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Author name code: provost
ADS astronomy entries on 2022-09-14
author:"Provost, Janine"
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Title: Detection of g modes in the asymptotic frequency range:
evidence for a rapidly rotating core
Authors: Ulrich, Roger K.; Fossat, Eric; Boumier, Patrick; Corbard,
Thierry; Provost, Janine; Salabert, David; Schmider, François-Xavier;
Gabriel, Alan; Grec, Gerard; Renaud, Catherine; Robillot, Jean-Maurice;
Roca Cortés, Teodoro; Turck-Chièze, Sylvaine
2017SPD....4810906U Altcode:
We present the identification of very low frequency g modes, in the
asymptotic regime, and two important parameters: the core rotation rate
and the asymptotic equidistant period spacing of these g modes. The
GOLF instrument on the SOHO space observatory has provided two
decades of full disk helioseismic data. The search for g modes in
GOLF measurements has been extremely difficult, due to solar and
instrumental noise. In the present study, the p modes of the GOLF
signal are analyzed differently, searching for possible collective
frequency modulations produced by periodic changes in the deep solar
structure. Such modulations provide access to only very low frequency
g modes, thus allowing statistical methods to take advantage of their
asymptotic properties. For oscillatory periods in the range between 9
and nearly 48 hours, almost 100 g modes of spherical harmonic degree
1 and more than 100 g modes of degree 2 are predicted. They are not
observed individually, but when combined, they unambiguously provide
their asymptotic period equidistance and rotational splittings,
in excellent agreement with the requirements of the asymptotic
approximations. P0, the g-mode period equidistance parameter, is
measured to be 34 min 01 s, with a 1 s uncertainty. The previously
unknown g-mode splittings have now been measured from a non synodic
reference with a very high accuracy, and they imply a mean weighted
rotation of 1277 ± 10 nHz (9-day period) of their kernels, resulting
in a rapid rotation frequency of 1644 ± 23 nHz (period of one week)
of the solar core itself, which is a factor 3:8 ± 0:1 faster than the
rotation of the radiative envelope.Acknowledgements. Ulrich is first
author on this abstract due to AAS rules, Fossat is the actual first
author. SOHO is a project of international collaboration between ESA and
NASA. We would like to acknowledge the support received continuously
during more than 3 decades from CNES. DS acknowledges the financial
support from the CNES GOLF grant and the Observatoire de la Côte
d’Azur for support during his stays. RKU acknowledges support from
NASA for his participation in this project and thanks John Bahcall
for enthusiastic encouragement for the g-mode search.
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Title: Asymptotic g modes: Evidence for a rapid rotation of the
solar core
Authors: Fossat, E.; Boumier, P.; Corbard, T.; Provost, J.; Salabert,
D.; Schmider, F. X.; Gabriel, A. H.; Grec, G.; Renaud, C.; Robillot,
J. M.; Roca-Cortés, T.; Turck-Chièze, S.; Ulrich, R. K.; Lazrek, M.
2017A&A...604A..40F Altcode: 2017arXiv170800259F
Context. Over the past 40 years, helioseismology has been enormously
successful in the study of the solar interior. A shortcoming has
been the lack of a convincing detection of the solar g modes, which
are oscillations driven by gravity and are hidden in the deepest
part of the solar body - its hydrogen-burning core. The detection
of g modes is expected to dramatically improve our ability to model
this core, the rotational characteristics of which have, until now,
remained unknown. <BR /> Aims: We present the identification of very
low frequency g modes in the asymptotic regime and two important
parameters that have long been waited for: the core rotation rate,
and the asymptotic equidistant period spacing of these g modes. <BR />
Methods: The GOLF instrument on board the SOHO space observatory has
provided two decades of full-disk helioseismic data. The search for
g modes in GOLF measurements has been extremely difficult because of
solar and instrumental noise. In the present study, the p modes of the
GOLF signal are analyzed differently: we search for possible collective
frequency modulations that are produced by periodic changes in the
deep solar structure. Such modulations provide access to only very low
frequency g modes, thus allowing statistical methods to take advantage
of their asymptotic properties. <BR /> Results: For oscillatory
periods in the range between 9 and nearly 48 h, almost 100 g modes
of spherical harmonic degree 1 and more than 100 g modes of degree 2
are predicted. They are not observed individually, but when combined,
they unambiguously provide their asymptotic period equidistance and
rotational splittings, in excellent agreement with the requirements
of the asymptotic approximations. When the period equidistance has
been measured, all of the individual frequencies of each mode can
be determined. Previously, p-mode helioseismology allowed the g-mode
period equidistance parameter P<SUB>0</SUB> to be bracketed inside a
narrow range, between approximately 34 and 35 min. Here, P<SUB>0</SUB>
is measured to be 34 min 01 s, with a 1 s uncertainty. The previously
unknown g-mode splittings have now been measured from a non-synodic
reference with very high accuracy, and they imply a mean weighted
rotation of 1277 ± 10 nHz (9-day period) of their kernels, resulting
in a rapid rotation frequency of 1644 ± 23 nHz (period of one week)
of the solar core itself, which is a factor 3.8 ± 0.1 faster than the
rotation of the radiative envelope. <BR /> Conclusions: The g modes
are known to be the keys to a better understanding of the structure
and dynamics of the solar core. Their detection with these precise
parameters will certainly stimulate a new era of research in this field.
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Title: Evolution of lithium abundance in the Sun and solar twins
Authors: Thévenin, F.; Oreshina, A. V.; Baturin, V. A.; Gorshkov,
A. B.; Morel, P.; Provost, J.
2017A&A...598A..64T Altcode: 2016arXiv161201331T
Evolution of the <SUP>7</SUP>Li abundance in the convection zone of the
Sun during different stages of its life time is considered to explain
its low photospheric value in comparison with that of the solar system
meteorites. Lithium is intensively and transiently burned in the early
stages of evolution (pre-main sequence, pMS) when the radiative core
arises, and then the Li abundance only slowly decreases during the
main sequence (MS). We study the rates of lithium burning during these
two stages. In a model of the Sun, computed ignoring pMS and without
extra-convective mixing (overshooting) at the base of the convection
zone, the lithium abundance does not decrease significantly during the
MS life time of 4.6 Gyr. Analysis of helioseismic inversions together
with post-model computations of chemical composition indicates the
presence of the overshooting region and restricts its thickness. It
is estimated to be approximately half of the local pressure scale
height (0.5H<SUB>P</SUB>) which corresponds to 3.8% of the solar
radius. Introducing this extra region does not noticeably deplete
lithium during the MS stage. In contrast, at the pMS stage, an
overshooting region with a value of approximately 0.18H<SUB>P</SUB>
is enough to produce the observed lithium depletion. If we conclude
that the dominant lithium burning takes place during the pMS stage,
the dispersion of the lithium abundance in solar twins is explained
by different physical conditions, primarily during the early stage of
evolution before the MS.
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Title: a Brief History of the Energy-Momentum Tensor: 1900-1912
Authors: Provost, J. -P.
2015mgm..conf.2054P Altcode:
A critical look at the history of relativistic dynamics.
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Title: Asymptotic and measured large frequency separations
Authors: Mosser, B.; Michel, E.; Belkacem, K.; Goupil, M. J.; Baglin,
A.; Barban, C.; Provost, J.; Samadi, R.; Auvergne, M.; Catala, C.
2013A&A...550A.126M Altcode: 2012arXiv1212.1687M
Context. With the space-borne missions CoRoT and Kepler, a large
amount of asteroseismic data is now available and has led to a variety
of work. So-called global oscillation parameters are inferred to
characterize the large sets of stars, perform ensemble asteroseismology,
and derive scaling relations. The mean large separation is such a key
parameter, easily deduced from the radial-frequency differences in
the observed oscillation spectrum and closely related to the mean
stellar density. It is therefore crucial to measure it with the
highest accuracy in order to obtain the most precise asteroseismic
indices. <BR /> Aims: As the conditions of measurement of the large
separation do not coincide with its theoretical definition, we revisit
the asymptotic expressions used for analyzing the observed oscillation
spectra. Then, we examine the consequence of the difference between
the observed and asymptotic values of the mean large separation. <BR
/> Methods: The analysis is focused on radial modes. We use series of
radial-mode frequencies in published analyses of stars with solar-like
oscillations to compare the asymptotic and observational values of
the large separation. This comparison relies on the proper use of the
second-order asymptotic expansion. <BR /> Results: We propose a simple
formulation to correct the observed value of the large separation
and then derive its asymptotic counterpart. The measurement of the
curvature of the radial ridges in the échelle diagram provides the
correcting factor. We prove that, apart from glitches due to stellar
structure discontinuities, the asymptotic expansion is valid from
main-sequence stars to red giants. Our model shows that the asymptotic
offset is close to 1/4, as in the theoretical development, for low-mass,
main-sequence stars, subgiants and red giants. <BR /> Conclusions:
High-quality solar-like oscillation spectra derived from precise
photometric measurements are definitely better described with the
second-order asymptotic expansion. The second-order term is responsible
for the curvature observed in the échelle diagrams used for analyzing
the oscillation spectra, and this curvature is responsible for the
difference between the observed and asymptotic values of the large
separation. Taking it into account yields a revision of the scaling
relations, which provides more accurate asteroseismic estimates
of the stellar mass and radius. After correction of the bias (6%
for the stellar radius and 3% for the mass), the performance of the
calibrated relation is about 4% and 8% for estimating, respectively,
the stellar radius and the stellar mass for masses less than 1.3
M<SUB>⊙</SUB>; the accuracy is twice as bad for higher mass stars
and red giants. <P />Table 1 is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>
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Title: Low frequency signal in the GOLF measurements
Authors: Grec, G.; Provost, J.; Renaud, C.
2011JPhCS.271a2050G Altcode:
This paper shows the results obtained using a revisited method to
normalize the velocity evaluation extracted from the measurements, for
roughly 14 years of GOLF data. For the search of g modes, we calculate
the low frequency power spectrum of the signal with 2 different
approaches: • The classical calculation of the power spectrum of the
velocity signal. • An alternative calculation, extracting first the
variations along the time of the p-mode frequencies, then calculating
the power spectrum of those frequency modulation [4]. Both spectra
are compared to the g-mode frequency spectrum calculated for a solar
model. Several observed frequencies are in close agreement with the
calculated g modes. A careful statistical analysis of this result
should now follow.
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Title: Open issues in probing interiors of solar-like oscillating
main sequence stars: 2. Diversity in the HR diagram
Authors: Goupil, M. J.; Lebreton, Y.; Marques, J. P.; Deheuvels, S.;
Benomar, O.; Provost, J.
2011JPhCS.271a2032G Altcode: 2011arXiv1102.0252G
We review some major open issues in the current modelling of low
and intermediate mass, main sequence stars based on seismological
studies. The solar case was discussed in a companion paper, here
several issues specific to other stars than the Sun are illustrated
with a few stars observed with CoRoT and expectations from Kepler data.
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Title: Implications of a new triple-α nuclear reaction
rate. Consequences for Cepheids
Authors: Morel, P.; Provost, J.; Pichon, B.; Lebreton, Y.; Thévenin,
F.
2010A&A...520A..41M Altcode:
Context. Recently the triple-α reaction rate has been re-evaluated. In
the temperature range, 10<SUP>7</SUP>-10<SUP>8</SUP> K, with
respect to the NACRE rate, the new rate is enhanced by up to 20
orders-magnitude. <BR /> Aims: To validate this new rate, we investigate
its consequences for the evolution of Cepheid models. <BR /> Methods:
The stellar evolutionary tracks are calculated with the CESAM code
and displayed in the domain 4-10 M_⊙. <BR /> Results: With the
new rate, the first dredge-up does not occur. For masses larger than
gse 4.5 M_⊙ each evolutionary track crosses the instability strip
only once. The luminosities are higher than with the previous rate,
then leading to smaller theoretical masses that better agree with the
pulsational mass. Conversely, and inconsistently with one century of
observations of more than two hundred Cepheids, the temporal derivative
of the period keeps a positive sign. Moreover the observed depletions of
atmospheric lithium and C/N ratio do not occur. A slight modification
of only a few percents of the new nuclear rate allows us however
to restore the loops inside the instability strip and the changes
of sign of the temporal derivative of periods. <BR /> Conclusions:
This preliminary work indicates that the new rate may solve some
of the long-lasting unsolved theoretical problems of Cepheids. Yet
indisputable observations argue against its pertinence. Nonetheless,
with regard to its theoretical importance, the triple-α new reaction
rate still needs to be confirmed or revisited.
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Title: Sensitivity of the sub-photospheric flow fields inferred from
ring-diagram analysis to the change on the solar model
Authors: Zaatri, A.; Provost, J.; Corbard, T.; Roth, M.
2010Ap&SS.328..135Z Altcode: 2007arXiv0704.2294Z; 2009Ap&SS.tmp..200Z
We study the effect of the change of solar model parameters on the
measurements of the horizontal velocity flow components based on the
analysis of high-degree modes using the ring-diagram local helioseismic
technique. We show that changing the equation of state, opacities,
surface heavy-element abundances or the modeling of convection do
not affect the sub-photospheric flow field measurements. However,
the modeling of outermost layers can affect the measurements if an
important amount of high radial order modes (high-frequency modes)
are included in the analysis.
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Title: A Multi-Site Campaign to Measure Solar-Like Oscillations in
Procyon. II. Mode Frequencies
Authors: Bedding, Timothy R.; Kjeldsen, Hans; Campante, Tiago L.;
Appourchaux, Thierry; Bonanno, Alfio; Chaplin, William J.; Garcia,
Rafael A.; Martić, Milena; Mosser, Benoit; Butler, R. Paul; Bruntt,
Hans; Kiss, László L.; O'Toole, Simon J.; Kambe, Eiji; Ando,
Hiroyasu; Izumiura, Hideyuki; Sato, Bun'ei; Hartmann, Michael;
Hatzes, Artie; Barban, Caroline; Berthomieu, Gabrielle; Michel,
Eric; Provost, Janine; Turck-Chièze, Sylvaine; Lebrun, Jean-Claude;
Schmitt, Jerome; Bertaux, Jean-Loup; Benatti, Serena; Claudi, Riccardo
U.; Cosentino, Rosario; Leccia, Silvio; Frandsen, Søren; Brogaard,
Karsten; Glowienka, Lars; Grundahl, Frank; Stempels, Eric; Arentoft,
Torben; Bazot, Michaël; Christensen-Dalsgaard, Jørgen; Dall, Thomas
H.; Karoff, Christoffer; Lundgreen-Nielsen, Jens; Carrier, Fabien;
Eggenberger, Patrick; Sosnowska, Danuta; Wittenmyer, Robert A.; Endl,
Michael; Metcalfe, Travis S.; Hekker, Saskia; Reffert, Sabine
2010ApJ...713..935B Altcode: 2010arXiv1003.0052B
We have analyzed data from a multi-site campaign to observe oscillations
in the F5 star Procyon. The data consist of high-precision velocities
that we obtained over more than three weeks with 11 telescopes. A
new method for adjusting the data weights allows us to suppress the
sidelobes in the power spectrum. Stacking the power spectrum in a
so-called échelle diagram reveals two clear ridges, which we identify
with even and odd values of the angular degree (l = 0 and 2, and l =
1 and 3, respectively). We interpret a strong, narrow peak at 446 μHz
that lies close to the l = 1 ridge as a mode with mixed character. We
show that the frequencies of the ridge centroids and their separations
are useful diagnostics for asteroseismology. In particular, variations
in the large separation appear to indicate a glitch in the sound-speed
profile at an acoustic depth of ~1000 s. We list frequencies for 55
modes extracted from the data spanning 20 radial orders, a range
comparable to the best solar data, which will provide valuable
constraints for theoretical models. A preliminary comparison with
published models shows that the offset between observed and calculated
frequencies for the radial modes is very different for Procyon than
for the Sun and other cool stars. We find the mean lifetime of the
modes in Procyon to be 1.29<SUP>+0.55</SUP> <SUB>-0.49</SUB> days,
which is significantly shorter than the 2-4 days seen in the Sun.
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Title: The quest for the solar g modes
Authors: Appourchaux, T.; Belkacem, K.; Broomhall, A. -M.; Chaplin,
W. J.; Gough, D. O.; Houdek, G.; Provost, J.; Baudin, F.; Boumier,
P.; Elsworth, Y.; García, R. A.; Andersen, B. N.; Finsterle, W.;
Fröhlich, C.; Gabriel, A.; Grec, G.; Jiménez, A.; Kosovichev, A.;
Sekii, T.; Toutain, T.; Turck-Chièze, S.
2010A&ARv..18..197A Altcode: 2010A&ARv.tmp....1A; 2009arXiv0910.0848A
Solar gravity modes (or g modes)—oscillations of the solar interior
on which buoyancy acts as the restoring force—have the potential
to provide unprecedented inference on the structure and dynamics of
the solar core, inference that is not possible with the well-observed
acoustic modes (or p modes). The relative high amplitude of the g-mode
eigenfunctions in the core and the evanesence of the modes in the
convection zone make the modes particularly sensitive to the physical
and dynamical conditions in the core. Owing to the existence of the
convection zone, the g modes have very low amplitudes at photospheric
levels, which makes the modes extremely hard to detect. In this article,
we review the current state of play regarding attempts to detect g
modes. We review the theory of g modes, including theoretical estimation
of the g-mode frequencies, amplitudes and damping rates. Then we go
on to discuss the techniques that have been used to try to detect g
modes. We review results in the literature, and finish by looking to
the future, and the potential advances that can be made—from both
data and data-analysis perspectives—to give unambiguous detections
of individual g modes. The review ends by concluding that, at the time
of writing, there is indeed a consensus amongst the authors that there
is currently no undisputed detection of solar g modes.
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Title: GOLF: Analysis of the Low Frequency Spectrum and Comparison
with a Calculated Solar g-Mode Spectrum
Authors: Grec, G.; Provost, J.; Renaud, C.
2009ASPC..416..209G Altcode:
The detection and identification of the g-mode frequency spectrum has
not really been achieved even after 13 yr of continuous measurement. We
use here the Global Oscillations at Low Frequencies (GOLF) data
to evaluate several types of an analysis using cross spectra. One
provides an averaged value of the g-mode splitting, resulting in a core
rotation faster than the surface rotation, with R<SUB>c</SUB> <
2R<SUB>s</SUB>. A g-mode frequency table is calculated from a solar
model, with the assumption of uniform solar rotation in the radiative
zone. We show the results of a template of phase-dependent analysis
of the cross spectrum and discuss the comparison of the observations
and the model. >From a statistical point of view, the search for a
single mode faces serious ambiguities. A global approach seems to be
the only realistic approach, but today we remain far from a conclusive
measurement of g-mode frequencies.
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Title: Had the planet Mars not existed: Kepler's equant model and
its physical consequences
Authors: Bracco, C.; Provost, J. -P.
2009EJPh...30.1085B Altcode: 2009arXiv0906.0484B
We examine the equant model for the motion of planets, which was the
starting point of Kepler's investigations before he modified it because
of Mars observations. We show that, up to first order in eccentricity,
this model implies for each orbit a velocity, which satisfies Kepler's
second law and Hamilton's hodograph, and a centripetal acceleration
with an r<SUP>-2</SUP> dependence on the distance to the Sun. If this
dependence is assumed to be universal, Kepler's third law follows
immediately. This elementary exercise in kinematics for undergraduates
emphasizes the proximity of the equant model coming from ancient
Greece with our present knowledge. It adds to its historical interest
a didactical relevance concerning, in particular, the discussion of
the Aristotelian or Newtonian conception of motion.
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Title: First asteroseismic results from CoRoT
Authors: Michel, E.; Baglin, A.; Weiss, W. W.; Auvergne, M.; Catala,
C.; Aerts, C.; Appourchaux, T.; Barban, C.; Baudin, F.; Briquet, M.;
Carrier, F.; Degroote, P.; De Ridder, J.; Garcia, R. A.; Garrido,
R.; Gutiérrez-Soto, J.; Kallinger, T.; Lefevre, L.; Neiner,
C.; Poretti, E.; Samadi, R.; Sarro, L.; Alecian, G.; Andrade, L.;
Ballot, J.; Benomar, O.; Berthomieu, G.; Boumier, P.; Charpinet, S.;
de Batz, B.; Deheuvels, S.; Dupret, M. -A.; Emilio, M.; Fabregat,
J.; Facanha, W.; Floquet, M.; Frémat, Y.; Fridlund, M.; Goupil,
M. -J.; Grotsch-Noels, A.; Handler, G.; Huat, A. -L.; Hubert, A. -M.;
Janot-Pacheco, E.; Kjeldsen, H.; Lebreton, Y.; Leroy, B.; Martayan,
C.; Mathias, P.; Miglio, A.; Montalban, J.; Monteiro, M. J. P. F. G.;
Mosser, B.; Provost, J; Regulo, C.; Renan de Medeiros, J.; Ribas,
I.; Roca Cortés, T.; Roxburgh, I.; Suso, J.; Thoul, A.; Toutain, T.;
Tiphene, D.; Turck-Chieze, S.; Vauclair, S.; Vauclair, G.; Zwintz, K.
2008CoAst.156...73M Altcode:
About one year after the end of the first observational run and
six months after the first CoRoT data delivery, we comment the data
exploitation progress for different types of stars. We consider first
results to illustrate how these data of unprecedented quality shed a
new light on the field of stellar seismology.
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Title: A Multisite Campaign to Measure Solar-like Oscillations in
Procyon. I. Observations, Data Reduction, and Slow Variations
Authors: Arentoft, Torben; Kjeldsen, Hans; Bedding, Timothy R.;
Bazot, Michaël; Christensen-Dalsgaard, Jørgen; Dall, Thomas H.;
Karoff, Christoffer; Carrier, Fabien; Eggenberger, Patrick; Sosnowska,
Danuta; Wittenmyer, Robert A.; Endl, Michael; Metcalfe, Travis S.;
Hekker, Saskia; Reffert, Sabine; Butler, R. Paul; Bruntt, Hans;
Kiss, László L.; O'Toole, Simon J.; Kambe, Eiji; Ando, Hiroyasu;
Izumiura, Hideyuki; Sato, Bun'ei; Hartmann, Michael; Hatzes, Artie;
Bouchy, Francois; Mosser, Benoit; Appourchaux, Thierry; Barban,
Caroline; Berthomieu, Gabrielle; Garcia, Rafael A.; Michel, Eric;
Provost, Janine; Turck-Chièze, Sylvaine; Martić, Milena; Lebrun,
Jean-Claude; Schmitt, Jerome; Bertaux, Jean-Loup; Bonanno, Alfio;
Benatti, Serena; Claudi, Riccardo U.; Cosentino, Rosario; Leccia,
Silvio; Frandsen, Søren; Brogaard, Karsten; Glowienka, Lars; Grundahl,
Frank; Stempels, Eric
2008ApJ...687.1180A Altcode: 2008arXiv0807.3794A
We have carried out a multisite campaign to measure oscillations in
the F5 star Procyon A. We obtained high-precision velocity observations
over more than three weeks with 11 telescopes, with almost continuous
coverage for the central 10 days. This represents the most extensive
campaign so far organized on any solar-type oscillator. We describe in
detail the methods we used for processing and combining the data. These
involved calculating weights for the velocity time series from the
measurement uncertainties and adjusting them in order to minimize the
noise level of the combined data. The time series of velocities for
Procyon shows the clear signature of oscillations, with a plateau of
excess power that is centered at 0.9 mHz and is broader than has been
seen for other stars. The mean amplitude of the radial modes is 38.1
+/- 1.3 cm s<SUP>-1</SUP> (2.0 times solar), which is consistent with
previous detections from the ground and by the WIRE spacecraft, and
also with the upper limit set by the MOST spacecraft. The variation
of the amplitude during the observing campaign allows us to estimate
the mode lifetime to be 1.5<SUP>+ 1.9</SUP><SUB>-0.8</SUB> days. We
also find a slow variation in the radial velocity of Procyon, with good
agreement between different telescopes. These variations are remarkably
similar to those seen in the Sun, and we interpret them as being due to
rotational modulation from active regions on the stellar surface. The
variations appear to have a period of about 10 days, which presumably
equals the stellar rotation period or, perhaps, half of it. The amount
of power in these slow variations indicates that the fractional area of
Procyon covered by active regions is slightly higher than for the Sun.
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Title: Oscillations in Procyon A: First results from a multi-site
campaign
Authors: Hekker, S.; Arentoft, T.; Kjeldsen, H.; Bedding, T. R.;
Christensen-Dalsgaard, J.; Reffert, S.; Bruntt, H.; Butler, R. P.;
Kiss, L. L.; O'Toole, S. J.; Kambe, E.; Ando, H.; Izumiura, H.;
Sato, B.; Hartmann, M.; Hatzes, A. P.; Appourchaux, T.; Barban, C.;
Berthomieu, G.; Bouchy, F.; García, R. A.; Lebrun, J. -C.; Martić,
M.; Michel, E.; Mosser, B.; Nghiem, P. A. P.; Provost, J.; Samadi,
R.; Thévenin, F.; Turck-Chièze, S.; Bonanno, S. A.; Benatti, S.;
Claudi, R. U.; Cosentino, R.; Leccia, S.; Frandsen, S.; Brogaard,
K.; Grundahl, F.; Stempels, H. C.; Bazot, M.; Dall, T. H.; Karoff,
C.; Carrier, F.; Eggenberger, P.; Sosnowska, D.; Wittenmyer, R. A.;
Endl, M.; Metcalfe, T. S.
2008JPhCS.118a2059H Altcode: 2007arXiv0710.3772H
Procyon A is a bright F5IV star in a binary system. Although the
distance, mass and angular diameter of this star are all known with high
precision, the exact evolutionary state is still unclear. Evolutionary
tracks with different ages and different mass fractions of hydrogen
in the core pass, within the errors, through the observed position of
Procyon A in the Hertzsprung-Russell diagram. For more than15 years
several different groups have studied the solar-like oscillations in
Procyon A to determine its evolutionary state. Although several studies
independently detected power excess in the periodogram, there is no
agreement on the actual oscillation frequencies yet. This is probably
due to either insufficient high-quality data (i.e., aliasing) or due
to intrinsic properties of the star (i.e., short mode lifetimes). Now
a spectroscopic multi-site campaign using 10 telescopes world-wide
(minimizing aliasing effects) with a total time span of nearly 4
weeks (increase the frequency resolution) is performed to identify
frequencies in this star and finally determine its properties and
evolutionary state.
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Title: CoRoT Measures Solar-Like Oscillations and Granulation in
Stars Hotter Than the Sun
Authors: Michel, Eric; Baglin, Annie; Auvergne, Michel; Catala,
Claude; Samadi, Reza; Baudin, Frédéric; Appourchaux, Thierry; Barban,
Caroline; Weiss, Werner W.; Berthomieu, Gabrielle; Boumier, Patrick;
Dupret, Marc-Antoine; Garcia, Rafael A.; Fridlund, Malcolm; Garrido,
Rafael; Goupil, Marie-Jo; Kjeldsen, Hans; Lebreton, Yveline; Mosser,
Benoît; Grotsch-Noels, Arlette; Janot-Pacheco, Eduardo; Provost,
Janine; Roxburgh, Ian W.; Thoul, Anne; Toutain, Thierry; Tiphène,
Didier; Turck-Chieze, Sylvaine; Vauclair, Sylvie D.; Vauclair,
Gérard P.; Aerts, Conny; Alecian, Georges; Ballot, Jérôme;
Charpinet, Stéphane; Hubert, Anne-Marie; Lignières, François;
Mathias, Philippe; Monteiro, Mario J. P. F. G.; Neiner, Coralie;
Poretti, Ennio; Renan de Medeiros, José; Ribas, Ignasi; Rieutord,
Michel L.; Roca Cortés, Teodoro; Zwintz, Konstanze
2008Sci...322..558M Altcode: 2008arXiv0812.1267M
Oscillations of the Sun have been used to understand its interior
structure. The extension of similar studies to more distant stars
has raised many difficulties despite the strong efforts of the
international community over the past decades. The CoRoT (Convection
Rotation and Planetary Transits) satellite, launched in December 2006,
has now measured oscillations and the stellar granulation signature
in three main sequence stars that are noticeably hotter than the
sun. The oscillation amplitudes are about 1.5 times as large as
those in the Sun; the stellar granulation is up to three times as
high. The stellar amplitudes are about 25% below the theoretic values,
providing a measurement of the nonadiabaticity of the process ruling
the oscillations in the outer layers of the stars.
---------------------------------------------------------
Title: NOSC: Nice OScillations Code
Authors: Provost, J.
2008Ap&SS.316..135P Altcode: 2007Ap&SS.tmp..432P
A short presentation of the Nice OScillations Code (NOSC) and of its
general properties is given here. We described the physics and the
various numerical tools, that we have developed to check the validity
and the internal consistency of the frequency calculations for a given
model. We present different examples of adiabatic calculations, with an
estimation of the achieved internal consistency and numerical accuracy.
---------------------------------------------------------
Title: The CoRoT evolution and seismic tools activity. Goals and tasks
Authors: Lebreton, Y.; Monteiro, M. J. P. F. G.; Montalbán, J.;
Moya, A.; Baglin, A.; Christensen-Dalsgaard, J.; Goupil, M. -J.;
Michel, E.; Provost, J.; Roxburgh, I. W.; Scuflaire, R.; ESTA Team
2008Ap&SS.316....1L Altcode: 2008arXiv0805.0977L; 2008Ap&SS.tmp..157L
The forthcoming data expected from space missions such as CoRoT
require the capacity of the available tools to provide accurate models
whose numerical precision is well above the expected observational
errors. In order to secure that these tools meet the specifications,
a team has been established to test and, when necessary, to improve
the codes available in the community. The CoRoT Evolution and Seismic
Tool Activity (ESTA) has been set up with this mission. Several groups
have been involved. The present paper describes the motivation and the
organisation of this activity, providing the context and the basis for
the presentation of the results that have been achieved so far. This
is not a finished task as future even better data will continue to
demand more precise and complete tools for asteroseismology.
---------------------------------------------------------
Title: Inter-comparison of the g-, f- and p-modes calculated using
different oscillation codes for a given stellar model
Authors: Moya, A.; Christensen-Dalsgaard, J.; Charpinet, S.; Lebreton,
Y.; Miglio, A.; Montalbán, J.; Monteiro, M. J. P. F. G.; Provost,
J.; Roxburgh, I. W.; Scuflaire, R.; Suárez, J. C.; Suran, M.
2008Ap&SS.316..231M Altcode: 2007arXiv0711.2587M; 2008Ap&SS.tmp...49M
In order to make asteroseismology a powerful tool to explore stellar
interiors, different numerical codes should give the same oscillation
frequencies for the same input physics. Any differences found when
comparing the numerical values of the eigenfrequencies will be an
important piece of information regarding the numerical structure of the
code. The ESTA group was created to analyze the non-physical sources
of these differences. The work presented in this report is a part
of Task 2 of the ESTA group. Basically the work is devoted to test,
compare and, if needed, optimize the seismic codes used to calculate
the eigenfrequencies to be finally compared with observations. The
first step in this comparison is presented here. The oscillation
codes of nine research groups in the field have been used in this
study. The same physics has been imposed for all the codes in order to
isolate the non-physical dependence of any possible difference. Two
equilibrium models with different grids, 2172 and 4042 mesh points,
have been used, and the latter model includes an explicit modelling of
semiconvection just outside the convective core. Comparing the results
for these two models illustrates the effect of the number of mesh points
and their distribution in particularly critical parts of the model,
such as the steep composition gradient outside the convective core. A
comprehensive study of the frequency differences found for the different
codes is given as well. These differences are mainly due to the use of
different numerical integration schemes. The number of mesh points and
their distribution are crucial for interpreting the results. The use
of a second-order integration scheme plus a Richardson extrapolation
provides similar results to a fourth-order integration scheme. The
proper numerical description of the Brunt-Väisälä frequency in
the equilibrium model is also critical for some modes. This influence
depends on the set of the eigenfunctions used for the solution of the
differential equations. An unexpected result of this study is the high
sensitivity of the frequency differences to the inconsistent use of
values of the gravitational constant ( G) in the oscillation codes,
within the range of the experimentally determined ones, which differ
from the value used to compute the equilibrium model. This effect can
provide differences for a given equilibrium model substantially larger
than those resulting from the use of different codes or numerical
techniques; the actual differences between the values of G used by
the different codes account for much of the frequency differences
found here.
---------------------------------------------------------
Title: Update on g-mode research
Authors: García, R. A.; Jiménez, A.; Mathur, S.; Ballot, J.;
Eff-Darwich, A.; Jiménez-Reyes, S. J.; Pallé, P. L.; Provost, J.;
Turck-Chièze, S.
2008AN....329..476G Altcode: 2008arXiv0802.4296G
Since the beginning of this century we have attended a blooming
of the gravity-mode research thanks to the unprecedented quality
of the data available, either from space with SoHO, or from the
ground-based networks as BiSON or GONG. From the first upper limit
of the gravity-mode amplitudes fixed at 10 mm/s at 200 μHz given
by Appourchaux et al. (2000), on one hand, a peak was supposed
to be a component of the ℓ = 1, n = 1 mixed mode (García et
al. 2001a, 2001b; Gabriel et al. 2002) and, on the other hand, a
couple of patterns - multiplets - were attributed to gravity modes
(Turck-Chièze et al. 2004; Mathur et al. 2007). One of these patterns,
found around 220 μHz, could be labeled as the ℓ = 2, n =-3 g mode,
which is expected to be the one with the highest surface amplitude
(Cox & Guzik 2004). Finally, in 2007, García et al. were able to
measure the fingertips of the dipole gravity modes looking for their
asymptotic properties. In the present paper we present an update of the
recent developments on this subject with special attention to the 220
μHz region, the dipole asymptotic properties and the impact of the
incoming g-mode observations on the knowledge of the solar structure
and rotation profile.
---------------------------------------------------------
Title: Asteroseismology of Procyon with SOPHIE
Authors: Mosser, B.; Bouchy, F.; Martić, M.; Appourchaux, T.; Barban,
C.; Berthomieu, G.; Garcia, R. A.; Lebrun, J. C.; Michel, E.; Provost,
J.; Thévenin, F.; Turck-Chièze, S.
2008A&A...478..197M Altcode: 2007arXiv0712.1368M
Context: This paper reports a 9-night asteroseismic observation
program conducted in January 2007 with the new spectrometer sophie
at the OHP 193-cm telescope, on the F5 IV-V target Procyon A. <BR
/>Aims: This first asteroseismic program with sophie was intended
to test the performance of the instrument with a bright but demanding
asteroseismic target and was part of a multisite network. <BR />Methods:
The sophie spectra have been reduced with the data reduction software
provided by OHP. The Procyon asteroseismic data were then analyzed
with statistical tools. The asymptotic analysis has been conducted
considering possible curvature in the échelle diagram analysis. <BR
/>Results: These observations have proven the efficient performance of
sophie used as an asteroseismometer, and succeed in a clear detection
of the large spacing. An échelle diagram based on the 54-μHz
spacing shows clear ridges. Identification of the peaks exhibits
large spacings varying from about 52 μHz to 56 μHz. Outside
the frequency range [0.9, 1.0 mHz] where the identification is
confused, the large spacing increases at a rate of about dΔν/dn
≃ 0.2 μHz. This may explain some of the different values of
the large spacing obtained by previous observations. <P />Based on
observations collected with the sophie échelle spectrometer mounted
on the 1.93-m telescope at OHP, France (program 06B.PNPS.BOU);
http://www.obs-hp.fr/www/guide/ sophie/sophie-eng.html Table of
radial velocity measurements is only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/197
---------------------------------------------------------
Title: Abundance Analysis of α, Centauri A
Authors: Bigot, L.; Thévenin, F.; Provost, J.; Berthomieu, G.
2008psa..conf..259B Altcode:
The α centauri system is a reference in stellar physics. The two
components, α Cen A (G2V) and α Cen B (K1V), have been extensively
studied because of their proximity (1.3pc) and similarity to the
Sun. The discovery of solar-like oscillations (Bouchy & Carrier
2002) and the recent interferometric measurements (Kervella et al. 2003)
make this system one of the best constrained and therefore one of
the most interesting to test both stellar evolution and atmospheric
models. The chemical composition of this metal-rich system is still
debated ([Fe/H] ≈ +0.1 to +0.2 dex) and is a source of uncertainty
in asteroseismic diagnostics. In this work, we propose to improve the
Iron abundance by the use of realistic 3D radiative hydrodynamical
(RHD) simulations. We present preliminary results for α Cen A and
found significant smaller overabundance. This result agrees well with
pulsation data.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Procyon (alpha CMi) radial
velocities (Mosser+, 2008)
Authors: Mosser, B.; Bouchy, F.; Martic, M.; Appourchaux, T.; Barban,
C.; Berthomieu, G.; Garcia, R. A.; Lebrun, J. C.; Michel, E.; Provost,
J.; Thevenin, F.; Turck-Chieze, S.
2007yCat..34780197M Altcode:
Time series of the radial velocities of Procyon recorder with the
echelle spectrometer SOPHIE at Observatoire de Haute Provence in
January 2007. <P />(1 data file).
---------------------------------------------------------
Title: Sensitivity of low degree oscillations to the change in
solar abundances
Authors: Zaatri, A.; Provost, J.; Berthomieu, G.; Morel, P.;
Corbard, T.
2007A&A...469.1145Z Altcode:
Context: The most recent determination of the solar chemical
composition, using a time-dependent, 3D hydrodynamical model of the
solar atmosphere, exhibits a significant decrease of C, N, O abundances
compared to their previous values. Solar models that use these new
abundances are not consistent with helioseismological determinations of
the sound speed profile, the surface helium abundance and the convection
zone depth. <BR />Aims: We investigate the effect of changes of solar
abundances on low degree p-mode and g-mode characteristics which
are strong constraints of the solar core. We consider particularly
the increase of neon abundance in the new solar mixture in order
to reduce the discrepancy between models using new abundances and
helioseismology. <BR />Methods: The observational determinations of
solar frequencies from the GOLF instrument are used to test solar
models computed with different chemical compositions. We consider in
particular the normalized small frequency spacings in the low degree
p-mode frequency range. <BR />Results: Low-degree small frequency
spacings are very sensitive to changes in the heavy-element abundances,
notably neon. We show that by considering all the seismic constraints,
including the small frequency spacings, a rather large increase of
neon abundance by about (0.5±0.05) dex can be a good solution to
the discrepancy between solar models that use new abundances and low
degree helioseismology, subject to adjusting slightly the solar age
and the highest abundances. We also show that the change in solar
abundances, notably neon, considerably affects g-mode frequencies,
with relative frequency differences between the old and the new models
higher than 1.5%.
---------------------------------------------------------
Title: Tracking Solar Gravity Modes: The Dynamics of the Solar Core
Authors: García, Rafael A.; Turck-Chièze, Sylvaine; Jiménez-Reyes,
Sebastian J.; Ballot, Jérôme; Pallé, Pere L.; Eff-Darwich, Antonio;
Mathur, Savita; Provost, Janine
2007Sci...316.1591G Altcode:
Solar gravity modes have been actively sought because they directly
probe the solar core (below 0.2 solar radius), but they have not
been conclusively detected in the Sun because of their small surface
amplitudes. Using data from the Global Oscillation at Low Frequency
instrument, we detected a periodic structure in agreement with the
period separation predicted by the theory for gravity dipole modes. When
studied in relation to simulations including the best physics of the
Sun determined through the acoustic modes, such a structure favors a
faster rotation rate in the core than in the rest of the radiative zone.
---------------------------------------------------------
Title: Asteroseismology and evolutionary status of Procyon A
Authors: Provost, J.; Berthomieu, G.; Martić, M.; Morel, P.
2006A&A...460..759P Altcode:
Models of Procyon A satisfying the actual observational constraints,
particularly the asteroseismic ones, are discussed. The oscillations
of these models were computed and analysed. We looked for seismic
signatures of the evolutionary status of Procyon A. We show that the
behavior of the small frequency spacings, particularly δν<SUB>01</SUB>
allows us to distinguish between main sequence and post-main sequence
models, all satisfying the observational constraints on mass,
effective temperature, radius, and surface metallicity of Procyon
A. We also introduce a new seismic evolution criterion, varepsilon,
based on the comparison of the low and high frequency parts of the
power spectrum. The comparison of the seismic properties of the models
with the available asteroseismic observations does not allow us to
definitely decide on the stage of evolution of Procyon A. Much more
accurate frequencies must be obtained especially in the low-frequency
domain to distinguish between the models.
---------------------------------------------------------
Title: Evaluation of the Scientific Performances for the Seismology
Programme
Authors: Appourchaux, T.; Berthomieu, G.; Michel, E.; Ballot, J.;
Barban, C.; Baudin, F.; Boumier, P.; De Ridder, J.; Floquet, M.;
Garcia, R. A.; Garrido, R.; Goupil, M. -J.; Lambert, P.; Lochard,
J.; Mazumdar, A.; Neiner, C.; Poretti, E.; Provost, J.; Roxburgh,
I.; Samadi, R.; Toutain, T.
2006ESASP1306..429A Altcode:
The Data Analysis Team of the Seismology Working Group of COROT
performed several hare-and-hound exercises. These exercises aimed at
putting the team in a situation as if they would analyze data coming
out of the COROT spacecraft. In total the team performed five different
exercises simulating solar-like stars (HH#1, HH#2, HH#3), classical
pulsators (HH#5), validating seismic calibration of stellar model (HH#2,
HH#3) and pushing the limit of detection (HH#4). This paper tries both
to serve as a summary and as a portal to other publications of the DAT.
---------------------------------------------------------
Title: Data Analysis Tools for the Seismology Programme
Authors: Appourchaux, T.; Berthomieu, G.; Michel, E.; Aerts, C.;
Ballot, J.; Barban, C.; Baudin, F.; Boumier, P.; De Ridder, J.;
Floquet, M.; Garcia, R. A.; Garrido, R.; Goupil, M. -J.; Lambert,
P.; Lochard, J.; Neiner, C.; Poretti, E.; Provost, J.; Roxburgh, I.;
Samadi, R.; Toutain, T.
2006ESASP1306..377A Altcode:
Tools developed by helioseismologists and by classical-pulsator
astronomers have been used in the hare-and-hound exercises for having
a several different ways of deriving the oscillation mode parameters
such as frequency or amplitude. These tools are used for deriving what
we call recipes that will allow us to obtain the mode parameters from
light curves either for solar-like stars or for classical pulsators. The
recipes are used for tagging the mode parameters as being those of
COROT. They will be used as reference or yardstick for other fitting
strategies. We will also address the issue of mode detection. Additional
tools such as time-frequency analysis will be presented.
---------------------------------------------------------
Title: Report on the CoRoT Evolution and Seismic Tools Activity
Authors: Monteiro, M. J. P. F. G.; Lebreton, Y.; Montalban, J.;
Christensen-Dalsgaard, J.; Castro, M.; Degl'Innocenti, S.; Moya, A.;
Roxburgh, I. W.; Scuflaire, R.; Baglin, A.; Cunha, M. S.; Eggenberger,
P.; Fernandes, J.; Goupil, M. J.; Hui-Bon-Hoa, A.; Marconi, M.;
Marques, J. P.; Michel, E.; Miglio, A.; Morel, P.; Pichon, B.; Prada
Moroni, P. G.; Provost, J.; Ruoppo, A.; Suarez, J. -C.; Suran, M.;
Teixeira, T. C.
2006ESASP1306..363M Altcode: 2006astro.ph..5685M
We present the work undertaken by the Evolution and Seismic Tools
Activity (ESTA) team of the CoRoT Seismology Working Group. We have
focused on two main tasks: Task 1 now finished has aimed at testing,
comparing and optimising seven stellar evolution codes which will
be used to model the internal structure and evolution of the CoRoT
target stars. Task 2, still underway, aims at testing, comparing and
optimising different seismic codes used to calculate the oscillations
of models for different types of stars. The results already obtained
are quite satisfactory, showing minor differences between the different
numerical tools provided the same assumptions on the physical parameters
are made. This work gives us confidence on the numerical tools that
will be available to interpret the future CoRoT seismic data.
---------------------------------------------------------
Title: The Seismology Programme of CoRoT
Authors: Michel, E.; Baglin, A.; Auvergne, M.; Catala, C.; Aerts,
C.; Alecian, G.; Amado, P.; Appourchaux, T.; Ausseloos, M.; Ballot,
J.; Barban, C.; Baudin, F.; Berthomieu, G.; Boumier, P.; Bohm, T.;
Briquet, M.; Charpinet, S.; Cunha, M. S.; De Cat, P.; Dupret, M. A.;
Fabregat, J.; Floquet, M.; Fremat, Y.; Garrido, R.; Garcia, R. A.;
Goupil, M. -J.; Handler, G.; Hubert, A. -M.; Janot-Pacheco, E.;
Lambert, P.; Lebreton, Y.; Lignieres, F.; Lochard, J.; Martin-Ruiz,
S.; Mathias, P.; Mazumdar, A.; Mittermayer, P.; Montalban, J.;
Monteiro, M. J. P. F. G.; Morel, P.; Mosser, B.; Moya, A.; Neiner,
C.; Nghiem, P.; Noels, A.; Oehlinger, J.; Poretti, E.; Provost, J.;
Renan de Medeiros, J.; De Ridder, J.; Rieutord, M.; Roca-Cortes, T.;
Roxburgh, I.; Samadi, R.; Scuflaire, R.; Suarez, J. C.; Theado, S.;
Thoul, A.; Toutain, T.; Turck-Chieze, S.; Uytterhoeven, K.; Vauclair,
G.; Vauclair, S.; Weiss, W. W.; Zwintz, K.
2006ESASP1306...39M Altcode: 2008arXiv0811.1080M
We introduce the main lines and specificities of the CoRoT Seismology
Core Programme. The development and consolidation of this programme has
been made in the framework of the CoRoT Seismology Working Group. With a
few illustrative examples, we show how CoRoT data will help to address
various problems associated with present open questions of stellar
structure and evolution.
---------------------------------------------------------
Title: Seismic Determination of Stellar Parameters
Authors: Provost, J.; Berthomieu, G.; Gonczi, G.; Morel, P.; Toutain,
T.; Barban, C.; Goupil, M. -J.; Lebreton, Y.; Michel, E.; Roxburgh, I.
2006ESASP1306..443P Altcode:
In the context of the preparation for CoRoT, we have studied some
theoretical properties of the frequencies of solar-like stars. In
order to prepare for the interpretation of future data, we have defined
between Meudon (LESIA) and Nice (Cassini) an hare and hounds exercise
as follows: from a set of frequencies provided by each group and given
to the other group, find the characteristics of the corresponding
stellar model. Here are reported preliminary results obtained by the
Nice group. A discussion on the numerical accuracy of theoretical
frequencies is also given.
---------------------------------------------------------
Title: The DynaMICS perspective
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.624E..24T Altcode: 2006soho...18E..24T
No abstract at ADS
---------------------------------------------------------
Title: How does the change on solar abundances affect low degree
modes?
Authors: Zaatri, A.; Provost, J.; Berthomieu, G.; Morel, P.;
Corbard, T.
2006ESASP.624E..92Z Altcode: 2006soho...18E..92Z
No abstract at ADS
---------------------------------------------------------
Title: Detection of periodic signatures in the solar power spectrum
On the track of l=1 gravity modes
Authors: García, R. A.; Turck-Chièze, S.; Jiménez-Reyes, S. J.;
Ballot, J.; Pallé, P. L.; Eff-Darwich, A.; Mathur, S.; Provost, J.
2006ESASP.624E..23G Altcode: 2006astro.ph.11806G; 2006soho...18E..23G
In the present work we show robust indications of the existence
of g modes in the Sun using 10 years of GOLF data. The present
analysis is based on the exploitation of the collective properties
of the predicted low-frequency (25 to 140 microHz) g modes: their
asymptotic nature, which implies a quasi equidistant separation of
their periods for a given angular degree (l). The Power Spectrum (PS)
of the Power Spectrum Density (PSD), reveals a significant structure
indicating the presence of features (peaks) in the PSD with near
equidistant periods corresponding to l=1 modes in the range n=-4 to
n=-26. The study of its statistical significance of this feature was
fully undertaken and complemented with Monte Carlo simulations. This
structure has a confidence level better than 99.86% not to be due to
pure noise. Furthermore, a detailed study of this structure suggests
that the gravity modes have a much more complex structure than the one
initially expected (line-widths, magnetic splittings...). Compared to
the latest solar models, the obtained results tend to favor a solar
core rotating significantly faster than the rest of the radiative
zone. In the framework of the Phoebus group, we have also applied the
same methodology to other helioseismology instruments on board SoHO
and ground based networks.
---------------------------------------------------------
Title: The internal structure of the Sun inferred from g modes and
low-frequency p modes
Authors: Elsworth, Y. P.; Baudin, F.; Chaplin, W; Andersen, B;
Appourchaux, T.; Boumier, P.; Broomhall, A. -M.; Corbard, T.;
Finsterle, W.; Fröhlich, C.; Gabriel, A.; García, R. A.; Gough,
D. O.; Grec, G.; Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii,
T.; Toutain, T.; Turck-Chièze, S.
2006ESASP.624E..22E Altcode: 2006soho...18E..22E
The Phoebus group is an international collaboration of
helioseismologists, its aim being to detect low-frequency solar g
modes. Here, we report on recent work, including the development and
application of new techniques based on the detection of coincidences
in contemporaneous datasets and the asymptotic properties of the g-mode
frequencies. The length of the time series available to the community is
now more than ten years, and this has reduced significantly the upper
detection limits on the g-mode amplitudes. Furthermore, low-degree p
modes can now be detected clearly at frequencies below 1000 μHz.
---------------------------------------------------------
Title: Knowledge of the solar core dynamics through g modes
Authors: Garcia, R. A.; Turck-Chièze, S.; Jimenez-Reyes, S. J.;
Ballot, J.; Pallé, P. L.; Eff-Darwich, A.; Mathur, S.; Provost, J.
2006IAUJD..17E...8G Altcode:
Helioseismology is able to study the solar interior through the
observation of the solar oscillation modes propagating inside the
Sun. Pressure-driven modes (p modes) provide a very detailed picture
of the external convective zone above 0.7 R[⊙]and the radiative zone
down to ~0.2 R[⊙] where only a few of such modes penetrate so far. To
study deeper layers, still containing more than 40% of the totals mass,
another type of oscillations are needed: the gravity-driven modes
(g modes). Since the early 19 80s, this type of mode has been looked
for. Only very recently have we have found some structures that are
compatible with some global properties of these modes in the GOLF/ SOHO
data. In this contribution we will show these signals. By explaining
them as the signature of the asymptotic properties of the ℓ = 1 g
modes, we could start constraining the solar core dynamics.
---------------------------------------------------------
Title: Scientific Objectives of the Novel Formation Flying Mission
Aspiics
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.164L Altcode: 2006soho...17E.164L
No abstract at ADS
---------------------------------------------------------
Title: The EUV Variability Experiment (EVE) on the Solar Dynamics
Observatory (SDO): Science Plan and Instrument Overview
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.165W Altcode: 2006soho...17E.165W
No abstract at ADS
---------------------------------------------------------
Title: Detection of the Periodic Signatures of l=1 Solar g Modes
with 10 Years of GOLF/SOHO Data
Authors: Garcia, Rafael A.; Turck-Chiéze, Sylvaine; Jiménez-Reyes,
Sebastián J.; Ballot, Jerome; Palle, Pere L.; Eff-Darwich, Antonio;
Mathur, Savita; Provost, Janine
2006ESASP.617E...3G Altcode: 2006soho...17E...3G
No abstract at ADS
---------------------------------------------------------
Title: Recent Progresses on g-Mode Search
Authors: Appourchaux, T.; Andersen, B.; Baudin, F.; Boumier, P.;
Broomhall, A. -M.; Chaplin, W.; Corbard, T.; Elsworth, Y.; Finsterle,
W.; Fröhlich, C.; Gabriel, A.; Garcia, R.; Gough, D. O.; Grec, G.;
Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii, T.; Toutain, T.;
Turck-Chièze, S.
2006ESASP.617E...2A Altcode: 2006soho...17E...2A
No abstract at ADS
---------------------------------------------------------
Title: The Dynamics Project
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.162T Altcode: 2006soho...17E.162T
No abstract at ADS
---------------------------------------------------------
Title: About Procyon modeling
Authors: Provost, J.; Berthomieu, G.; Martić, M.
2006MmSAI..77..474P Altcode:
Models of Procyon satisfying the actual observational constraints,
particularly the asteroseismic ones, are discussed. It is shown that
much more accurate frequencies must be obtained by asteroseismic
observations especially in the low frequency domain below 800 mu Hertz
to determine the Procyon evolutionary stage.
---------------------------------------------------------
Title: Effect of microscopic diffusion on asteroseismic properties
of intermediate-mass stars
Authors: Provost, J.; Berthomieu, G.; Bigot, L.; Morel, P.
2005A&A...432..225P Altcode:
Results on the effects of microscopic diffusion on the modeling and
oscillations of <P />solar-like stars are discussed. Comparisons
between models with and without microscopic diffusion, subjected to
observational constraints, namely effective temperature, luminosity,
surface metallicity and mass <P />derived from photometry, spectroscopy
and astrometry, are presented. We point out and discuss a signature
of microscopic diffusion on the oscillation frequencies.
---------------------------------------------------------
Title: JISCO: Jovian Interferometric Seismometer at Concordia
Observatory
Authors: Schmider, F. X.; Jacob, C.; Fossat, E.; Abe, L.; Gay, J.;
Valtier, J. -C.; Guillot, T.; Provost, J.; Mosser, B.; Gaulme, P.
2005EAS....14..285S Altcode:
Seismology is the only way to investigate the internal structure
of the giant planets, with a lot of scientific implications such
as high pressure physics and huge constraints on the scenario of
solar system formation. As compared to other existing possibilities
(ground based network, spacecraft), seismology of Jupiter will take
a maximum benefit from the peculiarities of the Concordia station as
an astronomical observatory. Indeed, the continuous temporal coverage
for all the winter season, and the quality of the atmospheric seeing,
are crucial parameters for this program. The jovian seismometer
SYMPA, already used for network observations, is perfectly suitable
for Dome C conditions. With the already existing small telescopes
deployed in the frame of site testing program, seismology of Jupiter
will constitute a excellent intermediate project with high scientific
return, before the installation of large telescopes. In a second step,
such an instrument could be a first light instrument for a 1.5 m class
automatic telescope, which is to be developed as an individual stone
for a large interferometer. With this diameter, the same scientific
program on Saturn could also be achieved.
---------------------------------------------------------
Title: About Models and Oscillations of the Solar-Like Star Procyon a
Authors: Provost, J.; Martic, M.; Berthomieu, G.
2004ESASP.559..594P Altcode: 2004soho...14..594P
No abstract at ADS
---------------------------------------------------------
Title: GOLF : Probing the Observed Low Frequency Spectrum with a
Numerical Model
Authors: Grec, G.; Provost, J.; Renaud, C.; Berthomieu, G.
2004ESASP.559..452G Altcode: 2004soho...14..452G
No abstract at ADS
---------------------------------------------------------
Title: New values of gravitational moments J<SUB>2</SUB> and
J<SUB>4</SUB> deduced from helioseismology
Authors: Mecheri, R.; Abdelatif, T.; Irbah, A.; Provost, J.;
Berthomieu, G.
2004SoPh..222..191M Altcode: 2009arXiv0911.5055R
By applying the theory of slowly rotating stars to the Sun, the solar
quadrupole and octopole moments J<SUB>2</SUB> and J<SUB>4</SUB> were
computed using a solar model obtained from CESAM stellar evolution
code (Morel, 1997) combined with a recent model of solar differential
rotation deduced from helioseismology (Corbard et al., 2002). This model
takes into account a near-surface radial gradient of rotation which
was inferred and quantified from MDI f-mode observations by Corbard and
Thompson (2002). The effect of this observational near-surface gradient
on the theoretical values of the surface parameters J<SUB>2</SUB>,
J<SUB>4</SUB> is investigated. The results show that the octopole
moment J<SUB>4</SUB> is much more sensitive than the quadrupole moment
J<SUB>2</SUB> to the subsurface radial gradient of rotation.
---------------------------------------------------------
Title: Erratum: “Looking for Gravity-Mode Multiplets with the GOLF
Experiment aboard SOHO” (<A href="/abs/2004ApJ...604..455T">ApJ,
604, 455 [2004]</A>)
Authors: Turck-Chièze, S.; García, R. A.; Couvidat, S.; Ulrich,
R. K.; Bertello, L.; Varadi, F.; Kosovichev, A. G.; Gabriel, A. H.;
Berthomieu, G.; Brun, A. S.; Lopes, I.; Pallé, P.; Provost, J.;
Robillot, J. M.; Roca Cortés, T.
2004ApJ...608..610T Altcode:
As a result of an error at the Press, the second panel of Figure 9
was repeated twice in the top row of the printed, black-and-white
version of this figure, and the first panel was omitted. This error
appears in the print edition and the PDF and postscript (PS) versions
available with the electronic edition of the journal, although the
panels of the color figure displayed in the electronic article itself
are correct. Please see below for the corrected print version of Figure
9. The Press sincerely regrets the error.
---------------------------------------------------------
Title: Looking for Gravity-Mode Multiplets with the GOLF Experiment
aboard SOHO
Authors: Turck-Chièze, S.; García, R. A.; Couvidat, S.; Ulrich,
R. K.; Bertello, L.; Varadi, F.; Kosovichev, A. G.; Gabriel, A. H.;
Berthomieu, G.; Brun, A. S.; Lopes, I.; Pallé, P.; Provost, J.;
Robillot, J. M.; Roca Cortés, T.
2004ApJ...604..455T Altcode:
This paper is focused on the search for low-amplitude solar gravity
modes between 150 and 400 μHz, corresponding to low-degree, low-order
modes. It presents results based on an original strategy that looks
for multiplets instead of single peaks, taking into consideration
our knowledge of the solar interior from acoustic modes. Five years
of quasi-continuous measurements collected with the helioseismic GOLF
experiment aboard the SOHO spacecraft are analyzed. We use different
power spectrum estimators and calculate confidence levels for the
most significant peaks. This approach allows us to look for signals
with velocities down to 2 mm s<SUP>-1</SUP>, not far from the limit
of existing instruments aboard SOHO, amplitudes that have never been
investigated up to now. We apply the method to series of 1290 days,
beginning in 1996 April, near the solar cycle minimum. An automatic
detection algorithm lists those peaks and multiplets that have a
probability of more than 90% of not being pure noise. The detected
patterns are then followed in time, considering also series of 1768 and
2034 days, partly covering the solar cycle maximum. In the analyzed
frequency range, the probability of detection of the multiplets
does not increase with time as for very long lifetime modes. This is
partly due to the observational conditions after 1998 October and the
degradation of these observational conditions near the solar maximum,
since these modes have a “mixed” character and probably behave as
acoustic modes. Several structures retain our attention because of
the presence of persistent peaks along the whole time span. These
features may support the idea of an increase of the rotation in the
inner core. There are good arguments for thinking that complementary
observations up to the solar activity minimum in 2007 will be decisive
for drawing conclusions on the presence or absence of gravity modes
detected aboard the SOHO satellite.
---------------------------------------------------------
Title: The diameter and evolutionary state of Procyon
A. Multi-technique modeling using asteroseismic and interferometric
constraints
Authors: Kervella, P.; Thévenin, F.; Morel, P.; Berthomieu, G.;
Bordé, P.; Provost, J.
2004A&A...413..251K Altcode: 2003astro.ph..9148K
We report the angular diameter measurement obtained with the
VINCI/VLTI instrument on the nearby star Procyon A (α CMi A, F5IV-V),
at a relative precision of ± 0.9%. We obtain a uniform disk angular
diameter in the K band of θ<SUB>UD</SUB> = 5.376±0.047 mas and a limb
darkened value of θ<SUB>LD</SUB> = 5.448±0.053 mas. Together with
the HIPPARCOS parallax, this gives a linear diameter of 2.048±0.025
D<SUB>⊙</SUB>. We use this result in combination with spectroscopic,
photometric and asteroseismic constraints to model this star with
the CESAM code. One set of modeling parameters that reproduces the
observations within their error bars are an age of 2314 Myr, an
initial helium mass fraction Y_i=0.301 and an initial mass ratio of
heavy elements to hydrogen (Z/X)<SUB>i</SUB>=0.0314. We also computed
the adiabatic oscillation spectrum of our model of Procyon A, giving
a mean large frequency separation of /line{Δν<SUB>0</SUB>}≈ 54.7
μHz. This value is in agreement with the seismic observations by
Martić et al. (\cite{martic}, \cite{martic01}). The interferometric
diameter and the asteroseismic large frequency spacing together suggest
a mass closer to 1.4 M<SUB>⊙</SUB> than to 1.5 M<SUB>⊙</SUB>. We
conclude that Procyon is currently ending its life on the main sequence,
as its luminosity class indicates.
---------------------------------------------------------
Title: VINCI/VLTI Observations of Main Sequence Stars
Authors: Kervella, P.; Thévenin, F.; Morel, P.; Provost, J.;
Berthomieu, G.; Sé Gransan, D.; Queloz, D.; Bordé, P.; di Folco,
E.; Forveille, T.
2004IAUS..219...80K Altcode: 2003astro.ph..9784K; 2003IAUS..219E.127K
The Main Sequence (MS) stars are by far the most numerous class in the
Universe. They are often somewhat neglected as they are relatively
quiet objects (but exceptions exist) though they bear testimony of
the past and future of our Sun. An important characteristic of the
MS stars particularly the solar-type ones is that they host the large
majority of the known extrasolar planets. Moreover at the bottom of the
MS the red M dwarfs pave the way to understanding the physics of brown
dwarfs and giant planets themselves. We have measured very precise
angular diameters from recent VINCI/VLTI observations of a number
of MS stars with spectral types between A1 and M5.5 which already
cover a wide range of effective temperatures and radii. Combined with
precise Hipparcos parallaxes photometry spectroscopy as well as the
asteroseismic information available for some of these stars the angular
diameters put strong constraints on the detailed models of these stars
and therefore on the physical processes at play.
---------------------------------------------------------
Title: The diameters of alpha Centauri A and B. A comparison of
the asteroseismic and VINCI/VLTI views
Authors: Kervella, P.; Thévenin, F.; Ségransan, D.; Berthomieu,
G.; Lopez, B.; Morel, P.; Provost, J.
2003A&A...404.1087K Altcode: 2003astro.ph..3634K
We compare the first direct angular diameter measurements obtained on
our closest stellar neighbour, alpha Centauri, to recent model diameters
constrained by asteroseismic observations. Using the VINCI instrument
installed at ESO's VLT Interferometer (VLTI), the angular diameters of
the two main components of the system, alpha Cen A and B, were measured
with a relative precision of 0.2% and 0.6% respectively. Particular care
has been taken in the calibration of these measurements, considering
that VINCI is estimating the fringe visibility using a broadband K
filter. We obtain uniform disk angular diameters for alpha Cen A and B
of theta<SUB>UD</SUB> [A] = 8.314 +/- 0.016 mas and theta<SUB>UD</SUB>
[B] = 5.856 +/- 0.027 mas, and limb darkened angular diameters of
theta<SUB>LD</SUB> [A] = 8.511 +/- 0.020 mas and theta<SUB>LD</SUB>
[B] = 6.001 +/- 0.034 mas. Combining these values with the parallax
from Söderhjelm (\cite{soderhjelm}), we derive linear diameters of
D[A] = 1.224 +/- 0.003 D<SUB>sun</SUB> and D[B] = 0.863 +/- 0.005
D<SUB>sun</SUB>. These values are compatible with the masses published
by Thévenin et al. (\cite{thevenin02}) for both stars.
---------------------------------------------------------
Title: Solar oblateness induced by its differential rotation
Authors: Mecheri, R.; Provost, J.; Abdelatif, T.; Irbah, A.
2003EAEJA....14676M Altcode:
By using the theory of Solar gravitational figure, the solar quadrupole
moment J2 was computed combined with a recent analytical model of
differential solar rotation (Corbard et al. 2002) taking into account
a near-surface radial gradient of rotation inferred and quantified
from MDI f-modes observations. This value of J2 obtained permits to
evaluate the solar oblateness and its induced latitudinal variation
of solar diameter. This variation was compared to those obtained
from observations.
---------------------------------------------------------
Title: Asteroseismology of alpha Centauri from Concordia
Authors: Grec, G.; Renaud, C.; Berthomieu, G.; Provost, J.
2003MSAIS...2..162G Altcode:
Following the significative progress in the knowledge of the
solar interior due to the analysis of the acoustical eigen modes,
the observationnal chalenge is presently to obtain similar data for
several other solar-like dwarf stars, leading to a new determination
of their fundamental data as mass and age. On a southern site, the
bright binary star alpha Centauri is the higher priority. Our group
works on the concept and realisation of an automated photometer usable
for long observations covering the antarctic night. An evolution to
the measurement of the variations of radial velocity of bright stars
is also considered.
---------------------------------------------------------
Title: New Determination of Solar Gravitational Moments j2 and J4.
Authors: Mecheri, Redouane; Provost, Janine; Abdelatif, Toufik E.;
Irbah, Abdenour
2003IAUJD..12E..11M Altcode:
By using the theory of Solar gravitational figure the solar quadrupole
and octopole moment respectively J2 and J4 were computed using Nice
Observatory solar model (P.Morel et al. (1997)) combined with a new
analytical model of solar differential rotation (Corbard et al. 2002)
taking into account a near-surface radial gradient of rotation inferred
and quantified from MDI f-modes observations. The values of J2 and
J4 obtained permit to evaluate the solar oblateness and it's induced
latitudinal variations of solar diameter in order to compare them
to those obtained from observations. We also use J2 to calculate its
contribution to the advance of the perihelion of Mercury for which the
found value is in agreement with the theory of General Relativity and
the measurements of Mercury's orbit by means of planetary ranging radar.
---------------------------------------------------------
Title: Revisited Calibration of Cen Binary System
Authors: Provost, J.; Berthomieu, G.; Thévenin, F.; Morel, P.;
Bouchy, F.; Carrier, F.
2003aahd.conf..557P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SYMPA: A Dedicated Instrument and a Network for Seismology
of Giant Planets
Authors: Schmider, F. -X.; Gay, J.; Jacob, C.; Fossat, E.; Valtier,
J. -C.; Mosser, B.; Mekarnia, D.; Guillot, T.; Provost, J.
2003aahd.conf..449S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asteroseismology and calibration of alpha Cen binary system
Authors: Thévenin, F.; Provost, J.; Morel, P.; Berthomieu, G.;
Bouchy, F.; Carrier, F.
2002A&A...392L...9T Altcode: 2002astro.ph..6283T
Using the oscillation frequencies of alpha Cen A recently discovered
by Bouchy & Carrier (\cite{bc01}, \cite{bc02}), the available
astrometric, photometric and spectroscopic data, we tried to improve
the calibration of the visual binary system alpha Cen. With the
revisited masses of Pourbaix et al. (\cite{pnm02}) we did not succeed
in obtaining a solution satisfying all the seismic observational
constraints. Relaxing the constraints on the masses, we have found
an age t<SUB>alpha Cen</SUB>=4850+/-500 Myr, an initial helium mass
fraction Y<SUB>i</SUB> = 0.300+/-0.008, and an initial metallicity
(Z/X)<SUB>i</SUB>=0.0459+/-0.0019, with M<SUB>A</SUB>=1.100+/-0.006
M<SUB>sun</SUB> and M<SUB>B</SUB>= 0.907+/-0.006 M<SUB>sun</SUB>
for alpha Cen A & B.
---------------------------------------------------------
Title: A search for solar g modes in the GOLF data
Authors: Gabriel, A. H.; Baudin, F.; Boumier, P.; García, R. A.;
Turck-Chièze, S.; Appourchaux, T.; Bertello, L.; Berthomieu, G.;
Charra, J.; Gough, D. O.; Pallé, P. L.; Provost, J.; Renaud, C.;
Robillot, J. -M.; Roca Cortés, T.; Thiery, S.; Ulrich, R. K.
2002A&A...390.1119G Altcode:
With over 5 years of GOLF data having some 90% continuity, a new
attempt has been made to search for possible solar g modes. Statistical
methods are used, based on the minimum of assumptions regarding the
solar physics; namely that mode line-widths are small compared with
the inverse of the observing time, and that modes are sought in the
frequency interval 150 to 400 mu Hz. A number of simulations are carried
out in order to understand the expected behaviour of a system consisting
principally of a solar noise continuum overlaid with some weak sharp
resonances. The method adopted is based on the FFT analysis of a time
series with zero-padding by a factor of 5. One prominent resonance at
284.666 mu Hz coincides with a previous tentative assignment as one
member of an n=1, l=1, p-mode multiplet. Components of two multiplets,
previously tentatively identified as possible g-mode candidates from
the GOLF data in 1998, continue to be found, although their statistical
significance is shown to be insufficient, within the present assumption
regarding the nature of the signal. An upper limit to the amplitude
of any g mode present is calculated using two different statistical
approaches, according to either the assumed absence (H0 hypothesis)
or the assumed presence (H1 hypothesis) of a signal. The former yields
a slightly lower limit of around 6 mm/s.
---------------------------------------------------------
Title: Global low frequency acoustic modes after half a solar cycle
aboard SOHO: an improved view of the nuclear core
Authors: Turck-Chièze, S.; Garcí, R. A.; Couvidat, S.; Kosovichev,
A. G.; Bertello, L.; Corbad, T.; Berthomieu, G.; Provost, J.;
Eff-Darwich, A.
2002ESASP.508..593T Altcode: 2002soho...11..593T
Solar global oscillations have now been measured for more than 20
years. The study of these modes has contributed to improve, along
time, the description of the solar core. We have now a proper access
to this part of the Sun, with ground networks observing for more than
10 years and the three instruments aboard SOHO in a quasi continuous
mode for now half a cycle. In this talk, we show the advantages of
the global acoustic modes measured at low frequency. They are due to
their longer lifetime and the reduced influence of the turbulent and
variable surface effects. As a consequence, we have converged last
year, after 30 years of unsuccess, to a boron-8 emitted neutrino flux
in perfect agreement with the better understood detection of these
neutrinos on earth. The splitting at low frequency is also now properly
determined but the extracted rotation information is still limited in
the core. It contains nevertheless the first dynamical vision of this
part of the radiative zone. We will focus on it up to the end of the
SOHO mission, together with the gravity mode region and the possible
internal signature of the magnetic field. Some limits are given on
these observables. Further improvements of their detectability are
under study and will be mentioned.
---------------------------------------------------------
Title: SYMPA: A Specified Instrument and a Dedicated Network for
Giant Planets' Sismology
Authors: Schmider, F. X.; Gay, Jean; Jacob, Cedric; Fossat, Eric;
Valtier, Jean-Claude; Mossier, Benoît; Mekarnia, Djamel; Guillot,
Tristan; Provost, Janine
2002sf2a.conf..611S Altcode:
The poster I will propose is about the 'SYMPA' project, an instrument
dedicated to the study of giant planets interiors, in paricular Jupiter,
based on principles of asterosismology. This instrument, developped in
collaboration between the department Fresnel of the Observatoire de la
Cote d'Azur, and the Laboratoire d'Astrophysique of Nice University,
is a Mach-Zender interferometer allowing observations of radial
velocities on jovien surface. The poster presents the contribution of
sismology to knowledge of planetary interiors, the principle of this
new imaging instrument and its performances, and some results from
first observations in february and march 2002.
---------------------------------------------------------
Title: Constraints derived from binary systems calibration: some
examples
Authors: Berthomieu, G.; Morel, P.; Provost, J.; Thevenin, F.
2002ASPC..274..199B Altcode: 2002ohds.conf..199B
No abstract at ADS
---------------------------------------------------------
Title: On the properties of solar-like oscillations: application
to Procyon
Authors: Provost, J.; Martić, M.; Berthomieu, G.; Morel, P.
2002ESASP.485..309P Altcode: 2002sshp.conf..309P
In order to interpret the ground-based observations of solar-like
stellar oscillations and prepare the scientific exploitation of future
spatial asteroseismic observations, we have studied the theoretical
properties of the frequencies of possible models for a given stellar
target, taking into account its observational constraints in the
Hertzsprung-Russell diagram. We have computed a set of "calibrated"
stellar models satisfying these constraints for a star of solar
metallicity. We present some results on the sensitivity of the
oscillation frequencies to the description of the convective transport
and to physical processes entering in the stellar modeling, like core
overshoot. We compare the seismic properties of our models with the
observations of Procyon by Martić et al. (2001).
---------------------------------------------------------
Title: P-Mode Observations on α Cen A with CORALIE
Authors: Carrier, F.; Bouchy, F.; Meynet, G.; Maeder, A.; Provost,
J.; Berthomieu, G.; Morel, P.; Thévenin, F.
2002ASPC..259..460C Altcode: 2002rnpp.conf..460C; 2002IAUCo.185..460C
No abstract at ADS
---------------------------------------------------------
Title: The zeta Herculis binary system revisited. Calibration and
seismology
Authors: Morel, P.; Berthomieu, G.; Provost, J.; Thévenin, F.
2001A&A...379..245M Altcode: 2001astro.ph.10004M
We have revisited the calibration of the visual binary system zeta
Herculis with the goal to give the seismological properties of the
G0 IV sub-giant zeta Her A. The sum of masses and the mass fraction
are derived from the most recent astrometric data mostly based on
the HIPPARCOS ones. We have derived the effective temperatures, the
luminosities and the metallicities from available spectroscopic data
and TYCHO photometric data and calibrations. For the calculations
of evolutionary models we have used updated physics and the most
recent physical data. A chi <SUP>2</SUP> minimization is performed
to approach the most reliable modeling parameters which reproduce
the observations within their error bars. For the age of the zeta Her
binary system we have obtained t<SUB>zeta Her</SUB>=3387 Myr, for the
masses m<SUB>zeta Her A</SUB>=1.45 M<SUB>sun</SUB> and m<SUB>zeta Her
B</SUB>=0.98 M<SUB>sun</SUB>, for the initial helium mass fraction
Y<SUB>i</SUB>=0.243, for the initial mass ratio of heavy elements to
hydrogen (Z/X)<SUB>i</SUB>= 0.0269 and for the mixing-length parameters
Lambda <SUB>zeta Her A</SUB>=0.92 and Lambda <SUB>zeta Her B</SUB>=0.90
using the Canuto & Mazitelli (\cite{cm91}, \cite{cm92}) convection
theory. Our results do not exclude that zeta Her A is itself a binary
sub-system as has been suspected many times in the past century;
the mass of the hypothetical unseen companion would be m<SUB>zeta Her
A</SUB>loa 0.05 M<SUB>sun</SUB>, a value significantly smaller than
previous determinations. A calibration made with an overshoot of the
convective core of zeta Her A leads to similar results but with a slight
increase of ~+250 Myr for the age. The adiabatic oscillation spectrum
of zeta Her A is found to be a complicated superposition of acoustic
and gravity modes. Some of these waves have a dual character. This
greatly complicates the classification of the non-radial modes. For
l=1 the modes all have both energy in the core and in the envelope;
they are mixed modes. For l=2,3 there is a succession of modes with
energy either in the core or in the envelope with a few mixed modes. The
echelle diagram used by the observers to extract the frequencies will
work for l=0, 2, 3. The large difference is found to be of the order of
/line{Delta nu<SUB>0</SUB> }~ 42 mu Hz, in agreement with the Martić
et al. (\cite{mlsab01}) seismic observations.
---------------------------------------------------------
Title: Solar Neutrino Emission Deduced from a Seismic Model
Authors: Turck-Chièze, S.; Couvidat, S.; Kosovichev, A. G.; Gabriel,
A. H.; Berthomieu, G.; Brun, A. S.; Christensen-Dalsgaard, J.; García,
R. A.; Gough, D. O.; Provost, J.; Roca-Cortes, T.; Roxburgh, I. W.;
Ulrich, R. K.
2001ApJ...555L..69T Altcode:
Three helioseismic instruments on the Solar and Heliospheric Observatory
have observed the Sun almost continuously since early 1996. This
has led to detailed study of the biases induced by the instruments
that measure intensity or Doppler velocity variation. Photospheric
turbulence hardly influences the tiny signature of conditions in the
energy-generating core in the low-order modes, which are therefore very
informative. We use sound-speed and density profiles inferred from GOLF
and MDI data including these modes, together with recent improvements
to stellar model computations, to build a spherically symmetric
seismically adjusted model in agreement with the observations. The
model is in hydrostatic and thermal balance and produces the present
observed luminosity. In constructing the model, we adopt the best
physics available, although we adjust some fundamental ingredients,
well within the commonly estimated errors, such as the p-p reaction
rate (+1%) and the heavy-element abundance (+3.5%); we also examine the
sensitivity of the density profile to the nuclear reaction rates. Then,
we deduce the corresponding emitted neutrino fluxes and consequently
demonstrate that it is unlikely that the deficit of the neutrino fluxes
measured on Earth can be explained by a spherically symmetric classical
model without neutrino flavor transitions. Finally, we discuss the
limitations of our results and future developments.
---------------------------------------------------------
Title: PICARD: solar diameter measure and g-mode search
Authors: Damé, L.; Appourchaux, T.; Berthomieu, G.; Boumier, P.;
Cugnet, D.; Gelly, B.; Provost, J.; Toutain, T.
2001ESASP.464..321D Altcode: 2001soho...10..321D
The PICARD microsatellite mission will provide 3 to 4 years simultaneous
measurements of the solar diameter, differential rotation and
solar constant to investigate the nature of their relations and
variabilities. The major instrument, SODISM, is a whole Sun imaging
telescope of Ø 110 mm which will deliver an absolute measure
(better than 4 mas) of the solar diameter and solar shape. Now in
Phase B, PICARD is expected to be launched by 2005. We recall the
scientific goals linked to the diameter measurement with emphasis on the
helioseismology g-mode interest, present the instrument optical concept
and present design, and give a brief overview of the program aspects.
---------------------------------------------------------
Title: α Centauri binary system: calibration and oscillations
Authors: Provost, J.; Berthomieu, G.; Morel, P.; Lebreton, Y.;
Thévenin, F.
2001ESASP.464..439P Altcode: 2001soho...10..439P
The two members of the visual binary α Centauri A & B provide
a great potentiality of testing stellar physics in conditions
slightly different from the solar ones and then deserve undivided
attention for internal structure modeling and oscillation frequencies
calculations. Detailed evolutionary models, including pre main-sequence
evolution have been performed using the recently determined masses
of Pourbaix et al. (1999). Models have been constructed with updated
physics including microscopic diffusion, different convection theories
and possible convective core overshoot. A χ<SUP>2</SUP> minimization
is empolyed to derive the age of the system, the initial helium
content, the initial mass ratio of heavy elements to hydrogen and the
convection parameters of each star model. A seismological analysis of
our calibrated models has been performed.
---------------------------------------------------------
Title: About structure inversions of simulated COROT data for a
solar like star
Authors: Berthomieu, G.; Toutain, T.; Gonczi, G.; Corbard, T.; Provost,
J.; Morel, P.
2001ESASP.464..411B Altcode: 2001soho...10..411B
We study the potential of exploring the internal structure of solar
like stars which could be observed by COROT. We consider a solar like
star of mass and age which allows stochastically excited oscillations
according to the results of Houdek et al (1999). Taking into account
COROT observational constraints we estimate a set of observable modes
with the uncertainties on their frequencies; then, in the same way
followed by Gough and Kosovichev (1993), we evaluate the possibility of
inferring structure properties of the star using inversion techniques.
---------------------------------------------------------
Title: g-mode detection: Where do we stand?
Authors: Appourchaux, T.; Andersen, B.; Berthomieu, G.; Chaplin, W.;
Elsworth, Y.; Finsterle, W.; Frölich, C.; Gough, D. O.; Hoeksema,
T.; Isaak, G.; Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.;
Toutain, T.
2001ESASP.464..467A Altcode: 2001soho...10..467A
We review the recent developments in determining the upper limits to
g-mode amplitudes obtained by SOHO instruments, GONG and BiSON. We
address how this limit can be improved by way of new helioseismic
instruments and/or new collaborations, hopefully providing in the not
too distant future unambiguous g-mode detection.
---------------------------------------------------------
Title: Calibrations of alpha Centauri A & B
Authors: Morel, P.; Provost, J.; Lebreton, Y.; Thévenin, F.;
Berthomieu, G.
2000A&A...363..675M Altcode: 2000astro.ph.10180M
Detailed evolutionary models of the visual binary alpha Centauri,
including pre main-sequence evolution, have been performed using the
masses recently determined by Pourbaix et al. (\cite{pnn99}). Models
have been constructed using the CEFF equation of state, OPAL opacities,
NACRE thermonuclear reaction rates and microscopic diffusion. A chi
<SUP>2</SUP>-minimization is performed to derive the most reliable set
of modeling parameters wp = {t<SUB>alpha Cen</SUB>,Y<SUB>i</SUB>,[frac
{FeH]<SUB>i</SUB>},alpha<SUB>A</SUB> ,alpha<SUB>B</SUB> }, where
t<SUB>alpha Cen</SUB> is the age of the system, Y<SUB>i</SUB> the
initial helium content, [frac {FeH]<SUB>i</SUB>} the initial metallicity
and, alpha<SUB>A</SUB> and alpha<SUB>B</SUB> the convection parameters
of the two components. Using the basic Böhm-Vitense (\cite{b58})
mixing-length theory of convection, we derive wp<SUB>BV</SUB> =2710 Myr,
0.284,0.257,1.53,1.57. We obtain a noticeably smaller age than estimated
previously, in agreement with Pourbaix et al. (\cite{pnn99}), mainly
because of the larger masses. If convective core overshoot is considered
we get wp<SUB>ov</SUB> =3530 Myr, 0.279,0.264,1.64,1.66\. The use of
Canuto & Mazitelli (\cite{cm91,cm92}) convection theory leads to
the set wp<SUB>CM</SUB> =4086 Myr, 0.271,0.264,0.964,0.986\. Using
the observational constraints adopted by Guenther & Demarque
(\cite{gd00}), and the basic mixing-length theory, we obtain
wp<SUB>GD</SUB> =5640 Myr, 0.300,0.296,1.86,1.97 and surface lithium
depletions close to their observed values. A seismological analysis of
our calibrated models has been performed. The determination of large and
small spacings between the frequencies of acoustic oscillations from
seismic observations would help to discriminate between the models of
alpha Cen computed with different masses and to confirm or rule out
the new determination of masses.
---------------------------------------------------------
Title: Observational Upper Limits to Low-Degree Solar g-Modes
Authors: Appourchaux, T.; Fröhlich, C.; Andersen, B.; Berthomieu, G.;
Chaplin, W. J.; Elsworth, Y.; Finsterle, W.; Gough, D. O.; Hoeksema,
J. T.; Isaak, G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.;
Sekii, T.; Toutain, T.
2000ApJ...538..401A Altcode:
Observations made by the Michelson Doppler Imager (MDI) and Variability
of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and
Heliospheric Observatory (SOHO) and by the ground-based Birmingham
Solar Oscillations Network (BiSON) and Global Oscillations Network
Group (GONG) have been used in a concerted effort to search for solar
gravity oscillations. All spectra are dominated by solar noise in the
frequency region from 100 to 1000 μHz, where g-modes are expected to be
found. Several methods have been used in an effort to extract any g-mode
signal present. These include (1) the correlation of data-both full-disk
and imaged (with different spatial-mask properties)-collected over
different time intervals from the same instrument, (2) the correlation
of near-contemporaneous data from different instruments, and (3) the
extraction-through the application of complex filtering techniques-of
the coherent part of data collected at different heights in the solar
atmosphere. The detection limit is set by the loss of coherence
caused by the temporal evolution and the motion (e.g., rotation)
of superficial structures. Although we cannot identify any g-mode
signature, we have nevertheless set a firm upper limit to the amplitudes
of the modes: at 200 μHz, they are below 10 mm s<SUP>-1</SUP> in
velocity, and below 0.5 parts per million in intensity. The velocity
limit corresponds very approximately to a peak-to-peak vertical
displacement of δR/R<SUB>solar</SUB>=2.3×10<SUP>-8</SUP> at the
solar surface. These levels which are much lower than prior claims,
are consistent with theoretical predictions.
---------------------------------------------------------
Title: Structure of the Solar Core: Effect of Asymmetry of Peak
Profiles
Authors: Basu, S.; Turck-Chièze, S.; Berthomieu, G.; Brun, A. S.;
Corbard, T.; Gonczi, G.; Christensen-Dalsgaard, J.; Provost, J.;
Thiery, S.; Gabriel, A. H.; Boumier, P.
2000ApJ...535.1078B Altcode: 2000astro.ph..1208B
Recent studies have established that peaks in solar oscillation
power spectra are not Lorentzian in shape but have a distinct
asymmetry. Fitting a symmetric Lorentzian profile to the peaks,
therefore, produces a shift in frequency of the modes. Accurate
determination of low-frequency modes is essential to infer the structure
of the solar core by inversion of the mode frequencies. In this paper
we investigate how the changes in frequencies of low-degree modes
obtained by fitting symmetric and asymmetric peak profiles change the
inferred properties of the solar core. We use data obtained by the
Global Oscillations at Low Frequencies (GOLF) project on board the
SOHO spacecraft. Two different solar models and inversion procedures
are used to invert the data in order to determine the sound speed in
the solar core. We find that for a given set of modes no significant
difference in the inferred sound speed results from taking asymmetry
into account when fitting the low-degree modes.
---------------------------------------------------------
Title: Non-axisymmetric oscillations of roAp stars
Authors: Bigot, L.; Provost, J.; Berthomieu, G.; Dziembowski, W. A.;
Goode, P. R.
2000A&A...356..218B Altcode:
We calculate the effect of a strong dipole magnetic field on
non-axisymmetric oscillations for roAp stars, with a typical range of
photospheric magnetic fields B_p [0.5-1.5] kG. As Dziembowski &
Goode (1996), we find that the oscillations are strongly affected by
such magnetic fields in two different ways. The first one concerns the
stability of modes, which are damped due to dissipation by Alfvénic
waves. It leads to a small imaginary part of the frequency, about
(1-15mu Hz). The real part of the frequencies is also affected and is
greater in the presence of magnetic field, with a shift of about 1-20 mu
Hz. We find that these shifts are strongly influenced by the geometry of
the mode, i.e. the value of the degree l, as it has already been shown
by Dziembowski & Goode (1996), and also by m, the azimuthal degree,
with a significant amplitude. The magnetic field, because it breaks
the spherical symmetry of the problem, raises partially the (2 l +1)
degeneracy of frequency in m. We find that the shift of both the real
and imaginary parts is always greater than in the case of axisymmetric
oscillations (m=0), except for sectoral modes (l=m), for which the
imaginary part is smaller. The second effect of large magnetic fields
is to complicate the mode identification. The perturbations cannot
be represented by pure single spherical harmonic, but by a series of
harmonics due to the angular dependence of the Lorentz force. It is
shown that this mixing of spherical harmonics also depends on the value
of m. However, our calculations do not explain the observed selection
of dipole modes in roAp stars, aligned with the magnetic axis, since
they do not minimize energy losses due to Alfvénic waves.
---------------------------------------------------------
Title: Calibration of iota Pegasi system
Authors: Morel, P.; Morel, Ch.; Provost, J.; Berthomieu, G.
2000A&A...354..636M Altcode: 1999astro.ph.12307M
Recent observations provide determinations of individual masses,
chemical composition and metallicity of the components of the
spectroscopic and interferometric binary iota Peg (Boden et
al. \cite{bkb99}). Using updated physics, to calibrate the system,
we have computed using the stellar evolutionary code CESAM (Morel
\cite{m97}), evolutionary sequences of stellar models with the
masses of iota Peg A 1.326 M_sun and iota Peg B 0.819 M_sun (Boden et
al. loc. cit) and with different values of the mixing-length parameter
alpha , the helium Y and the heavy element Z initial mass fraction
with the constraint of the observed metallicity. Adopting effective
temperatures and luminosities, as derived from observations with the
bolometric corrections, and the empirical scale of temperatures of
Alonso et al. (\cite{aam95}, \cite{aam96}), we find alpha_A =1.46,
alpha_B =1.36, Y=0.278, Z=0.017. The evolution time, including
pre-main sequence, is found within ~ 40 My<~ t_ev<~ 0.5 Gy. The
calibrated models of iota Peg. A and B are non homogeneous zero age
main sequence stars with the evolutionary time t_ev=56 My. Due to the
large uncertainties of their determinations, the values derived for the
mixing-length parameters are smaller than the solar one but however
marginally compatible with it. Our results ought to be improved as
soon as a more accurate value of the magnitude difference in the V
filter will be available. Detailed spectroscopic analysis for both
components looks practicable, so it is urgently needed.
---------------------------------------------------------
Title: Low-frequency p- and g-mode solar oscillations
Authors: Provost, J.; Berthomieu, G.; Morel, P.
2000A&A...353..775P Altcode:
In order to help the detection and identification of low-frequency p-
and g-modes in the solar spectrum observed by ground-based networks
and SoHO experiments, we study the properties of low degree (l=0 - 6)
low-frequency (100 - 2000 mu Hz) solar oscillations. The frequencies of
p- and g-modes have been computed for a set of solar models with updated
physics. We point out the specific properties of the oscillations of
mixed character, with noticeable amplitude both in central and external
layers. We analyze the sensitivity of low-frequency oscillations to
solar parameters like age, metallicity and luminosity, and to various
physical processes, like convective core overshoot and mass loss during
the beginning of solar evolution. We estimate the sensitivity of the
splittings of these low-frequency oscillations to the core rotation.
---------------------------------------------------------
Title: About the time of evolution of a solar model
Authors: Morel, P.; Provost, J.; Berthomieu, G.
2000A&A...353..771M Altcode: 1999astro.ph.10388M
The evolution of a solar model is initialized with homogeneous models
of either, pre-main sequence (P-models) or, zero-age main sequence
(Z-models). The zero-age of a solar model is conventionally referenced
as the time where the nuclear reactions just begin to dominate
gravitation as the primary source of energy. Fixing the physics,
we found that the structure of P- and Z-models computed with the same
physics are almost similar soon after the exhaustion of their convective
core. This similarity gives a connection between the age of the Sun
t_sun and the time t_cal elapsed in the calculation of calibrated
solar models. We found that a Z-model calibrated with t_cal=t_sun and
a P-model calibrated with t_cal=t_sun+25 My, are indistinguishable at
the relative accuracy level of a few 10<SUP>-4</SUP>.
---------------------------------------------------------
Title: Solar models and NACRE thermonuclear reaction rates
Authors: Morel, P.; Pichon, B.; Provost, J.; Berthomieu, G.
1999A&A...350..275M Altcode: 1999astro.ph..7381M
Using the most recent updated physics, calibrated solar models have
been computed with the new thermonuclear reaction rates of NACRE,
the recently available European compilation. Comparisons with models
computed with the reaction rates of Caughlan & Fowler (\cite{cf88})
and of Adelberger et al. (\cite{a98}) are made for global structure,
expected neutrinos fluxes, chemical composition and sound speed
profiles, helioseismological properties of p-modes and g-modes.
---------------------------------------------------------
Title: Non linear regularization for helioseismic
inversions. Application for the study of the solar tachocline
Authors: Corbard, T.; Blanc-Féraud, L.; Berthomieu, G.; Provost, J.
1999A&A...344..696C Altcode: 1999astro.ph..1112C
Inversions of rotational splittings have shown that there exists at
the base of the solar convection zone a region called the tachocline
in which high radial gradients of the rotation rate occur. The
usual linear regularization methods tend to smooth out any high
gradients in the solution, and may not be appropriate for the study
of this zone. In this paper we use, in the helioseismic context of
rotation inversions, regularization methods that have been developed
for edge-preserving regularization in computed imaging. It is shown
from Monte-Carlo simulations that this approach can lead directly to
results similar to those reached by linear inversions which however
required some assumptions on the shape of the transition in order to
be deconvolved. The application of this method to LOWL data leads to a
very thin tachocline. From the discussions on the parameters entering
the inversion and the Monte-Carlo simulations, our conclusion is that
the tachocline width is very likely below 0.05R_sun which lowers our
previous estimate of 0.05+/- 0.03R_sun obtained from the same dataset
(Corbard et al. 1998).
---------------------------------------------------------
Title: Light perturbation from stellar nonradial oscillations:
an application to solar oscillations
Authors: Toutain, T.; Berthomieu, G.; Provost, J.
1999A&A...344..188T Altcode:
We derive analytical expressions for the emerging intensity and
flux perturbations due to stellar nonradial oscillations taking into
account the sphericity of the emitting layers. These expressions are
derived using both the Eulerian and Lagrangian formulations. We show,
analytically and numerically, that these formulations are equivalent
and that they lead, in the limit of a plane-parallel atmosphere, to
analytical expressions derived in previous works. As an example, we
compute for a grey atmosphere intensity perturbations for low-degree
solar oscillations and show that some p and g modes can produce large
variations of intensity on the very limb of the solar disk. We also
compute the corresponding flux perturbations showing that differences
between spherical and plane-parallel computations for modes below
4 mHz do not exceed 15 percents, the better agreement being for low
frequencies.
---------------------------------------------------------
Title: Magnetic Effects on Stellar Oscillations
Authors: Bigot, L.; Provost, J.; Berthomieu, G.; Dziembowski, W. A.;
Goode, P. R.
1999RoAJ....9S.129B Altcode:
We calculate the effect of a strong dipole magnetic field (0.5-1.5 kG)
on stellar oscillations. To do this, we adopt a boundary layer approach,
by taking into account the dynamical effect of the magnetic field only
in a very thin layer, at the star surface. The magnetic field leads to
a damping of oscillations due to Alfvénic wave losses of energy. It
appears then an imaginary part of the frequency (~1-15 ?Hz) and a shift
of the real part (~1-15 ?Hz). The mode identification is complicated:
since the Lorentz force depends on the colatitude, one must represent
the oscillations by a linear combination of. We tackled non-axisymmetric
oscillations (m0) and then generalized the result of Dziembowski and
Goode (1996). These magnetic effects strongly depend on the geometric
nature of the mode (degree and azimuthal order m). We apply our
calculatio ns to roAp stars, whose oscillations appear essentially
as dipole modes ( = 1, m = 0) aligned with the magnetic axis. This
work does not explain this geometrical preference, since it does not
minimize Alfvénic losses of energy. However, it shows that one must
take into account the magnetic field to identify modes in roAp stars.
---------------------------------------------------------
Title: The acoustic cut-off frequency of roAp stars
Authors: Audard, N.; Kupka, F.; Morel, P.; Provost, J.; Weiss, W. W.
1998A&A...335..954A Altcode: 1997astro.ph.12126A
Some of the rapidly oscillating (roAp) stars, have frequencies which are
larger than the acoustic cut-off frequency determined from published
stellar models which usually assume a grey atmosphere. As the cut-off
frequency depends on the T(tau ) relation, we have computed models
and adiabatic frequencies for pulsating Ap stars with more realistic
atmospheres which include a frequency dependent treatment of radiative
transfer, take blanketing effects into account, and which have a better
treatment of the radiative pressure. In addition, we are using opacity
distribution functions specific to the atmospheric composition. With
these improvements over the classical stellar models the theoretical
acoustic cut-off frequency for roAp stars are increased by about
200 mu Hz, which brings them close to the observations. We restrict
the comparison of our computations with observations to those two
`pathological' roAp stars for which more reliable astrophysical
parameters are available, HD 24712 and alpha Cir, and comment briefly
on a third one, HD 134214. For alpha Cir we find models which have
indeed a cut-off frequency beyond the largest observed frequency and
which are well within the T<SUB>eff</SUB> - L/L_⊙ error box. For HD
24712 only models which are hotter by about 100 K and less luminous
by nearly 10% than what is actually the most probable value derived by
spectroscopy would have an acoustic cut-off frequency large enough. HD
134214 fits our models best, however, the error box for T<SUB>eff</SUB>
- L/L_⊙ is the largest of all three stars. One may thus speculate
that the old controversy about a mismatch between observed largest
frequencies and theoretical cut-off frequencies of roAp star models
is resolved. Based on hipparcos data.
---------------------------------------------------------
Title: Sensitivity of Low Frequency Oscillations to Updated Solar
Models
Authors: Provost, J.; Berthomieu, G.; Morel, P.
1998SSRv...85..117P Altcode:
A large number of acoustic frequencies have already been detected,
leading to a "seismic" model of the Sun rather close to the actual
standard solar models. The core however is not yet well constrained by
these observations and frequencies of low degree, low frequency modes
which penetrate deeply into the solar core are needed. We present here
a study on the sensitivity of low degree low frequency (50 - 900 µHz)
modes to the structure of the solar interior, in order to help their
detection and identification in the low frequency spectrum observed by
SoHO experiments like VIRGO and GOLF. The frequencies of p and g modes
have been computed for a set of solar models with updated physics (Morel
et al., 1997). We analyze their sensitivity to solar parameters like
age and metallicity, and to various physical processes, like convective
core overshoot and mass loss during the beginning of solar evolution.
---------------------------------------------------------
Title: Atmospheric structure and acoustic cut-off frequency of
roAp stars
Authors: Audard, N.; Kupka, F.; Morel, P.; Provost, J.; Weiss, W. W.
1998CoSka..27..304A Altcode: 1998astro.ph..5091A
Some of the rapidly oscillating (CP2) stars, have frequencies which are
larger than the theoretical acoustic cut-off frequency. As the cut-off
frequency depends on the T(tau) relation in the atmosphere, we have
computed models and adiabatic frequencies for pulsating Ap stars with
T(tau) laws based on Kurucz model atmospheres and on Hopf's purely
radiative relation. The frequency-dependent treatment of radiative
transfer as well as an improved calculation of the radiative pressure
in Kurucz model atmospheres increase the theoretical acoustic cut-off
frequency by about 200 microHz, which is closer to the observations. For
alpha Cir we find models with Kurucz atmospheres which have indeed a
cut-off frequency beyond the largest observed frequency and which are
well within the T(eff) - L error box. For HD 24712 only models which
are hotter by about 100 K and less luminous by nearly 10% than what
is actually the most probable value would have an acoustic cut-off
frequency large enough. One may thus speculate that the old controversy
about a mismatch between observed largest frequencies and theoretical
cut-off frequencies of roAp star models is resolved. However, the
observational errors for the astrophysical fundamental parameters have
to be reduced further and the model atmospheres refined.
---------------------------------------------------------
Title: Inferring the equatorial solar tachocline from frequency
splittings
Authors: Corbard, T.; Berthomieu, G.; Provost, J.; Morel, P.
1998A&A...330.1149C Altcode: 1997astro.ph.10319C
Helioseismic inversions, carried out for several years on various
ground-based and spatial observations, have shown that the solar
rotation rate presents two principal regimes: a quasi-rigid rotation in
the radiative interior and a latitude-dependent rotation in the whole
convection zone. The thin layer, named solar tachocline, between these
two regimes is difficult to infer through inverse techniques because
of the ill-posed nature of the problem that requires regularization
techniques which, in their global form, tend to smooth out any high
gradient in the solution. Thus, most of the previous attempts to study
the rotation profile of the solar tachocline have been carried out
through forward modeling. In this work we show that some appropriate
inverse techniques can also be used and we compare the ability of three
1D inverse techniques combined with two automatic strategies for the
choice of the regularization parameter, to infer the solar tachocline
profile in the equatorial plane. Our work, applied on LOWL (LOWL is
an abbreviation for low degree denoted by L) two years dataset, argue
in favor of a very sharp (0.05+/-0.03R_sun) transition zone located
at 0.695+/-0.005R_sun which is in good agreement with the previous
forward analysis carried out on Global Oscillations Network Group
(GONG), Big Bear Solar Observatory (BBSO) and LOWL datasets.
---------------------------------------------------------
Title: Sensitivity of the Sound Speed to the Physical Processes
Included in the Standard Solar Model
Authors: Turck-Chièze, S.; Basu, S.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Gabriel, M.; Morel, P.;
Provost, J.; Turcotte, S.; GOLF Team
1998ESASP.418..555T Altcode: 1998soho....6..555T
The accuracy of the present seismic data allows us to check the
solar internal sound speed down to the core. This is a great support
to check the hypothesis of the classical stellar evolution and to
predict the neutrino fluxes. The interpretation of these measurements
supposes an accurate determination of the structure of the standard
solar model as a first step. It is why a continuing effort has been
devoted to the knowledge of the physical quantities included in this
framework. In this poster we present 6 different solar models calculated
by different groups of the GOLF consortium. These models include the
most recent progress in atomic physics and nuclear physics. Then, we
discuss the sensitivity of the sound speed difference, between GOLF+MDI
observations and models, to different ingredients, in peculiar to the
opacity coefficients and the determination of the solar age.
---------------------------------------------------------
Title: Solar Sound Speed Inferred from SOHO Helioseismic Data
Authors: Gonczi, G.; Berthomieu, G.; Corbard, T.; Provost, J.; Morel,
P.; GOLF Team
1998ESASP.418..461G Altcode: 1998soho....6..461G
Inversions of the GOLF frequencies complemented with the 144 days MDI
data have been performed to obtain the solar sound speed and density. We
discuss the behavior of the sound speed in the solar core and in the
tachocline relatively to the parameters of the inversion and to the
solar model used.
---------------------------------------------------------
Title: Sounding solar and stellar interiors, IAU Symposium 181
(Posters)
Authors: Provost, Janine; Schmider, Francois-Xavier
1998IAUS..181P....P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The acoustic cut-off frequency of A to F stars
Authors: Audard, N.; Kupka, F.; Morel, P.; Provost, J.; Weiss, W. W.
1998IAUS..185..299A Altcode:
For some Ap stars, frequencies are observed which are larger than the
theoretical acoustic cut-off frequency, which strongly depends on the T
tau relation in the atmosphere. We have computed models and eigenmodes
for pulsating Ap stars. The internal stellar structure is obtained
with the CESAM code, and improved model atmospheres are constructed
with T tau laws derived from Kurucz's model atmospheres. These
models are compared to models whose atmospheres are derived from
the purely radiative Hopf's T tau law. Our main result is that the
frequency-dependent treatment of radiative transfer in Kurucz's model
atmospheres induces an increase of the theoretical acoustic cut-off
frequency, which brings us closer to the observations. As the cut-off
frequency is determined by the very outer layers, we point out the
necessity to compute very accurate model atmospheres.
---------------------------------------------------------
Title: Sensitivity of Low-frequency Oscillations to Updated Solar
Models
Authors: Provost, J.; Berthomieu, G.; Morel, P.
1998sce..conf..117P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observational Upper Limits for Low-Degree Solar g-modes
Authors: Fröhlich, C.; Finsterle, W.; Andersen, B.; Appourchaux, T.;
Chaplin, W. J.; Elsworth, Y.; D. O. Gough; Hoeksema, J. T.; Isaak,
G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.; Sekii, T.;
Toutain, T.
1998ESASP.418...67F Altcode: 1998soho....6...67F
No abstract at ADS
---------------------------------------------------------
Title: On the Use of Nonlinear Regularization in Inverse Methods
for the Solar Tachocline Profile Determination
Authors: Corbard, T.; Berthomieu, G.; Provost, J.; Blanc-Feraud, L.
1998ESASP.418..747C Altcode: 1998soho....6..747C; 1998astro.ph..6359C
Inferring the solar rotation from observed frequency splittings
represents an ill-posed problem in the sense of Hadamard and the
traditional approach used to override this difficulty consists in
regularizing the problem by adding some a priori information on the
global smoothness of the solution defined as the norm of its first or
second derivative. Nevertheless, inversions of rotational splittings
(e.g. Corbard et al., 1998; Schou et al., 1998) have shown that the
surface layers and the so-called solar tachocline (Spiegel & Zahn
1992) at the base of the convection zone are regions in which high
radial gradients of the rotation rate occur. %there exist high gradients
in the solar rotation profile near %the surface and at the base of
the convection zone (e.g. Corbard et al. 1998) %in the so-called solar
tachocline (Spiegel & Zahn 1992). Therefore, the global smoothness
a-priori which tends to smooth out every high gradient in the solution
may not be appropriate for the study of a zone like the tachocline which
is of particular interest for the study of solar dynamics (e.g. Elliot
1997). In order to infer the fine structure of such regions with high
gradients by inverting helioseismic data, we have to find a way to
preserve these zones in the inversion process. Setting a more adapted
constraint on the solution leads to non-linear regularization methods
that are in current use for edge-preserving regularization in computed
imaging (e.g. Blanc-Feraud et al. 1995). In this work, we investigate
their use in the helioseismic context of rotational inversions.
---------------------------------------------------------
Title: How Solar Models Fit the SoHO Observations?
Authors: Morel, P.; Provost, J.; Berthomieu, G.
1998ESASP.418..499M Altcode: 1998soho....6..499M
Solar models are computed with CESAM code using different physical
assumptions concerning the description of the surface layers, of the
convection, of the screening and of the mass loss during the first
stages of the evolution. The effect of the primeval evolution and of
the uncertainties in the global constraints (age, present-days Z/X and
radius values , protosolar abundances) are discussed. The agreement
with the observations is estimated by comparison with seismic models
derived from SoHO observations.
---------------------------------------------------------
Title: Comparative Studies of Low-Order and Low-Degree Solar p Modes
Authors: Appourchaux, T.; Andersen, B.; Chaplin, W.; Elsworth, Y.;
Finsterle, W.; Frohlich, C.; Gough, D.; Hoeksema, J. T.; Isaak, G.;
Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.; Toutain, T.
1998ESASP.418...95A Altcode: 1998soho....6...95A
The amplitudes of solar p-modes decrease steeply with decreasing
radial order below about 17. The background solar signal (solar noise)
in general increases steadily with decreasing frequency. For the
irradiance and radiance measurements with VIRGO or SOI/MDI on SOHO this
combination makes it difficult to detect low degree modes below about
1.8 mHz. The solar noise as observed in velocity with SOI/MDI or the
ground based BISON network is significantly lower in this region than
in intensity measurements. This allows low degree modes to be observed
close to 1 mHz. We present results of detection and charaterization
of the lowest order observable p-modes both in velocity and intensity
measurements. Where applicable the properties of the modes observed
with the two methods are compared.
---------------------------------------------------------
Title: Updated solar models.
Authors: Morel, P.; Provost, J.; Berthomieu, G.
1997A&A...327..349M Altcode: 1997astro.ph..5251M
Solar models computed with mass loss, microscopic diffusion of
helium and heavy element, and with updated physics have been evolved
from the pre-main sequence to present day; they are compared to
the observational constraints including lithium depletion and to
the seismic reference model of Basu et al. (1996ApJ...460.1064B),
derived by inversion. Microscopic diffusion significantly improves
the agreement with the observed solar frequencies and agree with the
seismic reference model within +/-0.2% for the sound velocity and +/-1%
for the density, but slightly worsens the neutrino problem. Neither
microscopic diffusion nor overshooting explain the observed lithium
depletion consistently with helioseismological constraints, while a mass
loss process does it. Models computed with OPAL equation of state and
opacities are in a better agreement with the seismic sound speed. To
reach the level of precision of helioseismological observations the
accuracy of solar models still needs to be improved by one order of
magnitude; any such improvement will necessitate equation of state
and opacity data taking into account of detailed changes in the mixture.
---------------------------------------------------------
Title: First View of the Solar Core from GOLF Acoustic Modes
Authors: Turck-Chièze, S.; Basu, S.; Brun, A. S.;
Christensen-Dalsgaard, J.; Eff-Darwich, A.; Lopes, I.; Pérez
Hernández, F.; Berthomieu, G.; Provost, J.; Ulrich, R. K.; Baudin,
F.; Boumier, P.; Charra, J.; Gabriel, A. H.; Garcia, R. A.; Grec,
G.; Renaud, C.; Robillot, J. M.; Roca Cortés, T.
1997SoPh..175..247T Altcode:
After 8 months of nearly continuous measurements the GOLF instrument,
aboard SOHO, has detected acoustic mode frequencies of more than 100
modes, extending from 1.4 mHz to 4.9 mHz. In this paper, we compare
these results with the best available predictions coming from solar
models. To verify the quality of the data, we examine the asymptotic
seismic parameters; this confirms the improvements achieved in solar
models during the last decade.
---------------------------------------------------------
Title: Solar internal rotation from LOWL data. A 2D regularized
least-squares inversion using B-splines.
Authors: Corbard, T.; Berthomieu, G.; Morel, P.; Provost, J.; Schou,
J.; Tomczyk, S.
1997A&A...324..298C Altcode:
Observations of surface oscillations of the Sun can be analyzed to
probe the solar interior. We use data obtained by the LOWL instrument
(LOWL is an abbreviation for low degree with degree denoted by L)
installed on Mauna Loa, Hawaii, since 1994 to investigate solar
internal rotation. A 2 Dimensional Regularized Least-Squares (2D RLS)
inverse method based on an expansion of the solution on B-splines of
arbitrary order is presented and applied to a 2 year dataset. This
method insures the regularity of the solution in the center and
introduces surface constraints. The choice of trade-off parameters in
the regularization term is discussed using an L-curves analysis and
we discuss the influence of the choice of the order of derivatives in
the regularization terms for the description of the deep interior. We
study the latitudinal resolution of the inversion of a-coefficients
compared to that of the inversion of individual splittings built from
these coefficients. Compared to the previous inversion of the first
three months of LOWL data made by Tomczyk et al. (1995ApJ...448L..57T),
our solution is extended up to the surface by adding high degree modes
and constraining the rotation to fit the spectrographic observations
(Snodgrass, 1984SPh....94...13S). In the radiative zone we obtain
more rigid rotation and our solution is compatible with a rotation of
the solar core of the order or smaller than the surface rotation at
mid latitude.
---------------------------------------------------------
Title: Theoretical solar models
Authors: Provost, J.
1997IAUS..181..121P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: First results from VIRGO on SoHO
Authors: Frohlich, C.; Andersen, B. N.; Appourchaux, T.; Berthomieu,
G.; Crommelynck, D. A.; Domingo, V.; Fichot, A.; Finsterle, W.;
Gómez, M. F.; Gough, D.; Jiménez, A.; Leifsen, T.; Lombaerts, M.;
Pap, J. M.; Provost, J.; Roca Cortés, T.; Romero, J.; Roth, H. -J.;
Sekii, T.; Telljohann, U.; Toutain, T.; Wehrli, C.
1997IAUS..181...67F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Three years of ANTENA: what we have done!
Authors: Belmonte, J. A.; Hernández, M. M.; Pérez Hernández, F.;
Vidal, I.; Roca Cortés, T.; Michel, E.; Auvergne, M.; Chevreton,
M.; Goupil, M. J.; Soufi, F.; Baglin, A.; Frandsen, S.; Viskum, M.;
Kjeldsen, H.; Christensen-Dalsgaard, J.; Schmider, F. X.; Fossat,
E.; Delache, Ph.; Provost, J.; Audard, N.; Berthomieu, G.; Paparó,
M.; Kovács, G.; Szabados, L.
1997IAUS..181..357B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sounding solar and stellar interiors
Authors: Provost, Janine; Schmider, Francois-Xavier
1997IAUS..181.....P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: First Results from VIRGO, the Experiment for Helioseismology
and Solar Irradiance Monitoring on SOHO
Authors: Fröhlich, Claus; Andersen, Bo N.; Appourchaux, Thierry;
Berthomieu, Gabrielle; Crommelynck, Dominique A.; Domingo, Vicente;
Fichot, Alain; Finsterle, Wolfgang; Gómez, Maria F.; Gough, Douglas;
Jiménez, Antonio; Leifsen, Torben; Lombaerts, Marc; Pap, Judit M.;
Provost, Janine; Roca Cortés, Teodoro; Romero, José; Roth, Hansjörg;
Sekii, Takashi; Telljohann, Udo; Toutain, Thierry; Wehrli, Christoph
1997SoPh..170....1F Altcode:
First results from the VIRGO experiment (Variability of solar IRradiance
and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and
Heliospheric Observatory) are reported. The observations started
mid-January 1996 for the radiometers and sunphotometers and near the
end of March for the luminosity oscillation imager. The performance of
all the instruments is very good, and the time series of the first 4-6
months are evaluated in terms of solar irradiance variability, solar
background noise characteristics and p-mode oscillations. The solar
irradiance is modulated by the passage of active regions across the
disk, but not all of the modulation is straightforwardly explained in
terms of sunspot flux blocking and facular enhancement. Helioseismic
inversions of the observed p-mode frequencies are more-or-less in
agreement with the latest standard solar models. The comparison of
VIRGO results with earlier ones shows evidence that magnetic activity
plays a significant role in the dynamics of the oscillations beyond
its modulation of the resonant frequencies. Moreover, by comparing
the amplitudes of different components ofp -mode multiplets, each of
which are influenced differently by spatial inhomogeneity, we have
found that activity enhances excitation.
---------------------------------------------------------
Title: The Current State of Solar Modeling
Authors: Christensen-Dalsgaard, J.; Dappen, W.; Ajukov, S. V.;
Anderson, E. R.; Antia, H. M.; Basu, S.; Baturin, V. A.; Berthomieu,
G.; Chaboyer, B.; Chitre, S. M.; Cox, A. N.; Demarque, P.; Donatowicz,
J.; Dziembowski, W. A.; Gabriel, M.; Gough, D. O.; Guenther, D. B.;
Guzik, J. A.; Harvey, J. W.; Hill, F.; Houdek, G.; Iglesias, C. A.;
Kosovichev, A. G.; Leibacher, J. W.; Morel, P.; Proffitt, C. R.;
Provost, J.; Reiter, J.; Rhodes, E. J., Jr.; Rogers, F. J.; Roxburgh,
I. W.; Thompson, M. J.; Ulrich, R. K.
1996Sci...272.1286C Altcode:
Data from the Global Oscillation Network Group (GONG) project and
other helioseismic experiments provide a test for models of stellar
interiors and for the thermodynamic and radiative properties, on which
the models depend, of matter under the extreme conditions found in the
sun. Current models are in agreement with the helioseismic inferences,
which suggests, for example, that the disagreement between the predicted
and observed fluxes of neutrinos from the sun is not caused by errors in
the models. However, the GONG data reveal subtle errors in the models,
such as an excess in sound speed just beneath the convection zone. These
discrepancies indicate effects that have so far not been correctly
accounted for; for example, it is plausible that the sound-speed
differences reflect weak mixing in stellar interiors, of potential
importance to the overall evolution of stars and ultimately to estimates
of the age of the galaxy based on stellar evolution calculations.
---------------------------------------------------------
Title: Differential Rotation and Dynamics of the Solar Interior
Authors: Thompson, M. J.; Toomre, J.; Anderson, E. R.; Antia, H. M.;
Berthomieu, G.; Burtonclay, D.; Chitre, S. M.; Christensen-Dalsgaard,
J.; Corbard, T.; De Rosa, M.; Genovese, C. R.; Gough, D. O.; Haber,
D. A.; Harvey, J. W.; Hill, F.; Howe, R.; Korzennik, S. G.; Kosovichev,
A. G.; Leibacher, J. W.; Pijpers, F. P.; Provost, J.; Rhodes, E. J.,
Jr.; Schou, J.; Sekii, T.; Stark, P. B.; Wilson, P. R.
1996Sci...272.1300T Altcode:
Splitting of the sun's global oscillation frequencies by large-scale
flows can be used to investigate how rotation varies with radius
and latitude within the solar interior. The nearly uninterrupted
observations by the Global Oscillation Network Group (GONG) yield
oscillation power spectra with high duty cycles and high signal-to-noise
ratios. Frequency splittings derived from GONG observations confirm
that the variation of rotation rate with latitude seen at the surface
carries through much of the convection zone, at the base of which is
an adjustment layer leading to latitudinally independent rotation at
greater depths. A distinctive shear layer just below the surface is
discernible at low to mid-latitudes.
---------------------------------------------------------
Title: VIRGO: Experiment for Helioseismology and Solar Irradiance
Monitoring
Authors: Fröhlich, Claus; Romero, José; Roth, Hansjörg; Wehrli,
Christoph; Andersen, Bo N.; Appourchaux, Thierry; Domingo, Vicente;
Telljohann, Udo; Berthomieu, Gabrielle; Delache, Philippe; Provost,
Janine; Toutain, Thierry; Crommelynck, Dominique A.; Chevalier,
André; Fichot, Alain; Däppen, Werner; Gough, Douglas; Hoeksema,
Todd; Jiménez, Antonio; Gómez, Maria F.; Herreros, José M.; Cortés,
Teodoro Roca; Jones, Andrew R.; Pap, Judit M.; Willson, Richard C.
1995SoPh..162..101F Altcode:
The scientific objective of the VIRGO experiment (Variability of solar
IRradiance and Gravity Oscillations) is to determine the characteristics
of pressure and internal gravity oscillations by observing irradiance
and radiance variations, to measure the solar total and spectral
irradiance and to quantify their variability over periods of days to
the duration of the mission. With these data helioseismological methods
can be used to probe the solar interior. Certain characteristics of
convection and its interaction with magnetic fields, related to, for
example, activity, will be studied from the results of the irradiance
monitoring and from the comparison of amplitudes and phases of the
oscillations as manifest in brightness from VIRGO, in velocity from
GOLF, and in both velocity and continuum intensity from SOI/MDI. The
VIRGO experiment contains two different active-cavity radiometers for
monitoring the solar `constant', two three-channel sunphotometers (SPM)
for the measurement of the spectral irradiance at 402, 500 and 862 nm,
and a low-resolution imager (LOI) with 12 pixels, for the measurement
of the radiance distribution over the solar disk at 500 um. In this
paper the scientific objectives of VIRGO are presented, the instruments
and the data acquisition and control system are described in detail,
and their measured performance is given.
---------------------------------------------------------
Title: Seismological comparison of giant planet interior models.
Authors: Gudkova, T.; Mosser, B.; Provost, J.; Chabrier, G.; Gautier,
D.; Guillot, T.
1995A&A...303..594G Altcode:
We investigate the possibility to characterize the differences between
interior models of Jupiter and Saturn with the help of seismological
criteria. For both planets we consider two groups of models: first,
models based on different descriptions of the hydrogen equation of
state (plasma phase transition (PPT) or interpolated EOS) and second,
models with different descriptions of the energy transport mechanism
(fully convective models and radiative-convective models). The acoustic
modes eigenfrequency patterns of both planets are calculated for the
different models for degrees up to 30 (Jupiter) or 15 (Saturn), and
for frequencies up to the tropospheric cutoff frequency. The different
treatments of the hydrogen pressure ionization lead to substantial
differences in the oscillation frequencies, up to 120μHz for Jupiter
and 40μHz for Saturn. These variations come partly from the fact that
the location of the rock/ice core depends strongly on the equation of
state in the fluid envelope. The differences between the oscillation
frequencies corresponding respectively to fully and non fully adiabatic
models vary from 0 to 80μHz for Jupiter and to 40μHz for Saturn. This
stems from the fact that the location of the PPT in the planetary
interior and the core size depend strongly on the characteristics of
the models. The amplitudes of the calculated variations suggest that
future seismological observations should provide stringent tests to
discriminate between various planetary interior models. Jupiter or
Saturn may in fact be used as natural high-pressure laboratories to
characterize the very nature of hydrogen pressure-metallization.
---------------------------------------------------------
Title: Predicted Intensity/velocity Amplitude and Phase Lag of
Gravity Modes
Authors: Toutain, T.; Berthomieu, J.; Provost, J.; Gouttebrouze, P.
1995ESASP.376b.419T Altcode: 1995soho....2..419T; 1995help.confP.419T
No abstract at ADS
---------------------------------------------------------
Title: Nonadiabatic Computations of Solar P-Modes
Authors: Gouttebroze, P.; Provost, J.; Berthomieu, G.; Toutain, T.;
Morel, P.
1995ESASP.376b..53G Altcode: 1995soho....2...53G; 1995help.confP..53G
A set of p-mode eigenfrequencies and eigenfunctions is computed
both in adiabatic and nonadiabatic case, using different solar
models. Concerning the treatment of radiation for the p-mode
computations, the effects diffusion and Eddington approximations
are compared. Convection effects are neglected, but the different
formulations of the "frozen" convection approximation (e.g. Unno
et al. 1989) are investigated. From the eigenfunctions so computed,
the authors deduce the phase difference between intensity and Doppler
shift variations integrated on the solar disk. The ratio of intensity
to velocity amplitudes is also determined. Eigenfrequencies, phase
differences and amplitude ratios are compared to available observations.
---------------------------------------------------------
Title: Solar Rotation from 2d Inversion
Authors: Corbard, Th.; Berthomieu, G.; Gonczi, G.; Provost, J.;
Morel, P.
1995ESASP.376b.289C Altcode: 1995soho....2..289C; 1995help.confP.289C
No abstract at ADS
---------------------------------------------------------
Title: Seismological effects of convective-core overshooting in
stars of intermediate mass.
Authors: Audard, N.; Provost, J.; Christensen-Dalsgaard, J.
1995A&A...297..427A Altcode:
We study the effects of convective-core overshooting on acoustic and
gravity modes of low degree l for stars of intermediate mass. Using
the CESAM code (Morel 1993) we have computed sequences of stars of 1.7
and 2M<SUB>sun</SUB>_ along the main sequence; both "classical" models,
without overshooting, and models including convective overshooting from
the core over 0.1 and 0.2 pressure scale-height are considered. We
compare the structure and the oscillation properties of models of
the same effective temperature. At given effective temperature,
overshooting increases the stellar radius, and the main effect on
oscillations is therefore to decrease the frequencies. This could
give rise to a problem of the identification of the radial order of
modes. The effects of overshooting on the deep stellar structure can
be examined through different frequency combinations. In particular,
the ratio (ν_n,0_+ν_n-1,0_-2ν_n-1,1_)/(ν_n,0_-ν_n-1,2_) (where
ν_n,l_ is the cyclic frequency of a mode of radial order n and
degree l) is very sensitive to the structure of the stellar core
throughout the whole main sequence, and could therefore be a good
indicator of the stellar age and of the extent of overshooting. The
estimation of stellar mass and age from seismological observations is
modified by convective core penetration, which must thus be taken into
account for asteroseismological calibration. We furthermore study the
evolution of p and g modes of low radial order along the main sequence,
and exhibit the exchange of physical nature between pairs of modes
whose frequencies approach very closely, related to the so-called
avoided crossing. Convective core penetration makes avoided crossing
occur at lower effective temperature, substantially changing the
distribution of the kinetic-energy density of mixed modes throughout
the stellar interior at a given effective temperature. Independently
of overshooting, these modes have kinetic energy both in the central
and external parts, and their observation would provide a powerful
tool for probing the deep interior of stars and for investigating the
importance of convective-core overshooting.
---------------------------------------------------------
Title: Neutrino Capture Rates Predicted by Standard Solar Models
Authors: Berthomieu, G.; Provost, J.; Morel, P.
1995ASPC...76..109B Altcode: 1995gong.conf..109B
No abstract at ADS
---------------------------------------------------------
Title: A New TEchnology Network for Asteroseismology - A.N.T.E.N.A.
Authors: Roca Cortes, T.; Belmonte, J. A.; Delache, P.; Michel, E.;
Frandsen, S.; Schmider, F. X.; Auvergne, M.; Fossat, E.; Vidal, I.;
Kjeldsen, H.; Douglas, N.; Lelievre, G.; Chevreton, M.; Vauclair,
G.; Audard, N.; Baglin, A.; Berthomieu, G.; Christensen-Dalsgaard,
J.; Dolez, N.; Goupil, M. J.; Perez Hernandez, F.; Pfeiffer, B.;
Provost, J.; Viskum, M.
1995ASPC...76..630R Altcode: 1995gong.conf..630R
No abstract at ADS
---------------------------------------------------------
Title: Low Temperature Opacities Applied to Solar Calibrated Models
Authors: Neuforge, C.; Provost, J.; Berthomieu, G.; Morel, P.
1995ASPC...78...75N Altcode: 1995aapn.conf...75N
No abstract at ADS
---------------------------------------------------------
Title: Lithium Depletion in the Sun
Authors: Morel, P.; Provost, J.; Berthomieu, G.; Matias, J.; Zahn,
J. P.
1995LIACo..32..395M Altcode: 1995sews.book..395M
No abstract at ADS
---------------------------------------------------------
Title: On the Solar Core Rotation - IRIS Results
Authors: Fossat, E.; Loudagh, S.; Gelly, B.; Grec, G.; Pantel, A.;
Provost, J.; Berthomieu, G.; Ehgamberdiev, S.; Khalikov, S.; Lazrek,
M.; Palle, P. L.; Regulo, C.
1995ASPC...76...24F Altcode: 1995gong.conf...24F
No abstract at ADS
---------------------------------------------------------
Title: Probing Convective-Core Overshooting through Seismology of
Intermediate-Mass Stars
Authors: Audard, N.; Provost, J.
1995ASPC...76..645A Altcode: 1995gong.conf..645A
No abstract at ADS
---------------------------------------------------------
Title: On the Solar Core Rotation - IRIS Results
Authors: Fossat, E.; Loudagh, S.; Gelly, B.; Grec, G.; Panel, A.;
Provost, J.; Berthomieu, G.; Ehgamberdiev, S.; Khalikov, S.; Lazrek,
M.; Palle, P. L.; Regulo, C.
1995ASPC...76....4F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Diffusion phenomena and probabilistic methods
Authors: Provost, J. -P.
1995cdhs.conf....1P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: About solar model calibration.
Authors: Morel, P.; Berthomieu, G.; Provost, J.; Lebreton, Y.
1995LNP...458..197M Altcode:
A new value of the ratio of the heavy elements content to hydrogen
abundance Z/X has been recently estimated in the solar atmosphere. The
authors present the consequences of this result on the solar standard
model and examine the sensitivity to Z/X of the solar neutrinos flux
predictions and of the oscillation frequencies.
---------------------------------------------------------
Title: Convective Penetration in the Sun in Presence of Microscopic
Diffusion
Authors: Provost, J.; Morel, P.; Berthomieu, G.; Zahn, J. P.
1995LIACo..32..201P Altcode: 1995sews.book..201P
No abstract at ADS
---------------------------------------------------------
Title: On P-mode oscillations in stars from 1M <SUB>⊙</SUB> to
2M <SUB>⊙</SUB>
Authors: Audard, N.; Provost, J.
1994SoPh..152..316A Altcode: 1994IAUCo.143..316A; 1994svs..coll..316A
The structure of stars more massive than about 1.2M<SUB>⊙</SUB>
is characterized by a convective core. We have studied the evolution
with age and mass of acoustic frequencies if high radial ordern and low
degree ℓ for models of stars of 1, 1.5 and 2M<SUB>⊙</SUB>. Using a
polynomial approximation for the frequency, the p-mode spectrum can be
characterized by derived global asteroseimic coefficients, i.e. the mean
separationv<SUB>0</SUB>∼v<SUB>n,ℓ</SUB>−v<SUB>n,−1,ℓ</SUB>
and the small frequency
separationΔv<SUB>0,2</SUB>∼v<SUB>n,ℓ=0</SUB>−v<SUB>n,−1,ℓ=2</SUB>.
The diagram(v<SUB>0</SUB>,Δ(v<SUB>0,2</SUB>/v<SUB>0</SUB> plotted
along the evolutionary tracks would help to separate the effects
of age and mass. We study of sensitivity of these coefficients
and other observable quantities, like the radius and luminosity,
the stellar parameters in the vicinity of 1M<SUB>⊙</SUB> and
2M<SUB>⊙</SUB>; this sensitivity substantially depends on the
stellar mass and must be taken into account for asteroseismic
calibration of stellar clusters. Considering finally some rapid
variations of the internal structure, we show that the second frequency
differenceδ<SUB>2</SUB>v=v<SUB>n,ℓ</SUB>−2v<SUB>n,−1,ℓ</SUB>+v<SUB>n,−2,ℓ</SUB>
exhibits and oscillatory behaviour well related to the rapid variation
of the adiabatic exponent γ in the HeII ionization zone.
---------------------------------------------------------
Title: Incorporating the atmosphere in stellar structure models:
the solar case
Authors: Morel, P.; van't Veer, C.; Provost, J.; Berthomieu, G.;
Castelli, F.; Cayrel, R.; Goupil, M. J.; Lebreton, Y.
1994A&A...286...91M Altcode:
The diffusion limit of the transfer equation used in the calculations
of stellar interior models is only valid at large Rosseland optical
depth. From atmosphere models obtained with ATLAS 9 (Kurucz), it is
shown here that the diffusion limit of the transfer equation becomes
valid only at Rosseland optical depths τ_R_ >~ 10 that is at a
location well inside the Sun's convective zone. For the calculations
of stellar evolution, the atmosphere is built from T(τ) laws that are
derived either from theory or from full atmosphere computations; such a
T(τ) law depends upon effective temperature and gravity, therefore on
the evolutionary state of the model. Hence, in general, when following
the evolution of a star, various T(τ) laws need to be introduced. In
the case of the Sun, however, we show here that the atmosphere can be
restored with the use of only one T(τ) law. Particular efforts have
been made to include physics as consistent as possible in both the
model atmosphere from which one derives T(τ) laws and the internal
structure calculations which use them; as a result, we can rebuild
the atmosphere in stellar models with an accuracy of about +/- 0.5%
for the sound speed and the pressure. Remaining discrepancies are of
small effect on solar calibrated models. For the solar oscillations,
such small discrepancies generate frequency differences no larger than
2μHz for low degrees modes to about 10μHz for modes of large degrees
around 400.
---------------------------------------------------------
Title: Jovian seismology: influence of the troposphere thermal
signature and seismological diagnosis
Authors: Gudkova, T.; Mosser, B.; Gautier, D.; Guillot, T.; Provost,
J.; Chabrier, G.
1994DPS....26.1307G Altcode: 1994BAAS...26.1109G
No abstract at ADS
---------------------------------------------------------
Title: Seismological properties of intermediate-mass stars
Authors: Audard, N.; Provost, J.
1994A&A...282...73A Altcode:
Stars more massive than about 1.2 solar mass are characterized by
a convective core, which induces at its frontier a rapid variation
of the density, sound speed and Brunt-Vaisala frequency, close to
a discontinuity. For three stars of 1, 1.5 and 2 solar mass we have
studied the properties of p-mode frequencies of high radial order and
low degree, and we present results on the effects on p-mode oscillations
of some rapid variations of the internal structure. We first point out
the difficulties of the classical asymptotic theory to represent with
accuracy the p-mode spectrum of the stars considered. We compare the
numerical frequencies with asymptotic and polynomial approximations
obtained from fits. The variation of the derived global coefficients
characterizing the p-mode spectrum along the evolutionary tracks has
been estimated; it would help to separate the effects of age and mass
of intermediate-mass stars. The sensitivity of these coefficients
to stellar parameters substantially depends on the stellar mass and
must be considered for asteroseismic calibration. The effects of rapid
variations in the stellar internal structure are finally considered. An
asymptotic formula taking into account the rapid variation of the
sound speed at the convective core boundary of the 1.5 and 2 solar
mass stars predicts an oscillatory behavior of the frequencies
with a very large period. We also show that the second frequency
difference delta<SUB>2</SUB>nu = nu<SUB>n, l</SUB> - 2nu<SUB>n-1,
l</SUB> + nu<SUB>n-2, l</SUB> exhibits a substantial oscillation
which corresponds to the region of the He II ionization of the 1,
1.5 and 2 solar mass stars.
---------------------------------------------------------
Title: On the equation of state in Jovian seismology
Authors: Provost, J.; Mosser, B.; Chabrier, G.
1994esa..conf..596P Altcode: 1994IAUCo.147..596P
No abstract at ADS
---------------------------------------------------------
Title: Symplectic geometry and physics: three introductory lectures.
Authors: Provost, J. -P.
1994mcag.conf..209P Altcode:
Contents: Lecture I: geometry and physics. Lecture II: the occurrence
of symplectic geometry in optics and mechanics. Lecture III: three
applications of symplectic geometry. Epilog: the cat's paradigm.
---------------------------------------------------------
Title: Standard Solar Models with CESAM Code: Neutrinos and
Helioseismology
Authors: Berthomieu, J.; Provost, J.; Morel, P.; Lebreton, Y.
1994snft.book...62B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The solar interior
Authors: Turck-Chièze, S.; Däppen, W.; Fossat, E.; Provost, J.;
Schatzman, E.; Vignaud, D.
1993PhR...230...57T Altcode:
This report confronts the different aspects of the solar interior from
the experimental and theoretical points of view, discussing photospheric
abundances, neutrinos and acoustic mode measurements. The theoretical
approach mainly concerns the classical framework of stellar evolution,
nevertheless, particle interpretation of the data and astrophysical
solutions invoked in the last 10 years are coherently examined.
---------------------------------------------------------
Title: A measurement of the I = I solar rotational splitting
Authors: Loudagh, S.; Provost, J.; Berthomieu, G.; Ehgamberdiev, S.;
Fossat, E.; Gelly, B.; Grec, G.; Khalikov, S.; Lazrek, M.; Palle,
P.; Regulo, C.; Sanchez, L.; Schmider, F. -X.
1993A&A...275L..25L Altcode:
A precise measurement of the l = 1 rotational splitting has been
derived from the 1991 IRIS data and it leads to a moderate rotation
rate in the solar core.
---------------------------------------------------------
Title: A New Asymptotic Formalism for Jovian Seismology
Authors: Provost, J.; Mosser, B.; Berthomieu, G.
1993A&A...274..595P Altcode:
In order to account for the core of the giant planets interior, a second
order asymptotic formalism has been adapted to Jovian seismology, for
low degree high frequency acoustic modes, starting from the work of
Tassoul (1980). We consider a spherical non-rotating model of Jupiter
presenting a strong discontinuity in density and sound speed at the
core frontier. We exhibit a peculiar behavior of the pressure modes
eigenfrequency pattern. Contrarily to the solar case, eigenfrequencies
are not almost equidistant, and this has to be taken into account when
interpreting an observed spectrum. A qualitative agreement with the
frequencies computed from a planetary model is obtained. Therefore
we use the asymptotic formalism to compare actual Jovian interior
models. The formalism developed here is applicable to any non rotating
object presenting a noncontinuous interior, provided the asymptotic
constraints are fulfilled. The limit of validity of this formalism is
discussed in the context of Jovian seismology.
---------------------------------------------------------
Title: Standard solar models with CESAM code - Neutrinos and
helioseismology
Authors: Berthomieu, G.; Provost, J.; Morel, P.; Lebreton, Y.
1993A&A...268..775B Altcode:
A new code for stellar evolution named CESAM has been constructed
and standard solar models have been computed using it. Their global
characteristics, predicted capture rates of neutrinos for the chlorine
and gallium experiments, and their seismological properties are given
and compared to the observational constraints. The emphasis is put on
the effect of the recent opacities of Livermore for different mixtures,
corresponding to recent abundances determination, and on the neutrino
predictions and solar oscillations.
---------------------------------------------------------
Title: Restoration of the atmosphere in solar models
Authors: Morel, P.; van't Veer, C.; Berthomieu, G.; Cayrel, R.;
Castelli, F.; Goupil, M. J.; Lebreton, Y.; Provost, J.
1993ASPC...40...57M Altcode: 1993IAUCo.137...57M; 1993ist..proc...57M
No abstract at ADS
---------------------------------------------------------
Title: CESAM solar models
Authors: Morel, P.; Berthomieu, G.; Provost, J.; Lebreton, Y.
1993ASPC...40...54M Altcode: 1993ist..proc...54M; 1993IAUCo.137...54M
No abstract at ADS
---------------------------------------------------------
Title: About seismological properties of intermediate mass stars
Authors: Audard, N.; Provost, J.
1993ASPC...40..544A Altcode: 1993ist..proc..544A; 1993IAUCo.137..544A
No abstract at ADS
---------------------------------------------------------
Title: Seismological constraints on convective penetration in the Sun.
Authors: Berthomieu, G.; Morel, P.; Provost, J.; Zahn, J. -P.
1993ASPC...40...60B Altcode: 1993IAUCo.137...60B; 1993ist..proc...60B
Penetrative convection is expected below stellar convection zones, where
it should achieve a nearly adiabatic stratification. A theoretical
prediction of the penetration depth has been recently made by
Zahn (1991) which includes an arbitrary parameter ζ depending
on the properties of the convective motions. The authors use the
helioseismological constraints to calibrate the value of this parameter.
---------------------------------------------------------
Title: Convective Penetration in the Sun
Authors: Berthomieu, G.; Morel, P.; Provost, J.; Zahn, J. -P.
1992ASPC...26..158B Altcode: 1992csss....7..158B
No abstract at ADS
---------------------------------------------------------
Title: The Spectrum of Gravity Modes as a Function of the Solar
Structure - Model with a Mixed Core
Authors: Provost, J.; Gavryuseva, E.; Gavryusev, V.; Berthomieu, G.
1991SoPh..133..139P Altcode:
The asymptotic properties of the gravity modes of solar models with a
mixed core have been investigated. Such models have been constructed
by Gavryusev and Gavryuseva (1984) to explain the low value of
the observed neutrino flux (Cleveland, Davis, and Rowly, 1984). The
strong enhancement of the Brunt-Väissälä frequency in the region of
variable chemical composition at the boundary of the mixed core gives
rise to a nonequidistant spectrum of gravity mode periods (Figure 1),
contrary to the case of `standard' models. These models do not satisfy
the helioseismological constraints given by the p-modes. However, the
peculiar behavior of the numerically computed periods of the gravity
modes is interesting to analyze, in view of observational detection
in solar and stellar spectra.
---------------------------------------------------------
Title: The asymptotic spectrum of gravity modes as a function of
the solar structure: Standard solar model
Authors: Berthomieu, G.; Provost, J.
1991SoPh..133..127B Altcode:
Some results are given on the properties of the second-order asymptotic
expression of the periods of low-degree gravity modes and on their
rotational splitting. These could be of some help for the detection
of these modes in the signal.
---------------------------------------------------------
Title: On the visibility of low frequency nonradial pulsations for
a grey solar atmosphere
Authors: Provost, J.; Berthomieu, G.
1991AdSpR..11d..39P Altcode: 1991AdSpR..11...39P
The visibility of low-frequency nonradial solar oscillations with
respect to their degree and frequency is examined in the framework
of ground-based and space-based helioseismology experiments. Two
effects leading to the variation of the observed flux are examined:
wave-induced temperature variation and opacity variation. The effect
of the wave-induced opacity perturbation on the intensity fluctuation
of gravity modes is considered in the grey-atmosphere approximation
for both adiabatic and nonadiabatic modes.
---------------------------------------------------------
Title: Héliosismologie: théorie.
Authors: Berthomieu, G.; Provost, J.
1991sed..conf...77B Altcode:
Contents: (1) Oscillations adiabatiques d'un modèle solaire: (A)
Propriétés générales. (B) Description asymptotique des modes
de pression et de gravité. (2) Structure du soleil déduite des
observations. (A) Méthode directe: sensibilité au modèle. (B)
Méthode inverse. (3) La rotation solaire. (A) Effet de la rotation
sur les fréquences d'oscillation. (B) Les coefficients a<SUB>i</SUB>
comme mesure du splitting des fréquences. (C) Inversion de la rotation
solaire. Résultats.
---------------------------------------------------------
Title: Non-Equidistant Spectrum of Gravity Modes of a Solar Model
with a Mixed Core
Authors: Provost, J.; Berthomieu, G.; Gavriuseva, E.; Gavriusev, V.
1990SoPh..128..111P Altcode: 1990IAUCo.121P.111P
The asymptotic properties of the gravity modes of solar models with a
mixed core have been investigated. In this model, the Brunt-Väissälä
frequency has a strong enhancement in the region of variable chemical
composition at the boundary of the mixed core, giving rise to a
non-equidistant spectrum of gravity modes periods. An asymptotic
expression for the periods is derived, which relates the main feature
of the departure from period equidistance to the stratification of the
model. Qualitative agreement with the numerical periods of the model
is obtained.
---------------------------------------------------------
Title: Investigation on Numerical Accuracy of ZAMS Models of One
Solar Mass
Authors: Morel, P.; Provost, J.; Berthomieu, G.
1990SoPh..128....7M Altcode: 1990IAUCo.121P...7M
Helioseismology requires solar models computed with great
accuracy. Results of investigations about the incidence in ZAMS
models of one solar mass of the numerical errors arising from the
interpolation of opacity tables and from the integration of the
atmosphere are reported.
---------------------------------------------------------
Title: Light and velocity visibility of solar g-mode oscillations
Authors: Berthomieu, G.; Provost, J.
1990A&A...227..563B Altcode:
The properties of the integrated intensity and velocity variations
of the solar gravity modes in the 40 to 130 microHz frequency range
are given in the adiabatic and nonadiabatic case. Grey atmosphere and
Eddington approximations have been used as a first step. Equipartition
of the energy has been assumed in order to give an estimation of the
amplitudes. For integration over the whole disk, low degree models l =
1, 2 have the highest amplitudes due to the spatial filtering, but a
decrease of this amplitude appears in the range 60 to 80 microHz due
to the intrinsic properties of the waves.
---------------------------------------------------------
Title: Integrated light and velocity of solar g modes oscillations.
Authors: Provost, J.; Berthomieu, G.
1988ESASP.286..387P Altcode: 1988ssls.rept..387P
The properties of the integrated intensity and velocity variations
of the solar gravity modes for different spatial filters are studied
in the adiabatic and nonadiabatic cases in the frequency range 40 -
120 μHz. Predicted amplitudes are given assuming equipartition of
energy between the modes. As far as the intensity is concerned, a lack
of amplitude has been pointed out around 60 μHz, which should have
implication on the whole disc Virgo and ground based observations.
---------------------------------------------------------
Title: Influence of the axial-vector coupling constant on solar
models - Solar neutrino fluxes, helium content and oscillations
Authors: Lebreton, Y.; Schatzman, E.; Berthomieu, G.; Provost, J.
1988A&A...200L...5L Altcode:
This paper examines the effects of axial-vector coupling constant g(A)
changes on the outputs of solar-models (such as helium content, neutrino
fluxes, and oscillations), using existing 'calibrated' solar models and
assuming that the other inputs of the models are well-known. The results
suggest that a very high value of g(A) (greater than 1.55) is required
to reconcile the theoretical and observed neutrino fluxes. This value
seems to be improbable with respect to the present range of measurements
of g(A); moreover, a solar model with such a high value of g(A) is
associated to a helium content that is above the usually accepted value.
---------------------------------------------------------
Title: A Solar Model with Turbulent Diffusion Mixing - Surface
Abundances and Oscillations
Authors: Lebreton, Y.; Berthomieu, G.; Provost, J.
1988IAUS..123...95L Altcode:
A solar model which includes the plausible presence of a mild mixing
in the solar inner radiative zone is presented. The model takes
into account the inhibition of turbulent motions. The properties
of the model are compared to the standard model properties and to
observational results: the turbulent diffusion mixing (TDM) improves
the results on surface abundances of the light elements (<SUP>7</SUP>Li,
<SUP>3</SUP>He) and does not reduce the solar neutrino flux relative to
the standard model. Moreover, the TDM weakly modifies the oscillation
frequencies.
---------------------------------------------------------
Title: Asymptotic Properties of Low Degree Gravity Modes
Authors: Berthomieu, G.; Provost, J.
1988IAUS..123..121B Altcode:
Asymptotic properties of low degree gravity modes and their relation to
the stratification of the model through the Brunt-Väissälä frequency
are discussed for a solar type model and for a 10 M_sun; model.
---------------------------------------------------------
Title: Effective Operators in Charge Exchange Studies
Authors: Levy, B.; Provost, J.; Roueff, E.
1987IAUS..120...25L Altcode:
The rate coefficient for the charge transfer reaction
C<SUP>+</SUP>+H→C+H<SUP>+</SUP> is calculated with the introduction
of the radial coupling between the two <SUP>3</SUP>π states
arising from both asymptotic atomic states. The derived
rate coefficient at a temperature of 10<SUP>4</SUP>K is
2×10<SUP>-15</SUP>cm<SUP>3</SUP>s<SUP>-1</SUP> which is two orders
of magnitude larger than the value previously estimated by Butler
and Dalgarno (1980) from a weak spin orbit coupling between the
<SUP>3</SUP>Σ<SUP>-</SUP> and <SUP>3</SUP>Σ<SUP>+</SUP> molecular
states of CH<SUP>+</SUP>.
---------------------------------------------------------
Title: Asymptotic properties of low degree solar gravity modes
Authors: Provost, J.; Berthomieu, G.
1986A&A...165..218P Altcode:
The application of the second-order asymptotic theory of Tassoul
(1980) to the low degree solar gravity modes is discussed. The standard
solar model of Schatzmann and Maeder (1981) is used to compute a set
of g-mode periods, and the possibility of recovering the coefficients
of the expression derived previously for the g-modes by a least square
analysis on the set of computed periods is tested. The coefficients
given by least squares analysis are compared to their values estimated
from the model. It is shown that, within the range of computed periods,
it is possible to recover some constraints on the solar interior and
that very large periods are required to derive the properties of the
stratification just below the convection zone.
---------------------------------------------------------
Title: Sismologie stellaire: problème direct.
Authors: Berthomieu, G.; Provost, J.
1986mma..conf..525B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Influence of turbulent diffusion on asymptotic low degree
solar gravity modes
Authors: Berthomieu, G.; Provost, J.; Schatzman, E.
1984MmSAI..55..107B Altcode:
The characteristic period P(0) separating the low-frequency solar
g-modes of the same (low) degree is calculated theoretically using
several published models of solar structure, and these model values
of P(0) are compared with observations. The asymptotic properties of
g-modes are reviewed, and the influence of turbulent mixing is studied
by comparing the predictions of the models of Schatzmann and Maeder
(1981) for pseudo-Reynolds numbers zero, 100, and 200. It is found that
the observed P(0) values (about 38.8 or 41 min) are consistent with a
moderate pseudo-Reynolds number, which can also account for the surface
He-3/He-4 ratio and Li depletion but conflicts with neutrino-flux data.
---------------------------------------------------------
Title: Solar gravity modes as a test of turbulent diffusion mixing
Authors: Berthomieu, G.; Provost, J.; Schatzman, E.
1984Natur.308..254B Altcode:
The Stanford group<SUP>1</SUP> has recently detected solar
global oscillations in the range 160-370 min and interpreted
them as internal gravity modes of degree l = 1 and l = 2. Other
observations<SUP>2,3</SUP> also indicate the existence of low-degree
solar gravity modes. Whereas the high-degree 5-min oscillations are
sensitive to the properties of the convective zone essentially, the
low-frequency modes (gravity modes) are sensitive to the physical
conditions in the solar core. Other constraints on the solar core
are given by the observed value of the neutrino flux, which is lower
than the flux predicted by the standard models, and by the splitting
of the low-degree 5-min oscillations. As far as the neutrino flux is
concerned, a possibility to reduce it has been explored by Schatzman
and Maeder<SUP>4</SUP> by introducing a turbulent diffusion mixing. In
this paper we study the influence of such mixing on the periods of
low-degree l gravity modes, which do not present the difficulties
of the high-degree gravity modes<SUP>5</SUP>. We find that these
periods depend strongly on the pseudo-Reynolds number<SUP>4</SUP>,
and we derive the range of this parameter compatible with the recent
observational results.
---------------------------------------------------------
Title: Solar Constraints
Authors: Provost, J.
1984IAUS..105...47P Altcode:
Accurate tests of the theory of stellar structure and evolution
are available from the Sun's observations. The solar constraints
are reviewed, with a special attention to the recent progress in
observing global solar oscillations. Each constraint is sensitive to
a given region of the Sun. The present solar models are discussed with
respect to neutrino flux, low and high degree five-minute oscillations
and low degree internal gravity modes. It appears that actually there
do not exist solar models able to fully account for all the observed
quantities.
---------------------------------------------------------
Title: Excitation of Non-Adiabatic Quasi-Toroidal Oscillations in
Double Stars
Authors: Provost, J.; Berthomieu, G.; Rocca, A.
1984LIACo..25..372P Altcode: 1984trss.conf..372P; 1984tpss.conf..372P
No abstract at ADS
---------------------------------------------------------
Title: Turbulent Diffusion Mixing - Solar and Stellar Constraints
Authors: Berthomieu, G.; Provost, J.; Schatzman, E.
1984apoa.conf..189B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Non-adiabatic quasi-toroidal modes in a slowly rotating star :
application to ZZ Ceti.
Authors: Berthomieu, G.; Provost, J.
1983A&A...122..199B Altcode:
A linear adiabatic and non-adiabatic analysis of the quasi-toroidal
modes of a uniformly slowly rotating star is presented and applied
to chemically stratified DA white dwarfs. These modes are unstable
for sufficiently high values of the rotation of the star and in some
range of the effective temperature and of the amount of hydrogen in the
outer envelope. The destabilizing mechanism and the instability strip
are the same as for the gravity modes considered by Dolez and Vauclair
(1981), but the growth rates are much smaller.
---------------------------------------------------------
Title: Les oscillations solaires et stellaires comme test de la
théorie de la structure interne.
Authors: Provost, J.
1983ihaa.conf..167P Altcode:
Contents: Introduction. Quelques propriétés théoriques
des oscillations stellaires. Les oscillations solaires et leur
interprétation. Perspectives de développement de la sismologie
solaire et stellaire.
---------------------------------------------------------
Title: Low Frequency Oscillations of a Slowly Rotating Star - Quasi
Toroidal Modes
Authors: Provost, J.; Berthomieu, G.; Rocca, A.
1981A&A....94..126P Altcode:
The radial structure and the frequencies of the nonaxisymmetric
quasi-toroidal modes of a slowly rotating star have been computed in
the case of rigid rotation. The main results are that these modes may
have a significant amplitude in the interior of the star and that they
are greatly influenced by the non-sphericity of the star.
---------------------------------------------------------
Title: Quasi Toroidal Modes in B-Stars
Authors: Berthomieu, G.; Provost, J.; Groupe Etoiles Variables de
L'Observatoire de Nice
1981pbs..work..337B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Theoretical Prediction of Eigen Frequencies of the Solar Five
Minute Oscillation
Authors: Berthomieu, G.; Cooper, A. J.; Gough, D. O.; Osaki, Y.;
Provost, J.; Rocca, A.
1980jfss.conf...32B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sensitivity of five minute eigenfrequencies to the structure
of the sun
Authors: Berthomieu, G.; Provost, J.; Rocca, A.; Cooper, A. J.; Gough,
D. O.; Osaki, Y.
1980LNP...125..307B Altcode: 1980nnsp.work..307B
The dependence of theoretical eigenfrequencies of five minute
oscillation modes on the parameters that determine model solar
envelopes has been investigated. It was found that the p mode
frequencies are quite strongly correlated with the depth of the
convection zone. Comparison of theory with observation suggests that
the solar convection zone is about 200,000 km deep.
---------------------------------------------------------
Title: Wave Reflections in the Solar Atmosphere
Authors: Provost, J.; Mein, N.
1979SoPh...64...43P Altcode:
The small phase-lag between velocities observed at different
chromospheric levels is interpreted as being due to acoustic waves
reflected by the very hot atmospheric layers of the chromosphere-corona
transition zone. We consider first an isothermal slab, then a
realistic solar atmospheric model and calculate weighting functions
for velocities in Ca II lines. It is shown that taking into account
these functions and integrating over horizontal wave numbers leads
to a good agreement with previous observations (Mein, 1977) in the
case of 8498 and 8542 Ca II lines. For the K line, the less good
agreement shows that magnetoacoustic waves become important in the
upper chromospheric layers.
---------------------------------------------------------
Title: Low-frequency Gravity Modes of a Rotating Star
Authors: Berthomieu, G.; Gonczi, G.; Graff, Ph.; Provost, J.; Rocca, A.
1978A&A....70..597B Altcode:
Summary. The frequencies of gravity modes of a slowly rotating star
have been calculated by an asymptotic method in the case where the
frequencies of the modes are of the same order than the angular
rotation speed. It is shown that the distortion of the star can
then be neglected. A general relationship is established between the
eigenfrequencies and the rotation in the limit of a large number of
radial nodes. Key Words. non-radial oscillations - stellar rotation
---------------------------------------------------------
Title: Propagation of an optically thin isothermal perturbation in
an atmosphere traversed by a radiation field.
Authors: Berthomieu, G.; Provost, J.; Rocca, A.
1976A&A....47..413B Altcode:
The propagation of optically thin isothermal perturbations in an
isothermal slab of an atmosphere traversed by a radiation flux is
considered. Such perturbations are amplified during their propagation
up to a finite limit which is a function of the effective gravity,
and which becomes infinite only in the rather unrealistic case where
this effective gravity is zero. Although this result depends on the
assumption made for the absorption coefficient, it shows that a nonlocal
analysis of the amplification is needed in order to be able to apply
it to the chromospheric heating of hot stars, a mechanism suggested
by Hearn (1972).
---------------------------------------------------------
Title: Filtering of acoustic waves in the solar atmosphere.
Authors: Provost, J.
1976A&A....46..159P Altcode:
The evolution with height of the power spectrum of the response of
the solar atmosphere to an excitation in a wide range of frequencies
is discussed. It is found that the layers under the photosphere
enhance a range of periods around 300 s, while the photospheric and low
chromospheric layers enhance 150-200 s periods. Linear filtering appears
to be a process relevant for the understanding of major characteristics
of solar atmospheric dynamics.
---------------------------------------------------------
Title: Filtering of acoustic waves in the solar atmosphere
Authors: Provost, J.
1976pmas.conf..281P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Response of a Bounded Atmosphere to a Non-Resonant
Excitation. I: Isothermal Case
Authors: Provost, J.
1975SoPh...40..257P Altcode:
The response of a bounded atmosphere to a non-resonant excitation
applied at its basis is studied. It is shown that the essential
feature related to this kind of excitation is that the distribution
of the energy of the velocity field relatively to the frequency and
horizontal wavelength is a function of height and merely depends
on the structure of the atmosphere above the level at which it is
considered. The preliminary results concerning an isothermal atmosphere
are presented and their relevance to the solar case is discussed.
---------------------------------------------------------
Title: Note on the Response of an Atmosphere to a Localized Turbulent
Source
Authors: Provost, Janine
1973SoPh...33..103P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A comparative detailed analysis of 22 Serpentis, a high
metallicity A2 star, and the standard F0 V: 9 Aurigae.
Authors: Provost, J.; van't Veer-Menneret, C.
1969A&A.....2..218P Altcode:
From photometric studies and high resolution spectrography of 22 Ser,
a supposed Am star, and of 9 Aur, a main sequence F0 star, we derive
the following atmospheric parameters: for 22 Ser: Q =0.65, logg=4.44,
for 9Aur: Q =O.7O, logg=4.44. Using the appropriate Mihalas models,
a comparative study of the two stars by the method of differential
curve of growth analysis confirms the Am character of 22 Ser by the
high microturbulence velocity and the abundance anomalies found. The
star 9 Aur shows a solar chemical composition, but a microturbulence
velocity, of 4 km/s, which is too high for a main sequence F0 star. Key
words: 22 Ser, 9 Aur, metaffic-line stars - detailed differential curve
of growth analysis - multicolourphotometry - chemical composition -
microturbulence velocity - abundance
