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2006A&A...446..155F - Astronomy and Astrophysics, volume 446, 155-170 (2006/1-4)

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

FORBRICH J., PREIBISCH T. and MENTEN K.M.

Abstract (from CDS):

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 λ=3.5cm 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.

Journal keyword(s): stars: pre-main sequence - stars: individual: R CrA - radio continuum: stars - X-rays: stars

Nomenclature: Table 3: [FPM2006] NN (Nos 1-15). Table 3: [TS84] IRS NNW (Nos 7E, 7W) added.