Dynamical Mass Constraints on Low‐Mass Pre–Main‐Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0
 M
 ⊙
 Primary and a 0.7
 M
 ⊙
 Secondary

Stassun, Keivan G.; Mathieu, Robert D.; Vaz, L. P. R.; Stroud, N. S.; Vrba, F. J.

doi:10.1086/382353

Cited by 92 publications

(101 citation statements)

References 51 publications

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“…For example, Siess et al (1999) found in their stellar evolution calculations that accretion reduces the efficiency of convection. This theoretical result agrees with another finding based on comparison of orbital masses of PMS stars with evolution models by Stassun et al (2004b), who found that TTSs seem to have lower convection efficiencies than MS stars. The reduced convection efficiency may lead to weaker dynamo action.…”

Section: The Suppression Of X-ray Emission By Accretionsupporting

confidence: 92%

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

Preibisch

Kim

Favata

et al. 2005

ASTROPHYS J SUPPL S

474

673

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The Chandra Orion Ultradeep Project (COUP) provides the most comprehensive data set ever acquired on the X-ray emission of pre-main-sequence stars. In this paper, we study the nearly 600 X-ray sources that can be reliably identified with optically well-characterized T Tauri stars (TTSs) in the Orion Nebula Cluster. With a detection limit of L X; min $ 10 27:3 ergs s À1 for lightly absorbed sources, we detect X-ray emission from more than 97% of the optically visible late-type (spectral types F-M) cluster stars. This proves that there is no ''X-ray-quiet'' population of late-type stars with suppressed magnetic activity. We use this exceptional optical, infrared, and X-ray data set to study the dependencies of the X-ray properties on other stellar parameters. All TTSs with known rotation periods lie in the saturated or supersaturated regime of the relation between activity and Rossby numbers seen for mainsequence ( MS) stars, but the TTSs show a much larger scatter in X-ray activity than that seen for the MS stars. Strong near-linear relations between X-ray luminosities, bolometric luminosities, and mass are present. We also find that the fractional X-ray luminosity L X /L bol rises slowly with mass over the 0:1 2 M range. The plasma temperatures determined from the X-ray spectra of the TTSs are much hotter than in MS stars but seem to follow a general solar-stellar correlation between plasma temperature and activity level. The scatter about the relations between X-ray activity and stellar parameters is larger than the expected effects of X-ray variability, uncertainties in the variables, and unresolved binaries. This large scatter seems to be related to the influence of accretion on the X-ray emission. While the X-ray activity of the nonaccreting TTSs is consistent with that of rapidly rotating MS stars, the accreting stars are less X-ray active (by a factor of $2-3 on average) and produce much less well-defined correlations than the nonaccretors. We discuss possible reasons for the suppression of X-ray emission by accretion and the implications of our findings on long-standing questions related to the origin of the X-ray emission from young stars, considering in particular the location of the X-ray-emitting structures and inferences for pre-main-sequence magnetic dynamos.

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Section: The Suppression Of X-ray Emission By Accretionsupporting

confidence: 92%

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

Preibisch

Kim

Favata

et al. 2005

ASTROPHYS J SUPPL S

474

673

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“…In this respect, the progresses in 2D and 3D radiative hydrodynamical simulations of convection in the past decade (Ludwig et al 1999;Trampedach et al 1999;Trampedach 2007) provided evidence of both variations in α, which can depends on both T eff and log g, and the possibility of theoretically calibrating the mixing length parameter (see also . Moreover, there appears to be a lower efficiency of the superadiabatic convection in lowmass stars (α ≈ 1) with respect to the solar-calibrated one according to observations of some binary systems (see e.g., Simon et al 2000;Steffen et al 2001;Stassun et al 2004), and 7 Li data of young open clusters (Ventura et al 1998;D'Antona & Montalbán 2003).…”

Section: Convectionmentioning

confidence: 95%

The Pisa pre-main sequence tracks and isochrones

Tognelli

Moroni

Degl’Innocenti

2011

A&A

270

419

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Context. In recent years new observations of pre-main sequence stars (pre-MS) with Z ≤ Z have been made available. To take full advantage of the continuously growing amount of data of pre-MS stars in different environments, we need to develop updated pre-MS models for a wide range of metallicity to assign reliable ages and masses to the observed stars. Aims. We present updated evolutionary pre-MS models and isochrones for a fine grid of mass, age, metallicity, and helium values. Methods. We use a standard and well-tested stellar evolutionary code (i.e. FRANEC), that adopts outer boundary conditions from detailed and realistic atmosphere models. In this code, we incorporate additional improvements to the physical inputs related to the equation of state and the low temperature radiative opacities essential to computing low-mass stellar models. Results. We make available via internet a large database of pre-MS tracks and isochrones for a wide range of chemical compositions (Z = 0.0002−0.03), masses (M = 0.2−7.0 M ), and ages (1−100 Myr) for a solar-calibrated mixing length parameter α (i.e. 1.68). For each chemical composition, additional models were computed with two different mixing length values, namely α = 1.2 and 1.9. Moreover, for Z ≥ 0.008, we also provided models with two different initial deuterium abundances. The characteristics of the models have been discussed in detail and compared with other work in the literature. The main uncertainties affecting theoretical predictions have been critically discussed. Comparisons with selected data indicate that there is close agreement between theory and observation.

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“…Stassun et al 2004;Boden et al 2005). The results obtained so far are rather ambiguous, and reveal the difficulty in finding a unique description of convection, holding in all cases.…”

Section: Introductionmentioning

confidence: 90%

“…α = 1. Stassun et al (2004) also found that models with inefficient convection in the interior should be preferred. In the case of the binary components of V1174Ori they found a very good agreement with the models by Montalban et al (2004), employing the FST convection both in the interior and in the atmospheres computed by Heiter et al (2002).…”

Section: Introductionmentioning

confidence: 98%

Updated pre-main sequence tracks at low metallicities for 0.1 $\mathsf \le\ M/M _\odot\ \le 1.5$

Criscienzo¹,

Ventura²,

D’Antona³

2009

A&A

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Context. Young populations at Z < Z are being examined to understand the role of metallicity in the first phases of stellar evolution. For the analysis it is necessary to assign mass and age to Pre-Main Sequence (PMS) stars. While it is well known that the mass and age determination of PMS stars is strongly affected by the convection treatment, extending any calibration to metallicities different from solar is very artificial, in the absence of any calibrators for the convective parameters. For solar abundance, Mixing Length Theory models have been calibrated by using the results of 2D radiative-hydrodynamical models (MLT-α 2D ), that are very similar to those computed with non-grey ATLAS9 atmosphere boundary conditions and a full spectrum of turbulence (FST) convection model both in the atmosphere and in the interior (NEMO-FST models). Aims. While MLT-α 2D models are not available for lower metallicities, we extend to lower Z the NEMO-FST models, under the hypothesis that in such a way we are simulating the results of MLT-α 2D models also at smaller Z. Methods. We use standard stellar computation techniques in which the atmospheric boundary conditions are derived making use of model atmosphere grids. This allows us to take into account the non greyness of the atmosphere, but adds a new parameter to the stellar structure uncertainty, namely the efficiency of convection in the atmospheric structure, if convection is computed in the atmospheric grid by a model different to the model adopted for the interior integration.Results. We present PMS models for low mass stars from 0.1 to 1.5 M for metallicities [Fe/H] = −0.5, −1.0 and −2.0. The calculations include the most recent interior physics and the latest generation of non-grey atmosphere models. At fixed luminosity more metal poor isochrones are hotter than solar ones by Δ log T eff /Δ log Z ∼ 0.03−0.05 in the range in Z from 0.02 to 0.0002 and for ages from 10 5 to 10 7 yr.

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Dynamical Mass Constraints on Low‐Mass Pre–Main‐Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 M _⊙ Primary and a 0.7 M _⊙ Secondary

Cited by 92 publications

References 51 publications

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

The Pisa pre-main sequence tracks and isochrones

Updated pre-main sequence tracks at low metallicities for 0.1 $\mathsf \le\ M/M _\odot\ \le 1.5$

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Dynamical Mass Constraints on Low‐Mass Pre–Main‐Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 M ⊙ Primary and a 0.7 M ⊙ Secondary

Cited by 92 publications

References 51 publications

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

The Origin of T Tauri X‐Ray Emission: New Insights from the Chandra Orion Ultradeep Project

The Pisa pre-main sequence tracks and isochrones

Updated pre-main sequence tracks at low metallicities for 0.1 $\mathsf \le\ M/M _\odot\ \le 1.5$

Contact Info

Product

Resources

About

Dynamical Mass Constraints on Low‐Mass Pre–Main‐Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 M _⊙ Primary and a 0.7 M _⊙ Secondary