Search for Pulsations in HydrogenDeficient Planetary Nebula Nuclei
Search for Pulsations in Hydrogen-Deficient Planetary Nebula Nuclei Jan-Erik Solheim, ITA, Oslo Jose M. Gonzalez Perez, IAC, Tenerife Gerard Vauclair, Obs-Mi. P, Toulouse
Content n n n n 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
The Inspiration In this paper: 6 new pulsators, making a total of 14 PG 1159 -035 pulsators or GW Vir stars
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
Our Search Criteria Hot Hydrogen-Deficient PNNs with PG 1159 or O VI spectra n Non sperical planetary nebulae shape n Question: Is there any sign of binarity in the temporal spectra? Ex: harmonics
Selection of objects – 11 targets
Possible Non Pulsators ? PG 1520+525 NGC 650 -1 NGC 7094 Is. We 1 NGC 5765 Abell 43 Abell 21 FAP = 1/20
Pulsators detected (or studied in detail): Name Jn 1 Teff (k. K) 150 log g Periods Comments (min) 6. 5 7. 5, 31 Suspected (BC) NGC 246 150 5. 7 8 - 76 VV 47 130 7. 0 Abell 43 110 5. 7 Variable 2 - 95 38 - 101 Stable? NGC 7094 110 5. 7 34 - 83 Stable? ? NGC 6852(K 1 -14 type) ? ? 18, 85: Unconfirmed NGC 2242 11 Maybe var. PN G 118. 0 -08. 6 85, 170 Long period Variable-known Teff and log g from Werner and Herwig 2006
NGC 6852 Observed two nights, First night: No Pulsations Next night: At least one pulse
VV 47 – highly variable temporal spectra:
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 εmechanism (unstable) Change during the same night
VV 47 compared with predictions P = 2681 - 4130 s (1181 - 5682) And 261 s (132 -280) Corsico et al. 2006
NGC 246 - followed 3 years (2000 -2003) 16 runs Changes the same night, July 21, 2000 Changes between two nights, July 21 -24, 2000
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) ?
NCC 246 - pulse in burst -morlet wavelet - sudden appearance of periodic signal
NGC 246 Rapid change of temporal spectrum
Harmonics of 227 μHz – sometimes with low amplitudes
NGC 246 – pulse shape with period P=4349 s = 72. 5 min 2 2 1 3 3
NGC 246 P=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
NGC 246 – a binary system with P=72. 5 min? n n n 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)
NGC 246 compared with predictions P = 600 - 2000 s No short periods Corsico et al. 2006
Abell 43 – pulsate or not pulsate? n n n n Ciardullo & Bond, 1996: possible variations P~2473 s Schuh et al, 2000: P~5500 s (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 3035 s(not in model with XC=0. 05) Quirion et al. 2005: (new atmosphere –> XC=0. 23) predict Pl=1: 2604 -5529 s Corsico et al 2006, predictions P > 2500 s Solheim et al. , 2007: 6 periods: 2380 -6075 s ¨ (2680 s and 5442 s are the strongest ~ 2 mma)
Abell 43 in June 2004 P=2600, 3035 s
A 43 model (Quirion et al 2005) X(H)=0. 35 X(He)=0. 42 X(C)=0. 22 X(O)=0 X(Z)=0. 01
Abell 43 observed in 2005: -4 n. (24 hrs) No high freq. peaks, 3 or more low freq. peaks
Abell 43: prewhitening – combined light curve 2 3 4 5 6
Abell 43 Observed and simulated light curve (6 periods)
NGC 7094 –almost identical to Abell 43 n T=110 000 K, log g= 5. 7, X(H)=0. 35, X(C)=0. 23 n Abell 43: X(He)=0. 42, X(O)=0. 00 NGC 7094: X(He)=0. 41, X(O)=0. 01 n n Predictions (Quirion et al 2005): ¨ Pl=1(Abell 43): 2604 -5529 s ¨ NGC 7094: 2550 -5413 s
Freq (μHz) Per (s) Ampl (mma) 202 4960 2. 7 335 2989 1. 7 490 2036 1. 0
NGC 7094 –almost identical to Abell 43 n T=110 000 K, log g= 5. 7, X(H)=0. 35, X(C)=0. 23 n Abell 43: X(He)=0. 42, X(O)=0. 00 NGC 7094: X(He)=0. 41, X(O)=0. 01 n n n Predictions (Quirion et al 2005): ¨ P(l=1) Abell 43: 2604 -5529 s ¨ NGC 7094: 2550 -5413 s Observations: ¨ Abell 43: 2378 -6075 s somewhat wider than predicted ¨ NGC 7094: 2036 -4960 shorter as predicted
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
New pulsator? NGC 2242 – possible of rapid change type P~11 min First part of night All night
New pulsator? PNG 118. 0 -08. 6 (Vy 1 -1) – long period Strong modulations (P~5 000 s and 10 000 s ) not present in comparison stars: Double humped orbital period of about 3 hrs?
Conclusions I n n n Abell 43 and NGC 7094 are stable long period pulsators (P > 2000 s) 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 n 2242: maybe rapidly variable, needs confirmation JN 1 and NGC 5852 need confirmation
Conclusions II n 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
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