FLUORINE VARIATIONS IN THE GLOBULAR CLUSTER NGC 6656 (M22): IMPLICATIONS FOR INTERNAL ENRICHMENT TIMESCALES

Journal Article · Sun Jan 20 04:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/763/1/22· OSTI ID:22167215

D'Orazi, Valentina ^[1]; Lucatello, Sara; Gratton, Raffaele G. ^[2]; Lugaro, Maria; Angelou, George ^[3]; Bragaglia, Angela; Carretta, Eugenio ^[4]; Alves-Brito, Alan ^[5]; Ivans, Inese I. ^[6]; Masseron, Thomas ^[7]; Mucciarelli, Alessio ^[8]

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1. Department of Physics and Astronomy, Macquarie University, Balaclava Road, North Ryde, NSW 2109 (Australia)
2. INAF Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, I-35122 Padova (Italy)
3. Monash Centre for Astrophysics (MoCA), School of Mathematical Sciences, Building 28, Monash University, Clayton, VIC 3800 (Australia)
4. INAF Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
5. Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia)
6. Department of Physics and Astronomy, The University of Utah, 115 South 1400 East, Salt Lake City, UT 84112-0830 (United States)
7. Institut d'Astronomie et d'Astrophysique, Universite libre de Bruxelles, Boulevard du Triomphe, B-1050, Brussels (Belgium)
8. Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, I-40127 Bologna (Italy)

Observed chemical (anti)correlations in proton-capture elements among globular cluster stars are presently recognized as the signature of self-enrichment from now extinct, previous generations of stars. This defines the multiple population scenario. Since fluorine is also affected by proton captures, determining its abundance in globular clusters provides new and complementary clues regarding the nature of these previous generations and supplies strong observational constraints to the chemical enrichment timescales. In this paper, we present our results on near-infrared CRIRES spectroscopic observations of six cool giant stars in NGC 6656 (M22): the main objective is to derive the F content and its internal variation in this peculiar cluster, which exhibits significant changes in both light- and heavy-element abundances. Across our sample, we detected F variations beyond the measurement uncertainties and found that the F abundances are positively correlated with O and anticorrelated with Na, as expected according to the multiple population framework. Furthermore, our observations reveal an increase in the F content between the two different sub-groups, s-process rich and s-process poor, hosted within M22. The comparison with theoretical models suggests that asymptotic giant stars with masses between 4 and 5 M {sub Sun} are responsible for the observed chemical pattern, confirming evidence from previous works: the difference in age between the two sub-components in M22 must be not larger than a few hundred Myr.

• OSTI ID: 22167215
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 763; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
ASYMPTOTIC SOLUTIONS
CAPTURE
COMPARATIVE EVALUATIONS
CORRELATIONS
COSMIC PROTONS
ELEMENT ABUNDANCE
ENRICHMENT
FLUORINE
GIANT STARS
LIMITING VALUES
MASS
NEAR INFRARED RADIATION
S PROCESS
STAR CLUSTERS
VARIATIONS