EDP Sciences
Free access
Volume 413, Number 2, January II 2004
Page(s) 669 - 679
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20034151

A&A 413, 669-679 (2004)
DOI: 10.1051/0004-6361:20034151

A large X-ray flare from the Herbig Ae star V892 Tau

G. Giardino1, F. Favata1, G. Micela2 and F. Reale3

1  Astrophysics Division - Research and Science Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2  INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
3  Università di Palermo - Dipartimento di Scienze Fisiche ed Astronomiche, Piazza del Parlamento 1, 90134 Palermo, Italy

(Received 1 August 2003 / Accepted 30 September 2003 )

We report the XMM-Newton observation of a large X-ray flare from the Herbig Ae star V892 Tau. The apparent low mass companion of V892 Tau, V892 Tau NE, is unresolved by XMM-Newton. Nevertheless there is compelling evidence from combined XMM-Newton and Chandra data that the origin of the flare is the Herbig Ae star V892 Tau. During the flare the X-ray luminosity of V892 Tau increases by a factor of ${\sim} 15$, while the temperature of the plasma increases from $kT
\simeq 1.5$  keV to $kT \simeq 8$ keV. From the scaling of the flare event, based on hydrodynamic modeling, we conclude that a 500 G magnetic field is needed in order to confine the plasma. Under the assumptions that a dynamo mechanism is required to generate such a confining magnetic field and that surface convection is a necessary ingredient for a dynamo, our findings provide indirect evidence for the existence of a significant convection zone in the stellar envelope of Herbig Ae stars.

Key words: stars: flare -- stars: coronae -- stars: formation -- stars: pre-main sequence -- stars: individual: V892 Tau

Offprint request: G. Giardino, ggiardin@rssd.esa.int

SIMBAD Objects in preparation

© ESO 2004