Rotating Stellar Models Can Account for the Extended Main-sequence Turnoffs in Intermediate-age Clusters

Brandt, Timothy D. and Huang, Chelsea X. ORCID: (2015) Rotating Stellar Models Can Account for the Extended Main-sequence Turnoffs in Intermediate-age Clusters. The Astrophysical Journal, 807 (1):25. pp. 1-7. ISSN 1538-4357

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We show that the extended main-sequence turnoffs seen in intermediate-age Large Magellanic Cloud (LMC) clusters, often attributed to age spreads of several 100 Myr, may be easily accounted for by variable stellar rotation in a coeval population. We compute synthetic photometry for grids of rotating stellar evolution models and interpolate them to produce isochrones at a variety of rotation rates and orientations. An extended main-sequence turnoff naturally appears in color-magnitude diagrams at ages just under 1 Gyr, peaks in extent between ∼1 and 1.5 Gyr, and gradually disappears by around 2 Gyr in age. We then fit our interpolated isochrones by eye to four LMC clusters with very extended main-sequence turnoffs: NGC 1783, 1806, 1846, and 1987. In each case, stellar populations with a single age and metallicity can comfortably account for the observed extent of the turnoff region. The new stellar models predict almost no correlation of turnoff color with rotational v{sin}i. The red part of the turnoff is populated by a combination of slow rotators and edge-on rapid rotators, while the blue part contains rapid rotators at lower inclinations.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 31 Mar 2022 01:22
Last Modified: 31 Mar 2022 01:22
Uncontrolled Keywords: galaxies: clusters: general; galaxies: clusters: individual (NGC 1783, NGC 1806, NGC 1846, NGC 1987); Hertzsprung-Russell and C-M diagrams; Magellanic Clouds; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
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