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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20140409T123000
DTEND;TZID=Atlantic/Canary:20140409T133000
UID:iactalks-632
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/632
CREATED:2014-04-09T12:30:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Atmospheric Dynamics in Mira Stars: A Spectropolarimetric Insight 
DESCRIPTION:Atmospheric Dynamics in Mira Stars: A Spectropolarimetric Insig
 ht \nDr. Nicolas Fabas\n\nTo study the extended atmosphere of evolved star
 s such as Mira-type variables, spectropolarimetry is an innovative tool. F
 or many kinds of stars, it has been used to measure global magnetic fields
  through circular polarization and the Zeeman effect. However, linear pola
 rization has seldom been used in the past years even though phenomena such
  as scattering and the Hanle effect can definitely be studied as well, as 
 it is done in solar physics. In this presentation, I am going to describe 
 original results coming from a spectropolarimetric survey of Mira stars wi
 th NARVAL@TBL. Such results concern spectral lines like the Balmer lines o
 f hydrogen and calcium lines. More specifically, I will focus on linear po
 larization and link this polarization to the propagation of the hypersonic
  radiative shock wave which is typical of Miras' atmospheres. In general, 
 these environements are very dynamical and scattering in an aspherical atm
 osphere and velocity gradients can induce a strong linear polarization, li
 kely to be further affected by weak magnetic fields. This analysis is very
  inspired of what is already done with solar spectra. In addition to that,
  I am going to present exclusive results about the first detection of a su
 rface magnetic field in a Mira star and explain how the shock wave can imp
 act this field. This work is likely to lead to collaborations with other d
 isciplines such as interferometry (geometry of the scattering environement
  and characterization of the shock) and radio-astronomy (study of the pola
 rization of masers).
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