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

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 mas 63 mas Peak-up Mg II k Inner Chromosphere Upper Chromosphere

Hinz et al. Nature mas 1000 mas 500 mas HST-STIS near-UV spectra Upper chromosphere Circumstellar Inner Dust Envelope MMT 9.8  m image 200 mas 400 mas 600 mas 0 mas 1000 mas 2000 mas 3000 mas

Mg II k 0 mas 63 mas 126 mas 200 mas 400 mas 600 mas 1000 mas 2000 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 I Fe II Al II C II

IRAS ISO Dust emission Input model SED T eff = 3500 K log(g) = DUSTY model best fit SED  9.8 =  m < grain size < 0.5  m T dust = 600 K 0.05  m < grain size < 0.5  m T dust = 800 K 1  m < grain size < 5  m T dust = 600 K

Observed Radial Dust Intensity 9.8  m DUSTY Model Intensity 9.8  m MMT MIRAC Model I  12.5  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?