J/MNRAS/434/966 Measurements of Li in T-Tauri stars (Sergison+, 2013)
No evidence for intense, cold accretion on to YSOs from measurements of
Li in T-Tauri stars.
Sergison D.J., Mayne N.J., Naylor T., Jeffries R.D., Bell C.P.M.
<Mon. Not. R. Astron. Soc., 434, 966-977 (2013)>
=2013MNRAS.434..966S 2013MNRAS.434..966S
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Abundances
Keywords: stars: pre-main-sequence -
open clusters and associations: individual: NGC 1976 -
open clusters and associations: individual: NGC 2264
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 6708Å lithium spectral line strengths. This
suggests that 'cold' accretion at high rates
(dM/dt≥5x10-4M☉/yr) occurs in the assembly phase of fewer
than 0.5 percent of 0.3≤M*≤1.9M☉ stars.
We also find that the dispersion in the strength of the 6708Å
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%
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 5x10-4M☉/yr are responsible.
Description:
The observations were made on the nights of 2011 November 20, 21 using
the AF2/WYFFOS multi-object fibre-fed spectrograph on the 4.2m William
Herschel Telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 114 127 Summary of derived parameters from this study
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See also:
J/ApJ/671/605 : NGC 2264 and ONC PMS stars in the infrared (Cieza+, 2007)
J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)
J/AJ/127/1117 : Halpha emission-line stars in NGC2264 (Reipurth+, 2004)
J/ApJS/208/28 : Hα survey in the ONC (Szegedi-Elek+, 2013)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Cluster name (ONC or NGC2264)
9- 10 I2 h RAh Right ascension (J2000)
12- 13 I2 min RAm Right ascension (J2000)
15- 19 F5.2 s RAs Right ascension (J2000)
21 A1 --- DE- Declination sign (J2000)
22- 23 I2 deg DEd Declination (J2000)
25- 26 I2 arcmin DEm Declination (J2000)
28- 32 F5.2 arcsec DEs Declination (J2000)
34- 39 F6.3 0.1nm W(Li) [-0.3/0.9] Lithium equivalent width (Å)
41- 46 F6.3 0.1nm e_W(Li) ?=-0.01 rms uncertainty on W(Li)
48- 53 F6.3 km/s RV [-8/10] Relative radial velocity (1)
55- 57 F3.1 km/s e_RV [2.8] rms uncertainty on RV
59- 70 F12.9 --- rj [-0.1/4.0] Accretion veiling
72- 82 F11.9 --- e_rj [0.0003/0.153] rms uncertainty on rj
84- 92 F9.4 0.1nm W(Ha) Hα equivalent width
(not corrected for veiling)
94- 99 F6.4 0.1nm e_W(Ha) rms uncertainty on W(Ha)
101-107 F7.3 km/s VHa [52/147] Hα velocity
108-114 F7.3 km/s e_VHa [1/272] rms uncertainty on VHa
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Note (1): radial velocities were determined using cross-correlation of
spectral lines in the range 6385-6510Å between each star and an
arbitrary (low v.sin(i)) single star reference in the field. No
absolute RV standards were measured as relative velocities are
sufficient for veiling analysis and cluster membership verification.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 01-Aug-2014