A.L obel SAO funding Spatially R RR Resolved STIS S SS Spectroscopy o oo of Betelgeuse’s U pper C CC Chromosphere and Circumstellar Dust Envelope.

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?