Observations with MOST

Observations with MOST

Pulsations in Wolf-Rayet

stars :

Pulsations in Wolf-Rayet

stars :

André-Nicolas Chené (NRC/HIA/CGO)Anthony F. J. Moffat (Université de

Montréal)

André-Nicolas Chené (NRC/HIA/CGO)Anthony F. J. Moffat (Université de

Montréal)

Wolf-Rayet starsWolf-Rayet stars

• Hot and dense wind• WN and WC

• Hot and dense wind• WN and WC

HeII

HeIIHeII

NIII

CIII

CIV

WN

WC

Evolution of massive stars

Evolution of massive stars

more than 75 M

O WNha → LBV → WN → WC SN

40 to 75 M

O LBV WN → WC SN

25 to 40 M

O WN SN RSG/LBV

Why observe WR star?Why observe WR star?• WR = epitome of hot stars with strong, stable winds• significant contributors to the ecology of the Universe• look for pulsations to (help) drive the winds:

• WR = epitome of hot stars with strong, stable winds• significant contributors to the ecology of the Universe• look for pulsations to (help) drive the winds:

Momentum problem:

[dM/dt v] / [L/c]

< 1 for O stars (~OK),

up to 10+ for WR (OK?)

Strange-Mode Pulsations

Strange-Mode Pulsations

• Glatzel 1993-99-08– Stars with a high L/M, where radiation pressure domines.

– The most violent SMPs are expected in Wolf-Rayet stars.

– Opacity bump due to iron.

– Periods of a few minutes or hours are expected (but, finally, maybe days…).

• Glatzel 1993-99-08– Stars with a high L/M, where radiation pressure domines.

– The most violent SMPs are expected in Wolf-Rayet stars.

– Opacity bump due to iron.

– Periods of a few minutes or hours are expected (but, finally, maybe days…).

Previous results with MOST

Previous results with MOST

Time series Fourier spectrum

Previous results with MOST

Previous results with MOST

Lines ~ 10% of broadband flux & vary relatively little

obs’d photometric variability must be related to pulsations of pulsations of the stellar corethe stellar core!!

delayed reaction of wind (lines) triggered by superposition of pulsation events

Lines ~ 10% of broadband flux & vary relatively little

obs’d photometric variability must be related to pulsations of pulsations of the stellar corethe stellar core!!

delayed reaction of wind (lines) triggered by superposition of pulsation events

WR103

WR123

Previous results with MOST

Previous results with MOST

Stochastic clumps have no effect on period detection

(Moffat et al. 2008)

WR 124WR 124

• WN8(h)– WN8 stars are peculiar:

1) single, 2) high proper motion, 3) far from galactic plane, 4) mostly isolated and 5) very variable

• WN8(h)– WN8 stars are peculiar:

1) single, 2) high proper motion, 3) far from galactic plane, 4) mostly isolated and 5) very variable

Cleaning the Light Curve : WR 124

Cleaning the Light Curve : WR 124

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Cleaning the Light Curve : WR 124

Cleaning the Light Curve : WR 124

WR124WR124

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comp1

comp2

Cleaning the Light Curve : WR 124

Cleaning the Light Curve : WR 124

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comp2

Periodogram : WR 124Periodogram : WR 124

Periodogram : WR 124Periodogram : WR 124

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0.29 c/d

0.71 c/d

P = 1.41 d, 3.45 dP = 1.41 d, 3.45 d

WR124. Levels [4.61/5.99/9.21/10.6] correspond to [90/95/99/99.5]% confidence

Period [days]

0 5 10 15 20 25 30

2

4

6

8

0 5 10 15 20 25 30-0.1

-0.05

0

0.05

0.1

HJD-2451545.0

Δ m

2 4 6 8 10 12 14 16 18

Spectroscopy : WR 124Spectroscopy : WR 124

• EW, skewness & Kurtosis

Binary?:

K=5 km/s Mcomp<2M if

i>10º

• EW, skewness & Kurtosis

Binary?:

K=5 km/s Mcomp<2M if

i>10º(Moffat et al. 2010)

Spectroscopy : WR 124Spectroscopy : WR 124

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WR124(WN8h)

WR123 (WN8)

WR 110WR 110

• WN5-6 (single)– Light-curve

• WN5-6 (single)– Light-curve

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(Chené et al. 2010)

1%

Spectroscopy : WR 110Spectroscopy : WR 110

Binary?: Mcomp<3M if i>20º

Binary?: Mcomp<3M if i>20º

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(Chené et al. 2010)

Spots? : WR 110Spots? : WR 110

€

Δm∝−2.5log(1+ γ sinicos2πφ e−τ )

€

where τ = dτz= z0

∞

∫ = k d za( ) r2 1− R*

r( )β ⎡

⎣ ⎢ ⎤ ⎦ ⎥

−1

z= z0

∞

∫

Lamontagne et al. (1996)

Δm

Δm

Spots+CIRs? : WR 110Spots+CIRs? : WR 110

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Cranmer & Owocki (1996)

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Spots+CIRs? : WR 110Spots+CIRs? : WR 110

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Morel et al. (1997)

WR6HeII4686

Cranmer & Owocki (1996)

Spots+CIRs? : WR 110Spots+CIRs? : WR 110

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WR 1(Chené & St-Louis 2010)

WR 134(Morel et al.1999)

WR 6(Morel et al.1997)

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WR 1

WR 110

WR 6

(Chené et al. 2010)

Origin of CIRsOrigin of CIRs

Magnetic wind or Pulsations

confinement

Magnetic wind or Pulsations

confinement

(R. Townsend, A. Ud-Doula)

The ENDThe END

Thank you very much

Thank you very much

André-Nicolas Chené (NRC/HIA/CGO)Anthony F. J. Moffat (Université de Montréal)

André-Nicolas Chené (NRC/HIA/CGO)Anthony F. J. Moffat (Université de Montréal)