Andrea Dupree SAO/CfA New England Space Science Consortium (NESSC) March 1, 2006
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Transcript of Andrea Dupree SAO/CfA New England Space Science Consortium (NESSC) March 1, 2006
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Andrea Dupree SAO/CfANew England Space Science Consortium (NESSC)March 1, 2006
Some Stellar Problems of Interest to Solar Physics
Global properties of the solar wind Stellar winds: more massive, different acceleration profiles Young stars: sector structure, discrete absorbing components? Inhomogeneities: cool material in warm winds; hotter material in warm wind
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Spatial Resolution only for
Sun and Betelgeuse
Global properties of Sunneeded for comparison tostars …
M-dot as function of solar activity.
Coronal hole area (divergence)as function of solar cycle.
Acceleration of individual ionsRadiative losses
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The Sun as an Examplein Search for Winds
Dupree, Penn, & Jones 1996
Extended blue wingof He I (10830A)signifying outflowfound in coronal holes, particularly in centers of supergranulation cells.
(Dupree et al. 1996)
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He I Wind Diagnostic in Evolved Cool Stars
Dupree et al. 2003
Extension of He Iabsorption to shorterwavelengths indicates fast chromospheric expansion (> 90 km/s)
P Cygni emission signals an extended atmosphere
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Far UV Lines Show Wind OpacityCool luminous stars show substantial line asymmetriesIn lines from 80000K – 300,000 K indicating massive winds.
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Hot, Fast
10-14 M
Cold, Slow
10-5 M
Warm,Moderate10-8 M
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Winds from Young Stars
The closest accreting T Tauri star faces us almost pole-on.Strong signatures of winds extend smoothly to T~300,000K and appear in absorption to ~-300 km/s.
The H-alpha line signals both accretion and outflow, includingdiscrete absorption features.
Modeling with PANDORAindicates M~4x10-10 Myr-1
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AB Doradus… a young cool rapidly rotating dwarf star
H-alpha spectra give photospheric spot distribution
Plus Zeeman measuresgive surface B whichcan be modeled for coronal equilibrium distribution
Closed fields Open fields
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AB Dor (cont.): FUSE spectra of O VI reveal structured atmosphere and
windWhen open field linespresent:Low fluxAbsorption in profile
Mean profile
Flare profile showsflare traversing stellardisk
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Alpha Ori: Extended (very)Inhomogeneous cool atmosphere
Gilliland & Dupree 1996, Lobel et al. 2004Uitenbroeck et al. 1998, Lim et al. 1998
The first direct imaging of the surface of a star (other than the Sun) revealed variable hot spots on the chromospheric surface.
H2O 0.5R
Radio 3800K 2R
Mg II 40 R
1 R = 700 R
Dust 600K 24R
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Cool Structures in Active Starsand Sun too?
Lines from T < 5.5 dex K are suspiciously weak both in Capella and the Sun.
Is absorption by neutral H the culprit?
Brickhouse et al 1996
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Hot Material Anchored in Warm Wind
FUSE spectra show Fe XVIIIat photospheric velocitiesin stars with warm winds.
Anchored features may be similarto coronal loops.