EDP Sciences
Free access
Issue
A&A
Volume 446, Number 1, January IV 2006
Page(s) 155 - 170
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20052871


A&A 446, 155-170 (2006)
DOI: 10.1051/0004-6361:20052871

Radio and X-ray variability of young stellar objects in the Coronet cluster

J. Forbrich1, 2, Th. Preibisch1 and K. M. Menten1

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: forbrich@mpifr-bonn.mpg.de
2  Astrophysikalisches Institut und Universitäts-Sternwarte Jena, Schillergäßchen 2-3, 07745 Jena, Germany

(Received 11 February 2005 / Accepted 7 September 2005 )

Abstract
The Coronet cluster in the nearby R CrA dark cloud offers the rare opportunity to study at least four "class I" protostellar sources as well as one candidate "class 0" source, a Herbig Ae star, and a candidate brown dwarf within a few square arcminutes - most of them detected at radio- and X-ray wavelengths. These sources were observed with the Very Large Array (VLA) at $\lambda = 3.5$ cm on nine occasions in 1998, spread over nearly four months. The source IRS 5, shown earlier to emit circularly polarized radio emission, was observed to undergo a flux increase accompanied by changes in its polarization properties. Comparison with VLA measurements taken in January 1997 allows analysis of longer-term variability. In addition to this radio monitoring, we analyze archival Chandra and XMM-Newton X-ray data of these sources. Three class I protostars are bright enough for X-ray spectroscopy, and we perform a variability analysis for these sources, covering a total of 154 ks spread over more than two and a half years. Also in X-rays, IRS 5 shows the most pronounced variability, whilst the other two class I protostars IRS 1 and IRS 2 have more stable emission. X-ray data is also analyzed for the recently identified candidate class 0 source IRS 7E, which shows strong variability as well as for the Herbig Ae star R CrA for which we find extremely hot X-ray-emitting plasma. For IRS 1, 2 and 5, the hydrogen column densities derived from the X-ray spectra are at about half the values derived with near-infrared techniques, a situation similar to what has been observed towards some other young stellar objects.


Key words: stars: pre-main sequence -- stars: individual: R CrA -- radio continuum: stars -- X-rays: stars

SIMBAD Objects



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