Cdrom/AJ/V106/P1059 Lithium in the Pleiades (Soderblom+ 1993) The Evolution of the Lithium Abundances of Solar-Type Stars. III



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CDROM/AJ/V106/P1059 Lithium in the Pleiades (Soderblom+ 1993) ================================================================================ 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 ================================================================================ 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 and quality code: Bo = Boesgaard et al. 1988b, ApJ, 327, 389 Bu = Butler et al. 1987, ApJ, 319, L19 P = 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 -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 18-Mar-1995

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