Are wide pre-main-sequence binaries coeval?

Hartigan, Patrick; Strom, K. M.; Strom, S. E.

doi:10.1086/174203

Cited by 170 publications

(203 citation statements)

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“…On the other hand, the comparison between theory and observation seems to suggest coevality, that is the components of binaries form at about the same age (see e.g. Hartigan et al 1994;Brandner & Zinnecker 1997;Palla & Stahler 2001). …”

Section: Comparison With Observationsmentioning

confidence: 99%

The Pisa pre-main sequence tracks and isochrones

Tognelli

Moroni

Degl’Innocenti

2011

A&A

272

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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Section: Comparison With Observationsmentioning

confidence: 99%

The Pisa pre-main sequence tracks and isochrones

Tognelli

Moroni

Degl’Innocenti

2011

A&A

272

419

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“…We assume that the primary is similar to the one in the system V807 Tau. On the basis of the published spectral type of V807 Tau, i.e., K7 (Hartigan et al 1994) and assuming that the primary is ∼2.5 Myr old, its radius and effective surface temperature are taken to be R * = 1.83 R , and T * = 4266 K, respectively, using a publicly available pre-main-sequence database (Siess et al 2000). It is assumed that the dust consists of pure silicates with a 0.1 μm grain size (Draine & Lee 1984).…”

Section: Fundamental Band Ro-vibrational Co Line Profilesmentioning

confidence: 99%

Spectral signatures of disk eccentricity in young binary systems

Regály

Sándor

Dullemond

et al. 2011

A&A

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Context. Star formation occurs via fragmentation of molecular clouds, which means that the majority of stars born are members of binary systems. There is growing evidence that planets might form in circumprimary disks of medium-separation ( 50 AU) binaries. The tidal forces caused by the secondary generally act to distort the originally circular circumprimary disk to an eccentric one. Since the disk eccentricity might play a major role in planet formation, it is of great importance to understand how it evolves. Aims. We investigate disk eccentricity evolution to reveal its dependence on the physical parameters of the binary system and the protoplanetary disk. To infer the disk eccentricity from high-resolution near-IR spectroscopy, we calculate the fundamental band (4.7 μm) emission lines of the CO molecule emerging from the atmosphere of the eccentric disk. Methods. We model circumprimary disk evolution under the gravitational perturbation of the orbiting secondary using a 2D gridbased hydrodynamical code, assuming α-type viscosity. The hydrodynamical results are combined with our semianalytical spectral code to calculate the CO molecular line profiles. Our thermal disk model is based on the double-layer disk model approximation. We assume LTE and canonical dust and gas properties for the circumprimary disk. Results. We find that the orbital velocity distribution of the gas parcels differs significantly from the circular Keplerian fashion. The line profiles are double-peaked and asymmetric in shape. The magnitude of asymmetry is insensitive to the binary mass ratio, the magnitude of viscosity (α), and the disk mass. In contrast, the disk eccentricity, thus the magnitude of the line profile asymmetry, is influenced significantly by the binary eccentricity and the disk geometrical thickness. Conclusions. We demonstrate that the disk eccentricity profile in the planet-forming region can be determined by fitting the highresolution CO line profile asymmetry using a simple 2D spectral model that accounts for the velocity distortions caused by the disk eccentricity. Thus, with our novel approach the disk eccentricity can be inferred from high-resolution near-IR spectroscopy data acquired prior to the era of high angular resolution optical (ELT) or radio (ALMA, E-VLA) direct-imaging. By determining the disk eccentricity in medium-separation young binaries, we might be able to constrain the planet formation theories.

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“…The broad wavelength range of the nonphotospheric emission and the frequent presence of significant circumstellar reddening in CTTSs make it difficult to find a wavelength at which to obtain photometry of the star itself from which to estimate the stellar luminosity. The method used most frequently to derive the bolometric luminosity of the stellar photosphere includes applying a bolometric correction to a single-band measurement corrected for extinction (e.g., Kenyon & Hartmann 1995;Hartigan et al 1994). It is usually argued that the J band, at 1.25 m, is the best representation of the photospheric emission.…”

Section: Introductionmentioning

confidence: 99%

Evidence forJ‐ andH‐Band Excess in Classical T Tauri Stars and the Implications for Disk Structure and Estimated Ages

Cieza¹,

Kessler-Silacci²,

Jaffe³

et al. 2005

ApJ

103

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We argue that classical T Tauri stars (CTTSs) possess significant nonphotospheric excess in the J and H bands (1.25 and 1.66 m, respectively). We first show that normalizing the spectral energy distributions (SEDs) of CTTSs to the J band leads to a poor fit of the optical fluxes (which are systematically overestimated), while normalizing the SEDs to the I C band (0.8 m) produces a better fit to the optical bands and in many cases reveals the presence of a considerable excess at J and H. Near-infrared spectroscopic veiling measurements from the literature support this result. We find that J-and H-band excesses correlate well with the K-band (2.2 m) excess and that the J À K and H À K colors of the excess emission are consistent with that of a blackbody at the dust sublimation temperature ($1500-2000 K). We propose that this near-IR excess originates at a hot inner rim, analogous to those suggested to explain the ''near-IR bump'' in the SEDs of Herbig Ae/ Be stars. To test our hypothesis, we use the model presented by Dullemond and coworkers to fit the photometry data between 0.5 and 24 m of 10 CTTSs associated with the Chamaeleon II molecular cloud. We find that simple models that include luminosities calculated from I C -band magnitudes and an inner rim may account for the reported J-and H-band excesses. The models that best fit the data are those in which the inner radius of the disk is larger than expected for a rim in thermal equilibrium with the photospheric radiation field alone. In particular, we find that large inner rims are necessary to account for the midinfrared fluxes (3.6-8.0 m) obtained by the Spitzer Space Telescope (Spitzer). The large radius could be explained if, as proposed by D'Alessio and colleagues, the UV radiation from the accretion shock significantly affects the sizes of the inner holes in disks around CTTSs. Finally, we argue that deriving the stellar luminosities of CTTSs by making bolometric corrections to the J-band fluxes, which is the ''standard'' procedure for obtaining CTTS luminosities, systematically overestimates these luminosities. The overestimated luminosities translate into underestimated ages when the stars are placed in the H-R diagram. Thus, the results presented herein have important implications for the dissipation timescale of inner accretion disks.

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Are wide pre-main-sequence binaries coeval?

Cited by 170 publications

References 0 publications

The Pisa pre-main sequence tracks and isochrones

The Pisa pre-main sequence tracks and isochrones

Spectral signatures of disk eccentricity in young binary systems

Evidence forJ‐ andH‐Band Excess in Classical T Tauri Stars and the Implications for Disk Structure and Estimated Ages

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