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J/AJ/112/545  Proton capture chains in globular clusters. I. (Pilachowski+ 1996)

Proton capture chains in globular cluster stars. I. Evidence for deep mixing based on sodium and magnesium abundances in M13 giants Pilachowski C.A., Sneden C., Kraft R.P., Langer G.E. <Astron. J. 112, 545 (1996)> =1996AJ....112..545P
ADC_Keywords: Clusters, globular ; Stars, giant ; Abundances ; Effective temperatures Abstract: Sodium abundances have been derived for 130 giant stars in the globular cluster M13 from spectra of the Na I doublet at λ5682 and 5685A obtained using the KPNO 4-m Hydra fiber positioner and bench spectrograph. Magnesium abundances have also been obtained for the brightest 98 stars in the sample from the nearby Mg I line at λ5711A. The stars observed in M13 range from the faintest at MV~+1.0 and log(g)∼2.6 up to the tip of the giant branch, and include 18 stars on the asymptotic giant branch. Among the lower luminosity giants, the sodium abundances have a large star-to-star range, approximately from -0.3≤[Na/Fe]≤+0.5. However, the sodium abundances of the most luminous giants (Mv←1.7) are usually high; typically, [Na/Fe]≥+0.3, with a much smaller star-to-star scatter. The asymptotic giant branch stars have smaller sodium abundances on average than do the red giant branch tip stars. The spread in [Na/Fe] ratios is larger in M13 than it is among halo field giants of comparable metallicity; M13 contains many more stars with high [Na/Fe] ratios than can be found in the field, even at relatively low luminosities on the giant branch. Magnesium is uniformly overabundant ([Mg/Fe]~+0.3) in all stars with a low sodium abundance, but the [Mg/Fe] ratio ranges from approximately -0.3 to +0.3 in stars with a high sodium abundance. These sodium and magnesium abundance variations in M13 are discussed in the context of proton capture and deep mixing hypotheses. In addition to the CN and ON hydrogen burning chains previously discussed in the literature, the NeNa and MgAl burning chains have also contributed to the abundance mixture observed in M13 giants. At least some of the products of proton capture chains have been produced in situ in the giants, and brought to the surface, most probably via deep mixing. Evidence in support of the occurrence of proton capture nucleosynthesis and deep mixing among M13 stars includes (1) the absence of sodium-poor stars at the red giant tip, (2) the fact that asymptotic branch stars have lower sodium abundances on average than do stars near the red giant tip, and (3) the existence of a positive correlation between sodium and nitrogen abundances as well as a partial anti-correlation of sodium and magnesium abundances. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 16 41.7 +36 27 M 13 = NGC 6205 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 72 168 M13 star basic data and results table1.tex 108 264 AASTeX version of table1.dat
See also: J/AJ/113/279 : Proton Capture Chains. II (Kraft+ 1997) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Star *Primary designation 8- 14 A7 --- Alt *Alternate designation 16- 20 F5.2 mag Vmag *V magnitude 22- 26 F5.2 mag B-V *[]? B-V color 28- 32 F5.1 mag Mvo Estimated absolute V magnitude 35- 37 A3 --- Branch Evolutionary status (Red Giant Branch, RGB, Asymptotic Giant Branch, AGB) 38 A1 --- u_Branch [?] Branch uncertainty flag 40 I1 --- Code *Analysis code 42- 46 I5 K Teff []? Effective temperature 48- 52 F5.2 [cm/s2] log(g) []? log(10) of the surface gravity 54- 58 F5.2 km/s vt []? Microturbulence 60- 65 F6.2 --- [Na/Fe] []? Sodium abundance relative to iron 67- 72 F6.2 --- [Mg/Fe] []? Magnesium abundance relative to iron
Note on Star: Primary star name references: L = Ludendorf, (1905POPot..50....1L) K = Kadla, (1966IzPul.181...93K) CM = Cudworth & Monet, (1979AJ.....84..774C) Note on Alt: Alternate star name references: SA, SB = Savedoff, (1956AJ.....61..254S) V (variable stars) = Hogg, (1973PDDO....3....6S) BAUM = Baum, (1954AJ.....59..422B) "Roman numerals" = Arp, (1955AJ.....60..317A) remaining designations appear either in Arp & Johnson, (1955ApJ...122..171A) (their Figure 4) or in Sandage, (1970ApJ...162..841S) (his Figure 5). Note on Vmag, B-V: V and B-V from Cudworth & Monet, (1979AJ.....84..774C) Note on Code: Definitions of the code numbers: 1 = good enough spectrum to derive both sodium and magnesium abundances 2 = good enough spectrum to derive a sodium abundance, but not magnesium 3 = essentially no flux in the reduced spectrum; mis-positioned fiber? 4 = very weak absorption spectrum; possibly a warm star? 5 = hot horizontal branch star 6 = poor signal-to-noise in the reduced spectrum
Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 13-Aug-1996
(End) [CDS] 30-Jan-1997
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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