WOCS Variability: Monitoring NGC6939

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WOCS VariabilityMonitoring NGC6939

• S. Kafka (IUB)
• D. Gibbs II (Univ. of Wyoming)
• A. Henden (US Naval Obs.)
• R.K.Honeycutt (IUB)

BGSU, April 3, 2004
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WIYN Open Cluster Study
Establish a standard database of open clusters

• Age
• Reddening
• Metallicity
• Abundances
• Astrometric info
• Variability
• http//www.astro.ufl.edu/ata/wocs/

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Our motivationCataclysmic Variables

• Interacting binaries
• WD accretes H-rich material from its low-mass,
  Roche-lobe filling companion
• Unique natural laboratories for studying
• Accretion Physics
• Classical Novae
• SNe Ia progenitors ?

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Why Open Clusters?

• Bonus age, distance, metallicity
• Not many CVs known in globular/open clusters
• Only 3 CVs known in all open clusters!

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NGC 6939

• Age 1.6 0.3 Gyr
• 0.29 lt E(B-V) lt 0.41
• 12.21 lt m-M lt 12.39
• (Rosvick Balam 2002)
• Fe/H -0.140.13
• (Friel et al 2002)
• Variability study 6 vars
• (Robb Cardinal 1998)

Credit J. Burkle, D. Gibbs, D. Hoffmann, S.
Kafka, WIYN 0.9m, IU REU 2003
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Data
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E
NGC 6939 WIYN 0.9m
N
NGC 6939 USNOFS 1.3m R- filter
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Data Reduction
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CMD
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Results
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Results
P0.5668d P1.143d
Pgt95d
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Oddities
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NGC 6939 USNOFS 1.3m R- filter
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Oddities
Glushkova Rastorguev 1991 Monet et al. 2003
(USNO-B)
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Conclusions
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• Conclusions
• No CVs found in the cluster
• Cluster depleted of faint variables???
• Future work
• X-rays?
• More data!
• More Clusters!

Kafka et al, 2004, AJ, 127, 1622