scholarly journals Classical T Tauri stars: accretion, wind, dust

2021 ◽  
Vol 2 (1) ◽  
pp. 1-8
Author(s):  
Petr Petrov
Keyword(s):  
Accretion Disks ◽  
Accretion Rate ◽  
T Tauri Stars ◽  
Evolutionary Stage ◽  
Gas Flows ◽  
Spectroscopic Monitoring ◽  
T Tauri ◽  
Dynamical Parameters ◽  
Wind Flows ◽  
Magnetospheric Accretion

Classical T Tauri stars (CTTS) are at the early evolutionary stage when the processes of planet formation take place in the surrounding accretion disks. Most of the observed activity in CTTS is due to magnetospheric accretion and wind flows. Observations of the accreting gas flows and appearance of the line-dependent veiling of the photospheric spectrum in CTTS are considered. Evidence for the dusty wind causing the observed irregular variability of CTTS is presented. Photometric and spectroscopic monitoring of two CTTS, RY Tau and SU Aur, has been carried out atthe Crimean Astrophysical Observatory since 2013 aimed at studying the dynamics of accretion and wind flows on time scales from days to years. The observed variations in the dynamical parameters may be caused by changes in the accretion rate and in the global magnetic fields of CTTS.

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 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.

scholarly journals Brown dwarf jets: Investigating the universality of jet launching mechanisms at the lowest masses

2010 ◽  
Vol 6 (S275) ◽  
pp. 396-399
Author(s):  
Emma Teresa Whelan ◽  
Francesca Bacciotti ◽  
Tom Ray ◽  
Catherine Dougados
Keyword(s):  
Accretion Rate ◽  
T Tauri Stars ◽  
Brown Dwarf ◽  
Central Mass ◽  
Mass Accretion Rate ◽  
T Tauri ◽  
Mass Outflow ◽  
The Common ◽  
Protostellar Objects

AbstractRecently it has become apparent that proto-stellar-like outflow activity extends to the brown dwarf (BD) mass regime. While the presence of accretion appears to be the common ingredient in all objects known to drive jets fundamental questions remain unanswered. The more prominent being the exact mechanism by which jets are launched, and whether this mechanism remains universal among such a diversity of sources and scales. To address these questions we have been investigating outflow activity in a sample of protostellar objects that differ considerably in mass and mass accretion rate. Central to this is our study of brown dwarf jets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decoding the launching mechanism. Here we shall summarise what is understood so far of BD jets and the important constraints observations can place on models. We will focus on the comparison between jets driven by objects with central mass <0.1M⊙ and those driven by CTTSs. In particular we wish to understand how the the ratio of the mass outflow to accretion rate compares to what has been measured for CTTSs.

Accretion disks around T Tauri stars. II - Balmer emission

1989 ◽  
Vol 341 ◽  
pp. 340 ◽  
Author(s):  
Gibor Basri ◽  
Claude Bertout
Keyword(s):  
Accretion Disks ◽  
T Tauri Stars ◽  
T Tauri

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 T Tauri stars and flare stars: common properties and differences

1990 ◽  
Vol 137 ◽  
pp. 209-213
Author(s):  
I. Appenzeller
Keyword(s):  
Accretion Disks ◽  
T Tauri Stars ◽  
The Other ◽  
Late Type ◽  
Physical Origin ◽  
Other Hand ◽  
T Tauri ◽  
Low Mass ◽  
Flare Stars

T Tauri stars and flare stars are both magnetically active late-type stars of low mass and low to moderate luminosities. The flares observed in these two classes of variables show similar properties and, thus, probably have the same physical origin. On the other hand, at least the majority of the classical T Tauri stars seem to be surrounded by cool, dusty (accretion) disks, which are absent or undetectable in most classical flare stars.

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 Stellar wind flows in T Tauri stars

1987 ◽  
Vol 122 ◽  
pp. 105-106
Author(s):  
C. Sá ◽  
M.T.V.T. Lago ◽  
M.V. Penston
Keyword(s):  
Stellar Wind ◽  
General Pattern ◽  
T Tauri Stars ◽  
Emission Lines ◽  
High Dispersion ◽  
T Tauri ◽  
Wind Flows ◽  
Using Data

Following the successful modelling of the wind from RU Lupi using data at moderate and high dispersion we report on similar observations of other T Tauri stars where the general pattern of the wind, as deduced from the widths of the emission lines of the various species, seems to be similar.

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