On the Reliability of Stellar Ages and Age Spreads Inferred from Pre-Main Sequence Evolutionary Models

Abstract

We revisit the problem of low-mass pre-main-sequence (PMS) stellar evolution and its observational consequences for where stars fall on the Hertzsprung-Russell diagram (HRD). In contrast to most previous work, our models follow stars as they grow from small masses via accretion, and we perform a systematic study of how the stars' HRD evolution is influenced by their initial radius, by the radiative properties of the accretion flow, and by the accretion history, using both simple idealized accretion histories and histories taken from numerical simulations of star cluster formation. We compare our numerical results to both non-accreting isochrones and to the positions of observed stars in the HRD, with a goal of determining whether both the absolute ages and the age dispersions inferred from non-accreting isochrones are reliable. We show that non-accreting isochrones can sometimes overestimate stellar ages for more massive stars (those with effective temperatures above \sim 3500 K), thereby explaining why non-accreting isochrones often suggest a systematic age difference between more and less massive stars in the same cluster. However, we also find the only way to produce a similar overestimate for the ages of cooler stars is by selecting parameters that are strongly inconsistent with both theoretical models and observational constraints. We therefore conclude that inferred ages and age spreads for cool stars are reliable, at least to the extent that the observed bolometric luminosities and temperatures are accurate. Finally, we note that the time-dependence of the mass accretion rate has remarkably little effect on low-mass stars' evolution on the HRD, and that such time-dependence may be neglected for all stars except those with effective temperatures above \sim 4000 K.

13 pages, 10 figures, accepted for publication in ApJ

References in corpus (16)

• Slow Star Formation in Dense Gas: Evidence and Implications
• The Effects of Radiative Transfer on Low-Mass Star Formation
• Evolution of Massive Protostars via Disk Accretion
• Effect of episodic accretion on the structure and the lithium depletion of low-mass stars and planet-hosting stars
• Equilibrium Star Cluster Formation
• Evolutionary Signatures in the Formation of Low-Mass Protostars. II. Towards Reconciling Models and Observations
• A Multi-color Optical Survey of the Orion Nebula Cluster. II. the H-R diagram
• Recurrent Planet Formation and Intermittent Protostellar Outflows Induced by Episodic Mass Accretion
• A Large-Area Search for Low-Mass Objects in Upper Scorpius II: Age and Mass Distributions
• The Age, Stellar Content and Star Formation Timescale of the B59 Dense Core
• A New Method for the Assessment of Age and Age-Spread of Pre-Main Sequence Stars in Young Stellar Associations of the Magellanic Clouds
• Surprising dissimilarities in a newly formed pair of 'identical twin' stars
• The Protostellar Mass Function
• An assessment of Li abundances in weak-lined and classical T Tauri stars of the Taurus-Auriga association
• Accretion properties of T Tauri stars in sigma Ori
• Accretion in rho-Ophiuchi brown dwarfs: infrared hydrogen line ratios

Cited by in corpus (117)

• Star Formation in the Milky Way and Nearby Galaxies
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Star Clusters Across Cosmic Time
• Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation
• Formation of Primordial Supermassive Stars by Rapid Mass Accretion
• The Pisa pre-main sequence tracks and isochrones. A database covering a wide range of Z, Y, mass, and age values
• Pre-main-sequence isochrones -- II. Revising star and planet formation timescales
• The First Stars: Mass Growth Under Protostellar Feedback
• The Formation and Early Evolution of Low-mass Stars and Brown Dwarfs
• Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Protostellar Core Formation
• SLUG - Stochastically Lighting Up Galaxies I: Methods and Validating Tests
• Resolving the Luminosity Problem in Low-Mass Star Formation
• Rapidly Accreting Supergiant Protostars: Embryos of Supermassive Black Holes?
• A Near-IR Spectroscopic Survey of FU Orionis Objects
• Observed luminosity spread in young clusters and Fu Ori stars: a unified picture
• Collapse of a molecular cloud core to stellar densities: stellar core and outflow formation in radiation magnetohydrodynamics simulations
• Evolution of Protostellar Outflow around Low-mass Protostar
• Radiation-Hydrodynamic Simulations of Massive Star Formation with Protostellar Outflows
• Molecular Outflows Driven by Low-Mass Protostars. I. Correcting for Underestimates When Measuring Outflow Masses and Dynamical Properties
• Overview of the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) Project
• The Physics of Star Cluster Formation and Evolution
• The Turbulent Origin of Spin-Orbit Misalignment in Planetary Systems
• Quantitative Evidence for an Intrinsic Age Spread in the Orion Nebula Cluster
• Continuum Variability of Deeply Embedded Protostars as a Probe of Envelope Structure
• Infall-Driven Protostellar Accretion and the Solution to the Luminosity Problem
• IN-SYNC IV - The Young Stellar Population in the Orion A Molecular Cloud
• HST measures of Mass Accretion Rates in the Orion Nebula Cluster
• Empirical Tests of Pre-Main-Sequence Stellar Evolution Models with Eclipsing Binaries
• Episodic accretion: the interplay of infall and disc instabilities
• HOPS 383: An Outbursting Class 0 Protostar in Orion
• The Formation of Population III Stars in Gas Accretion Stage: Effects of Magnetic Fields
• Investigations of Protostellar Outflow Launching and Gas Entrainment: Hydrodynamic Simulations and Molecular Emission
• Formation of primordial supermassive stars by burst accretion
• Instantaneous starburst of the massive clusters Westerlund 1 and NGC 3603 YC
• Rotation, inflation, and lithium in the Pleiades
• IN-SYNC I: Homogeneous Stellar Parameters from High Resolution APOGEE Spectra for Thousands of Pre-main Sequence Star
• Simulations of protostellar collapse using multigroup radiation hydrodynamics. II. The second collapse
• On the Origin of Stellar Masses
• On the Origin of Mass Segregation in NGC 3603
• Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. II. Optical and Near Infrared Star Formation History of the Starburst Cluster NGC 2070 in 30 Doradus
• Rapid Star Formation and Global Gravitational Collapse
• Physical Processes in Star Formation
• The Structure, Dynamics and Star Formation Rate of the Orion Nebula Cluster
• The ALMA early science view of FUor/EXor objects - V: continuum disc masses and sizes
• The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation
• Direct diagnostics of forming massive stars: stellar pulsation and periodic variability of maser sources
• The Formation of Stellar Clusters in Magnetized, Filamentary Infrared Dark Clouds
• Self-consistent evolution of accreting low-mass stars and brown dwarfs
• From Birth to Death of Protoplanetary Disks: Modeling Their Formation, Evolution, and Dispersal
• Revisiting the pre-main-sequence evolution of stars I. Importance of accretion efficiency and deuterium abundance
• Observing Simulated Protostars with Outflows: How Accurate are Protostellar Properties Inferred from SEDs?
• Testing pre-main sequence models: the power of a Bayesian approach
• Radiation Transfer of Models of Massive Star Formation. III. The Evolutionary Sequence
• The JCMT Transient Survey: Stochastic and Secular Variability of Protostars and Disks In the Sub-Millimeter Observed Over Eighteen Months
• The chemistry of episodic accretion in embedded objects. 2D radiation thermo-chemical models of the post-burst phase
• The IACOB project. VI. On the elusive detection of massive O-type stars close to the ZAMS
• Photoevaporative Dispersal of Protoplanetary Disks around Evolving Intermediate-mass Stars
• Gravitational fragmentation and formation of giant protoplanets on tens-of-au orbits
• What Sets the Initial Rotation Rates of Massive Stars?
• Simulations of protostellar collapse using multigroup radiation hydrodynamics. I. The first collapse
• Variable Accretion Rates and Fluffy First Stars
• Explaining the luminosity spread in young clusters: proto and pre-main sequence stellar evolution in a molecular cloud environment
• Accretion discs as regulators of stellar angular momentum evolution in the ONC and Taurus-Auriga
• A High-Resolution Multiband Survey of Westerlund 2 With the Hubble Space Telescope I: Is the Massive Star Cluster Double?
• Revisiting the pre-main-sequence evolution of stars II. Consequences of planet formation on stellar surface composition
• The Formation of Very Massive Stars
• Evolution of the Water Snow Line in Magnetically Accreting Protoplanetary Disks
• Star formation in the first galaxies - III. Formation, evolution, and characteristics of the first stellar cluster
• Giant protostellar flares: accretion-driven accumulation and reconnection-driven ejection of magnetic flux in protostars
• YSO jets in the Galactic Plane from UWISH2: II - Outflow Luminosity and Length distributions in Serpens and Aquila
• Extreme infrared variables from UKIDSS - II. an end-of-survey catalogue of eruptive YSOs and unusual stars
• A Hot Gap Around Jupiter's Orbit in the Solar Nebula
• Mass and luminosity evolution of young stellar objects
• The effect of accretion on the pre-main-sequence evolution of low-mass stars and brown dwarfs
• Gravitoviscous protoplanetary disks with a dust component. II. Spatial distribution and growth of dust in a clumpy disk
• Stellar models and isochrones from low-mass to massive stars including pre-main sequence phase with accretion
• On the episodic excursions of massive protostars in the Hertzsprung-Russell diagram
• APEX/SABOCA observations of small-scale structure of infrared-dark clouds I. Early evolutionary stages of star-forming cores
• Extension of HOPS Out to 500 ParSecs (eHOPS). I. Identification and Modeling of Protostars in the Aquila Molecular Clouds
• Episodic excursions of low-mass protostars on the Hertzsprung-Russell diagram
• Imprint of planet formation in the deep interior of the Sun
• Pulsational instability of pre-main sequence models from accreting protostars. I. Constraining the input physics for accretion with spectroscopic parameters and stellar pulsations
• Multi-dimensional structure of accreting young stars
• Strong Biases in Estimating the Time Dependence of Mass Accretion Rates in Young Stars
• A Novel Survey for Young Substellar Objects with the W-band filter II. The Coolest and Lowest Mass Members of the Serpens-South Star-forming Region
• Accreting pre-main sequence models and abundance anomalies in globular clusters
• A Detached Protostellar Disk around a $\sim$0.2$M_{\odot }$ protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus
• No evidence for intense, cold accretion onto YSOs from measurements of Li in T-Tauri stars
• Planet gap opening across stellar masses
• Measuring the Initial Mass Function of Low Mass Stars and Brown Dwarfs
• The effect of spots on the luminosity spread of the Pleiades
• Transport of Protostellar Cosmic Rays in Turbulent Dense Cores
• The distance to the young cluster NGC 7129 and its age
• Episodic accretion and mergers during growth of massive protostars
• Pulsational instability of pre-main-sequence models from accreting protostars II. Modelling echelle diagrams of $\delta$ Scuti stars without rotational splitting
• VLT near- to mid-IR imaging and spectroscopy of the M17 UC1-IRS5 region
• The influence of metallicity on a combined stellar and disk evolution
• The Pre-main Sequence: Challenges and Prospects for Asteroseismology
• A multi-wavelength characterization of proto-brown dwarf candidates in Serpens
• Protostellar accretion in low mass metal poor stars and the cosmological lithium problem
• WTP10aaauow: Discovery of a new FU Ori outburst towards the RCW49 star-forming region in NEOWISE data
• Latest news on the Physics of Brown dwarfs
• GeMS in the Outer Galaxy: Near-Infrared Imaging of Three Young Clusters at Large Galactic Radii
• Theoretical predictions of surface light element abundances in protostellar and pre-Main Sequence phase
• Haffner 16: A Young Moving Group in the Making
• What governs the spin distribution of very young < 1 Myr low mass stars
• A Model for Protostellar Cluster Luminosities and the Impact on the CO-H${}_2$ Conversion Factor
• Circumstellar disk accretion across the Lagoon Nebula: the influence of environment and stellar mass
• Turn up the light: Radiative efficiency of protostars at birth
• Star Formation in the Starburst Cluster in NGC 3603
• An Observational Perspective of the IMF: Progress and Challenges
• Precise determination of circumstellar disk lifetimes: Disk evolution in a single star-forming region
• Constraints on star formation in Orion A from Gaia
• When did the initial mass function become bottom-heavy?
• Benchmarking pre-main sequence stellar evolutionary tracks using disk-based dynamical stellar masses
• Rotational Velocities and Radii Estimates of Low-Mass Pre-Main Sequence Stars in NGC 2264
• Star Forming Regions