SEISMOLOGY OF STELLAR ATMOSPHERES Zdzislaw Musielak Zdzislaw Musielak Physics Department Physics Department University of Texas at Arlington (UTA) University.

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