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SEISMOLOGY OF STELLAR SEISMOLOGY OF STELLAR ATMOSPHERESATMOSPHERES
Zdzislaw MusielakZdzislaw Musielak
Physics Department Physics Department
University of Texas at Arlington (UTA)University of Texas at Arlington (UTA)
OUTLINEOUTLINE
Stellar Activity in the H-R DiagramStellar Activity in the H-R Diagram
Stellar Activity and ExoplanetsStellar Activity and Exoplanets
Atmospheric Oscillations Atmospheric Oscillations
Models and Theoretical PredictionsModels and Theoretical Predictions
Atmospheric SeismologyAtmospheric Seismology
Active SunActive Sun
Solar MagnetogramSolar Magnetogram
Solar structureSolar structure
Model of the Solar AtmosphereModel of the Solar Atmosphere
Averett and Loeser (2008)
Forms of Stellar ActivityForms of Stellar Activity
Chromospheric activity (Ca II, Mg II)Chromospheric activity (Ca II, Mg II)
Transition-region activity (C IV, N V, O VI)Transition-region activity (C IV, N V, O VI)
Coronal activity (X-rays, Fe XII, Fe XV)Coronal activity (X-rays, Fe XII, Fe XV)
Wind activity (tenuous and massive winds)Wind activity (tenuous and massive winds)
Atmospheric oscillationsAtmospheric oscillations
The H-R DiagramThe H-R Diagram
Chromospheric activityChromospheric activity
Rutten et al. (1987) and Schrijver et al. (1999)
Coronal and Wind ActivityCoronal and Wind Activity
Haisch & Schmidt (1991)
Stellar Activity and ExoplanetsStellar Activity and Exoplanets
Enhancement of stellar activityEnhancement of stellar activity by exoplanets (e.g., Ca II H+K by exoplanets (e.g., Ca II H+K
and X-rays)and X-rays)
Interaction between the stellar Interaction between the stellar and planetary magnetic fieldsand planetary magnetic fields
Fint ~ Bs Bp1/3 Vc / d2 Rp
2 FX1/6
Cuntz, Saar & Musielak (2000)
Orbital modulations of Ca II in 3 systems
Hot spot following the planet in HD179949
Shkolnik, Walker & Bohlender (2003)
White Dwarfs (WD)White Dwarfs (WD)
DAB – H + neutral He lines
DAO – H + ionized He linesDAZ – H + “metal” lines
DAV and DBV – pulsating WD
DC – no lines in optical
DQ – strong carbon lines
Activity of White DwarfsActivity of White Dwarfs Chromospheric:Chromospheric: GD 356 (DA) – Balmer lines in GD 356 (DA) – Balmer lines in
emission (Greenstein 1985)emission (Greenstein 1985)
G 227-5 and G 35-26 (DQ) G 227-5 and G 35-26 (DQ) N I, O I, Si I and C I lines in N I, O I, Si I and C I lines in
emission emission (Shipman et al. 2003)(Shipman et al. 2003)
Coronal (X-rays) Coronal (X-rays) – NONE – NONE (Cavallo et al. 1993,(Cavallo et al. 1993, Musielak et al. 1995, 2003)Musielak et al. 1995, 2003)
Chandra X-ray
imageof GD 358 (DBV)
H
GD 356
Energy InputEnergy Input
From stellar photospheres:From stellar photospheres:
acoustic and magnetic wavesacoustic and magnetic waves
Produced in situ:Produced in situ:
reconnective processesreconnective processes
From stellar coronae:From stellar coronae:
heat conductionheat conduction
Tube Waves and SpectraTube Waves and Spectra
Solar wave spectra Solar wave spectra
Wave Energy and Radiative LossesWave Energy and Radiative Losses
Physical ModelPhysical Model
Chromospheric ModelsChromospheric Models
Purely TheoreticalPurely Theoretical Two-ComponentTwo-Component Self-ConsistentSelf-Consistent Time-DependentTime-Dependent
Stellar parametersStellar parameters: effective temperature,: effective temperature,
gravity, metallicity and filling factor. gravity, metallicity and filling factor.
Models versus ObservationsModels versus Observations
BaseBase - acoustic waves - acoustic waves MiddleMiddle - magnetic tube waves - magnetic tube waves UpperUpper – other waves and / or – other waves and / or
non-wave heatingnon-wave heating
Fawzy et al. (2002a, b, c)
Heating gaps!
Other Heating MechanismsOther Heating Mechanisms
Energy carried by torsional tube wavesEnergy carried by torsional tube waves
Magnetic reconnection at very smallMagnetic reconnection at very small
scales – “nanoflares” (Mendoza- Briceno scales – “nanoflares” (Mendoza- Briceno et al. 2002; Parker 1988)et al. 2002; Parker 1988)
Magnetic carpet – flux tube tectonics Magnetic carpet – flux tube tectonics (Priest et al. 2002; Schrijver et al. 1998)(Priest et al. 2002; Schrijver et al. 1998)
zxxxx
e
ezxT u
zHz
u
tg
tz
ug
tt
u
t
uuuS
1
],[ˆ111
2
2
0
4/10
2 22 2
1 12 2ˆ [ ]K K KL v c v
t z
1/ 41 0xv v 0
04 ( )K
e
Bc
4K
K
c
H
Generation of Transverse Tube Waves
The wave operator
The source function
with
, ,
Solutions
Fourier transform in time and spaceFourier transform in time and space
Asymptotic Fourier transformsAsymptotic Fourier transforms
Turbulent velocity correlationsTurbulent velocity correlations
Evaluation of convolution integralsEvaluation of convolution integrals
zxTK uuSvL ,ˆˆ1
Turbulent velocity correlations
Spatial turbulent energy spectrum – modified Kolmogorov turbulent spectrum
Temporal turbulent energy spectrum – modified Gaussian frequency factor
Wave Energy Spectra and Fluxes
Stellar wave spectra Stellar wave fluxes
Linear transverse tube waves
Musielak & Ulmschneider (2003)
Solar Chromospheric OscillationsSolar Chromospheric Oscillations
Response of the solar chromosphere to propagating Response of the solar chromosphere to propagating acoustic waves – 3-min oscillations (Fleck & Schmitz acoustic waves – 3-min oscillations (Fleck & Schmitz 1991, Kalkofen et al. 1994, Sutmann et al. 1998)1991, Kalkofen et al. 1994, Sutmann et al. 1998)
Oscillations of solar magnetic flux tubes (chromospheric Oscillations of solar magnetic flux tubes (chromospheric network) – 7 min oscillations (Hasan & Kalkofen 1999, network) – 7 min oscillations (Hasan & Kalkofen 1999, Musielak & Ulmschneider 2002, 2003)Musielak & Ulmschneider 2002, 2003)
Chromospheric oscillations are not cavity modes!
P-modes
22
2
22
2
2
2 ][ˆ pz
ct
pL DTT
22AS
AST
cc
ccc
2
0 0
pp
B
2
2 2
9 1 1
16 2ST
DA
cc
H c
Excitation of Oscillations by Tube Waves I
The wave operator for longitudinal tube waves is
with
and the cutoff frequency (Defouw 1976)
,
2 22 2
1 12 2ˆ [ ]K K KL v c v
t z
1/ 41 0xv v 0
04 ( )K
e
Bc
4K
K
c
H
Excitation of Oscillations by Tube Waves II
The wave operator for transverse tube waves is
with
,
and the cutoff frequency (Spruit 1982)
Initial Value Problems
0ˆ1 vLK 0ˆ
2 pLT and
0lim 1
0
t
vt
tVztvz
010
,lim
IC: 0,lim 10
ztvt
and
BC: and 0,lim 1
ztvz
Laplace transforms and inverse Laplace transforms
Solar Flux Tube Oscillations
Longitudinal tube waves Transverse tube waves
Observation of Chromospheric Oscillations IObservation of Chromospheric Oscillations I
Tritschler, Schmidt & Wedemeyer (2005)
Observation of Chromospheric Oscillations IIObservation of Chromospheric Oscillations II
Tritschler, Schmidt & Wedemeyer (2005)
3-min 5-min 8.3-min
Solar Atmospheric OscillationsSolar Atmospheric Oscillations
Solar Chromosphere: 100 – 250 sSolar Chromosphere: 100 – 250 s
Solar Transition Region: 200 – 400 sSolar Transition Region: 200 – 400 s
Solar Corona: 2 – 600 sSolar Corona: 2 – 600 s
TRACE and SOHOTRACE and SOHO
Observations Observations
A German – UTA team A German – UTA team A. Nesis, H. Schleicher and R. Hammer - Kiepenheuer A. Nesis, H. Schleicher and R. Hammer - Kiepenheuer
Institut fur Sonnenphysik (KIS) in Freiburg, GermanyInstitut fur Sonnenphysik (KIS) in Freiburg, Germany
Z.E. MusielakZ.E. Musielak and S. Routhand S. Routh - - UTA UTA
was granted time to observe was granted time to observe solar oscillationssolar oscillations by the by the Vacuum Tower Telescope (VTT) at the Observatorio Vacuum Tower Telescope (VTT) at the Observatorio
del Teide, Tanerife, Spain, in October 2008. del Teide, Tanerife, Spain, in October 2008.
The data analysis will be performed at KIS and UTA. The data analysis will be performed at KIS and UTA.
Atmospheric Oscillations in Solar-Type StarsAtmospheric Oscillations in Solar-Type Stars
Response of stellar chromospheres Response of stellar chromospheres to a spectrum of propagating and to a spectrum of propagating and non-propagating acoustic and non-propagating acoustic and
magnetic tube wavesmagnetic tube waves
The chromospheres oscillate with The chromospheres oscillate with
the corresponding acoustic or tube the corresponding acoustic or tube cutoff frequencycutoff frequency
Performed studies: Performed studies:
F5 V with TF5 V with Teff eff = 6440 K = 6440 K
G5 V with TG5 V with Teff eff = = 5330 K 5330 K
M0 V with TM0 V with Teffeff = 3850 K = 3850 K
Fawzy, Musielak & Ulmschneider (2005)
Z = 0 km
Z = 1000 km
Z = 1500 km
F5 V
Theoretical Predictions ITheoretical Predictions I
F5 V star: 4.5 – 5.0 mHz (non-magnetic)F5 V star: 4.5 – 5.0 mHz (non-magnetic)
3.5 – 4.5 mHz (magnetic)3.5 – 4.5 mHz (magnetic)
G5 V star: 5.5 – 6.5 mHz (non-magnetic)G5 V star: 5.5 – 6.5 mHz (non-magnetic)
5.0 – 6.0 mHz (magnetic)5.0 – 6.0 mHz (magnetic)
M0 V star: 8.5 – 11.0 mHz (non-magnetic)M0 V star: 8.5 – 11.0 mHz (non-magnetic)
9.0 – 10.0 mHz (magnetic)9.0 – 10.0 mHz (magnetic)
Maximum amplitudes range from 0.4 km/s in F5 V to 0.2 km/s in M0 V
Stellar P-mode OscillationsStellar P-mode Oscillations P-mode oscillations have P-mode oscillations have
been observed in been observed in
3 main-sequence stars 3 main-sequence stars (Sun and (Sun and α Cen A and B)α Cen A and B)
2 subgiants (α CMi or 2 subgiants (α CMi or Procyon A and η Boo)Procyon A and η Boo)
and 2 giants (α UMa and and 2 giants (α UMa and Arcturus)Arcturus)
The p-mode oscillations inThe p-mode oscillations in Procyon A seem to be Procyon A seem to be inconclusive!inconclusive!
α Cen A
Procyon A
Bonanno et al. (2003)
The HAO group
Stellar Atmospheric OscillationsStellar Atmospheric Oscillations
White-light oscillations with period of White-light oscillations with period of 220 s220 s observed in a couple of RS CVn observed in a couple of RS CVn stars during flaresstars during flares
Mathioudakis et al (2003, 2006)Mathioudakis et al (2003, 2006)
X-ray oscillations with period of X-ray oscillations with period of 750 s750 s observed in an active M-dwarfobserved in an active M-dwarf
Mitra-Kraev et al (2006)Mitra-Kraev et al (2006)
Atmospheric Oscillations in White DwarfsAtmospheric Oscillations in White Dwarfs
Theory predicts large acoustic Theory predicts large acoustic fluxes for white dwarfs (Bohm & fluxes for white dwarfs (Bohm & Cassinelli 1971, Arcoragi & Cassinelli 1971, Arcoragi & Fontaine 1980, Musielak 1982)Fontaine 1980, Musielak 1982)
Atmospheric oscillations as a new Atmospheric oscillations as a new indicator of chromospheric activity indicator of chromospheric activity (Musielak, Winget & Montgomery (Musielak, Winget & Montgomery 2005)2005)
Performed studies:Performed studies:
DA stars with convection zonesDA stars with convection zones
DB stars with convection zonesDB stars with convection zonesDA star with log g = 8 and Teff = 12500 K
Acoustic waves
Theoretical Predictions IITheoretical Predictions IIDA stars:DA stars:
log g = 7 and Tlog g = 7 and Teff eff = 11000 K has = 11000 K has P = 2 sP = 2 s and and LLOO / L / LS S = 0.02= 0.02
log g = 8 and Tlog g = 8 and Teff eff = 12000 K = 12000 K has has P = 0.2 sP = 0.2 s and and LLOO / L / LS S = 0.004= 0.004
DB stars:DB stars:
log g = 7 and Tlog g = 7 and Teff eff = 23000 K has = 23000 K has P = 0.8 sP = 0.8 s and and LLOO / L / LS S = 0.01= 0.01
log g = 8 and Tlog g = 8 and Teff eff = 21000 K has = 21000 K has P = 0.08 sP = 0.08 s and LO / LS = 0.02
Best candidates:Best candidates: GD 356, G 227-5, G 35-26, BMP 17088GD 356, G 227-5, G 35-26, BMP 17088
and and SDSS J123410.37-022802.9SDSS J123410.37-022802.9
Atmospheric SeismologyAtmospheric Seismology
Is atmospheric seismology possible?Is atmospheric seismology possible?
Sun Sun – no problem!– no problem!
Late-type starsLate-type stars – stars with – stars with magnetic magnetic spots spots and giantsand giants
White dwarfsWhite dwarfs – magnetic (GD 356) – magnetic (GD 356)
CONCLUSIONS CONCLUSIONS Late-type dwarfs, subgiants, giant, supergiants and white Late-type dwarfs, subgiants, giant, supergiants and white
dwarfs show chromospheric activity. The proximity of giant dwarfs show chromospheric activity. The proximity of giant planets may increase this activity.planets may increase this activity.
Current theoretical models of stellar chromospheres predict Current theoretical models of stellar chromospheres predict “heating gaps”, which can be explained by including transverse “heating gaps”, which can be explained by including transverse and torsional waves and reconnective events in the models.and torsional waves and reconnective events in the models.
Oscillations driven by longitudinal and transverse tube waves Oscillations driven by longitudinal and transverse tube waves can account for 3-min oscillations in the lower chromosphere can account for 3-min oscillations in the lower chromosphere but cannot account for 7-min in the upper chromosphere.but cannot account for 7-min in the upper chromosphere.
Theoretical predictions of expected chromospheric oscillations Theoretical predictions of expected chromospheric oscillations in solar-type and DA and DB stars were made. We suggestedin solar-type and DA and DB stars were made. We suggested
that atmospheric oscillations in white dwarfs may become a that atmospheric oscillations in white dwarfs may become a new indicator of chromospheric activity in these stars. new indicator of chromospheric activity in these stars.
Supported by NSF, NASA, NATO and The Alexander von Humboldt Foundation