Forbidden line and H-alpha profiles in T Tauri star spectra - A probe of anisotropic mass outflows and circumstellar disks

Edwards, Suzan; Cabrit, S.; Strom, S. E.; Heyer, I.; Strom, K. M.; Anderson, E.

doi:10.1086/165646

Cited by 197 publications

(130 citation statements)

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“…Figures 1 and 2 show the line variance, the median value, and the autocorrelation matrix at different velocities for the hydrogen and Ca II lines. The hydrogen Balmer lines are, as expected (Edwards et al 1987;Appenzeller et al 1989;Muzerolle et al 2001), very complex and asymmetric. They often have selfabsorptions that may correspond to colder wind/infall components, which can dilute the correlations or otherwise produce very complex patterns.…”

Section: A Pixel-by-pixel Dynamical View Of the Broad Componentsupporting

confidence: 72%

Accretion dynamics of EX Lupi in quiescence

Sicilia‐Aguilar¹,

Fang²,

Roccatagliata³

et al. 2015

A&A

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Context. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims. We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods. We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results. We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions. We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion.

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Section: A Pixel-by-pixel Dynamical View Of the Broad Componentsupporting

confidence: 72%

Accretion dynamics of EX Lupi in quiescence

Sicilia‐Aguilar¹,

Fang²,

Roccatagliata³

et al. 2015

A&A

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“…Studies of the tidal interaction between a circumstellar disc and a binary companion indicate that tidal truncation occurs at a ratio of binary separation to disc radius D/R 3 for an equal mass binary (Artymowicz & Lubow 1994;Larwood et al 1996;Kley & Nelson 2008). Given that 30 AU is smaller than typical disc sizes observed in T Tauri systems (Edwards et al 1987), protostellar discs in many binary systems are often going to experience strong tidal effects.…”

Section: Introductionmentioning

confidence: 99%

Evolution of warped and twisted accretion discs in close binary systems

Fragner

Nelson

2010

A&A

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Context. There are numerous examples of accretion discs in binary systems where the disc midplane is believed to be inclined relative to the binary orbit plane. Examples include the X-ray binaries Her X-1 and SS433, and the young stellar binary HK Tau. Under suitable physical conditions, such a configuration is expected to induce warping and rigid-body precession of the disc. Aims. We aim to examine the detailed disc structure that arises in a misaligned binary system as a function of the disc aspect ratio h, viscosity parameter α, disc outer radius R, and binary inclination angle γ F . We also aim to examine the conditions that lead to an inclined disc being disrupted by strong differential precession. Methods. We use a grid-based hydrodynamic code to perform 3D simulations. This code has a relatively low numerical viscosity compared with the SPH schemes that have been used previously to study inclined discs. This allows the influence of viscosity on the disc evolution to be tightly controlled. Results. We find that for thick discs (h = 0.05) with low α, efficient warp communication in the discs allows them to precess as rigid bodies with very little warping or twisting. Such discs are observed to align with the binary orbit plane on the viscous evolution time. Thinner discs with higher viscosity, in which warp communication is less efficient, develop significant twists before achieving a state of rigid-body precession. Under the most extreme conditions we consider (h = 0.01, α = 5 × 10 −3 and α = 0.1), we find that discs can become broken or disrupted by strong differential precession. Discs that become highly twisted are observed to align with the binary orbit plane on timescales much shorter than the viscous timescale, possibly on the precession time. Conclusions. We find agreement with previous studies that show that thick discs with low viscosity experience mild warping and precess rigidly. We also find that as h is decreased substantially, discs may be disrupted by strong differential precession, but for disc thicknesses that are significantly less (h = 0.01) than those found in previous studies (h = 0.03).

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“…Forbidden lines in the optical range are common in T Tauri stars and have been the subject of studies for quite some time (Jankovics et al 1983, Edwards et al 1987, Hamann 1994, Hartigan et al 1995. Early studies reported the presence of blueshifted line emission and associated it with some sort of disk wind whose redshifted emission is obscured by the protoplanetary disk.…”

Section: Atomic Tracersmentioning

confidence: 99%

The Gas Disk: Evolution and Chemistry

et al. 2016

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Protoplanetary disks are the birthplaces of planetary systems. The evolution of the star-disk system and the disk chemical composition determines the initial conditions for planet formation. Therefore a comprehensive understanding of the main physical and chemical processes in disks is crucial for our understanding of planet formation. We give an overview of the early evolution of disks, discuss the importance of the stellar high-energy radiation for disk evolution and describe the general thermal and chemical structure of disks. Finally we provide an overview of observational tracers of the gas component and disk winds.

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Forbidden line and H-alpha profiles in T Tauri star spectra - A probe of anisotropic mass outflows and circumstellar disks

Cited by 197 publications

References 0 publications

Accretion dynamics of EX Lupi in quiescence

Accretion dynamics of EX Lupi in quiescence

Evolution of warped and twisted accretion discs in close binary systems

The Gas Disk: Evolution and Chemistry

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