Colloquia

Keiichi Ohnaka : Spatially resolving the gas dynamics over the surface of red supergiants with the Very Large Telescope Interferometer

The mass-loss mechanism in red supergiants is one of the long-standing problems in stellar astrophysics. For solving this
problem, it is crucial to probe the dynamics of the outer atmosphere. The milliarcsecond angular resolution achieved by
infrared long-baseline interferometry provides us with the only way to spatially resolve this key region. We present high
spatial and high spectral resolution observations of the 2.3 micron CO lines in the red supergiants Betelgeuse and
Antares using the Very Large Telescope Interferometer (VLTI). We have succeeded in “velocity-resolved” aperturesynthesis
imaging of stars for the first time, which allows us to probe not only inhomogeneous structures over the
surface of stars but also their kinematics, as routinely done in solar physics. We have detected vigorous upwelling and
downdrafting motions of large CO gas clumps (as large as the radius of the stars) at up to 20-30 km/s within 1.5 stellar
radii. Our VLTI observations suggest the following new picture: the material within 1.5 stellar radii is strongly stirred
possibly by magnetohydrodynamical processes and/or pulsation and may be violently flung out.

Lugar :
Instituto de Astronomia

Fecha:
Martes 03 de Diciembre 2013

Hora:
15:00 horas