Search for Pulsations in Hydrogen-Deficient Planetary Nebula Nuclei

Jan-Erik Solheim, ITA,OsloJose M. Gonzalez Perez, IAC, TenerifeGerard Vauclair, Obs-MiP, Toulouse

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

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 PG1159 or O VI spectra

Non sperical planetary nebulae shape

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 7094

NGC 5765

NGC 650-1

FAP = 1/20

IsWe 1

Abell 43

Abell 21

Pulsators detected (or studied in detail):

Name Teff

(kK)

log g Periods

(min)

Comments

Jn 1 150 6.5 7.5, 31 Suspected (BC)

NGC 246 150 5.7 8 - 76 Variable-known

VV 47 130 7.0 2 - 95 Variable

Abell 43 110 5.7 38 - 101 Stable?

NGC 7094 110 5.7 34 - 83 Stable??

NGC 6852(K1-14 type) ? ? 18, 85: Unconfirmed

NGC 2242 11 Maybe var.

PN G118.0-08.6 85, 170 Long period

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 ε-mechanism (unstable)

Change during the same night

Corsico et al.2006

VV 47 compared with predictions

P = 2681- 4130s

(1181- 5682)

And 261s

(132-280)

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 246Rapid 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 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

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)

Corsico et al.2006

NGC 246 compared with predictions

P = 600 - 2000s

No short periods

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)

Abell 43 in June 2004 P=2600,3035s

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

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

Observedand simulatedlight curve(6 periods)

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

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

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

Corsico et al.2006

Abell 43 and NGC 7094 compared with predicitions

Abell 43: 2378-6075 s NGC 7094: 2036-4960 s No short periods

NGC 7094

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 000s and 10 000s ) not present in comparison stars: Double humped orbital period of about 3hrs?

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

Conclusions II

Need better analytical tools for analysis of the unstable light curves....Wavelet analysis..or betterRatios 0.87 for trapped modesHarmonics related to orbital periodsModel predictionsMultisite campaigns