J/ApJ/742/37 Abundances of six RGB stars in M22 (Roederer+, 2011)
Characterizing the heavy elements in globular cluster M22 and an empirical
s-process abundance distribution derived from the two stellar groups.
Roederer I.U., Marino A.F., Sneden C.
<Astrophys. J., 742, 37 (2011)>
=2011ApJ...742...37R 2011ApJ...742...37R
ADC_Keywords: Clusters, globular ; Abundances ; Stars, giant ; Radial velocities
Keywords: globular clusters: individual (NGC 6656) - stars: AGB and post-AGB -
nuclear reactions, nucleosynthesis, abundances - stars: abundances -
stars: Population II
Abstract:
We present an empirical s-process abundance distribution derived with
explicit knowledge of the r-process component in the low-metallicity
globular cluster M22. We have obtained high-resolution, high
signal-to-noise spectra for six red giants in M22 using the Magellan
Inamori Kyocera Echelle spectrograph on the Magellan-Clay Telescope at
Las Campanas Observatory. In each star we derive abundances for 44
species of 40 elements, including 24 elements heavier than zinc (Z=30)
produced by neutron-capture reactions. Previous studies determined
that three of these stars (the "r+s group") have an enhancement of
s-process material relative to the other three stars (the "r-only
group"). We confirm that the r+s group is moderately enriched in Pb
relative to the r-only group. Both groups of stars were born with the
same amount of r-process material, but s-process material was also
present in the gas from which the r+s group formed. The s-process
abundances are inconsistent with predictions for asymptotic giant
branch (AGB) stars with M≤3M☉ and suggest an origin in more
massive AGB stars capable of activating the 22Ne(α,n)25Mg
reaction. We calculate the s-process "residual" by subtracting the
r-process pattern in the r-only group from the abundances in the r+s
group. In contrast to previous r- and s-process decompositions, this
approach makes no assumptions about the r- and s-process distributions
in the solar system and provides a unique opportunity to explore
s-process yields in a metal-poor environment.
Description:
Six probable members of M22 were observed with the Magellan Inamori
Kyocera Echelle (MIKE) spectrograph on the 6.5m Magellan-Clay
Telescope at Las Campanas Observatory on 2011 March 17-18; with a
complete wavelength coverage from 3350 to 9150Å and a resolving
power of R∼41000 in the blue and R∼35000 in the red.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 73 6 Photometry, atmospheric parameters, radial
velocities, exposure times, and S/N estimates
table2.dat 75 267 Line-by-line abundances
refs.dat 205 43 References for log(gf)
--------------------------------------------------------------------------------
See also:
J/A+A/541/A15 : Abundances of M22 subgiants (Marino+, 2012)
J/AcA/62/357 : Proper motions of 6 globular clusters (Zloczewski+, 2012)
J/ApJ/705/1481 : Spectroscopy of stars in 6 GCs (Da Costa+, 2009)
J/MNRAS/349/1278 : BVI photometry of M22 (Monaco+, 2004)
J/A+A/373/899 : New variables in M22 globular cluster (Kaluzny+, 2001)
J/PASP/107/32 : uvby-hk photometry in M22 (Anthony-Twarog+ 1995)
J/ApJS/99/637 : Equivalent widths for 54 red giants (Norris+ 1995)
J/A+AS/109/487 : Color-magnitude study of M 22 (Samus+, 1995)
J/A+A/303/468 : Spec. & IR-phot. in globular clusters (Minniti, 1995)
J/ApJ/420/612 : Proper motions + radial velocities in M22 (Peterson+ 1994)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Star name (1)
8- 12 F5.2 mag Vmag V-band magnitude (2)
14- 17 F4.2 mag (B-V)0 B-V color index (2)
19- 22 I4 K Teff Effective temperature from Marino et al.
2011A&A...532A...8M 2011A&A...532A...8M
24- 27 F4.2 [cm/s2] logg Surface gravity from Marino et al.
2011A&A...532A...8M 2011A&A...532A...8M
29- 32 F4.2 km/s Vt Turbulent velocity
34- 38 F5.2 [-] [Fe/H] Metallicity
40- 45 F6.1 km/s HRV Heliocentric radial velocity
47- 50 I4 s Texp Exposure time
52- 53 I2 --- S/N3 [40/50] 395nm signal to noise ratio
54- 55 A2 --- --- [/1]
57- 59 I3 --- S/N4 [90/125] 455nm signal to noise ratio
60- 61 A2 --- --- [/1]
63- 65 I3 --- S/N5 [95/140] 520nm signal to noise ratio
66- 67 A2 --- --- [/1]
69- 71 I3 --- S/N6 [210/340] 675nm signal to noise ratio
72- 73 A2 --- --- [/1]
--------------------------------------------------------------------------------
Note (1): The six observed stars are all cool giants on the M22 red giant
branch (RGB).
Note (2): Photometry from the Stetson database (2010, private
communication, corrected for differential reddening as in Marino et
al. 2011A&A...532A...8M 2011A&A...532A...8M).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Species identification
7- 13 F7.2 0.1nm lambda Wavelength
15- 18 F4.2 eV ExPot Excitation Potential
20- 24 F5.2 [-] log(gf) log of the oscillator strength
26- 27 I2 --- r_log(gf) Reference for log(gf) (see refs.dat file)
29 A1 --- l_I-37 Limit flag on I-37
30- 34 F5.2 [-] I-37 ? abundance for star I-37 (logε)
35 A1 --- u_I-37 Uncertainty flag on I-37 of order 0.2dex
37 A1 --- l_III-33 Limit flag on III-33
38- 42 F5.2 [-] III-33 ? abundance for star III-33 (logε)
43 A1 --- u_III-33 Uncertainty flag on III-33 of order 0.2dex
45 A1 --- l_IV-59 Limit flag on I-59
46- 50 F5.2 [-] IV-59 ? abundance for star IV-59 (logε)
51 A1 --- u_IV-59 Uncertainty flag on IV-59 of order 0.2dex
53 A1 --- l_I-27 Limit flag on I-27
54- 58 F5.2 [-] I-27 ? abundance for star I-27 (logε)
59 A1 --- u_I-27 Uncertainty flag on I-27 of order 0.2dex
61 A1 --- l_I-53 Limit flag on I-53
62- 66 F5.2 [-] I-53 ? abundance for star I-53 (logε)
67 A1 --- u_I-53 Uncertainty flag on I-53 of order 0.2dex
69 A1 --- l_I-80 Limit flag on I-80
70- 74 F5.2 [-] I-80 ? abundance for star I-80 (logε)
75 A1 --- u_I-80 Uncertainty flag on I-80 of order 0.2dex
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode Bibcode
24- 54 A31 --- Aut Author's name
56-205 A150 --- Comm Comment
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 26-Mar-2013