Accretion disks around T Tauri stars

Bertout, C.; Basri, Gibor; Bouvier, J.

doi:10.1086/166476

Cited by 370 publications

(289 citation statements)

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“…The application of this method to the stars in NGC 2264 has an advantage because the amount of interstellar reddening toward the optically visible stars in the cluster (á Sung et al 1997) is low compared to that toward other clusters in different spiral Spectral features caused by accretion activities can also influence the observed colors. The standard accretion model demonstrates that accretion flows from a circumstellar disk fall onto the stellar surface along the magnetosphere (Uchida & Shibata 1985;Bertout et al 1988;Königl 1991). Hot continuum excess emission and a large variety of recombination lines driven by the accretion process are observed in many young low-mass PMS stars (Calvet & Gullbring 1998;Hartmann 1999).…”

Section: Estimation Of Effective Temperaturementioning

confidence: 99%

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-Main Sequence Stars

Lim

Sung

Kim

et al. 2016

ApJ

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The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (). Li abundance under the condition of local thermodynamic equilibrium (LTE) was derived using the conventional curve of growth method. After correction for non-LTE effects, we find that the initial Li abundance of NGC 2264 is. From the distribution of the Li abundances, the underlying age spread of the visible PMS stars is estimated to be about 3-4 Myr and this, together with the presence of embedded populations in NGC 2264, suggests that the cluster formed on a timescale shorter than 5 Myr.

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Section: Estimation Of Effective Temperaturementioning

confidence: 99%

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-Main Sequence Stars

Lim

Sung

Kim

et al. 2016

ApJ

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“…The masses of the probable YSO candidates can be estimated by comparing their locations on the CMD with the evolutionary models of PMS stars. To estimate the stellar masses, the J luminosity is recommended rather than that of H or Ks, as J is less affected by the emission from circumstellar material (Bertout et al 1988). The dashed oblique lines denote the reddening vectors for PMS stars of 1 Myr having masses in the range of 0.3 − 3.5 M .…”

Section: Mass Function Of Identified Ysos Populationmentioning

confidence: 99%

A multiwavelength investigation of the H ii region S311: young stellar population and star formation

Yadav

Pandey

Sharma

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a multiwavelength investigation of the young stellar population and star formation activities around the H ii region Sharpless 311. Using our deep near-infrared observations and archival Spitzer-IRAC observations, we have detected a total of 125 young stellar objects (YSOs) in an area of ∼86 arcmin 2 . The YSOs sample include 8 Class I and 117 Class II candidate YSOs. The mass completeness of the identified YSOs sample is estimated to be 1.0 M . The ages and masses of the majority of the candidate YSOs are estimated to be in the range of ∼0.1−5 Myr and ∼0.3−6 M , respectively. The 8 µm image of S311 displays an approximately spherical cavity around the ionizing source which is possibly created due to the expansion of the H ii region. The spatial distribution of the candidate YSOs reveals that a significant number of them are distributed systematically along the 8 µm emission with a majority clustered around the eastern border of the H ii region. Four clumps/compact H ii regions are detected in the radio continuum observations at 1280 MHz, which might have been formed during the expansion of the H ii region. The estimated dynamical age of the region, main-sequence lifetime of the ionizing source, the spatial distribution and ages of the candidate YSOs indicate triggered star formation in the complex.

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“…The stars closer to the main sequence are the WTTSs (from Gómez de Castro, 1997) added either to black bodies or to the spectra of standard stars reproduce the UV continuum reasonably well (Calvet et al, 1984;Bertout et al, 1988;Simon et al, 1990). The fits yield chromospheric-like electron temperatures of (1-5) × 10 4 K. Three different mechanisms have been proposed to generate this hot plasma and its UV continuum: (1) a dense chromosphere (Calvet et al, 1984), (2) the release of the gravitational binding energy from the infalling material (Bertout et al, 1988;Simon et al, 1990;Gullbring et al, 2000), and (3) an outflow (Ferro-Fontán and Gómez de Castro, 2003;Gómez de Castro and Ferro-Fontán, 2005). This uncertainty in the formation of the UV emission points out why high-resolution UV spectroscopy and monitoring are so crucial for understanding and constraining the physics of the engine.…”

Section: Uv Observations Of the Jet Engine In Low-mass Starsmentioning

confidence: 94%

“…Furthermore, the cooling timescales at considerable heights above the disk can be much smaller than the dominant microphysical processes and therefore, recombi- Fig. 1 Ionisation stages of oxygen in a self-consistent calculation of a galactic outflow (wind) (Breitschwerdt and Schmutzler, 1999). The initial temperature of the flow is T = 2.5 × 10 6 K nation of highly ionised species lags behind (Breitschwerdt and Schmutzler, 1999).…”

Section: Halo-disk Interaction In the Milky Waymentioning

confidence: 99%

“…1 Ionisation stages of oxygen in a self-consistent calculation of a galactic outflow (wind) (Breitschwerdt and Schmutzler, 1999). The initial temperature of the flow is T = 2.5 × 10 6 K nation of highly ionised species lags behind (Breitschwerdt and Schmutzler, 1999). An example is the O VI ion that is abundant over a large range of temperatures from 4 × 10 5 K to temperatures as low as 10 4 K (Fig.…”

Section: Halo-disk Interaction In the Milky Waymentioning

confidence: 99%

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UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

Castro

Lecavelier

D’Avillez

et al.

Fundamental Questions in Astrophysics: Guidelines for Future UV Observatories

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Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation:The physics of the ISM. Stars form from dense molecular clouds that contain ∼30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system -the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. ing star formation, the so-called accretion-outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion-outflow engine is between 3000 and 10 7 K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion-outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H 2 , CO, etc.) that are observed in the UV.Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H 2 , CO, OH, CS, Springer 34 Astrophys Space Sci (2006) 303:33-52 S 2 , CO + 2 , C 2 , O 2 , O 3 , etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.

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Accretion disks around T Tauri stars

Cited by 370 publications

References 0 publications

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-Main Sequence Stars

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-Main Sequence Stars

A multiwavelength investigation of the H ii region S311: young stellar population and star formation

UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

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