Volume 499, Number 2, May IV 2009
|Page(s)||529 - 533|
|Section||Interstellar and circumstellar matter|
|Published online||16 April 2009|
The X-ray emission from Z Canis Majoris during an FUor-like outburst and the detection of its X-ray jet
INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy e-mail: firstname.lastname@example.org
2 European Southern Observatory, Casilla 19001, Santiago 19, Chile
3 Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
4 Observatory and Planetarium of Johann Palisa, VŠB–TU Ostrava, Czech Republic
5 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
Accepted: 16 March 2009
Accretion shocks have been recognized as an important X-ray emission mechanism for pre-main sequence stars, and yet the X-ray properties of FUor outbursts, events that are caused by violent accretion, have been given little attention. We observed the FUor object Z CMa during optical outburst and quiescence with Chandra. No significant changes in X-ray brightness and spectral shape were found, suggesting that the X-ray emission is coronal. The binary nature of Z CMa makes the origin of the X-ray source ambiguous. However, the moderate hydrogen column density derived from our data makes it unlikely that the embedded primary star is the X-ray source. The secondary star, which is the FUor object, is thus responsible for both the X-ray emission and the ongoing accretion outburst, which seem, however, to be unrelated phenomena. The secondary is also known to drive a large outflow and jet, which we detect here for the first time in X-rays. The distance of the X-ray emitting outflow source to the central star is greater than in jets of low-mass stars.
Key words: X-rays: stars / accretion, accretion disks / stars: pre-main sequence / stars: variables: general / stars: activity / stars: winds, outflows
© ESO, 2009
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