UF Astronomy Colloquium

  • 21 Apr 2016
  • 12:45 PM - 1:45 PM
  • Room 217 of Bryant Space Science Building, University of Florida

Title: The Young Open Cluster Berkeley 87 -- A Very Curious Mess

This week’s colloquium will be given by Dr. Paul Eskridge

Berkeley 87 is a nearby (D = 0.9 to 1.2 kpc), young (age estimated between 1 and 5 Myr) open cluster in Cygnus.  It is part of the Cyg OB star forming complex, and appears to be related to the Cyg ON2 molecular cloud complex.  One of its members, St 3, is the nearest known WO star. The interaction of the stellar wind from St 3 and the embedded ISM is apparently the source of the x-ray and gamma ray emission from the cluster. The cluster also contains V439 Cyg, an evolved star that has changed from having a late-type spectrum in 1950 to having an O9/B0 spectrum in the 1990s. However there has been only one photometric study of Berkeley 87, published in the early 1980s and based on photoelectric and photographic data. One possible reason for this is the large and variable foreground extinction (E(B-V) averages 1.4 mag, and Av ranges from  0 up to 5 mag).  This makes analysing photometric data for the cluster a great challenge.  I discuss new CCD observations of the cluster core that extend some 4 mag fainter than the earlier data.  The new observations were obtained with the 0.5 m telescope at Andreas Observatory.  These, along with archival NIR data from the 2MASS catalog allow a much deeper study of the cluster contents, and demonstrate evidence for an age range in the cluster stars.

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