J/AJ/149/204 Spectroscopy of 25 stars in M68 (Schaeuble+, 2015)
A detailed study of giants and horizontal branch stars in M68: atmospheric
parameters and chemical abundances.
Schaeuble M., Preston G., Sneden C., Thompson I.B., Shectman S.A.,
Burley G.S.
<Astron. J., 149, 204 (2015)>
=2015AJ....149..204S 2015AJ....149..204S
ADC_Keywords: Clusters, globular ; Stars, giant ; Stars, horizontal branch ;
Abundances ; Equivalent widths
Keywords: primordial nucleosynthesis - stars: abundances - stars: evolution -
stars: horizontal branch
Abstract:
In this paper, we present a detailed high-resolution spectroscopic
study of post main sequence stars in the globular cluster (GC) M68.
Our sample, which covers a range of 4000K in Teff, and 3.5dex in
log(g), is comprised of members from the red giant, red horizontal,
and blue horizontal branch, making this the first high-resolution GC
study covering such a large evolutionary and parameter space.
Initially, atmospheric parameters were determined using photometric as
well as spectroscopic methods, both of which resulted in unphysical
and unexpected Teff, log(g), ξt, and [Fe/H] combinations. We
therefore developed a hybrid approach that addresses most of these
problems, and yields atmospheric parameters that agree well with other
measurements in the literature. Furthermore, our derived stellar
metallicities are consistent across all evolutionary stages, with
<[Fe/H]≥-2.42 (σ=0.14) from 25 stars. Chemical abundances
obtained using our methodology also agree with previous studies and
bear all the hallmarks of GCs, such as a Na-O anti-correlation,
constant Ca abundances, and mild r-process enrichment.
Description:
We obtained high resolution spectra of 11 Red Giant Branch (RGB), 9
Red Horizontal Branch (RHB), and 5 Blue Horizontal Branch (BHB)
members of M68. All of our program stars were selected from the
photometric survey of Walker 1994 (cat. J/AJ/108/555), whose V and B-V
values are listed in in Table 2.
Our spectra were gathered with the Magellan Inamori Kyocera Echelle
(MIKE) spectrograph of the the Las Campanas Observatory (LCO) Magellan
Clay 6.5m telescope. The spectrograph was configured with a 0.7"
entrance aperture that yielded an ultimate resolving power of
R=λ/Δλ∼40000 for both the blue and red arms of
instrument. The useful spectral coverage of the blue arm was
3500-5000Å, and that of the red arm was 5000-9000Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 26 25 Photometric parameters
table3.dat 335 260 Equivalent widths for the 25 stars
table4.dat 52 25 Atmospheric parameters
table8.dat 159 28 Average abundances for individual stars
refs.dat 57 19 References
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See also:
II/331 : M68 variable star light curves (Rosino+, 1953)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/AJ/132/85 : Equivalent width of 33 metal-poor RHB (Preston+, 2006)
J/AJ/108/555 : BVI photometry in globular cluster M68 (Walker, 1994)
J/AJ/107/622 : M68 variable star light curves (Brocato+, 1994)
J/ApJ/412/183 : RR Lyr in M68 (Clement+, 1993)
J/AJ/99/1831 : M 68 BVRI photometry (Alcaino+ 1990)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Stage Star evolutionary stage (RGB, RHB, or BHB) (4)
5- 7 I3 --- Star [36/547] Star identification number (5)
9- 14 F6.3 mag Vmag [12.6/15.8] The V-band magnitude (5)
16- 20 F5.3 mag B-V The (B-V) color index (5)
22- 26 F5.3 mag V-I The (V-I) color index (5)
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Note (4): The 3 evolutionary stages are:
RGB = Red Giant Branch;
RHB = Red Horizontal Branch;
BHB = Blue Horizontal Branch.
Note (5): From the photometric survey of Walker 1994 (cat. J/AJ/108/555).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda [3412/8195] Wavelength; in Å
9- 13 A5 --- Ion Line of atomic species
15- 19 F5.3 eV EP [0/10]? Line excitation potential (1)
21- 26 F6.3 [-] loggf [-10/0.7]? The log oscillator strength (1)
28- 33 F6.1 0.1pm EW1 ? Measured Equivalent Width of star 57; in mÅ
35- 39 F5.2 [-] loge1 ? The logε abundance for star 57
41- 45 F5.1 0.1pm EW2 ? Measured Equivalent Width of star 79; in mÅ
47- 51 F5.2 [-] loge2 ? The logε abundance for star 79
53- 57 F5.1 0.1pm EW3 ? Measured Equivalent Width of star 117; in mÅ
59- 63 F5.2 [-] loge3 ? The logε abundance for star 117
65- 69 F5.1 0.1pm EW4 ? Measured Equivalent Width of star 160; in mÅ
71- 75 F5.2 [-] loge4 ? The logε abundance for star 160
77- 81 F5.1 0.1pm EW5 ? Measured Equivalent Width of star 172; in mÅ
83- 87 F5.2 [-] loge5 ? The logε abundance for star 172
89- 93 F5.1 0.1pm EW6 ? Measured Equivalent Width of star 226; in mÅ
95- 99 F5.2 [-] loge6 ? The logε abundance for star 226
101-105 F5.1 0.1pm EW7 ? Measured Equivalent Width of star 256; in mÅ
107-111 F5.2 [-] loge7 ? The logε abundance for star 256
113-117 F5.1 0.1pm EW8 ? Measured Equivalent Width of star 440; in mÅ
119-123 F5.2 [-] loge8 ? The logε abundance for star 440
125-129 F5.1 0.1pm EW9 ? Measured Equivalent Width of star 450; in mÅ
131-135 F5.2 [-] loge9 ? The logε abundance for star 450
137-141 F5.1 0.1pm EW10 ? Measured Equivalent Width of star 472; in mÅ
143-147 F5.2 [-] loge10 ? The logε abundance for star 472
149-153 F5.1 0.1pm EW11 ? Measured Equivalent Width of star 481; in mÅ
155-159 F5.2 [-] loge11 ? The logε abundance for star 481
161-165 F5.1 0.1pm EW12 ? Measured Equivalent Width of star 36; in mÅ
167-171 F5.2 [-] loge12 ? The logε abundance for star 36
173-177 F5.1 0.1pm EW13 ? Measured Equivalent Width of star 47; in mÅ
179-183 F5.2 [-] loge13 ? The logε abundance for star 47
185-189 F5.1 0.1pm EW14 ? Measured Equivalent Width of star 202; in mÅ
191-195 F5.2 [-] loge14 ? The logε abundance for star 202
197-201 F5.1 0.1pm EW15 ? Measured Equivalent Width of star 334; in mÅ
203-207 F5.2 [-] loge15 ? The logε abundance for star 334
209-213 F5.1 0.1pm EW16 ? Measured Equivalent Width of star 403; in mÅ
215-219 F5.2 [-] loge16 ? The logε abundance for star 403
221-225 F5.1 0.1pm EW17 ? Measured Equivalent Width of star 454; in mÅ
227-231 F5.2 [-] loge17 ? The logε abundance for star 454
233-237 F5.1 0.1pm EW18 ? Measured Equivalent Width of star 458; in mÅ
239-243 F5.2 [-] loge18 ? The logε abundance for star 458
245-249 F5.1 0.1pm EW19 ? Measured Equivalent Width of star 533; in mÅ
251-255 F5.2 [-] loge19 ? The logε abundance for star 533
257-261 F5.1 0.1pm EW20 ? Measured Equivalent Width of star 547; in mÅ
263-267 F5.2 [-] loge20 ? The logε abundance for star 547
269-273 F5.1 0.1pm EW21 ? Measured Equivalent Width of star 170; in mÅ
275-279 F5.2 [-] loge21 ? The logε abundance for star 170
281-285 F5.1 0.1pm EW22 ? Measured Equivalent Width of star 289; in mÅ
287-291 F5.2 [-] loge22 ? The logε abundance for star 289
293-297 F5.1 0.1pm EW23 ? Measured Equivalent Width of star 324; in mÅ
299-302 F4.2 [-] loge23 ? The logε abundance for star 324
304-308 F5.1 0.1pm EW24 ? Measured Equivalent Width of star 337; in mÅ
310-314 F5.2 [-] loge24 ? The logε abundance for star 337
316-320 F5.1 0.1pm EW25 ? Measured Equivalent Width of star 391; in mÅ
322-326 F5.2 [-] loge25 ? The logε abundance for star 391
328-332 A5 --- Meth Method of deriving abundance (EW or SYNTH) (2)
334-335 I2 --- r_loggf [1/19] Reference for log(gf); in refs.dat file
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Note (1): Blank values indicate hyperfine structure (hfs)
Note (2): EW=Equivalent width; SYNTH=Spectral synthesis.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star [36/547] Star identification number
5 A1 --- f_Star [ab] Flag on Star (1)
7- 9 I3 --- S/N [30/230] Signal-to-noise ratio (2)
11- 14 I4 K Teff1 Photometric effective temperature
16- 19 F4.2 [cm/s2] logg1 Log of photometric surface gravity
22- 25 I4 K Teff2 ? Spectroscopic effective temperature
28- 31 F4.2 [cm/s2] logg2 ? Log of spectroscopic surface gravity
33- 36 I4 K Teff [4168/7848] Adopted effective temperature (3)
38- 41 F4.2 [cm/s2] logg [0.18/3.5] Adopted log of surface gravity (3)
43- 47 F5.2 [-] [Fe/H] [-2.65/-2.06] Adopted metallicity (3)
49- 52 F4.2 km/s Vt [1.97/3.81] Adopted microturbulent velocity
ξt (3)
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Note (1): The flags are defined as follows:
a = Star represented with green marker in Figures 2, 8, and 9 (see section 4.2
for details);
b = In Table 2, the star #377 was a mistake for #337 (corrected from author).
Note (2): Estimated using the no routine of SPECTRE at around 6600Å.
Note (3): Derived from a combination of photometry and spectroscopy.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- [X/Fe] Ion
11- 15 F5.2 [Sun] <Abd1> ? The average [X/Fe] abundance for Star 57
17- 21 F5.2 [Sun] <Abd2> ? The average [X/Fe] abundance for Star 79
23- 27 F5.2 [Sun] <Abd3> ? The average [X/Fe] abundance for Star 117
29- 33 F5.2 [Sun] <Abd4> ? The average [X/Fe] abundance for Star 160
35- 39 F5.2 [Sun] <Abd5> ? The average [X/Fe] abundance for Star 172
41- 45 F5.2 [Sun] <Abd6> ? The average [X/Fe] abundance for Star 226
47- 51 F5.2 [Sun] <Abd7> ? The average [X/Fe] abundance for Star 256
53- 57 F5.2 [Sun] <Abd8> ? The average [X/Fe] abundance for Star 440
59- 63 F5.2 [Sun] <Abd9> ? The average [X/Fe] abundance for Star 450
65- 69 F5.2 [Sun] <Abd10> ? The average [X/Fe] abundance for Star 472
71- 75 F5.2 [Sun] <Abd11> ? The average [X/Fe] abundance for Star 481
77- 81 F5.2 [Sun] <Abd12> ? The average [X/Fe] abundance for Star 36
83- 87 F5.2 [Sun] <Abd13> ? The average [X/Fe] abundance for Star 47
89- 93 F5.2 [Sun] <Abd14> ? The average [X/Fe] abundance for Star 202
95- 99 F5.2 [Sun] <Abd15> ? The average [X/Fe] abundance for Star 334
101-105 F5.2 [Sun] <Abd16> ? The average [X/Fe] abundance for Star 403
107-111 F5.2 [Sun] <Abd17> ? The average [X/Fe] abundance for Star 454
113-117 F5.2 [Sun] <Abd18> ? The average [X/Fe] abundance for Star 458
119-123 F5.2 [Sun] <Abd19> ? The average [X/Fe] abundance for Star 533
125-129 F5.2 [Sun] <Abd20> ? The average [X/Fe] abundance for Star 547
131-135 F5.2 [Sun] <Abd21> ? The average [X/Fe] abundance for Star 170
137-141 F5.2 [Sun] <Abd22> ? The average [X/Fe] abundance for Star 289
143-147 F5.2 [Sun] <Abd23> ? The average [X/Fe] abundance for Star 324
149-153 F5.2 [Sun] <Abd24> ? The average [X/Fe] abundance for Star 337
155-159 F5.2 [Sun] <Abd25> ? The average [X/Fe] abundance for Star 391
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref [1/19] Reference identifier
4- 22 A19 --- BibCode Bibliographic code
24- 38 A15 --- Aut Author's name
40- 57 A18 --- Cat Catalog identifier in VizieR database
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 16-Jun-2015