Emission‐Line Diagnostics of T Tauri Magnetospheric Accretion. II. Improved Model Tests and Insights into Accretion Physics

2001 ◽  
Vol 550 (2) ◽  
pp. 944-961 ◽  
Author(s):  
James Muzerolle ◽  
Nuria Calvet, ◽  
Lee Hartmann
Keyword(s):  
Emission Line ◽  
Model Tests ◽  
T Tauri ◽  
Accretion Physics ◽  
Improved Model ◽  
Magnetospheric Accretion

Emission-Line Diagnostics of T Tauri Magnetospheric Accretion. I. Line Profile Observations

1998 ◽  
Vol 116 (1) ◽  
pp. 455-468 ◽  
Author(s):  
James Muzerolle ◽  
Lee Hartmann ◽  
Nuria Calvet
Keyword(s):  
Emission Line ◽  
Line Profile ◽  
T Tauri ◽  
Magnetospheric Accretion

scholarly journals What do weak magnetic fields mean for magnetospheric accretion in Herbig AeBe star+disk systems?

2013 ◽  
Vol 9 (S302) ◽  
pp. 80-83
Author(s):  
A. N. Aarnio ◽  
J. D. Monnier ◽  
T. J. Harries ◽  
D. M. Acreman
Keyword(s):  
Main Sequence ◽  
Planetary System ◽  
Spectral Lines ◽  
Data Set ◽  
T Tauri ◽  
Weak Magnetic Fields ◽  
Fundamental Process ◽  
Dipolar Fields ◽  
Solar Analogs ◽  
Magnetospheric Accretion

AbstractIn the presently favored picture of star formation, mass is transferred from disk to star via magnetospheric accretion and out of the system via magnetically driven outflows. This magnetically mediated mass flux is a fundamental process upon which the evolution of the star, disk, and forming planetary system depends. Our current understanding of these processes is heavily rooted in young solar analogs, T Tauri Stars (TTS). We have come to understand recently, however, that the higher mass pre-main sequence (PMS) Herbig AeBe (HAeBe) stars have dramatically weaker dipolar fields than their lower mass counterparts. We present our current observational and theoretical efforts to characterize magnetospherically mediated mass transfer within HAeBe star+disk systems. We have gathered a rich spectroscopic and interferometric data set for several dozen HAeBe stars in order to measure accretion and mass loss rates, assess wind and magnetospheric accretion properties, and determine how spectral lines and interferometric visibilities are diagnostic of these processes. For some targets, we have observed spectral line variability and will discuss ongoing time-series spectroscopic efforts.

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 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 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 The accretion rates and mechanisms of Herbig Ae/Be stars

2020 ◽  
Vol 493 (1) ◽  
pp. 234-249 ◽  
Author(s):  
C Wichittanakom ◽  
R D Oudmaijer ◽  
J R Fairlamb ◽  
I Mendigutía ◽  
M Vioque ◽  
...  
Keyword(s):  
Accretion Rate ◽  
High Mass ◽  
Be Stars ◽  
Alpha Emission ◽  
T Tauri ◽  
Accretion Model ◽  
Accretion Rates ◽  
Theoretical Considerations ◽  
Gaia Dr2 ◽  
Magnetospheric Accretion

ABSTRACT This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30 objects. Stellar parameters such as temperature, reddening, mass, luminosity, and age are homogeneously determined. Mass accretion rates are determined from $\rm H\alpha$ emission line measurements. Our data is complemented with the X-Shooter sample from previous studies and we update results using Gaia DR2 parallaxes giving a total of 78 objects with homogeneously determined stellar parameters and mass accretion rates. In addition, mass accretion rates of an additional 85 HAeBes are determined. We confirm previous findings that the mass accretion rate increases as a function of stellar mass, and the existence of a different slope for lower and higher mass stars, respectively. The mass where the slope changes is determined tobe $3.98^{+1.37}_{-0.94}\, \rm M_{\odot }$. We discuss this break in the context of different modes of disc accretion for low- and high-mass stars. Because of their similarities with T Tauri stars, we identify the accretion mechanism for the late-type Herbig stars with the Magnetospheric Accretion. The possibilities for the earlier-type stars are still open, we suggest the Boundary Layer accretion model may be a viable alternative. Finally, we investigated themass accretion–age relationship. Even using the superior Gaia based data, it proved hard to select a large enough sub-sample to remove the mass dependence in this relationship. Yet, it would appear that the mass accretion does decline with age as expected from basic theoretical considerations.

scholarly journals Observations of T Tauri Disks at Sub‐AU Radii: Implications for Magnetospheric Accretion and Planet Formation

2005 ◽  
Vol 623 (2) ◽  
pp. 952-966 ◽  
Author(s):  
J. A. Eisner ◽  
L. A. Hillenbrand ◽  
R. J. White ◽  
R. L. Akeson ◽  
A. I. Sargent
Keyword(s):  
Planet Formation ◽  
T Tauri ◽  
Magnetospheric Accretion

scholarly journals Magnetospheric accretion on the T Tauri star BP Tauri

2008 ◽  
Vol 386 (3) ◽  
pp. 1234-1251 ◽  
Author(s):  
J.-F. Donati ◽  
M. M. Jardine ◽  
S. G. Gregory ◽  
P. Petit ◽  
F. Paletou ◽  
...  
Keyword(s):  
Tauri Star ◽  
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.

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