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Bucharest,  8 - 12 April 2008
B star seismology W.A. Dziembowski, Warsaw
University Obsevatory and Copernicus
Astronomical Center
BRITE WorkShop
Vienna, July 1-4, 2008
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B star seismology
goals
To improve data on massive main sequence stars
To constrain parameters of stellar modeling
To determine interior rotation rate
contexts
Be and Bp stars
Distances and ages of young stellar systems.
Chemical evolution of galaxies
tools
Interpretation of frequency and amplitude data
Construction of seismic stellar models
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Unsolved problems in modeling upper MS stars
Macroscopic mixing processes overshooting,
semiconvection , meridional cirulation, rotation
induced turbulence
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Unsolved problems in modeling upper MS stars
macroscopic mixing processes overshooting,
semiconveciton , meridional cirulation, rotation
induced turbulence size of the mixed
core element abundance in atmosphere
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Unsolved problems in modeling upper MS stars
macroscopic mixing processes overshooting,
semiconvection , meridional cirulation, rotation
induced turbulence size of the mixed
core element abundance in atmosphere
evolution of internal rotation merdional,
circulation, viscous and magnetic torque, (e.g.
Meynet 2008, Spruit 2006).
Active role of oscillations (Ando 1983, Lee
Saio 1993)
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Unsolved problems in modeling upper MS stars
macroscopic mixing processes overshooting,
semiconvection , meridional cirulation, rotation
induced turbulence size of the mixed
core element abundance in atmosphere
evolution of internal rotation merdional,
circulation, viscous and magnetic torque, (e.g.
Meynet 2008, Spruit 2006).
Active role of oscillations (Ando 1983, Lee
Saio 1993)
mass and angular momentum loss
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Estimate of internal rotation rate is the most
important task for B star seismology
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B-type pulsators progenitors of Cepheids, White
Dwarfs and SNe
SNe
?
WDs
from PamyatnykhZdravkov (2007)
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Two instability domains and single driving
mechanism
two types of unstable modes ? two instability
domains
low order g- and p-modes ? ? Cep
high order g-modes ? SPB
there are hybrid pulsators
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There are both very rapid and very slow rotators
among B-type pulsators
Rapid rotation does not change the essence of
the driving mechanism
Downward extention of the instability
domain Savonije, Townsend (2005) , Lee (2006)
Large extention of frequency range (in the
inertial frame)
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? Cephei stars excellent targets for BRITE
almost ignored by MOST
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• b Cep stars
• data after Stankov Handler (2005)
• 93 stars
• periods 0.05-0.32 d
• AVlt0.1 mag
• BRITE Catalogue
• Vlt4 29 stars
• Vlt6 68 stars

PamyatnykhZdravkov 2007
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Two encouraging examples

? Eridani V3.9 mag Handler et al. 2003 Aerts et
al. 2003 De Rider et al. 2004 Jerzykiewicz et
al. 2005
12 Lacertae V5.3 mag Handler et al. 2006
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Finding l s, and ms
mode amplitudes from multiband data
For slow rotators
temperature
geometry
f may be calculated, eliminated or determined and
used as a constraint (Jagoda D.-D. and Rafa G.
talks)
For rapid rotators
more complicated but doable (D.-D. et al.2007)
ms from fitting line profile changes
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Seismic models of n Eri and 12 Lac
DP (2008)
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? Eri Fitting frequencies of the l0 and two
l1 modes constraints on ?ov
Constraint on ?ov rests on accuracy of Teff
from Pamyatnykh et al.. 2004. also Ausselos et
al.. 2004
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Seismic models of ? Eri dependence on opacity
and the mixture
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Seismic models of n Eri with two overshooting
parameters
DP (2008)
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More modes more constraints

• ? Eri observed minus calculated frequencies
• prospects for learning more about overshooting
• the problem with fitting l1, p2 mode

DP (2008)
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Probing internal rotation
? Eri
?c/?egt5.5 , Vrot6 km/s
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A more difficult case 12 Lac faster rotation,
lack of complete multiplets
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12 Lac calculated frequencies of all l ?2
modes in seismic models based on four dominant
peaks. Measured peak frequencies shown as bars.
DP (2008)
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More work on the theory side is still needed.
Instability coefficient (normalized growth
rate) in models of n Eri and 12 Lac (OP, A04)
DP2008
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A plea to the BRITE Consortium for more
frequencies in individual objects, especially
for missing components of multiplets.
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Detected modes do not saturate driving - there
must be more excited modes
Finite ampliude devlopement of radial mode
instability
Nonlinear modeling of radial modes (Smolec
Moskalik, 2007)
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A plea to the BRITE Consortium for more
frequencies in individual objects, especially
for missing components of multiplets.
There must be more excited modes but we cannot be
sure that these are the ones we most need.
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A plea to the BRITE Consortium for more
frequencies in individual objects, especially
for missing components of multiplets.
There must be more excited modes but we cannot be
sure that these are the ones we most need.
In order to disentangle role of rotation in
element mixing it is important to have data on
slowly and rapidly rotating stars
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SPB stars
intriguing data from MOST
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• SPB stars
• Data after De Cat et al.. (2006-2007)
• gt90 known
• Periods 0.4-5.0 d
• AVlt0.03 mag
• BRITE Catalogue
• Vlt4 3 stars
• Vlt6 6 stars

PamyatnykhZdravkov 2007
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A slowly rotating SPB star (?rot0.035 d-1?)
B5II/III V9.3 mag
from Aerts et al.(2006)
nearly equidistant pattern
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A slowly rotating SPB star (?rot0.035 d-1?)
g-mode asymototics
?rot0.053 d-1?
from Aerts et al.(2006)
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No seismic model yet for HD 163830 nor for any
SPB star
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The most interesting result from MOST rich
oscillation spectra of five SPB stars
HD 163868 (B5 Ve, vsin i250 km/s)
B (l2, m2)
A (l1, m-1)
B (l1, m1)
from (Walker et al.. 2005)
m gt0 prograde
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Similar pattern in three SPBe stars, in ?CMi
only sequence B. in all the cases consistent
with the critical rotation rate
from (Cameron et al.. 2008)
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Do consecutive peaks within sequences correspond
to consecutive modes?
NO In the case of HD 127756 and 217543 (Cameron
et al.2008) BUT
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Peaks in the C sequence interpreted as l2 m2
modes
unstable modes (n--29-15) frequencies from (D.
et al. 2007)
prospects for a fit ? differential rotation ?
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A plea to the BRITE Consortium for more
oscillation spectra of Be stars
Good frequency resolution important !