An Assessment of Dynamical Mass Constraints on Pre-Main-Sequence Evolutionary Tracks

By L. Hillenbrand, Russel J. White. 2003

258 citations recorded by the source corpus.

We have assembled a database of stars having both masses determined from measured orbital dynamics and sufficient spectral and photometric information for their placement on a theoretical H-R diagram. Our sample consists of 115 low-mass (M < 2.0 M☉) stars, 27 pre-main-sequence and 88 main-sequence. We use a variety of available pre-main-sequence evolutionary calculations to test the consistency of predicted stellar masses with dynamically determined masses. Despite substantial improvements in model physics over the past decade, large systematic discrepancies still exist between empirical and theoretically derived masses. For main-sequence stars, all models considered predict masses consistent with dynamical values above 1.2 M☉ and some models predict consistent masses at solar or slightly lower masses, but no models predict consistent masses below 0.5 M☉, with all models systematically underpredicting such low masses by 5%-20%. The failure at low masses stems from the poor match of most models to the empirical main sequence below temperatures of 3800 K, at which molecules become the dominant source of opacity and convection is the dominant mode of energy transport. For the pre-main-sequence sample we find similar trends. There is generally good agreement between predicted and dynamical masses above 1.2 M☉ for all models. Below 1.2 M☉ and down to 0.3 M☉ (the lowest mass testable), most evolutionary models systematically underpredict the dynamically determined masses by 10%-30%, on average, with the Lyon group models predicting marginally consistent masses in the mean, although with large scatter. Over all mass ranges, the usefulness of dynamical mass constraints for pre-main-sequence stars is in many cases limited by the random errors caused by poorly determined luminosities and especially temperatures of young stars. Adopting a warmer-than-dwarf temperature scale would help reconcile the systematic pre-main-sequence offset at the lowest masses, but the case for this is not compelling, given the similar warm offset at older ages between most sets of tracks and the empirical main sequence. Over all age ranges, the systematic discrepancies between track-predicted and dynamically determined masses appear to be dominated by inaccuracies in the treatment of convection and in the adopted opacities.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

Stellar Multiplicity (2013, background): “However, uncertainties in PMS evolutionary models (Hillenbrand & White 2004) and the possibility of circumstellar dust emission and differential extinction could work to smooth out and/or bias the genuine mass ratio distributions, particularly for photometrically estimated mass ratios (Woitas,…”
The star formation history and accretion-disc fraction among the K-type members of the Scorpius–Centaurus OB association (2016, background): “Hillenbrand & White (2004) have compared dynamically constrained masses with predictions from pre-MS evolutionary models and found that the models systematically underpredict the masses of stars 5%-20% for masses under 0.5 M .”
The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, methodology): “…for a few dozen pre-main-sequence stars, and compilations of these data have been used to characterize the sizes of systematic errors in various sets of models and the possible sources of those errors (Baraffe et al. 2002, Hillenbrand & White 2004, Luhman et al. 2003b, Mathieu et al. 2007).”
The Spectroscopically Determined Substellar Mass Function of the Orion Nebula Cluster (2004, methodology): “A detailed analysis and comparison of the models is given by Hillenbrand & White (2004).”
A Decreased Probability of Habitable Planet Formation around Low-Mass Stars (2007, methodology): “For instance, if we assume L⋆ ∝ M 4 ⋆ (a rough fit to Hillenbrand & White 2004), then the location of the HZ, rHZ , scales with the stellar mass as rHZ ∝ L 1/2 ⋆ ∝ M 2 ⋆ .”
MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, background): “The mass of a given sample could be systematically uncertain by as much as 20% (e.g. Hillenbrand & White 2004), and individual masses could be uncertain by factors of 2 or more due to unresolved multiplicity or the intrinsic variability that young stars often display (from accretion or rotational…”
The Initial Mass Function of the Massive Star-forming Region NGC 3603 from Near-Infrared Adaptive Optics Observations (2007, methodology): “Among currently available PMS evolutionary models, the B98 model has been reported to have the best consistency with dynamical mass determination for stellar masses below 1.2 M⊙ (Hillenbrand & White 2004).”
THE PALOMAR/KECK ADAPTIVE OPTICS SURVEY OF YOUNG SOLAR ANALOGS: EVIDENCE FOR A UNIVERSAL COMPANION MASS FUNCTION (2008, background): “Although Luhman’s conclusion relies on theoretical isochrones from Baraffe et al. (1998), the models in question have been shown to most successfully and, on average, fairly accurately predict the fundamental properties of pre-mainsequence stars (Hillenbrand & White 2004).”
A STELLAR CENSUS OF THE TUCANA–HOROLOGIUM MOVING GROUP (2014, background): “These system velocities are more uncertain due to the significant systematic uncertainties in pre-main sequence evolutionary models (e.g., Hillenbrand & White 2004), but based on the members which can be independently confirmed from lithium or Hα (and hence should be comoving with Tuc-Hor), we…”
The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. IX. The Serpens YSO Population as Observed with IRAC and MIPS (2007, methodology): “…is problematic, because the determination of mass depends on the placement of the star on an HR diagram and the use of model evolutionary tracks for which there is significant uncertainty at the level of at least a factor of 1.5 – 2 in the literature (Hillenbrand & White 2004; Stassun et al. 2004).”
A Moving Cluster Distance to the Exoplanet 2M1207b in the TW Hydrae Association (2005, background): “Considering the variations between published evolutionary tracks, especially for stars which are young and low-mass (Hillenbrand & White 2004), the cluster parallax distance should be considered an improved estimate.”
Y2 Isochrones with an Improved Core Overshoot Treatment (2004, methodology): “A useful assessment of validity of the Y 2 stellar models and other models including a detailed comparison with observational data for stars in the pre–mainsequence and early post–main-sequence phases of evolution has recently been published by Hillenbrand & White (2004).”
THE STELLAR-ACTIVITY–ROTATION RELATIONSHIP AND THE EVOLUTION OF STELLAR DYNAMOS (2011, background): “…color-BC conversion is 2% for all stars with V −Ks 6 (the majority of stars in our sample), excluding uncertainties in the distance used, the age of the cluster or systematic errors in the evolutionary tracks (see e.g. Hillenbrand & White 2004, for a discussion of the accuracy of these tracks).”
Accurate masses and radii of normal stars: modern results and applications (2009, methodology): “Comparison with stellar evolution models is one of the most prominent uses of accurate binary data (see, e.g., Pols et al. 1997; Lastennet & Valls-Gabaud 2002; Hillenbrand & White 2004) and features in most modern papers on binary system parameters.”
Optical Spectroscopy of the Surface Population of the ρ Ophiuchi Molecular Cloud: The First Wave of Star Formation (2005, background): “0.5 dex in log (age) (e.g., Hillenbrand & White 2004).”
The Origin of T Tauri X-Ray Emission: New Insights from the Chandra Orion Ultradeep Project (2005, background): “…from PMS evolutionary models are subject to significant uncertainties; different PMSmodels and/or temperature scales can lead to differences by as much as a factor of 2 in the mass estimates (for detailed investigations of these uncertainties see, e.g., Luhman 1999 or Hillenbrand & White 2004).”
THE ASTRALUX LARGE M-DWARF MULTIPLICITY SURVEY (2012, background): “Conversely, for the youngest systems and lowest masses, the theoretical mass–luminosity relationships (e.g., Burrows et al. 1997; Chabrier et al. 2000), which are increasingly uncertain under such conditions, can be better constrained (e.g., Hillenbrand & White 2004; Konopacky et al. 2010).”
The Spitzer c2d Survey of Weak-Line T Tauri Stars. II. New Constraints on the Timescale for Planet Building (2007, background): “Stellar ages of PMS stars are very difficult to estimate due to the large observational and model uncertainties involved (Hillenbrand & White, 2004) and they are often taken with a high degree of (healthy) skepticism.”