Search for Pulsations in Hydrogen-Deficient Planetary Nebula Nuclei

1. Search for Pulsations in Hydrogen-Deficient Planetary Nebula Nuclei Jan-Erik Solheim, ITA,Oslo Jose M. Gonzalez Perez, IAC, Tenerife Gerard Vauclair, Obs-MiP, Toulouse

2. Content • Introduction, why search for variability? • selection of targets - bipolar nebulae • results of first campaigns – the non pulsators • 3 years of NGC 246 - variability on many time scales • repeated studies of two “hybrid PG 1159 stars” • new results • conclusions

3. The Inspiration In this paper: 6 new pulsators, making a total of 14 PG 1159-035 pulsators or GW Vir stars

4. The basic (1996) results The hot PNNs with O VI (early WC) have: --longer periods than GW Vir white dwarfs --low amplitudes --highly variable temporal spectra on time scales months or less Bond and Ciardullo 1996

5. Our Search Criteria • Hot Hydrogen-Deficient PNNs with PG1159 or O VI spectra • Non sperical planetary nebulae shape Question: Is there any sign of binarity in the temporal spectra? Ex: harmonics

6. Selection of objects – 11 targets

7. Possible Non Pulsators ? NGC 650-1 PG 1520+525 IsWe 1 NGC 7094 NGC 5765 Abell 21 Abell 43 FAP = 1/20

8. Pulsators detected (or studied in detail): Teff and log g from Werner and Herwig 2006

9. NGC 6852 Observed two nights, First night: No Pulsations Next night: At least one pulse

10. VV 47 – highly variable temporal spectra:

11. VV 47 comparison of peaks of different runs • 1,2) Harmonics  Sign of binarity • 3) Ratio 0.87  sign of trapped modes • The high frequency spectrum: g-modes driven by ε-mechanism (unstable) • Change during the same night

12. VV 47 compared with predictions P = 2681- 4130s (1181- 5682) And 261s (132-280) Corsico et al.2006

13. NGC 246 - followed 3 years (2000-2003)16 runs Changes the same night, July 21, 2000 Changes between two nights, July 21-24,2000

14. NGC 246:Changes from night to night –and possible harmonics of 227 μHz (73 min) May we interprete 227 μHz as an orbital period (73 min) ?

15. NCC 246- pulse in burst-morlet wavelet- sudden appearance of periodic signal

16. NGC 246Rapid change of temporal spectrum

17. Harmonics of 227 μHz – sometimes with low amplitudes

18. NGC 246 –pulse shape with period P=4349 s = 72.5 min 2 2 1 3 3

19. NGC 246P=72.5 min is stable over 3 yrs: Orbital period  Most stable Superhump period (in disk)  most harmonics Rotation period  too fast if single star

20. NGC 246 – a binary system with P=72.5 min? • Stable period over 3 yrs • Pulse form varies between single, double and triple humped • Period is close to expected CV minium • He II in emission – sign of accretion • Strong wind works against accretion • Shape of nebulae indicate common envelope interaction with substellar companion – planet or brown dwarf (Soker 1997)

21. NGC 246 compared with predictions P = 600 - 2000s No short periods Corsico et al.2006

22. Abell 43 – pulsate or not pulsate? • Ciardullo & Bond, 1996: possible variations P~2473s • Schuh et al, 2000: P~5500s (2473 is an artifact) • Gonalez Perez et al, 2007: no variations(obs 2000) • Quirion et al. 2004: no pulsations expected (composition) • Vauclair et all, 2005: 2 periods: 2600 and 3035s(not in model with XC=0.05) • Quirion et al. 2005: (new atmosphere –> XC=0.23) predict Pl=1:2604-5529s • Corsico et al 2006, predictions P > 2500 s • Solheim et al., 2007: 6 periods:2380-6075s • (2680 s and 5442s are the strongest ~ 2 mma)

23. Abell 43 in June 2004 P=2600,3035s

24. A43 model (Quirion et al 2005) X(H)=0.35 X(He)=0.42 X(C)=0.22 X(O)=0 X(Z)=0.01

25. Abell 43 observed in 2005: -4 n. (24 hrs) No high freq. peaks, 3 or more low freq. peaks

26. Abell 43: prewhitening – combined light curve 2 3 4 5 6

27. Abell 43Observedand simulatedlight curve(6 periods)

28. NGC 7094 –almost identical to Abell 43 • T=110 000K, log g= 5.7, X(H)=0.35, X(C)=0.23 • Abell 43: X(He)=0.42, X(O)=0.00 • NGC 7094: X(He)=0.41, X(O)=0.01 • Predictions (Quirion et al 2005): • Pl=1(Abell 43): 2604-5529s • NGC 7094: 2550-5413s

30. NGC 7094 –almost identical to Abell 43 • T=110 000K, log g= 5.7, X(H)=0.35, X(C)=0.23 • Abell 43: X(He)=0.42, X(O)=0.00 • NGC 7094: X(He)=0.41, X(O)=0.01 • Predictions (Quirion et al 2005): • P(l=1) Abell 43: 2604-5529s • NGC 7094: 2550-5413s • Observations: • Abell 43: 2378-6075 s somewhat wider than predicted • NGC 7094: 2036-4960 shorter as predicted

31. Abell 43 and NGC 7094 compared with predicitions NGC 7094 • Abell 43: 2378-6075 s • NGC 7094: 2036-4960 s • No short periods Corsico et al.2006

32. New pulsator?NGC 2242 – possible of rapid change type P~11 min First part of night All night

33. New pulsator?PNG 118.0-08.6 (Vy 1-1) – long period Strong modulations (P~5 000s and 10 000s ) not present in comparison stars: Double humped orbital period of about 3hrs?

34. Conclusions I • Abell 43 and NGC 7094 are stable long period pulsators (P > 2000s) • PNG 118.0-08.6 (Vy 1-1): maybe also long period variable, needs confirmation • VV 47 and NGC 246 are rapidly variable – short timescale modulations – long and short periods • Stable long period – maybe orbital (P=72 min for NGC 246) • NGC 2242: maybe rapidly variable, needs confirmation • JN1 and NGC 5852 need confirmation

35. Conclusions II • Need better analytical tools for analysis of the unstable light curves.... • Wavelet analysis..or better • Ratios 0.87 for trapped modes • Harmonics related to orbital periods • Model predictions • Multisite campaigns