First Results on Pre–Main-Sequence Evolution, Including a Magnetic Field

D’Antona, Francesca; Ventura, P.; Mazzitelli, I.

doi:10.1086/318172

Cited by 63 publications

(55 citation statements)

References 11 publications

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“…The effects of magnetic fields on the evolution of stars have already begun to be explored by theorists (e.g., D'Antona et al 2000;Mullan & MacDonald 2001;Maeder & Meynet 2003; although the latter authors focus on more massive stars), and initial comparisons with observations are encouraging. One area where this is likely to have a significant impact is the study of T Tauri stars, which are typically very active.…”

Section: Discussionmentioning

confidence: 99%

The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar‐Type Stars

Torres

Lacy

Marschall

et al. 2006

ApJ

103

117

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We present spectroscopic and photometric observations of the eclipsing system V1061 Cyg (P ¼ 2:35 days). A third star is visible in the spectrum, and the system is a hierarchical triple. We combine the radial velocities for the three stars, times of eclipse, and intermediate astrometric data from the Hipparcos mission (abscissa residuals) to establish the elements of the outer orbit, which is eccentric and has a period of 15.8 yr. We determine accurate values for the masses, radii, and effective temperatures of the binary components: M Aa ¼ 1:282 AE 0:015 M , R Aa ¼ 1:615 AE 0:017 R , and T Aa eA ¼ 6180 AE 100 K for the primary (star Aa), and M Ab ¼ 0:9315 AE 0:0068 M , R Ab ¼ 0:974 AE 0:020 R , and T Ab eA ¼ 5300 AE 150 K for the secondary (Ab). The mass of the tertiary is determined to be M B ¼ 0:925 AE 0:036 M and its effective temperature is T B eA ¼ 5670 AE 150 K. Current stellar evolution models agree well with the properties of the primary but show a very large discrepancy in the radius of the secondary, in the sense that the predicted values are $10% smaller than observed (a $5 effect). In addition, the temperature is cooler than predicted, by some 200 K. These discrepancies are quite remarkable given that the star is only 7% less massive than the Sun, the calibration point of all stellar models. We identify the chromospheric activity as the likely cause of the effect. Inactive stars agree very well with the models, while active ones such as V1061 Cyg Ab appear systematically too large and too cool.

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Section: Discussionmentioning

confidence: 99%

The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar‐Type Stars

Torres

Lacy

Marschall

et al. 2006

ApJ

103

117

View full text Add to dashboard Cite

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“…This is an important point to emphasize because the inclusion of these processes affects the evolution of pre-MS models introducing additional sources of uncertainty (see e.g., Pinsonneault et al 1990;D'Antona et al 2000;Siess 2001;Stahler & Palla 2004;Baraffe et al 2009;Hosokawa et al 2011).…”

Section: The Modelsmentioning

confidence: 99%

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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“…Mendes, D'Antona & Mazzitelli 1999;Burke et al 2004), the effects of the consequent dynamo-generated magnetic fields may be more significant (e.g. Ventura et al 1998;D'Antona, Ventura & Mazzitelli 2000). There is growing observational evidence from fast-rotating, magnetically active stars in tidally-locked eclipsing binaries, young clusters and the field, that magnetic activity may increase the radii of low-mass stars (Lopez-Morales 2007; Morales, Ribas & Jordi 2008;Jackson, Jeffries & Maxted 2009;Stassun et al 2012).…”

Section: Introductionmentioning

confidence: 99%

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

Jackson

Jeffries

2014

Monthly Notices of the Royal Astronomical Society

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In a coeval group of low-mass stars, the luminosity of the sharp transition between stars that retain their initial lithium and those at slightly higher masses in which Li has been depleted by nuclear reactions, the lithium depletion boundary (LDB), has been advanced as an almost model-independent means of establishing an age scale for young stars. Here we construct polytropic models of contracting pre-main sequence stars (PMS) that have cool, magnetic starspots blocking a fraction β of their photospheric flux. Starspots slow the descent along Hayashi tracks, leading to lower core temperatures and less Li destruction at a given mass and age. The age, τ LDB , determined from the luminosity of the LDB, L LDB , is increased by a factor (1 − β) −E compared to that inferred from unspotted models, where E ≃ 1 + d log τ LDB /d log L LDB and has a value ∼ 0.5 at ages < 80 Myr, decreasing to ∼ 0.3 for older stars. Spotted stars have virtually the same relationship between K-band bolometric correction and colour as unspotted stars, so this relationship applies equally to ages inferred from the absolute K magnitude of the LDB. Low-mass PMS stars do have starspots, but the appropriate value of β is highly uncertain with a probable range of 0.1 < β < 0.4. For the smaller β values our result suggests a modest systematic increase in LDB ages that is comparable with the maximum levels of theoretical uncertainty previously claimed for the technique. The largest β values would however increase LDB ages by 20-30 per cent and demand a re-evaluation of other age estimation techniques calibrated using LDB ages.

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First Results on Pre–Main-Sequence Evolution, Including a Magnetic Field

Cited by 63 publications

References 11 publications

The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar‐Type Stars

The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar‐Type Stars

The Pisa pre-main sequence tracks and isochrones

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

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