J/ApJ/819/135 Lithium-rich giants in globular clusters (Kirby+, 2016)
Lithium-rich giants in globular clusters.
Kirby E.N., Guhathakurta P., Zhang A.J., Hong J., Guo M., Guo R.,
Cohen J.G., Cunha K.
<Astrophys. J., 819, 135 (2016)>
=2016ApJ...819..135K 2016ApJ...819..135K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Abundances ; Stars, giant
Keywords: globular clusters: general; stars: abundances;
stars: chemically peculiar; stars: evolution
Abstract:
Although red giants deplete lithium on their surfaces, some giants are
Li-rich. Intermediate-mass asymptotic giant branch (AGB) stars can
generate Li through the Cameron-Fowler conveyor, but the existence of
Li-rich, low-mass red giant branch (RGB) stars is puzzling. Globular
clusters are the best sites to examine this phenomenon because it is
straightforward to determine membership in the cluster and to identify
the evolutionary state of each star. In 72 hours of Keck/DEIMOS
exposures in 25 clusters, we found four Li-rich RGB and two Li-rich
AGB stars. There were 1696 RGB and 125 AGB stars with measurements or
upper limits consistent with normal abundances of Li. Hence, the
frequency of Li-richness in globular clusters is (0.2±0.1)% for the
RGB, (1.6±1.1)% for the AGB, and (0.3±0.1)% for all giants.
Because the Li-rich RGB stars are on the lower RGB, Li self-generation
mechanisms proposed to occur at the luminosity function bump or He
core flash cannot explain these four lower RGB stars. We propose the
following origin for Li enrichment: (1) All luminous giants experience
a brief phase of Li enrichment at the He core flash. (2) All post-RGB
stars with binary companions on the lower RGB will engage in mass
transfer. This scenario predicts that 0.1% of lower RGB stars will
appear Li-rich due to mass transfer from a recently Li-enhanced
companion. This frequency is at the lower end of our confidence
interval.
Description:
We observed 25 GCs with Keck/DEIMOS over eight years (spanning 2006
Feb 2 to 2014 Aug 30); see table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 94 25 Globular clusters observed
table2.dat 53 81 DEIMOS observations
table3.dat 31 356 Line list
table4.dat 111 2227 Stellar properties and Lithium abundances;
updated version sent by the author
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/MNRAS/449/4038 : Li abundance of giants in 3 GCs (D'Orazi+, 2015)
J/A+A/554/A96 : Spectra of LiI(670.8nm) line in metal-poor stars (Lind+, 2013)
J/A+A/551/A36 : Metallicity of M dwarfs. III. (Neves+, 2013)
J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)
J/A+A/539/A157 : Li and Na in globular cluster M4 (Monaco+, 2012)
J/A+A/538/A36 : Lithium abundances of bulge RGB stars (Lebzelter+, 2012)
J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)
J/MNRAS/403/1413 : Updated stellar yields from AGB models (Karakas, 2010)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/A+A/504/829 : Spectroscopic survey of youngest field stars (Guillout+, 2009)
J/A+A/503/545 : Equivalent widths of Li, Na, Fe, Ca in NGC 6397 (Lind+, 2009)
J/A+A/503/541 : Li in late-type stars non-LTE calculations (Lind+, 2009)
J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)
J/A+A/469/529 : UBVI photometry of NGC 6864 (Kravtsov+, 2007)
J/ApJ/622/1102 : The planet-metallicity correlation. (Fischer+, 2005)
J/PASP/117/37 : BVRI photometry in NGC 2419, Pal 4, and Pal 14 (Saha+, 2005)
J/A+A/415/1153 : [Fe/H] for 98 extra-solar planet-host stars (Santos+, 2004)
J/AJ/124/915 : VI photometry of NGC 5634 (Bellazzini+, 2002)
J/AJ/122/2569 : VI photometry of NGC 288, 362 and 1851 (Bellazzini+, 2001)
J/A+A/371/943 : Lithium abundances for 185 main-sequence stars (Chen+, 2001)
J/AJ/121/916 : HST obs. of NGC 2298, 5897, 6535, and 6626 (Testa+, 2001)
J/A+AS/144/5 : Nearby GCs photometric catalog (Rosenberg+, 2000)
J/A+A/352/117 : Galactic lithium evolution revisited (Romano+, 1999)
J/ApJ/518/262 : CCD VIc Photometry of M30 Stars (Sandquist+, 1999)
J/AJ/108/555 : BVI photometry in globular cluster M68 (Walker, 1994)
J/ApJ/420/612 : Proper motions + radial velocities in M22 (Peterson+ 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- GC Globular cluster identifier
10- 12 A3 --- OID Messier number
14- 15 I2 h RAh Hour of Right Ascension (J2000) (2)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 21 I2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- Sign of the Declination (J2000) (2)
24- 25 I2 deg DEd Degree of Declination (J2000) (2)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of Declination (J2000)
33- 94 A62 --- r_GC Reference for GC catalog (3)
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Note (2): Cluster coordinates are from the compilation of
Harris (1996, VII/202; updated 2010 1012.3224) and
references therein.
Note (3):
Stetson = photometry by P.B. Stetson. Most of the photometry is available at
http://www2.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/community/STETSON/standards/,
but Stetson provided some of it directly to us.
SDSS = photometry from the Sloan Digital Sky Survey
(Abazajian et al. 2009, II/294).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- GC Globular cluster identifier
10- 12 A3 --- OID Messier number
14- 20 A7 --- Slit Slitmask name
22 A1 --- f_Slit [a] a: Observations by
Simon & Geha (2007ApJ...670..313S 2007ApJ...670..313S)
24- 26 I3 --- Nt [22/177]? Number of targets on the slitmask
28- 38 A11 "Y/M/D" Date UT date of observation
40- 42 F3.1 --- Airmass [1/2.1]? Airmass
44- 46 F3.1 arcsec Seeing [0.5/1.2]? Seeing
48 I1 --- Nx [1/5]? Number of exposures
50- 53 I4 s Exp [300/7200]? Total exposure time
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.4 0.1nm lambda [6697.1/6717] Wavelength in air
11- 13 A3 --- Species Element or molecule name
15- 16 A2 --- State ? Ionization state
18- 23 F6.3 eV EP [0/14.5] Excitation potential
25- 31 F7.4 --- log(gf) [-5.1/0.4] Oscillator strength
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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 A3 --- OID Messier globular cluster identifier
5- 12 A8 --- GC Globular cluster identifier
14- 28 A15 --- Name Star name
30- 31 I2 h RAh Hour of Right Ascension (J2000)
33- 34 I2 min RAm Minute of Right Ascension (J2000)
36- 40 F5.2 s RAs Second of Right Ascension (J2000)
42 A1 --- DE- Sign of the Declination (J2000)
43- 44 I2 deg DEd Degree of Declination (J2000)
46- 47 I2 arcmin DEm Arcminute of Declination (J2000)
49- 52 F4.1 arcsec DEs Arcsecond of Declination (J2000)
54- 56 A3 --- Branch "RGB" or "AGB" star
58- 62 F5.2 mag Vmag [11.9/21.9] Extinction-corrected apparent
V magnitude
64- 67 F4.2 mag B-V [0.2/1.9]? Reddening-corrected B-V color index
69- 72 F4.2 mag V-I [0.4/1.8]? Reddening-corrected V-I color index
74- 78 F5.2 mag VMag [-2.9/3.4] Extinction-corrected absolute
V magnitude
80- 83 I4 K Teff [3852/6727] Effective temperature
85- 88 F4.2 [cm/s2] log(g) [0.2/3.6] Log surface gravity
90- 94 F5.2 [Sun] [Fe/H] [-3.1/-0.3] Log Iron abundance relative
to the Sun
96- 99 F4.2 [Sun] e_[Fe/H] [0.1/1] Uncertainty in [Fe/H]
101 A1 --- l_A(Li) Upper limit flag for A(Li)
102-106 F5.2 --- A(Li) [-1.4/7.5] Lithium abundance
108-111 F4.2 --- e_A(Li) [0.1/0.4]? Uncertainty in A(Li)
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History:
From electronic version of the journal
22-Jun-2016: Insert into VizieR
06-Sep-2018: Table 4 updated with corrected coordinates for 105 M2 stars.
Acknowledgements:
Evan Kirby [Caltech Department of Astronomy & Astrophysics]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-May-2016