Magnetic activity of COROT targets

1
Magnetic activity of COROT targets
A. Baglin, C. Catala, J.-F. Donati, P. Petit, B.
Mosser, E. Michel, F. Bouchy, F. Thévenin, R.
Samadi
Goals

• study magnetism of FG type stars, using COROT
  results and additional groundbased
  spectroscopolarimetric data
• provide independent measurements of vsini, Prot,
  sini, surface differential rotation

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The case of HD 49933 (1)

• observed with HARPS in Jan. 2004 (cf Mosser),
  for detecting and analysing p-modes
• p-modes detected, but additional low frequency,
  high amplitude Vrad variation
• clearly seen in line bisectors
• attributed to stellar activity

3
The case of HD 49933 (2)

• study of line profile variations, using average
  line profiles (LSD method)
• modulation by rotation
• one or two dark spots

4
The case of HD 49933 (3)

• Doppler imaging technique
• one large spot at high and intermediate latitude
• second smaller dark spot on opposite side

vsini 9 - 2 km/s, i 60, R 1.4 Rsolar
Prot (equator) 164 hrs
Prot (spothigh latitudes) 195 - 3 hrs
surface differential rotation
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The next step
use Espadons, the new spectropolarimeter _at_
CFHT observing run scheduled Dec. 2005 Jan 2006
(HD 49933) additional photometry _at_ OSN

• direct detection of magnetic field, via
  spectropolarimetry
• mapping magnetic field, using Zeeman-Doppler
  imaging technique
• confirm Prot inclination angle
• measure surface differential rotation

• when coupled to these G/B results, COROT data
  will provide the first ever complete ensemble of
  data to study dynamo
• ingredients convection, rotation, differential
  rotation
• products magnetic field intensity, topology

6
Other stars
F G type stars vsini 5 km/s
HD 43587, F9V, mV5.7, vsini 6 km/s HD 49434,
F1V, mV5.7, vsini 79 km/s HD 171834, F3V,
mV5.4, vsini 64 km/s HD 177552, F1V, mV6.5,
vsini 41 km/s secondary targets

• continue programme on Espadons _at_ CFHT a few
  nights per semester
• extend programme on Narval _at_ TBL many nights
  per semester, starting 2006B
• provide at the same time data to study nonradial
  pulsations of high degree for medium and fast
  rotators