scholarly journals The Frequency of YY Orionis Objects among the T Tauri Stars

1977 ◽  
Vol 42 ◽  
pp. 80-87 ◽  
Author(s):  
I. Appenzeller
Keyword(s):  
Statistical Analysis ◽  
Present Theory ◽  
T Tauri Stars ◽  
Early Evolution ◽  
Low Mass Stars ◽  
T Tauri ◽  
Uv Excess ◽  
Low Mass ◽  
Good Agreement

A list of 24 T Tauri stars belonging to the YY Orionis subclass is presented. From a statistical analysis it is estimated that at least 75% (and possibly all) UV-excess T Tauri stars are YY Orionis stars. Since about 50% of all known T Tauri stars show a strong UV-excess, the percentage of YY Orionis stars among the T Tauri stars is estimated to be 40 - 50%. This relative high percentage is in good agreement with the present theory of the formation and early evolution of low mass stars.

scholarly journals Evidence of Collective Formation of Low Mass Stars in the Dark Cloud Kh141

1987 ◽  
Vol 115 ◽  
pp. 64-66
Author(s):  
Yoshio Tomita ◽  
Hiroshi Ohtani
Keyword(s):  
Star Formation ◽  
Massive Stars ◽  
T Tauri Stars ◽  
Low Mass Stars ◽  
Dark Cloud ◽  
T Tauri ◽  
Low Mass ◽  
Cloud Complex

To find evidence for collective star formation without massive stars in the dark cloud complex Kh141 (Saito 1980), a search for T-Tauri stars has been made.

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.

scholarly journals Dense Cores and Young Stars in Dark Clouds

1987 ◽  
Vol 115 ◽  
pp. 33-43
Author(s):  
Philip C. Myers
Keyword(s):  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Low Mass Stars ◽  
Iras Source ◽  
Dark Clouds ◽  
Dense Cores ◽  
T Tauri ◽  
Circumstellar Extinction ◽  
Molecular Lines ◽  
Low Mass

Dark clouds within a few hundred pc of the Sun contain hundreds of condensations with typical size 0.1 pc, density 104 molecules per cubic cm, mass 1 M⊙, and temperature 10 K. These “dense cores” are defined by maps of molecular lines, such as the (J,K)=(1,1) line of ammonia at 1.3 cm wavelength. They are associated with regions of opaque visual obscuration, groups of T Tauri stars, and other cores. They are closely correlated with steep-spectrum, low-luminosity (1-10 L⊙) IRAS sources! of about 60 cores with ammonia maps, half have an IRAS source within one map diameter. Thus cores form low-mass stars, which are probably precursors of T Tauri stars. Simple models indicate that time for a core to wait before collapsing, to collapse and form a star, and to disperse are each of order 105 yr. Cores with stars have broader lines and bigger velocity gradients than cores without stars, suggesting interaction between the star and the core due to gravity and/or outflow. Stars in cores have about 30 mag greater circumstellar extinction, and greater likelihood of CO outflow, than stars near, but not in, cores. Models of the 1-100 μm spectra of stars in cores suggest that inside of ∼100 A.U., the typical star suffers relatively little line-of-sight extinction but is accompanied by a source of significant luminosity at 5-25 μm. Models involving circumstellar disks provide good fits to the observed spectra.

Recent Photoelectric and Spectroscopic Observations of YY Orionis Stars

1979 ◽  
Vol 46 ◽  
pp. 519-520
Author(s):  
R. Mundt
Keyword(s):  
T Tauri Stars ◽  
Spectroscopic Evidence ◽  
Spectroscopic Observations ◽  
T Tauri ◽  
Hydrodynamic Evolution ◽  
Uv Excess ◽  
Low Mass

AbstractThe YY Orionis Stars are a subclass of the T Tauri stars, which have a particularly strong UV-excess and show spectroscopic evidence for infailing envelopes, like the occurrence of inverse P Cygni profiles. They have been interpreted as low mass protostars in the final stages of their hydrodynamic evolution (Walker 1972, Appenzeller and Wolf 1977, Wolf et al. 1977).

scholarly journals The Interaction of T-Tauri Stars with Molecular Clouds

1980 ◽  
Vol 87 ◽  
pp. 165-172 ◽  
Author(s):  
Joseph Silk ◽  
Colin Norman
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
T Tauri Stars ◽  
Mass Star ◽  
Internal Source ◽  
Low Mass Stars ◽  
Dark Cloud ◽  
Nearby Star ◽  
T Tauri ◽  
Low Mass

Winds from T-Tauri stars may provide an important dynamical input into cold molecular clouds. If the frequency of T-Tauri stars exceeds 20 pc-3, wind-driven shells collide and form ram pressure confined clumps. The supersonic clump motions can account for cloud line widths. Clumps collide inelastically, coalescing and eventually becoming Jeans unstable. For characteristic dark cloud temperatures low mass stars form, and we speculate that in this manner clouds can be self-sustaining for 107 − 108 yr. Only when either the gas supply is exhausted or an external trigger stimulates massive star formation (for example, by heating the cloud or enhancing the clump collision rate), will the cloud eventually be disrupted. A natural consequence of this model is that dark cloud lifetimes are identified with the duration of low mass star formation, inferred to exceed 107 yr from studies of nearby star clusters. Other implications include the prediction of the existence of embedded low mass stars in turbulent cloud cores, the presence of an internal source of radiation in dark clouds, and a clumpy structure for cold molecular clouds.

scholarly journals Circumstellar maher of young low-mass stars: Observations versus theory

1987 ◽  
Vol 122 ◽  
pp. 23-38 ◽  
Author(s):  
Claude Bertout
Keyword(s):  
T Tauri Stars ◽  
Young Stellar Objects ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Region I ◽  
Low Mass ◽  
Infrared Sources

After presenting NGC 7129 as a prototypical star-forming region, I discuss what can be learned from the radio spectra of embedded infrared sources. I then review available observational evidence for disks around young stellar objects, with emphasis on accretion disks around T Tauri stars. Finally, new results on the role of magnetic fields in the circumstellar activity of T Tauri stars are presented.

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 Observations of the Chemistry in Circumstellar Disks

2000 ◽  
Vol 197 ◽  
pp. 415-423 ◽  
Author(s):  
A. Dutrey ◽  
S. Guilloteau ◽  
M. Guélin
Keyword(s):  
Temperature Profile ◽  
Chemical Evolution ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Molecular Gas ◽  
Low Mass Stars ◽  
T Tauri ◽  
Low Mass ◽  
Significant Chemical ◽  
Gas Component

Circumstellar disks around classical T Tauri stars have still large amounts of primary molecular gas and dust, which may evolve to form planetary systems. Although it is the remnant of the parental cloud, the gas component shows significant chemical evolution. Fundamental disk properties (kinematics, size, temperature profile) can be derived from observations of CO lines with mm arrays. Less abundant molecules have been discovered with the IRAM 30-m telescope, in the DM Tau and GG Tau disks. Despite the high depletion factors which are measured with respect to the nearby Taurus cloud, these molecules allow independent measurements of the disk density. These observations provide an overview of the properties of young (a few Myr) proto-planetary disks around low-mass stars as seen by current mm instruments.

scholarly journals NMA Imaging of Envelopes and Disks around Low Mass Protostars and T Tauri Stars

1997 ◽  
Vol 182 ◽  
pp. 381-390
Author(s):  
Yoshimi Kitamura ◽  
Masao Saito ◽  
Ryohei Kawabe ◽  
Kazuyoshi Sunada
Keyword(s):  
Accretion Disks ◽  
Molecular Clouds ◽  
Protoplanetary Disks ◽  
Hierarchical Structures ◽  
T Tauri Stars ◽  
Mass Star ◽  
Low Mass Stars ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass

We are intensively studying low mass star formation with the radio telescopes at Nobeyama in Japan. Using both the Nobeyama 45 m dish equipped with a 2 × 2 array receiver and the Nobeyama Millimeter Array (NMA), we can cover a very wide spatial range from overall molecular clouds down to compact protoplanetary disks. With the 45 m dish we are investigating hierarchical structures of molecular clouds including star-forming cores. With NMA we are imaging disklike structures (i.e., envelopes, accretion disks, and protoplanetary disks) around protostars and T Tauri stars. Recently, we have completed our survey for dense disklike envelopes around eleven Class 0 & I protostars by NMA. In this paper, we will present our recent results of the disklike envelopes in addition to the previous NMA results of the disks around three T Tauri stars. On the basis of the data, we will discuss the evolution of the disklike structures (dense envelopes → tenuous ones → dispersing ones → accretion disks → protoplanetary ones), and propose a new scenario for the formation of low mass stars.

scholarly journals Very Low Mass Stars and Brown Dwarfs in Taurus

2003 ◽  
Vol 211 ◽  
pp. 143-144
Author(s):  
Russel White ◽  
Gibor Basri
Keyword(s):  
High Resolution ◽  
Brown Dwarfs ◽  
Optical Spectra ◽  
T Tauri Stars ◽  
Low Mass Stars ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass

We present high resolution optical spectra obtained with the Keck I telescope of low mass T Tauri stars and brown dwarfs in the Taurus star forming region. Based on the inferred photospheric and circumstellar properties, we conclude that objects in Taurus with masses as low as 50 Jupiters form and evolve in the same way as higher-mass T Tauri stars, but with smaller disks and shorter disk lifetimes.

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