High-resolution line profiles of T Tauri stars

Aims. In this paper, we aim to characterise the surface magnetic fields of a sample of eight T Tauri stars from high-resolution near-infrared spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetric studies. Our goals are firstly to apply Zeeman broadening modelling to T Tauri stars with high-resolution data, secondly to expand the sample of stars with measured surface magnetic field strengths, thirdly to investigate possible rotational or long-term magnetic variability by comparing spectral time series of given targets, and fourthly to compare the magnetic field modulus ⟨B⟩ tracing small-scale magnetic fields to those of large-scale magnetic fields derived by Stokes V Zeeman Doppler Imaging (ZDI) studies. Methods. We modelled the Zeeman broadening of magnetically sensitive spectral lines in the near-infrared K-band from high-resolution spectra by using magnetic spectrum synthesis based on realistic model atmospheres and by using different descriptions of the surface magnetic field. We developped a Bayesian framework that selects the complexity of the magnetic field prescription based on the information contained in the data. Results. We obtain individual magnetic field measurements for each star in our sample using four different models. We find that the Bayesian Model 4 performs best in the range of magnetic fields measured on the sample (from 1.5 kG to 4.4 kG). We do not detect a strong rotational variation of ⟨B⟩ with a mean peak-to-peak variation of 0.3 kG. Our confidence intervals are of the same order of magnitude, which suggests that the Zeeman broadening is produced by a small-scale magnetic field homogeneously distributed over stellar surfaces. A comparison of our results with mean large-scale magnetic field measurements from Stokes V ZDI show different fractions of mean field strength being recovered, from 25–42% for relatively simple poloidal axisymmetric field topologies to 2–11% for more complex fields.

Download Full-text

Winds from T Tauri stars. II - Balmer line profiles for inner disk winds

The Astrophysical Journal ◽

10.1086/171009 ◽

1992 ◽

Vol 386 ◽

pp. 229 ◽

Cited By ~ 29

Author(s):

Nuria Calvet ◽

Lee Hartmann ◽

Robert Hewett

Keyword(s):

T Tauri Stars ◽

Balmer Line ◽

Line Profiles ◽

T Tauri

Download Full-text

High-resolution X-ray spectroscopy of T Tauri stars in the Taurus-Auriga complex

Astronomy and Astrophysics ◽

10.1051/0004-6361:20066193 ◽

2007 ◽

Vol 468 (2) ◽

pp. 443-462 ◽

Cited By ~ 61

Author(s):

A. Telleschi ◽

M. Güdel ◽

K. R. Briggs ◽

M. Audard ◽

L. Scelsi

Keyword(s):

High Resolution ◽

T Tauri Stars ◽

X Ray ◽

T Tauri

Download Full-text

GIARPS High-resolution Observations of T Tauri stars (GHOsT)

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038534e ◽

2021 ◽

Vol 647 ◽

pp. C3

Author(s):

M. Gangi ◽

B. Nisini ◽

S. Antoniucci ◽

T. Giannini ◽

K. Biazzo ◽

...

Keyword(s):

High Resolution ◽

T Tauri Stars ◽

T Tauri

Download Full-text

GIARPS High-resolution Observations of T Tauri stars (GHOsT)

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038534 ◽

2020 ◽

Vol 643 ◽

pp. A32

Author(s):

M. Gangi ◽

B. Nisini ◽

S. Antoniucci ◽

T. Giannini ◽

K. Biazzo ◽

...

Keyword(s):

High Resolution ◽

Complex Structure ◽

Central Star ◽

T Tauri Stars ◽

Resolving Power ◽

High Resolution Spectroscopy ◽

Young Stellar Objects ◽

Clear Correlation ◽

Low Velocity ◽

T Tauri

Context. Disk winds play a fundamental role in the evolution of protoplanetary systems. The complex structure and dynamics can be investigated through the emission of atomic and molecular lines detected in high-resolution optical/IR spectra of young stellar objects. Despite their great importance, however, studies connecting the atomic and molecular components are lacking so far. Aims. In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we aim to characterize the atomic and molecular winds in a sample of classical T Tauri stars (CTTs) of the Taurus-Auriga region, focusing on a statistical analysis of the kinematic properties of the [O I] 630 nm and H2 2.12 μm lines and their mutual relationship. Methods. We analyzed the flux calibrated [O I] 630 nm and H2 2.12 μm lines in a sample of 36 CTTs observed at the Telescopio Nazionale Galileo with the HARPS-N spectrograph (resolving power of R = 115 000) and with the GIANO spectrograph (R = 50 000). We decomposed the line profiles into different kinematic Gaussian components and focused on the most frequently detected component, the narrow low-velocity (vp < 20 km s−1) component (NLVC). Results. We found that the H2 line is detected in 17 sources (~50% detection rate), and [O I] is detected in all sources but one. The NLV components of the H2 and [O I] emission are kinematically linked, with a strong correlation between the peak velocities and the full widths at half maximum of the two lines. Assuming that the line width is dominated by Keplerian broadening, we found that the [O I] NVLC originates from a disk region between 0.05 and 20 au and that of H2 in a region from 2 and 20 au. We also found that H2 is never detected in sources where [O I] originates in regions below 1 au, as well as in sources of early (~F-G) spectral type with a luminosity >1 L⊙. Moreover, in seven sources, both H2 and [O I] have clear blueshifted peaks and prominent [O I] high-velocity components. These components have also been detected in sources with no relevant centroid shift. Finally, we did not find any clear correlation between vp of the H2 and [O I] NVLC and the outer disk inclination. This result is in line with previous studies. Conclusions. Our results suggest that molecular and neutral atomic emission in disk winds originate from regions that might overlap, and that the survival of molecular winds in disks strongly depends on the gas exposure to the radiation from the central star. The presence of jets does not necessarily affect the kinematics of the low-velocity winds. Our results demonstrate the potential of wide-band high-resolution spectroscopy in linking tracers of different manifestations of the same phenomenon.

Download Full-text

High Quality Echelle Observations of T Tauri Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900034847 ◽

1988 ◽

Vol 132 ◽

pp. 99-104

Author(s):

G. Basri

Keyword(s):

High Resolution ◽

Line Profile ◽

T Tauri Stars ◽

Young Stars ◽

Emission Lines ◽

Current Understanding ◽

General Nature ◽

High Quality ◽

T Tauri ◽

Made In

This is a very brief review of the high resolution line profile work that has been done on very young stars. The spectral anamolies peculiar to these stars are mentioned, with some discussion of what may give rise to them. The Hα line is discussed most extensively, as the most work has been done with it. While progress has been made in understanding the general nature of T Tauri spectra, there are very large gaps in our current understanding of the emission lines from these stars.

Download Full-text

Magnetospheric Accretions and the Inner Winds of Classical T Tauri Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314001720 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 54-63

Author(s):

Ryuichi Kurosawa ◽

M. M. Romanova

Keyword(s):

T Tauri Stars ◽

Line Profiles ◽

Low Mass Stars ◽

Disk Wind ◽

Accretion Flows ◽

Mhd Simulations ◽

T Tauri ◽

Low Mass ◽

Rayleigh Taylor Instability ◽

The Difference

AbstractRecent spectropolarimetric observations suggest that young low-mass stars such as classical T Tauri stars (CTTSs) possess relatively strong (~kG) magnetic field. This supports a scenario in which the final accretion onto the stellar surface proceeds through a magnetosphere, and the winds are formed in magnetohydrodynamics (MHD) processes. We examine recent numerical simulations of magnetospheric accretions via an inclined dipole and a complex magnetic fields. The difference between a stable accretion regime, in which accretion occurs in ordered funnel streams, and an unstable regime, in which gas penetrates through the magnetosphere in several unstable streams due to the magnetic Rayleigh-Taylor instability, will be discussed. We describe how MHD simulation results can be used in separate radiative transfer (RT) models to predict observable quantiles such as line profiles and light curves. The plausibility of the accretion flows and outflows predicted by MHD simulations (via RT models) can be tested against observations. We also address the issue of outflows/winds that arise from the innermost part of CTTSs. First, we discuss the line formations in a simple disk wind and a stellar wind models. We then discuss the formation of the conically shaped magnetically driven outflow that arises from the disk-magnetosphere boundary when the magnetosphere is compressed into an X-type configuration.

Download Full-text

Magnetospheric accretion in the intermediate-mass T Tauri star HQ Tauri

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038086 ◽

2020 ◽

Vol 642 ◽

pp. A99 ◽

Cited By ~ 1

Author(s):

K. Pouilly ◽

J. Bouvier ◽

E. Alecian ◽

S. H. P. Alencar ◽

A.-M. Cody ◽

...

Keyword(s):

Magnetic Field ◽

Strong Magnetic Field ◽

Main Sequence ◽

T Tauri Stars ◽

Line Profiles ◽

Main Sequence Stars ◽

Intermediate Mass ◽

Accretion Process ◽

T Tauri ◽

Magnetospheric Accretion

Context. Classical T Tauri stars are pre-main sequence stars surrounded by an accretion disk. They host a strong magnetic field, and both magnetospheric accretion and ejection processes develop as the young magnetic star interacts with its disk. Studying this interaction is a major goal toward understanding the properties of young stars and their evolution. Aims. The goal of this study is to investigate the accretion process in the young stellar system HQ Tau, an intermediate-mass T Tauri star (1.9 M⊙). Methods. The time variability of the system is investigated both photometrically, using Kepler-K2 and complementary light curves, and from a high-resolution spectropolarimetric time series obtained with ESPaDOnS at CFHT. Results. The quasi-sinusoidal Kepler-K2 light curve exhibits a period of 2.424 d, which we ascribe to the rotational period of the star. The radial velocity of the system shows the same periodicity, as expected from the modulation of the photospheric line profiles by surface spots. A similar period is found in the red wing of several emission lines (e.g., HI, CaII, NaI), due to the appearance of inverse P Cygni components, indicative of accretion funnel flows. Signatures of outflows are also seen in the line profiles, some being periodic, others transient. The polarimetric analysis indicates a complex, moderately strong magnetic field which is possibly sufficient to truncate the inner disk close to the corotation radius, rcor ∼ 3.5 R⋆. Additionally, we report HQ Tau to be a spectroscopic binary candidate whose orbit remains to be determined. Conclusions. The results of this study expand upon those previously reported for low-mass T Tauri stars, as they indicate that the magnetospheric accretion process may still operate in intermediate-mass pre-main sequence stars, such as HQ Tauri.

Download Full-text