Details

Autor(en) / Beteiligte

• PLATAIS, I
• Melo, C
• Quinn, S N
• Clem, J L
• de Mink, S E
• Dotter, A
• KOZHURINA-PLATAIS, V
• Latham, D W
• Bellini, A

Titel

THE EFFECTS OF DIFFERENTIAL REDDENING AND STELLAR ROTATION ON THE APPEARANCE OF MULTIPLE POPULATIONS IN STAR CLUSTERS: THE CASE OF TRUMPLER 20

Ist Teil von

• Astrophysical journal. Letters, 2012-05, Vol.751 (1), p.1-6

Ort / Verlag

United States

Erscheinungsjahr

2012

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• We present a detailed analysis of the upper main sequence of the ~1.3 Gyr old open cluster Trumpler 20. High-accuracy BVI photometry combined with the Very Large Telescope/FLAMES medium-resolution spectroscopy of 954 stars is essential to understanding the unusual appearance of the color-magnitude diagram (CMD), initially suggesting multiple populations in Trumpler 20. We show that differential reddening is a dominant contributor to the apparent splitting/widening of the main-sequence turnoff region. At its extreme, the excess differential reddening reaches A (B - V) ~ 0.1 while the adopted minimum reddening for the cluster is E(B - V) = 0.36. A unique sample of measured projected rotational velocities indicates that stellar rotation is high near the main-sequence turnoff, reaching v sin i ~ 180 km s super(-1). By dividing the upper main-sequence stars into two equal groups of slow and fast rotators, we find that fast rotators have a marginal blueshift of delta (V - I) ~ -0.01, corresponding to a difference in the median v sin i of ~60 km s super(-1) between these subsamples. We conclude that stellar rotation has an insignificant effect on the morphology of the upper main sequence of this intermediate-age open cluster. Trumpler 20 appears to contain a single coeval population of stars but there is evidence that the red clump is extended.