical identity.
A comparison of the intensity ratios among the transient absorptions suggests
a solar-like composition for most of the CS gas. This confirms previous results
and excludes a very metal-rich environment as the general cause of the transient features in UXOR stars. These data are a very useful tool for constraining
and validating theoretical models of the chemical and physical conditions of the
CS gas around young stars; in particular, it is suggested 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.
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.
All these results have been published by Mora et al. 2002 and Mora et al.
2004.
Rotational velocities for a large sample of pre-main sequence and Vega-type
stars have been determined from high resolution (λ/∆λ = 49000) echelle spectra. The first minimum of the Fourier transform of many photospheric line profiles has been used to estimate the velocities. The resulting velocities have been
published, along with spectral types determined by other co-authors, by Mora
et al. 2001.
Keywords:
Stars: formation, Stars: pre-main sequence, Stars: circumstellar matter, Accretion: accretion disks, Lines: profiles, Stars: individual: BF Ori, SV Cep, UX Ori,
WW Vul, XY Per, Stars: rotation
Introduction
In this talk, the most original topics discussed in the PhD thesis recently
defended by Alcione Mora have been presented. The slides used in the presentation are included in the following pages. The full PhD thesis dissertation
document can be found at http://arxiv.org/abs/astro-ph/0411205.
References
A. Mora, B. Merin, E. Solano et al. EXPORT: Spectral classification and projected rotational
velocities of Vega-type and pre-main sequence stars. A&A 378:116-131, 2001
A. Mora, A. Natta, C. Eiroa et al. A dynamical study of the circumstellar gas in UX Orionis.
A&A 393:259-271, 2002
A. Mora, C. Eiroa, A. Natta et al. Dynamics of the circumstellar gas in the Herbig Ae stars BF
Orionis, SV Cephei, WW Vulpeculae and XY Persei. A&A 419:225-240, 2004
Kinematics of the circumstellar
gas around UXOR stars
A. Mora, C. Eiroa, A. Natta and EXPORT
JENAM 2004. Granada. September 16th 2004
Introduction: Motivation

Planet formation proceeds via the growth of
planetesimals

β Pic: Redshifted Absorption Components (RACs)
fTheoretical explanation: Planetesimals (FEBs)

PMS UXOR stars: Probable β Pic progenitors
fRACs have been detected in UXOR spectra
fBACs: Blueshifted Absorption Components
fTACs: Transient Absorption Components = RACs + BACs
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Observations: EXPORT proposal

Utrecht Echelle Spectrograph (UES)
fNasmyth focus of WHT 4.2m telescope
fSpectral range λ: 3800-5900 Å
fSpectral resolution λ/∆λ = 49000
fReduction: standard procedures

Stars: BF Ori, SV Cep, UX Ori, WW Vul & XY Per
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Analysis: Subtraction of the synthetic
photospheric continuum

Stellar parameters Î Fit to the spectrum
fEffective temperature, Teff
fSurface gravity, log g
fProjected rotation velocity, v sin i
fHeliocentric radial velocity, vrad
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Analisis: R Multicomponent gaussian
fitting