A.A. Lobel SAO fundingLobel SAO funding

SpatiallySpatially Resolved Resolved STISSTIS SpectroscopySpectroscopy ofof

Betelgeuse’sBetelgeuse’s UpperUpper Chromosphere and Chromosphere and Circumstellar Dust EnvelopeCircumstellar Dust Envelope

Jan 1998 HST-FOC Near-UV Images Inner Chromosphere

Apr 1998

Sep 1998

Mar 1999

HST-STIS Near-UV spectroscopy Lobel & Dupree ApJ 2001

1000 mas

600 mas

400 mas

200 mas

126 mas63 masPeak-up Mg II k

Inner

Chromosphere

UpperChromosphere

2002-2003

Hinz et al. Nature 1998

4000 mas

1000 mas500 mas

HST-STIS near-UV spectra Upper chromosphere

2002-2003

Circumstellar Inner Dust Envelope MMT 9.8 m image

200 mas400 mas600 mas

0 mas

1000 mas

2000 mas3000 mas

Mg II k0 mas

63 mas126 mas200 mas400 mas600 mas

1000 mas2000 mas

0 mas

25 mas

50 mas

75 mas

200 mas

400 mas

600 mas

1000 mas

Si I 2516

Log of integrated emission line intensity

Mg II k

Mg II h

Fe IFe II Al IIC II

IRAS ISO Dust emission

Input model SED Teff = 3500 K log(g) = - 0.5

DUSTY model best fit SED

9.8 = 0.015

0.05 m < grain size < 0.5 m Tdust = 600 K0.05 m < grain size < 0.5 m Tdust = 800 K1 m < grain size < 5 m Tdust = 600 K

Observed Radial Dust Intensity 9.8 m

DUSTY Model Intensity 9.8 m

MMT MIRAC

Model

I12.5 m

18 m

Model Circumstellar Dust Envelope

Model Inner Chromosphere

Model Upper Chromosphere

Conclusions on Betelgeuse• Emission lines of upper chromosphere observed

far inside inner dust envelope to 3 arcseconds or ~120 R*

• First evidence of outward accelerating upper chromospheric wind from increasing emission line asymmetry

• Emission lines of upper chromosphere form at kinetic gas temperatures Tgas > 2600 K far inside inner Circumstellar Dust Envelope

• Ambient gas temperature in the CDE Tgas < 600 K required for dust formation

• Warm chromospheric gas and cool dusty gas co-exist far beyond dust condensation radius of dust-driven wind models

• New observations require wind driving physics sustaining warm and cool gas in upper chromosphere

• Evidence for shock wave propagation in the upper chromosphere?

• Outflow caused by radiation pressure onto dust at the inner chromosphere, or initiated by acoustic energy propagation from the photosphere?

Where do we go from here?