Document Magnetism and Activity of the Sun and Stars
J. Arnaud and N. Meunier (eds)
EAS Publications Series, Vol. 9, 2003
DOI: 10.1051/eas:2003115
Activity of protostars and brown dwarfs
N. GrossoMax-Planck-Institut für extraterrestrische Physik, P.O. Box 1312, 85741 Garching bei München, Germany
Abstract
The first evidences for magnetic activity in low-mass protostars and
brown dwarfs were found in the mid-1990's by the old generation of X-ray satellites,
namely ROSAT and ASCA. I will show that these first X-ray detections have opened
a promising observational window to study the activity of protostars, deeply
embedded in their molecular cloud and optically invisible. However these early
observations gave only access to the tip of the iceberg, detecting protostars
mainly during phases of high activity. I will review recent results obtained
with the new generation of X-ray satellites, namely Chandra and XMM-Newton,
which now give access to the X-ray spectral study of protostars also during their
quiescent phase, and which are also enough sensitive to detect young brown dwarfs
in star-forming regions.
I will also review evidences of activity from radio observations,
and for brown dwarfs, evidences of activity from optical observations.
© EAS, EDP Sciences 2003