No evidence for intense, cold accretion on to YSOs from measurements of Li in T-Tauri stars

Sergison, Darryl J.; Mayne, N. J.; Naylor, Tim; Jeffries, R. D.; Bell, Cameron P. M.

Abstract

We have used medium-resolution spectra to search for evidence that proto-stellar objects accrete at high rates during their early ‘assembly phase’. Models predict that depleted lithium and reduced luminosity in T-Tauri stars are key signatures of ‘cold’ high-rate accretion occurring early in a star's evolution.

We found no evidence in 168 stars in NGC 2264 and the Orion nebula cluster for strong lithium depletion through analysis of veiling-corrected 6708 Å lithium spectral line strengths. This suggests that ‘cold’ accretion at high rates (Ṁ ≥ 5 × 10−4 M⊙ yr−1) occurs in the assembly phase of fewer than 0.5 per cent of 0.3 ≤ M⋆ ≤ 1.9 M⊙ stars.

We also find that the dispersion in the strength of the 6708 Å lithium line might imply an age spread that is similar in magnitude to the apparent age spread implied by the luminosity dispersion seen in colour–magnitude diagrams. Evidence for weak lithium depletion (<10 per cent in equivalent width) that is correlated with luminosity is also apparent, but we are unable to determine whether age spreads or accretion at rates less than 5 × 10−4 M⊙ yr−1 are responsible.

Citation

Sergison, D. J., Mayne, N. J., Naylor, T., Jeffries, R. D., & Bell, C. P. M. (2013). No evidence for intense, cold accretion on to YSOs from measurements of Li in T-Tauri stars. Monthly Notices of the Royal Astronomical Society, 434(2), 966-977. https://doi.org/10.1093/mnras/stt973

• Journal Article Type: Article
• Acceptance Date: Jun 3, 2013
• Online Publication Date: Jul 17, 2013
• Publication Date: Sep 11, 2013
• Deposit Date: Jun 16, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 434
• Issue: 2
• Pages: 966-977
• DOI: https://doi.org/10.1093/mnras/stt973
• Keywords: Space and Planetary Science; Astronomy and Astrophysics; stars: pre-main-sequence; open clusters and associations: individual: NGC 1976; open clusters and associations: individual: NGC 2264