Strong biases in estimating the time dependence of mass accretion rates in young stars

Da Rio, N.; Jeffries, R. D.; Manara, C. F.; Robberto, M.

Abstract

The temporal decay of mass accretion in young stars is a fundamental tracer of the early evolution of circumstellar discs. Through population syntheses, we study how correlated uncertainties between the estimated parameters of young stars (luminosity, temperature, mass and age) and mass accretion rates M˙acc
⁠, as well as observational selection effects, can bias the temporal decay of mass accretion rates (⁠M˙acc∝t−η
⁠) inferred from a comparison of measured M˙acc
with isochronal ages in young stellar clusters.

We find that the presence of realistic uncertainties reduces the measured value of η by up to a factor of 3, leading to the inference of shallower decays than the true value. This suggests a much faster temporal decay of M˙acc
than generally assumed. When considering the minimum uncertainties in ages affecting the Orion Nebula Cluster, the observed value η ∼ 1.4, typical of Galactic star-forming regions, can only be reproduced if the real decay exponent is η ≳ 4. This effect becomes more severe if one assumes that observational uncertainties are larger, as required by some fast star formation scenarios. Our analysis shows that while selection effects due to sample incompleteness do bias η, they cannot alter this main result and strengthen it in many cases. A remaining uncertainty in our work is that it applies to the most commonly used and simple relationship between M˙acc⁠, the accretion luminosity and the stellar parameters. We briefly explore how a more complex interplay between these quantities might change the results.

Citation

Da Rio, N., Jeffries, R. D., Manara, C. F., & Robberto, M. (2014). Strong biases in estimating the time dependence of mass accretion rates in young stars. Monthly Notices of the Royal Astronomical Society, 439(4), 3308-3328. https://doi.org/10.1093/mnras/stu149

• Journal Article Type: Article
• Acceptance Date: Jan 20, 2014
• Online Publication Date: Mar 4, 2014
• Publication Date: Apr 21, 2014
• Deposit Date: Jun 16, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 0035-8711
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 439
• Issue: 4
• Pages: 3308-3328
• DOI: https://doi.org/10.1093/mnras/stu149
• Keywords: Space and Planetary Science; Astronomy and Astrophysics; circumstellar matter, stars: formation, stars: fundamental parameters, Hertzsprung–Russell and colour–magnitude diagrams, stars: pre-main-sequence