Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
T. Preibisch:
An extremely X-ray luminous proto-Herbig
Ae/Be star in the Serpens
star forming region
Astronomy & Astrophysics 345, 583-591
(1999)
Abstract.
We present near-infrared spectra for the highly obscured, optically
invisible young stellar object EC 95 in the
Serpens molecular cloud, from which we recently could detect strong
X-ray emission with ROSAT. Its location in
the HR diagram suggests this object to be an extremely young (~ 2 x
10^5 yr old) intermediate-mass (~ 4 M_sun)
star, which is most likely the progenitor of a B-type or early A-type
main sequence star. The only reasonable
explanation for its extremely strong X-ray emission (L_x ~ 1.2 x 10^33
erg/sec) seems to be coronal, i.e. magnetic
activity; this view is also supported by the strong radio emission of
EC 95. This is quite surprising, since one
usually does not expect a magnetic field on intermediate-mass stars,
which are thought to lack surface convection
zones, the prerequisite for a solar-like dynamo effect. A possible
explanation might be that EC 95 currently goes
through a short period of deuterium shell burning, which causes
convection near the stellar surface and might give
rise to a dynamo effect and a corona.
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