Seismology of Herbig stars with SIAMOIS

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Seismology of Herbigstars with SIAMOIS

• Torsten Böhm, Marc-Antoine Dupret
• Claude Catala, Marie-Jo Goupil, Evelyne Alecian
• Observatoire de Paris-Meudon
• Observatoire Midi-Pyrénées

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Lets talk about

• 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

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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, .

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HR diagram
ZAMS
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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, .

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Discovery of pulsating Herbig Ae stars

• - the d Scuti 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 lt 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)

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Potential of Herbig stars for asteroseismology
Probing the internal physics of stars in the
early stages of evolution
Location of the convective core
Initial nuclear burning (CNO cycle)
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Probing the convective core in the early stages
of evolution
Evolution tracks
Brunt Vaisala freq.
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Comparison PreMS PostMS frequencies
Small separation
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Potential of Herbig stars for asteroseismology
Probing the internal physics of stars in the
early stages of evolution
Location of the convective core
Initial nuclear burning (CNO cycle)
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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 A4IVesh
• Vsini 12km/s
• Highly active and variable (spectro)
• Stellar wind 500km/s
• Multiple system (spectrosc. binary)

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Previous work
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High resolution spectroscopic data base

• SAAO 04/1999 1 week
• SAAO 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

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SAAO at Sutherland
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Orbital analysis
SAAO Avril Mt Stromlo Avril 2000
SAAO Mai 2000
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5 ascertained 3 probable frequencies
Böhm et al. 2004, AA 427, 907
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5 ascertained 3 probable frequencies
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1999
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1999 3 probables frequencies?
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2000 (total)
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Observations and modelisation 1999
SAAO
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Rotational Modulation - 95 hrs Period
Halpha
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Preliminary seismic study
ZAMS
A primary B secondary
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Preliminary seismic study
M2.7 M0
M2.2 M0
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Preliminary seismic study
Observed frequencies
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Preliminary seismic study
M2.7 M0
M2.2 M0
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Preliminary seismic study
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Preliminary seismic study
M2.7 M0
M2.2 M0
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Second order effect
More splittings could be detected by SIAMOIS
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Small separation (mHz)
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Small separation (mHz)
M2.3 M0 Y0.27 Fe/H0
M2.23 M0 Y0.29 Fe/H0
M2.41 M0 Y0.27 Fe/H0.2
( Dif. 0.1 mHz) Possible with SIAMOIS
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Preliminary seismic study
Excitation mechanism
Unknown up to now
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Improvements with SIAMOIS
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Major results on HD 104237

• -Orbital study mass ratio primary/secondary 1.29
  /- 0.02
• Palla Stalers evolutionary tracks secondary
  K3, 0.5 Lsol
• Multi-periodic pulsations (5 frequencies
  ascertained 3 potential)
• frequences characteristical of d 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

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Next steps

• -Modeling -Internal structure of HD 104237?
• -model of pulsating HD 104237 -gt modes -gt
  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 (D phase, A?)

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First asterosismological models (1)

• Teff 8250 K
•  low  radial modes
• large separation not matching

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First Asterosismological models (2)

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

Model by Marc Antoine Dupret, OBSPM, Paris, France