scholarly journals Modeling the Hαline emission around classical T Tauri stars using magnetospheric accretion and disk wind models

2010 ◽  
Vol 522 ◽  
pp. A104 ◽  
Author(s):  
G. H. R. A. Lima ◽  
S. H. P. Alencar ◽  
N. Calvet ◽  
L. Hartmann ◽  
J. Muzerolle
Keyword(s):  
T Tauri Stars ◽  
Disk Wind ◽  
T Tauri ◽  
Magnetospheric Accretion

scholarly journals Time variable funnel flows

2007 ◽  
Vol 3 (S243) ◽  
pp. 71-82 ◽  
Author(s):  
Silvia H. P. Alencar
Keyword(s):  
Field Configuration ◽  
Time Variable ◽  
T Tauri Stars ◽  
Magnetic Field Configuration ◽  
Accretion Process ◽  
T Tauri ◽  
Model Predictions ◽  
The Magnetic Field ◽  
Disk Region ◽  
Magnetospheric Accretion

AbstractMagnetospheric accretion models are the current consensus to explain the main observed characteristics of classical T Tauri stars. In recent years the concept of a static magnetosphere has been challenged by synoptic studies of classical T Tauri stars that show strong evidence for the accretion process to be dynamic on several timescales and governed by changes in the magnetic field configuration. At the same time numerical simulation results predict evolving funnel flows due to the interaction between the stellar magnetosphere and the inner disk region. In this contribution we will focus on the main recent observational evidences for time variable funnel flows and compare them with model predictions.

scholarly journals Observations of magnetic fields in Herbig Ae/Be stars

2018 ◽  
Vol 14 (A30) ◽  
pp. 123-123
Author(s):  
Markus Schöller ◽  
Swetlana Hubrig
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
T Tauri Stars ◽  
Be Stars ◽  
T Tauri ◽  
Weak Magnetic Fields ◽  
Order Of Magnitude ◽  
Field Geometry ◽  
Herbig Ae Stars ◽  
Magnetospheric Accretion

AbstractModels of magnetically driven accretion reproduce many observational properties of T Tauri stars. For the more massive Herbig Ae/Be stars, the corresponding picture has been questioned lately, in part driven by the fact that their magnetic fields are typically one order of magnitude weaker. Indeed, the search for magnetic fields in Herbig Ae/Be stars has been quite time consuming, with a detection rate of about 10% (e.g. Alecian et al. 2008), also limited by the current potential to detect weak magnetic fields. Over the last two decades, magnetic fields were found in about twenty objects (Hubrig et al. 2015) and for only two Herbig Ae/Be stars was the magnetic field geometry constrained. Ababakr, Oudmaijer & Vink (2017) studied magnetospheric accretion in 56 Herbig Ae/Be stars and found that the behavior of Herbig Ae stars is similar to T Tauri stars, while Herbig Be stars earlier than B7/B8 are clearly different. The origin of the magnetic fields in Herbig Ae/Be stars is still under debate. Potential scenarios include the concentration of the interstellar magnetic field under magnetic flux conservation, pre-main-sequence dynamos during convective phases, mergers, or common envelope developments. The next step in this line of research will be a dedicated observing campaign to monitor about two dozen HAeBes over their rotation cycle.

New Tests of Magnetospheric Accretion in T Tauri Stars

2002 ◽  
Vol 573 (2) ◽  
pp. 685-698 ◽  
Author(s):  
Christopher M. Johns‐Krull ◽  
April D. Gafford
Keyword(s):  
T Tauri Stars ◽  
T Tauri ◽  
Magnetospheric Accretion

scholarly journals Dynamics of wind and the dusty environments in the accreting T Tauri stars RY Tauri and SU Aurigae

2018 ◽  
Vol 483 (1) ◽  
pp. 132-146 ◽  
Author(s):  
P P Petrov ◽  
K N Grankin ◽  
J F Gameiro ◽  
S A Artemenko ◽  
E V Babina ◽  
...  
Keyword(s):  
T Tauri Stars ◽  
Gas Flows ◽  
Photometric Variability ◽  
Outflow Velocity ◽  
T Tauri ◽  
Photometric Observations ◽  
Accretion Model ◽  
Circumstellar Extinction ◽  
Magnetospheric Accretion

Abstract Classical T Tauri stars with ages of less than 10 Myr possess accretion discs. Magnetohydrodynamic processes at the boundary between the disc and the stellar magnetosphere control the accretion and ejections gas flows. We carried out a long series of simultaneous spectroscopic and photometric observations of the classical T Tauri stars, RY Tauri and SU Aurigae, with the aim to quantify the accretion and outflow dynamics at time-scales from days to years. It is shown that dust in the disc wind is the main source of photometric variability of these stars. In RY Tau, we observed a new effect: during events of enhanced outflow, the circumstellar extinction becomes lower. The characteristic time of changes in outflow velocity and stellar brightness indicates that the obscuring dust is near the star. The outflow activity in both stars is changing on a time-scale of years. Periods of quiescence in the variability of the Hα profile were observed during the 2015–2016 period in RY Tau and during the 2016–2017 period in SU Aur. We interpret these findings in the framework of the magnetospheric accretion model, and we discuss how the global stellar magnetic field can influence the long-term variations of the outflow activity.

scholarly journals Magnetospheric Accretion in T Tauri Stars

1997 ◽  
Vol 163 ◽  
pp. 515-519
Author(s):  
Philip J. Armitage
Keyword(s):  
T Tauri Stars ◽  
Stellar Surface ◽  
Photometric Variability ◽  
Accretion Flows ◽  
Rotation Rates ◽  
T Tauri ◽  
Show Evidence ◽  
Magnetospheric Accretion

AbstractMany, perhaps most, accreting T Tauri stars show evidence for magnetically dominated accretion flows near the stellar surface. I discuss the implications of this for the rotation rates and long-term photometric variability of T Tauri stars.

Spectroscopic evidence for magnetospheric accretion in classical T Tauri stars

1994 ◽  
Vol 108 ◽  
pp. 1056 ◽  
Author(s):  
S. Edwards ◽  
P. Hartigan ◽  
L. Ghandour ◽  
C. Andrulis
Keyword(s):  
T Tauri Stars ◽  
Spectroscopic Evidence ◽  
T Tauri ◽  
Magnetospheric Accretion

scholarly journals Magnetospheric Accretions and the Inner Winds of Classical T Tauri Stars

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.

Magnetospheric Accretion Models for the Hydrogen Emission Lines of T Tauri Stars

1998 ◽  
Vol 492 (2) ◽  
pp. 743-753 ◽  
Author(s):  
James Muzerolle ◽  
Nuria Calvet ◽  
Lee Hartmann
Keyword(s):  
T Tauri Stars ◽  
Emission Lines ◽  
Hydrogen Emission ◽  
T Tauri ◽  
Hydrogen Emission Lines ◽  
Magnetospheric Accretion

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

2020 ◽  
Vol 642 ◽  
pp. A99 ◽  
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.

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