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.

scholarly journals Flares in T Tauri Stars

1995 ◽  
Vol 151 ◽  
pp. 202-211 ◽  
Author(s):  
Gösta F. Gahm
Keyword(s):  
Time Scales ◽  
T Tauri Stars ◽  
Light Curves ◽  
Rapid Variability ◽  
Strong Emission ◽  
T Tauri ◽  
New Concepts ◽  
Circumstellar Extinction ◽  
Higher Sensitivity

This review concerns rapid variability, on time-scales of a few hours or less, occurring on T Tauri stars (TTS). There are several recent reviews on observed properties of TTS (e.g. Appenzeller & Mundt 1989, Bertout 1989, Gahm 1990a, Kuhi & Cram 1989), some with more emphasis on “flare-like” activity (Feigelson et al. 1991, Gahm 1990b, Montmerle 1991, Montmerle et al. 1993), and the ambition below has been to summarize more recent work. We will also give a compilation of published works on observations of optical variability on these time-scales and a related statistical overview. Some early, very interesting and extensive studies of this kind were made here at the Sonneberg Observatory, where for instance Götz & Wenzel (1967) concluded that the light-curve of RW Aurigae contains several components: quasi-periodic fluctuations over days, ‘waves’ over several hours, rapid outbursts with symmetric light-curves, rapid outbursts with asymmetric (flare-like) light-curves (see also Fürtig & Wenzel 1964) and small fluctuations with very small amplitudes, which they postulated could be due to changes in the emission line fluxes. Modern photometric results of higher sensitivity and time-resolution confirm the existence of these different types of rapid variations in classical TTS (CTTS), having strong emission (lines and continuous, so called veiling) superimposed on the photospheric absorption line spectrum. As described in the subsequent chapters there are new concepts for the interpretation of the short-lived fluctuations. Concerning the long-term quasi-periodic variations we can now usually relate them to the stellar rotational period (bright or dark spots), let be that RW Aur still is an uncertain case. There are other slow changes most likely related to variable circumstellar extinction in circumstellar dust in the line-of-sight to the star. The long-term optical changes were most recently discussed by Herbst et al. (1994).

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 Long-Term Multicolour Photometry of the Young Stellar Objects FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cygni

2015 ◽  
Vol 32 ◽  
Author(s):  
S. I. Ibryamov ◽  
E. H. Semkov ◽  
S. P. Peneva
Keyword(s):  
Gulf Of Mexico ◽  
Young Stellar Objects ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Photometric Variability ◽  
The North ◽  
Dense Molecular Cloud ◽  
Photometric Observations ◽  
All Optical

AbstractResults from long-term multicolour optical photometric observations of the pre-main-sequence stars FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cyg collected during the period from 1997 June to 2014 December are presented. The objects are located in the dense molecular cloud L935, named ‘Gulf of Mexico’, in the field between the North America and Pelican nebulae. All stars from our study exhibit strong photometric variability in all optical passbands. Using our BVRI observations and data published by other authors, we tried to define the reasons for the observed brightness variations. The presented paper is a part of our long-term photometric study of the young stellar objects in the region of ‘Gulf of Mexico’.

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 Optical photometric variable stars towards Cygnus OB7

2019 ◽  
Vol 487 (2) ◽  
pp. 1765-1776 ◽  
Author(s):  
Somnath Dutta ◽  
Soumen Mondal ◽  
Santosh Joshi ◽  
Ramkrishna Das
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Rates ◽  
T Tauri ◽  
Photometric Observations ◽  
Sky Survey ◽  
Magnitude Diagram

ABSTRACT We present optical I-band light curves of the stars towards a star-forming region Cygnus OB7 from 17-night photometric observations. The light curves are generated from a total of 381 image frames with very good photometric precision. From the light curves of 1900 stars and their periodogram analyses, we detect 31 candidate variables including five previously identified. 14 out of 31 objects are periodic and exhibit the rotation rates in the range of 0.15–11.60 d. We characterize those candidate variables using optical/infrared colour–colour diagram and colour–magnitude diagram (CMD). From spectral indices of the candidate variables, it turns out that four are probably Classical T-Tauri stars (CTTSs), rest remain unclassified from present data, they are possibly field stars or discless pre-main-sequence stars towards the region. Based on their location on the various CMDs, the ages of two T Tauri Stars were estimated to be ∼5 Myr. The light curves indicate at least five of the periodic variables are eclipsing systems. The spatial distribution of young variable candidates on Planck 857 GHz (350 $\mu$m) and 2MASS (Two Micron All Sky Survey) Ks images suggest that at least two of the CTTSs are part of the active star-forming cloud Lynds 1003.

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 The Unusual Photometric Variability of the PMS Star GM Cep

2015 ◽  
Vol 32 ◽  
Author(s):  
E. H. Semkov ◽  
S. I. Ibryamov ◽  
S. P. Peneva ◽  
T. R. Milanov ◽  
K. A. Stoyanov ◽  
...  
Keyword(s):  
Open Cluster ◽  
High Amplitude ◽  
Outer Radius ◽  
T Tauri Stars ◽  
Photometric Data ◽  
Spectral Studies ◽  
Photometric Variability ◽  
T Tauri ◽  
Young Open Cluster ◽  
Photometric Monitoring

AbstractResults from UBVRI photometric observations of the pre-main sequence star GM Cep obtained in the period 2011 April–2014 August are reported in the paper. Presented data are a continuation of our photometric monitoring of the star started in 2008. GM Cep is located in the field of the young open cluster Trumpler 37 and over the past years it has been an object of intense photometric and spectral studies. The star shows a strong photometric variability interpreted as a possible outburst from EXor type in previous studies. Our photometric data for a period of over six years show a large amplitude variability (ΔV ~ 2.3 mag) and several deep minimums in brightness are observed. The analysis of the collected multicolour photometric data show the typical of UX Ori variables a colour reversal during the minimums in brightness. The observed decreases in brightness have a different shape, and evidences of periodicity are not detected. At the same time, high amplitude rapid variations in brightness typical for the classical T Tauri stars also present on the light curve of GM Cep. The spectrum of GM Cep shows the typical of classical T Tauri stars wide Hα emission line and absorption lines of some metals. We calculate the outer radius of the Hα emitting region as 10.4 ± 0.5 R⊙ and the accretion rate as 1.8 × 10− 7 M⊙ yr− 1.

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
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