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Variability Monitoring of NGC 6939: Insights into Open Clusters and Cataclysmic Variables

This study investigates the variability of stars in the open cluster NGC 6939, aiming to establish a comprehensive database to enhance our understanding of cataclysmic variables (CVs) and their environments. Despite the significance of open clusters as laboratories for accretion physics and stellar evolution, our observations reveal a scarcity of known CVs within NGC 6939. We present detailed analyses of variability patterns and discuss the cluster's age, reddening, and metallicity, providing essential data for future research on stellar dynamics and CV phenomena.

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Variability Monitoring of NGC 6939: Insights into Open Clusters and Cataclysmic Variables

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  1. WOCS Variability:Monitoring NGC6939 S. Kafka (IUB) D. Gibbs II (Univ. of Wyoming) A. Henden (US Naval Obs.) R.K.Honeycutt (IUB) BGSU, April 3, 2004

  2. 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/

  3. Our motivation:Cataclysmic 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 ?

  4. Why Open Clusters? • Bonus: age, distance, metallicity • Not many CVs known in globular/open clusters • Only 3 CVs known in all open clusters!

  5. NGC 6939 • Age = 1.6 ± 0.3 Gyr • 0.29 < E(B-V) < 0.41 • 12.21 < m-M < 12.39 (Rosvick & Balam 2002) • [Fe/H] = -0.14±0.13 (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

  6. Data

  7. E NGC 6939 WIYN 0.9m N NGC 6939 USNOFS 1.3m R- filter

  8. Data Reduction

  9. V R V-R B-V CMD

  10. P=0.3548d P=0.4511d P=0.2419d P=0.2946d R R P=0.3601d P=0.2951d P=0.11142d P=0.3379d R R 0 0.5 1 1.5 0 0.5 1 1.5 0 0.5 1 1.5 0 0.5 1 1.5 Phase Phase Results

  11. s28 s33 R V467Cep V470Cep V10 V466Cep V V2 Phase V1, V8 V7 V3 V9 V4 V6 V5 R B-V JD - 2452700 Results P=0.5668d P=1.143d P>95d

  12. Oddities

  13. NGC 6939 USNOFS 1.3m R- filter

  14. V4 NGC 6939 V9 µDe s28 V470 Cep V8 µRA Oddities Glushkova & Rastorguev 1991 Monet et al. 2003 (USNO-B)

  15. Conclusions:

  16. 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

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