Letters of Intent received in 2017

LoI 2019-1978
The physics and evolution of intermediate mass stars

Date: 1 July 2019 to 5 January 2019
Location: Paris, France
Contact: Richard Monier (Richard.Monier@obspm.fr)
Coordinating division: Division G Stars and Stellar Physics
Chair of SOC: Richard Monier (Observatoire de Paris)
Chair of LOC: ()



- New observational results on Intermediate Mass Stars (IMS) with an emphasis on asteroseismology, high accuracy velocimeters, Interferometry, spectropolarimetry
- Physical processes in the interiors and atmospheres of IMS: pulsations, convection, granulation, rotation, diffusion, rotation-pulsation interactions, magnetism, accretion
- Progenitors and descendants of IMS: PMS and Herbig stars, giants and supergiants
- Current state-of-the art modelling of the atmospheres, interiors and evolution of IMS
- Circumstellar environments of IMS: disks and exoplanets around IMS



The physics and evolution of intermediate mass stars:

The IMS in the region 7000 < T_{eff} < 15000 K are home to a variety of distinct physical processes occuring in their atmospheres and envelopes: radiative diffusion, pulsation, rotation, magnetic fields, shallow surface convection and accretion.
The region on the Main Sequence stretching from spectral type B5 to F5 is an excellent laboratory to study these processes and their interactions. Indeed it harbors several groups of stars where at least one of these processes is deemed to be dominant or absent.
As these various groups have similar effective temperatures and luminosities, the effects of rotation, diffusion, pulsation, convection and magnetic fields can be isolated and studied. In contrast to their hotter counterparts (the O and early B stars), no strong winds have been detected in the B5 to F5 main-sequence stars and convection occurs in a shallow superficial region of very small mass.
Their atmospheres and envelopes can safely be assumed to be quiescent
and radiative diffusion can occur through the bulk of these objects at least from B5 to A5. At spectral types later than A5V, convection affects a larger and deeper part of the stellar interior and erases the subtle effects of diffusion.

This symposium will focus on the physical processes that control the structure and evolution of intermediate mass stars (IMS)
on the main sequence and their descendants. The last IAU Symposium closely related to this subject was the IAU S 224 "The A-star puzzle" held in Poprad (Slovakia) in 2004.
Since then, observations have made a quantum leap forward. Continuous space-based photometry from the CoRoT and Kepler missions have revolutionised asteroseismology.
Velocimeters have improved tenfold in precision and spectropolarimeters now provide high signal-to-noise Stokes profiles.
In the laboratory, spectroscopy of various atoms and ions has produced a wealth of important new atomic data relevant for the interpretation of spectra of IMS and the construction of Non-LTE model atmospheres. On the theoretical side, the modelling of radiative hydrodynamical processes, in particular convection, in the envelopes of the A5 to F5 dwarfs has improved. We therefore believe that the time is ripe to propose another conference on the physics and evolution of intermediate mass stars.

The SOC of this conference is composed of:

Richard Monier (Chairperson, Observatoire de Paris, France), Hans Ludwig (Heidelberg, Germany), Friedrich Kupka (Goettingen, Germany), Simon Murphy (University of Sydney, Australia), Glenn Wahlgren (STSCI, USA), Charles Cowley (Univ. of Michigan, USA),
Elizabeth Griffin (DAO, Canada), Oleg Kochukhov (Uppsala, Sweden), Gautier Mathys (ESO), Hiromoto Shibahashi (Tokyo, Japan), Coralie Neiner (Observatoire de Paris, France),
Margarida Cunha (Univ. of Porto, Portugal),
Constanze Zwintz (Innsbruck, Austria), Karine Perraut (IPAG, France), Theresa Lueftinger (Vienna, Austria), Lyudmila Mashonkina (IOA, Russia)

Session titles:
- New observational results on IMS
- Physical processes in the interiors and atmospheres of IMS
- Progenitors and descendants of IMS
- Current state-of-the art modelling of the atmospheres, interiors and evolution of IMS
- Circumstellar environments of IMS