scholarly journals The magnetic obliquity of accreting T Tauri stars

2020 ◽  
Vol 497 (2) ◽  
pp. 2142-2162
Author(s):  
Pauline McGinnis ◽  
Jérôme Bouvier ◽  
Florian Gallet
Keyword(s):  
Radial Velocity ◽  
Rotational Velocity ◽  
T Tauri Stars ◽  
Rotational Axis ◽  
Stellar Rotation ◽  
Magnetic Pole ◽  
T Tauri ◽  
Significant Difference ◽  
Tentative Evidence ◽  
Accretion Shock

ABSTRACT Classical T Tauri stars (CTTSs) accrete material from their discs through their magnetospheres. The geometry of the accretion flow strongly depends on the magnetic obliquity, i.e. the angle between the rotational and magnetic axes. We aim at deriving the distribution of magnetic obliquities in a sample of 10 CTTSs. For this, we monitored the radial velocity variations of the He i λ5876 Å line in these stars’ spectra along their rotational cycle. He i is produced in the accretion shock, close to the magnetic pole. When the magnetic and rotational axes are not aligned, the radial velocity of this line is modulated by stellar rotation. The amplitude of modulation is related to the star’s projected rotational velocity, vsin i, and the latitude of the hotspot. By deriving vsin i and He i λ5876 radial velocity curves from our spectra, we thus obtain an estimate of the magnetic obliquities. We find an average obliquity in our sample of 11.4° with an rms dispersion of 5.4°. The magnetic axis thus seems nearly, but not exactly aligned with the rotational axis in these accreting T Tauri stars, somewhat in disagreement with studies of spectropolarimetry, which have found a significant misalignment (≳20°) for several CTTSs. This could simply be an effect of low number statistics, or it may be due to a selection bias of our sample. We discuss possible biases that our sample may be subject to. We also find tentative evidence that the magnetic obliquity may vary according to the stellar interior and that there may be a significant difference between fully convective and partly radiative stars.

scholarly journals Stellar Rotation of T Tauri Stars in the Orion Star-forming Complex

2021 ◽  
Vol 923 (2) ◽  
pp. 177
Author(s):  
Javier Serna ◽  
Jesus Hernandez ◽  
Marina Kounkel ◽  
Ezequiel Manzo-Martínez ◽  
Alexandre Roman-Lopes ◽  
...  
Keyword(s):  
Large Scale ◽  
Rotational Velocity ◽  
T Tauri Stars ◽  
Evolutionary Models ◽  
Stellar Rotation ◽  
Low Mass Stars ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass ◽  
Early Phases

Abstract We present a large-scale study of stellar rotation for T Tauri stars in the Orion star-forming complex. We use the projected rotational velocity ( v sin ( i ) ) estimations reported by the APOGEE-2 collaboration as well as individual masses and ages derived from the position of the stars in the HR diagram, considering Gaia-EDR3 parallaxes and photometry plus diverse evolutionary models. We find an empirical trend for v sin ( i ) decreasing with age for low-mass stars (0.4M ⊙ < M * < 1.2M ⊙). Our results support the existence of a mechanism linking v sin ( i ) to the presence of accreting protoplanetary disks, responsible for regulating stellar rotation on timescales of about 6 Myr, which is the timescale in which most of the T Tauri stars lose their inner disk. Our results provide important constraints to models of rotation in the early phases of evolution of young stars and their disks.

scholarly journals Formation of Fe X-Fe XIV coronal lines in the accretion shock of T Tauri stars

2001 ◽  
Vol 369 (3) ◽  
pp. 965-970 ◽  
Author(s):  
S. A. Lamzin ◽  
H. C. Stempels ◽  
N. E. Piskunov
Keyword(s):  
T Tauri Stars ◽  
T Tauri ◽  
Accretion Shock

scholarly journals X-ray emission from dense plasma in classical T Tauri stars: hydrodynamic modeling of the accretion shock

2008 ◽  
Vol 491 (2) ◽  
pp. L17-L20 ◽  
Author(s):  
G. G. Sacco ◽  
C. Argiroffi ◽  
S. Orlando ◽  
A. Maggio ◽  
G. Peres ◽  
...  
Keyword(s):  
Dense Plasma ◽  
Hydrodynamic Modeling ◽  
T Tauri Stars ◽  
X Ray ◽  
T Tauri ◽  
Accretion Shock

scholarly journals The Structure and Emission of the Accretion Shock in T Tauri Stars

1998 ◽  
Vol 509 (2) ◽  
pp. 802-818 ◽  
Author(s):  
Nuria Calvet ◽  
Erik Gullbring
Keyword(s):  
T Tauri Stars ◽  
T Tauri ◽  
Accretion Shock

scholarly journals The Rotation and Variability of T Tauri Stars: Results of Two Decades of Monitoring at Van Vleck Observatory

2001 ◽  
Vol 183 ◽  
pp. 177-186
Author(s):  
W. Herbst
Keyword(s):  
T Tauri Stars ◽  
Orion Nebula ◽  
Stellar Rotation ◽  
Rotation Rates ◽  
T Tauri ◽  
History Of ◽  
Peculiar Object ◽  
Photometric Monitoring ◽  
Van Vleck ◽  
Cluster 2

AbstractA brief history of photometric monitoring of T Tauri stars with a 0.6 m telescope at Wesleyan University is given. This is followed by discussion of three recent results: 1) the mass dependence of stellar rotation rates in the Orion Nebula Cluster, 2) a check on stellar radii estimates of pre-main sequence stars, and 3) the nature of a very peculiar object in NGC 2264.

scholarly journals The implications of close binary stars for star-disk interactions

2007 ◽  
Vol 3 (S243) ◽  
pp. 315-324 ◽  
Author(s):  
Robert D. Mathieu
Keyword(s):  
Binary Stars ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Close Binary ◽  
Close Binaries ◽  
Spectral Energy ◽  
Stellar Rotation ◽  
Single Star ◽  
Accretion Flows ◽  
T Tauri

AbstractThe presence of close (≲ 0.1 AU) stellar companions must greatly alter the circumstellar environment of classical T Tauri stars, including severe truncation if not elimination of circumstellar disks. It is thus remarkable how little impact the presence of a close companion has on our observable diagnostics for accretion and outflow. Emission line shapes, degrees of continuum veiling, and spectral energy distributions are all indistinguishable between single classical T Tauri stars and classical T Tauri close binaries. Some of the most classical T Tauri stars that laid the foundation for our single-star accretion-disk paradigm have turned out to have close companions. Periodicities in spectral signatures are suggestive of the presence of accretion flows from circumbinary disks to the circumstellar regions; the subsequent flow of material through the circumstellar region to the stellar surface in the presence of a stellar magnetosphere is unstudied. Observations of stellar rotation distributions in close binaries suggest that inner disk regions may act to regulate stellar angular momentum.

scholarly journals The Structure and Emission of the Accretion Shock in T Tauri Stars. II. The Ultraviolet‐Continuum Emission

2000 ◽  
Vol 544 (2) ◽  
pp. 927-932 ◽  
Author(s):  
Erik Gullbring ◽  
Nuria Calvet ◽  
James Muzerolle ◽  
Lee Hartmann
Keyword(s):  
T Tauri Stars ◽  
Continuum Emission ◽  
Ultraviolet Continuum ◽  
T Tauri ◽  
Accretion Shock

scholarly journals The Surface Magnetic Activity of the Weak-Line T Tauri Stars TWA 7 and TWA 25

2021 ◽  
Author(s):  
B A Nicholson ◽  
G Hussain ◽  
J-F Donati ◽  
D Wright ◽  
C P Folsom ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Radial Velocity ◽  
Large Scale ◽  
T Tauri Stars ◽  
Doppler Imaging ◽  
Weak Line ◽  
T Tauri ◽  
Wide Range ◽  
Velocity Variations ◽  
Scale Surface

Abstract We present an analysis of spectropolarimetric observations of the low-mass weak-line T Tauri stars TWA 25 and TWA 7. The large-scale surface magnetic fields have been reconstructed for both stars using the technique of Zeeman Doppler imaging. Our surface maps reveal predominantly toroidal and non-axisymmetric fields for both stars. These maps reinforce the wide range of surface magnetic fields that have been recovered, particularly in pre-main sequence stars that have stopped accreting from the (now depleted) central regions of their discs. We reconstruct the large scale surface brightness distributions for both stars, and use these reconstructions to filter out the activity-induced radial velocity jitter, reducing the RMS of the radial velocity variations from 495 m s −1 to 32 m s −1 for TWA 25, and from 127 m s −1 to 36 m s −1 for TWA 7, ruling out the presence of close-in giant planets for both stars. The TWA 7 radial velocities provide an example of a case where the activity-induced radial velocity variations mimic a Keplerian signal that is uncorrelated with the spectral activity indices. This shows the usefulness of longitudinal magnetic field measurements in identifying activity-induced radial velocity variations.

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