Atomic diffusion and mixing in old stars - IV. Weak abundance trends in the globular cluster NGC 6752

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Volume 555 (July 2013)

A&A, 555 (2013) A31

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Table 5

Mean stellar parameters using (b − y) photometry and derived mean abundances for stars in NGC 6752 from spectra having the same S/N ~ 60.

Group	T_eff	log g	ξ	[Fe/H]	log ε(Mg)^a	log ε(Sc)^b	log ε(Ti)^c	log ε(Ca)^d	log ε(Ba)^e
	(K)	(cgs)	(km s^-1)	(dex)	NLTE	LTE	LTE	NLTE	NLTE

TOP_ave	6068	4.00	2.00	−1.74 ± 0.05	6.01 ± 0.07	1.23 ± 0.09	3.39 ± 0.09	4.88 ± 0.07	0.46 ± 0.04
SGB_mean	5793	3.79	1.50	−1.68 ± 0.10	6.05 ± 0.07	1.21 ± 0.09	3.28 ± 0.08	4.76 ± 0.10	0.44 ± 0.03
bRGB_mean	5256	3.26	1.40	−1.67 ± 0.03	6.18 ± 0.04	1.32 ± 0.05	3.45 ± 0.03	4.91 ± 0.02	0.48 ± 0.01
RGB_mean	5031	2.58	1.45	−1.66 ± 0.03	6.12 ± 0.03	1.33 ± 0.04	3.45 ± 0.02	4.96 ± 0.02	0.42 ± 0.06

Δ[TOP-RGB]	1037	1.42		−0.08 ± 0.06	−0.11 ± 0.08	−0.10 ± 0.10	−0.06 ± 0.09	−0.08 ± 0.07	0.04 ± 0.07

Notes.The average TOP-star abundances were derived from the co-added TOP-star spectrum while the abundances for the other groups are computed as the mean abundance of the abundances derived for the individual stars within each group. Hence, row 1 (TOP_ave) is identical to row 1 in Table 4. The uncertainties on the abundances for the TOP-group correspond to the standard deviation. For the other groups, they correspond to the standard error of the mean (see text).

^(a)

Based on Mg I λλ5528 and 5711. RGB_ave Mg abundance derived by disregarding star 548.

^(b)

Based on Sc II λλ5031, 5526 and 5657. Note that the Sc abundances for the bRGB and RGB stars can be slightly overestimated due to ignoring HFS.

^(c)

Based on Ti II λλ5129, 5154, 5185, 5226 and 5336.

^(d)

Based on Ca I λλ6169 and 6493.

^(e)

Based on Ba II λ6141. The Ba II λ6496 line was disregarded due to telluric contamination. TOP_ave Ba abundance derived by disregarding star 3988 and using T_eff = 6070 K, log g = 4.00, and ξ = 2.00 km s^-1.

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