2007A&A...475..667J


Query : 2007A&A...475..667J

2007A&A...475..667J - Astronomy and Astrophysics, volume 475, 667-675 (2007/11-4)

Lithium abundances of very low mass members of Chamaeleon I.

JOHNAS C.M.S., GUENTHER E.W., JOERGENS V., SCHWEITZER A. and HAUSCHILDT P.H.

Abstract (from CDS):

We present the first study of the lithium abundances of very low mass objects in Chamaeleon I close to the hydrogen burning mass limit based on atmospheric models and high-resolution spectroscopic observations. The studied objects, Cha Hα 2, 3, 4, 5, 6 and 8, are very young brown dwarf candidates and very low mass stars on the verge of lithium depletion.For this analysis, we have computed a new ``GAIA-cond'' class model grid over effective temperatures from 2600K to 3100K, surface gravities from log(g)=3.5 to 5.5, and lithium abundances from logε=0.0 to 3.7, for two different line profile setups introduced in previous work. Calculated synthetic spectra are compared with high-resolution UVES/VLT echelle spectra of the objects.We find good descriptions of the lithium resonance doublet lines at 6708Å and of the surrounding pseudo-continuum and determine a consistent set of lithium abundances (log(ε)=1.55). However, the derived lithium abundances are lower than the meteoritic one (log(ε)=3.31) and that of higher mass stars in ChaI (log(ε)=3.1/3.4 for LTE-/non-LTE-calculations). By modeling the TiO-line, we demonstrate that veiling does not make the lithium lines appear weaker. We can also rule out that the results are spoiled by the presence of spots.A possible explanation for these results would be that the objects are either more massive, or much older, than previously thought, so that the lithium depletion has already started. Although the uncertainties of the masses and ages are large, they are not large enough as to explain the observed lithium depletion. Therefore, the most likely explanation is either a lack of understanding of the details of the formation of the lithium line, or a lack of understanding of the internal structure of the very young low-mass objects.

Abstract Copyright:

Journal keyword(s): stars: atmospheres - line: profiles - stars: low-mass, brown dwarfs - stars: pre-main sequence - ISM: individual objects: Chamaeleon I

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* SY Cha Or* 10 56 30.3882538728 -77 11 39.402450501         11.29 K5Ve 117 0
2 V* TW Cha Or* 10 59 01.0608276980 -77 22 40.946475900     13.40   11.68 K8Ve 118 0
3 Hen 3-545 Or* 10 59 06.9712894449 -77 01 40.309036535   12.91 11.136   9.596 K4Ve 193 0
4 V* CS Cha Or* 11 02 24.8849252208 -77 33 35.683462615   12.88 11.69   10.123 K2Ve 203 0
5 NAME Cha 1 MoC 11 06 48 -77 18.0           ~ 1023 1
6 V* DI Cha Or* 11 07 20.7272524388 -77 38 07.303742740   12.02 10.74 10.72   G2Ve 149 0
7 V* HK Cha Or* 11 07 42.3440888366 -77 33 59.381952754   21.9 19.8   15.26 ~ 76 0
8 [NC98] Cha HA 8 SB* 11 07 46.0905760052 -77 40 08.918571132   22.2 20.1   15.61 ~ 42 1
9 V* HL Cha Or* 11 07 52.2571569898 -77 36 57.045566163   21.5 19.51   15.07 ~ 45 0
10 V* VW Cha Or* 11 08 01.3974165580 -77 42 28.579297348 13.91 14.04 12.80   10.69 K7+M0 170 0
11 CHSM 12180 Em* 11 08 18.9689267002 -77 39 17.141407943   20.5 18.52   14.50 ~ 39 0
12 ISO-ChaI 144 Em* 11 08 24.1180053004 -77 41 47.441399459   21.3 19.18   14.85 ~ 46 0
13 V* HQ Cha Or* 11 08 39.5016839836 -77 34 16.747297668   21.7 19.75   15.06 ~ 61 0
14 NAME Chamaeleon Region SFR 11 55 -78.0           ~ 717 0
15 V* EK Dra BY* 14 39 00.2109485496 +64 17 29.977371998   8.243 7.604     G1.5V 392 0

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2021.08.01-14:15:36

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