existing and future instruments

© JF Donati

High resolution echelle spectropolarimetry: ESPaDOnS/CFHT & NARVAL/TBL

With high resolution (R~60,000) echelle spectropolarimetry, one can detect Zeeman signatures in stellar specta (through thousands of spectral lines simultaneously) and derive maps of the medium- and large-scale magnetic topologies from time resolved data sets covering the full stellar rotation cycles. The new generation high resolution echelle spectropolarimeters ESPaDOnS at CFHT and NARVAL at TBL, covering the entire optical domain (from 370 to 1000nm in a single exposure) are the most efficient instruments for this kind of observations.

Low resolution spectropolarimetry: FORS1/VLT

For stars featuring simple magnetic fields (averaging out to non-zero net longitudinal magnetic fields over the visible stellar hemisphere), low resolution (R~1,000) spectropolarimetry is also an interesting possibility for measuring Zeeman signatures in Balmer and metal lines and mapping the large-scale magnetic field; this option is especially interesting in the Balmer lines of rapidly rotating massive stars. FORS1 on the VLT has proved efficient in this particular research area.

High resolution infrared spectroscopy: Phoenix

Since Zeeman splitting increases linearily with wavelength with respect to Doppler widths, infrared high-resolution (R~50,000) spectroscopic observations is an obvious way to go to detect stellar magnetic fields through the significant broadening they generate in magnetically sensitive spectral lines. Moreover, spot/photosphere contrasts being smaller in the infrared than in the optical, magnetic fields concentrating in cool spots of active stars are also more accessible. Phoenix (mounted on either KPNO, Gemini, SOAR) has proved very successful in this area.

Future instruments: high-resolution echelle infrared spectropolarimetry?

A new instrument combining the advantage of high resolution spectropolarimetry and infrared spectroscopy would of course be of obvious interest for studies on stellar magnetic fields, especially for projects on stellar formation with magnetic fields and on dynamo action in low-mass stars. SPIRou, an infrared ESPaDOnS-like high resolution echelle spectropolarimeter, is an ongoing (yet unfunded) project along these lines.

Core team and collaborators

Thread coordinator: JF Donati, J Landstreet, P Petit, S Bagnulo
Agency/Country Core team Collaborators
F Delfosse, Donati, Forveille, Petit, Semel Bouvier, Dougados, Lopez-Ariste, Ménard, Paletou, Ramirez
O Bagnulo, Cameron, Harries, Howarth, Keller, Martin, Mathys
C Bohlender, Lanstreet, Wade, Walker Moffat, StLouis
T Lim, Trung, Wang
US Johns-Krull, Valenti