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

2. Age Reddening Metallicity Abundances Astrometric info Variability http://www.astro.ufl.edu/~ata/wocs/ Age Reddening Metallicity Abundances Astrometric info Variability http://www.astro.ufl.edu/~ata/wocs/ WIYN Open Cluster Study Establish a standard database of open clusters

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 TelescopeDates of Obs.(2003) Filter# obs WIYN 0.91m 31 March – 14 Sept R174 USNOFS 1.3m 07 April – 16 Jun R120 WIYN 0.91m 13 Jul BVI3 USNOFS 1m April/June BVRI16

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

8. StrengthsLimitations DAOPHOT/ APPhot ( Stetson, 1987 PASP, v 99, p. 191-222) Aperture/PSF photometry for every star in the image Not optimized for variability studies ASTROVAR (Honeycutt, R.K, 1992, PASP, 104, 435-440) Incomplete ensemble photometry Error analysis & graphics tools Periodogram and light curve folding interface Requires magnitudes as input Data Reduction

9. CMD V R B-V V-R

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

11. Results R R Phase JD - 2452700 V B-V s33 s28 V467Cep V470CepV10 V466Cep V2 V7 V1, V8 V3 V4 V9 V6 V5 P=0.5668d P=1.143d P>95d

12. Oddities

13. NGC 6939 USNOFS 1.3m R- filter

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

15. Conclusions:

16. 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