Kick-off meeting SIAMOIS Paris, 15-16 mai 2006 PMS targets Seismology of Herbig stars with SIAMOIS...

Kick-off meeting SIAMOISParis, 15-16 mai 2006 PMS targets

Seismology of Herbigstars with SIAMOIS

Torsten Böhm, Marc-Antoine DupretClaude Catala, Marie-Jo Goupil, Evelyne Alecian

Observatoire de Paris-MeudonObservatoire Midi-Pyrénées


• Main observational properties of Herbig stars

• Seismic potential of Herbig stars:

probing the internal structure of PMS stars

• HD 104237 : a very good target for SIAMOIS

• Discovery of 8 pulsating modes in HD 104237

• Preliminary seismic study of HD 104237

• Improvements expected with SIAMOIS

Let’s talk about…


Herbig Ae/Be stars

- very young pre-main sequence objects- observational definition (Herbig, 1960): - spectral type earlier than F0

- presence of emission lines- embedded region - proximity of reflection nebula

- intermediate masses (1.5 - 8 solar masses)- signs of intense activity and strong stellar winds

- In addition: jets, outflows, IR excess, X-ray sources, presence of CS disks, detection of magnetic fields, ….


HR diagram

ZAMS


Herbig Ae/Be stars

- very young pre-main sequence objects- observational definition (Herbig, 1960): - spectral type earlier than F0

- presence of emission lines- embedded region - proximity of reflection nebula

- intermediate masses (1.5 - 8 solar masses)- signs of intense activity and strong stellar winds

- In addition: jets, outflows, IR excess, X-ray sources, presence of CS disks, detection of magnetic fields, ….


Discovery of pulsating Herbig Ae stars

- theScuti instability strip crosses the location of HAeBes in the HR diagram

- Until now, only some Herbig stars between A2 and F0 have been identified pulsating:

- V588 Mon & - V599 Mon P < 3h (multip.) (Breger,1972)- HR5999 P approx 6 hrs (Kurtz & Marang 1995)- HD 104237 P approx 40 minutes (Donati, 1997)…

+ some recent discoveries (approx 15 stars as of today)


Potential of Herbig stars for asteroseismology

Probing the internal physics of stars in the early stages of evolution

Location of the convective core

Initial nuclearburning (CNO

cycle)


Brunt Vaisala freq.

Evolution tracks

Probing the convective core in the early stages of evolution


Small separation

Comparison PreMS – PostMS frequencies


Potential of Herbig stars for asteroseismology

Probing the internal physics of stars in the early stages of evolution

Location of the convective core

Initial nuclearburning (CNO

cycle)

Internal rotation

Transport of angular momentum


HD 104237 - a PMS prototype star

-Emission line star (Herbig Ae *)

-Southern hemisphere (-78°)

-mV approx 6.5

-Mass: 2.3 solar masses

-Luminosity: 35 solar lum

-Log Teff: 3.93

-Spectral type: A4IVe+sh

-Vsini 12km/s

-Highly active and variable (spectro)

-Stellar wind 500km/s

-Multiple system (+spectrosc. binary)


Previous work…


High resolution spectroscopic data base

SAAO 04/1999 1 weekSAAO 04/2000 1 week GIRAFFE…SAAO 05/2000 2 weeks Mt Stromlo 04/00 1 week

data reduction ESPRIT/ LSD (multiplex information)+ cross-correllation of telluric lines

100m/s precision on vrad (per spectrum)

-1888 spectra- total of 42 nights


Orbital analysis

SAAO AvrilMt Stromlo Avril 2000

SAAO Mai 2000

SAAO Avril 1999

Amplitude!


5 ascertained +3 probable frequencies

Böhm et al. 2004, A&A 427, 907


5 ascertained +3 probable frequencies


1999


1999: 3 probables frequencies…?


2000 (total)


Observations and modelisation 1999

SAAO


Rotational Modulation - 95 hrs Period

Halpha


A: primaryB: secondary

ZAMS

Preliminary seismic study

Van den Ancker et al.Teff=8500 K

Grady et al.Teff=7500 K

Bohm et al. (in prep.)Teff=8250 K



M=2.2 M0

M=2.7 M0


Observed frequencies




M=2.2 M0

M=2.7 M0


Rot. Splitting ? (~ 3Hz)


Second ordereffect

More splittingscould be detected

by SIAMOIS


Small separation (Hz)


Small separation (Hz)

M=2.3 M0 Y=0.27 [Fe/H]=0

M=2.23 M0 Y=0.29 [Fe/H]=0

M=2.41 M0 Y=0.27 [Fe/H]=0.2

( Dif. ~ 0.1 Hz)Possible with

SIAMOIS



Excitation mechanism Unknown up to now

Stochastic excitation

Scuti type -driving

No convection zone

Too high frequencies

RoAp type driving ? Helium settling, winds, magnetic f.

Enhanced -driving in the H partial ionization zone

In collaboration withS. Theado, Liège


Improvements with SIAMOIS

Many new modes

3 – 4 monthsDuty cycle: 90-95 %

Noise level : 0.8-1 m/s (120h)Frequency precision : 0.1 Hz

Rotational splittings

Internal rotation

Small difference

Constraining the Internal physics

Excitation mechanisms


Major results on HD 104237

-Orbital study: mass ratio primary/secondary 1.29 +/- 0.02-Palla & Staler’s evolutionary tracks: secondary K3, 0.5 Lsol

-Multi-periodic pulsations (5 frequencies ascertained + 3 potential)-frequences characteristical of Scuti stars

-Strong variation of amplitudes between seasons

-Coherence of the modes on at least 2 month (resolved periodogram)

-Rotational modulation of 95hrs (to be confirmed)

-Separation between frequencies indicates presence of non-radial modes; first asterosismological models


Next steps-Modeling -Internal structure of HD 104237?

-model of pulsating HD 104237 -> modes -> frequencies-need for precise Teff, log g, metallicities

-Activity -Confirm rotational modulation -Search for correlation of HeI5876A, H alpha with orbital period -Search for accretion tracers CS environment - star-study of the wind-study of the forbidden lines, tracers of CS environment

-Pulsation -systematic search for patterns (dynamical spectra)-2D Periodicity analysis-moment method -Selectif LSD for specific elements ( phase, A?)


First asterosismological models (1)

• Teff = 8250 K• « low » radial modes• large separation not matching


First Asterosismological models (2)

• Teff = 7650 K (?)• « high » radial modes• large separation « matching »

Model by Marc Antoine Dupret, OBSPM, Paris, France

Kick-off meeting SIAMOIS Paris, 15-16 mai 2006 PMS targets Seismology of Herbig stars with SIAMOIS...

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Transcript of Kick-off meeting SIAMOIS Paris, 15-16 mai 2006 PMS targets Seismology of Herbig stars with SIAMOIS...