CDROM/AJ/V106/P1059
Lithium in the Pleiades (Soderblom+ 1993)
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The Evolution of the Lithium Abundances of Solar-Type Stars. III. The
Pleiades
David R. Soderblom, Burton F. Jones, Suchitra Balachandran, John
R. Stauffer, Douglas K. Duncan, Stephen B. Fedele, & J. Daniel
Hudon
<1993, AJ, 106, 1059>
=1993AJ....106.1059S
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Abstract:
We report new measurements of lithium in more than 100 Pleiades F, G,
and K dwarfs. Abundances were determined from spectrum synthesis fits
to the data as well as from use of new curves of growth for the Li 6708
A
feature (presented in an Appendix). We confirm the intrinsic spread in
lithium abundance within the Pleiades seen by Duncan & Jones [ApJ, 271,
663 (1983)], but we establish more observational constraints on Li in
this cluster: First, for stars near 1.0 M(sun) [about 0.60 to 0.75 in
(B-V)o], the scatter in the relation between log N(Li) (defined as
N(Li)) and T(eff) is consistent with our observational uncertainty.
That means that most late-F and early-G dwarfs in the Pleiades are
consistent with the tight N(Li) versus mass relation seen in the Hyades
in the same mass range. Second, at (B-V)o approx. 0.8 (M approx. 0.9
M(sun)), large and real star-to-star differences in N(Li) appear. The
range in N(Li) at (B-V)o approx. 0.8 is about 1 dex, and grows to as
much as 1.5 dex for less massive stars. Third, the most Li-rich stars
have abundances at or near the primordial level for Population I (N(Li)
approx. 3.2), and none exceed that level by a significant amount.
Fourth, at any given color the stars that rotate fastest have the most
Li and have the strongest chromospheric activity. We consider the ways
in which an apparent spread in N(Li) could arise from an intrinsically
tight N(Li)-mass relation and conclude that the spread is probably real
and is not an artifact of line formation conditions or inhomogeneous
atmospheres on the stars. It is possible to produce large apparent
changes in N(Li) by covering a significant fraction of a star's surface
with cooler regions ("spots"), but doing so has other ramifications
that conflict with the observations. Some current models lead to a
spread in N(Li) in which the fastest rotators (those that have lost the
least angular momentum) have the most Li, and that mechanism may
account for what is seen. A comparison of the Pleiades to the Alpha
Persei cluster shows that most Alpha Persei stars have Li abundances
comparable to their Pleiades counterparts, but there is a significant
fraction (about 30%) of Alpha Persei stars that lie below the Pleiades
in N(Li) by 1 dex or more. Some of these anomolous stars have even
less Li than Hyades stars of the same T(eff). If these stars are bona
fide Alpha Persei members (and they probably are), their Li abundances
strain our understanding of Li depletion. The Pleiades, considered
together with Alpha Persei and the Hyades, shows that stars with [Fe/H]
>= 0.0 and which are more massive than about 1.25 M(sun) do not deplete
Li prior to reaching main the sequence. Moreover, solar-abundance
stars
([Fe/H] approx. 0.0) with M >~ 1.1 M(sun) do not experience
pre-main-sequence depletion either. Pleiades dwarfs near T(eff) = 6700
K
show evidence of being depleted in Li, indicating that an incipient Li
"chasm" is present even at an age of 70 Myr.
File Summary:
------------------------------------------------------------------------------File Name
Lrecl
Records
Explanations
------------------------------------------------------------------------------table1.dat
76
131
Observations of Lithium in Pleiades F,
G, and
K Dwarfs
table2.dat
96
61
Lithium abundances for the 6708 A
feature
table3.dat
85
51
Lithium abundances for the 6104 A
feature
------------------------------------------------------------------------------Byte-by-byte Description of file: table1.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1- 4
A4
--fgk
*fgk no., Soderblom et al. 1993, ApJS,
85, 315
5
1X
----Blank
6- 9
A4
--HII
*Hertzsprung (H II) designation
10
1X
----Blank
11-16
A6
--Sp
Spectral type
17-22
F6.3
mag
B-Vo
Dereddened (B-V)
23-28
I6
K
Teff
Effective temperature
29
1X
----Blank
30-33
A4
km/s
vsini
*v sin i
34-39
F6.2
--RHa
*[]? Ratio of Halpha flux to stellar
bolometric flux
40-45
F6.2
--R8542
*[]? Ratio of 8542A CaII line flux to
bolometric flux
46-50
I5
10-4nm
W7699
[]? Equivalent width of K I 7699A line
51
1X
----Blank
52
A1
--f_W6717 *[{] Flags equiv. width of Ca I 6717 A
line
53-55
I3
10-4nm
W6717
[]? Equivalent width of Ca I 6717 A
line
56
A1
--fc1
[}] companion to left brace in f_W6717
57
1X
----Blank
58
A1
--f_W6708 *[{<] Brace or a limiting character '<'
59-61
I3
10-4nm
W6708
*Equivalent width of Li I 6708 A line
62
A1
--fc2
[}] companion to left brace in f_W6708
63
1X
----Blank
64-69
A6
--SQ
*Source and quality code
70
A1
--l_N_Li
Limiting character for lithium
abundance
71-75
F5.2
--N_Li
*Abundance of lithium
76
A1
--q_N_Li
':' in one case, star f105
------------------------------------------------------------------------------Notes for file: table1.dat
------------------------------------------------------------------------------fgk:
fgk number from Soderblom et al. 1993, ApJS, 85, 315 (hereafter SSHJ,
see directory /apjs/v85/p315 on the AAS CD-ROM Series, Volume I, or
/volume1/apjs/v85/p315 in the AAS CD-ROM Series, Volume IV)
HII:
Hertzsprung (H II) designation.
A "P" prefix denotes a Pels star.
vsini:
v sin i. This field contains imbedded non-numeric characters: '<'
in byte 30, ':' in byte 33, and ' SB2' indicating a double-lined
spectroscopic binary whose v sin i values are given in table 2 of
SSHJ.
RHa:
Ratio of the Halpha flux to the stellar bolometric flux, log
R(Halpha) from SSHJ
R8542:
Ratio of the 8542 A Ca II line flux to the stellar bolometric flux,
log R(8542) from SSHJ
f_W6717, f_W6708:
'{' if equivalent width the line has been compensated for spectrum
dilution by the following factors:
H II 102, 1.33;
H II 173, 1.40;
H II 248 and 2147, 1.20;
H II 298, 571, 1100, and 2406, 1.10;
H II 320, 1.15;
H II 1101, 1.25.
W6708:
Equivalent width of Li I 6708 A line, corrected for Fe I 6707.441.
SQ:
Source
Bo =
Bu =
P =
and quality code:
Boesgaard et al. 1988b, ApJ, 327, 389
Butler et al. 1987, ApJ, 319, L19
Pilachowski et al. 1987, PASP, 99, 1288
Codes a to d denote Lick data and are in descending order of
quality, with approximate uncertainties of 12, 18, 25, and 40
milliAngstroms, respectively.
N_Li:
Abundance of lithium, logarithmically, on a scale where log N(H) = 12
------------------------------------------------------------------------------Comments for file: table2.dat
------------------------------------------------------------------------------Conventional curves of growth (COGs) provide a convenient graphical means
of
combining the observed strengths of a number of lines of an atomic
species in
order to derive an abundance. Soderblom et al. present a more convenient
representation that is well suited to two-dimensional interpolation with
available routines (see e.g. Press et al. 1986, Numerical Recipes
(Cambridge
University Press, Cambridge))
A grid of curves of growth was computed for every 250 K in T(eff) from
4000 to
6500 K, and for every 0.2 dex in log N(Li). A microturbulent velocity of
1.0
km/s was used for the tables given here, but computations for Xi = 2 km/s
differ little. One dimensional interpolation was done to create points
evenly
spaced in log W(lambda) with log N(Li) as the dependant variable.
------------------------------------------------------------------------------Byte-by-byte Description of file: table2.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1- 7
F7.2
10-4nm W6708
Log of equivalent width of Li 6708
line
8
1X
----Blank
9-15
F7.3
--T4000
log N(Li) corr. to log(EW) for Teff =
4000 K
16-22
F7.3
--T4250
log N(Li) corr. to log(EW) for Teff =
4250 K
23-29
F7.3
--T4500
log N(Li) corr. to log(EW) for Teff =
4500 K
30-36
F7.3
--T4750
log N(Li) corr. to log(EW) for Teff =
4750 K
37-43
F7.3
--T5000
log N(Li) corr. to log(EW) for Teff =
5000 K
44-50
F7.3
--T5250
log N(Li) corr. to log(EW) for Teff =
5250 K
51-57
F7.3
--T5500
log N(Li) corr. to log(EW) for Teff =
5500 K
58-64
F7.3
--T5750
log N(Li) corr. to log(EW) for Teff =
5750 K
65-71
F7.3
--T6000
log N(Li) corr. to log(EW) for Teff =
6000 K
72-78
F7.3
--T6250
log N(Li) corr. to log(EW) for Teff =
6250 K
79-85
F7.3
--T6500
log N(Li) corr. to log(EW) for Teff =
6500 K
------------------------------------------------------------------------------Comments for file: table3.dat
------------------------------------------------------------------------------Conventional curves of growth (COGs) provide a convenient graphical means
of
combining the observed strengths of a number of lines of an atomic
species in
order to derive an abundance. Soderblom et al. present a more convenient
representation that is well suited to two-dimensional interpolation with
available routines (see e.g. Press et al. 1986, Numerical Recipes
(Cambridge
University Press, Cambridge))
A grid of curves of growth was computed for every 250 K in T(eff) from
4000 to
6500 K, and for every 0.2 dex in log N(Li). A microturbulent velocity of
1.0
km/s was used for the tables given here, but computations for Xi = 2 km/s
differ little. One dimensional interpolation was done to create points
evenly
spaced in log W(lambda) with log N(Li) as the dependant variable.
------------------------------------------------------------------------------Byte-by-byte Description of file: table3.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1- 7
F7.2
10-4nm W6104
Log of equivalent width of Li 6104
line
8
1X
----Blank
9-15
F7.3
--T4000
log N(Li) corr. to log(EW) for Teff =
4000 K
16-22
F7.3
--T4250
log N(Li) corr. to log(EW) for Teff =
4250 K
23-29
F7.3
--T4500
log N(Li) corr. to log(EW) for Teff =
4500 K
30-36
F7.3
--T4750
log N(Li) corr. to log(EW) for Teff =
4750 K
37-43
F7.3
--T5000
log N(Li) corr. to log(EW) for Teff =
5000 K
44-50
F7.3
--T5250
log N(Li) corr. to log(EW) for Teff =
5250 K
51-57
F7.3
--T5500
log N(Li) corr. to log(EW) for Teff =
5500 K
58-64
F7.3
--T5750
log N(Li) corr. to log(EW) for Teff =
5750 K
65-71
F7.3
--T6000
log N(Li) corr. to log(EW) for Teff =
6000 K
72-78
F7.3
--T6250
log N(Li) corr. to log(EW) for Teff =
6250 K
79-85
F7.3
--T6500
log N(Li) corr. to log(EW) for Teff =
6500 K
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(End)
Lee Brotzman [ADS] 18Mar-1995