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The white dwarf cooling sequence in NGC 6791

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 نشر من قبل Luigi Bedin Rolly
 تاريخ النشر 2005
  مجال البحث فيزياء
والبحث باللغة English
 تأليف L. R. Bedin




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In the old, populous, and metal-rich open cluster NGC 6791 we have used deep HST/ACS images to track the white dwarf cooling sequence down to m_F606W~28.5. The white dwarf luminosity function shows a well defined peak at m_F606W~27.4, and a bending to the blue in the color--magnitude diagram. If this peak corresponds to the end of the white dwarf cooling sequence the comparison with theoretical isochrones provides a cluster age estimate of ~2.4 Gyr, in sharp contrast with the age of 8--9 Gyr inferred from the main-sequence turn-off. If the end is at fainter magnitudes, the peak at m_F606W~27.4 is even more enigmatic. We discuss possible causes, none of them very convincing.



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