Sixteenth Marcel Grossmann Meeting

The Great Dimming of Betelgeuse as viewed by high-resolution spectra from the Stratosphere, and ground based TiO Photometry

8 Jul 2021, 17:25

20m

Invited talk in the parallel session The "Fall and Rise" of Betelgeuse The "Fall and Rise" of Betelgeuse

Speaker

Graham Harper (Center for Astrophysics and Space Astronomy, University of Colorado Boulder)

Description

NASA-DLR's Stratospheric Observatory for Infrared Astronomy (SOFIA) observed Betelgeuse during the 2019/2020 Great V-Band Dimming event. High spectral resolution emission-line spectra were obtained with EXES at [Fe II] 25.99 microns and [S I] 25.25 microns before and during the event, and with upGREAT at [O I] 63.2 microns and [C II] 157.5 microns shortly after minimum. The line fluxes and profiles revealed that the circumstellar envelope was essentially unchanged in February/March 2020.

An analysis of ground-based TiO photometry revealed that the mean photospheric temperature had dropped significantly, to a record low, and that it correlated strongly with the photospheric radial velocity. ESO Very Large Telescope-SPHERE images also revealed a non-uniform photosphere during the Great Dimming. A cool multi-component photosphere can explain the multi-band photometry, and it is not necessary to invoke dust as an explanation for the Great V-band Dimming. This does not, however, exclude the possibility that some dust formed during this dynamic event.