J/AJ/127/1579 Abundances of faint M13 stars (Briley+, 2004)
The chemical inhomogeneity of faint M13 stars: carbon and nitrogen abundances.
Briley M.M., Cohen J.G., Stetson P.B.
<Astron. J., 127, 1579-1587 (2004)>
=2004AJ....127.1579B 2004AJ....127.1579B
ADC_Keywords: Clusters, globular ; Abundances ; Photometry
Keywords: globular clusters: general - globular clusters: individual (M13) -
stars: abundances - stars: evolution
Abstract:
Building upon earlier observations that demonstrate substantial
star-to-star differences in the carbon abundances of M13 subgiants, we
present new Keck LRIS spectra reaching more that 1.5mag below the M13
main-sequence turnoff (to V∼20). Our analysis reveals a distribution
of C abundances similar to that found among the subgiants, implying
little change in the compositions of the M13 stars at least through
the main-sequence turnoff. We presume these differences to be the
result of some process operating early in the cluster history.
Additional spectra of previously studied bright M13 giants have been
obtained with the 5m Hale Telescope.
Objects:
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RA (2000) DE Designation(s)
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16 41 41.4 +36 27 37 M 13 = NGC 6205
19 53 46.1 +18 46 42 M 71 = NGC 6838
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 54 51 M13 Current Program Stars: Photometry, Indices,
and Abundances
table4.dat 42 103 M13 Subgiants from Briley & Cohen
(2002ApJ...579L..17B 2002ApJ...579L..17B): Program Stars,
Photometry, Indices, and Abundances
table5.dat 46 76 M71 Subgiants from Briley & Cohen
(2001AJ....122..242B 2001AJ....122..242B): Program Stars,
Photometry, Indices, and Abundances
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See also:
J/AJ/122/3219 : M3 and M13 CCD BV photometry (Rey+, 2001)
J/AJ/120/1364 : Abundances in M3 and M13 (Cavallo+, 2000)
J/A+AS/144/227 : BV photometry of M71 (Geffert+, 2000)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- [BCS2004] Star identification, "MMSSs_MMSS" for position
16:MM:SS.s +36:MM:SS
12- 16 F5.2 mag Vmag The Johnson V-band magnitude
18- 22 F5.2 mag Icmag The Cousins I-band magnitude
24- 27 F4.2 mag V-Ic The (V-Ic) color index
29- 34 F6.3 --- I(CH) Cohen ( 1999AJ....117.2434C 1999AJ....117.2434C) CH index (1)
36- 41 F6.3 --- sNH ? Briley & Smith (1993PASP..105.1260B 1993PASP..105.1260B) NH index
43- 47 F5.2 [---] [C/Fe] ? Logarithm of the carbon-to-iron abundance
49- 53 F5.2 [---] [N/Fe] ? Logarithm of the nitrogen-to-iron abundance
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Note (1): Compares the flux removed by the G band with the adjacent continuum
on both sides.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- [BCS2004] Star identification, "MMSSs_MMSS" for position
16:MM:SS.s +36:MM:SS
12- 16 F5.2 mag Vmag ? The Johnson V-band magnitude
18- 22 F5.2 mag Icmag The Cousins I-band magnitude
24- 27 F4.2 mag V-Ic ? The (V-Ic) color index
29- 34 F6.3 --- I(CH) Cohen (1999AJ....117.2434C 1999AJ....117.2434C) CH index (1)
36- 40 F5.2 [---] [C/Fe] ? Logarithm of the carbon-to-iron abundance
42 A1 --- f_[C/Fe] [a] when [C/Fe] is absent (2)
--------------------------------------------------------------------------------
Note (1): Compares the flux removed by the G band to the adjacent continuum
with both sides.
Note (2): [C/Fe] is not determined for stars near the main-sequence turn-off,
because of the weakness of the CH bands.
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- [BCS2004] Star identification, "CMMSSs+MMSS for position
19:MM:SS.s +18:MM:SS
13- 17 F5.2 mag Rcmag The Cousins R-band magnitude
19- 22 F4.2 mag B-Rc The (B-Rc) band magnitude
24- 28 F5.3 --- I(CH) Cohen (1999AJ....117.2434C 1999AJ....117.2434C) CH index (1)
30- 34 F5.3 --- S(3839) The S(3839) index
36- 40 F5.2 [---] [C/Fe] ? Logarithm of the carbon-to-iron abundance
42- 46 F5.2 [---] [N/Fe] ? Logarithm of the nitrogen-to-iron abundance
--------------------------------------------------------------------------------
Note (1): Compares the flux removed by the G band to the adjacent continuum
with both sides.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 02-Jul-2004