Multi-wavelength study of X-ray emitting A- and B-stars testing the companion hypothesis
Beate Stelzer (INAF -- Osservatorio Astronomico di Palermo)
No mechanism is known that produces X-rays in late B-type and early A-type
stars: they are not massive enough to drive strong stellar winds, nor do they
possess convective zones that could sustain a magnetic dynamo. Nevertheless
their detection has been reported from virtually all X-ray satellites, and has
remained a mystery to date. We use a multi-wavelength approach to test the most
wide-spread hypothesis that the X-rays are generated by late-type magnetically
active companions. Our high spatial resolution observations of A/B-type stars in
the IR using adaptive optics uncover hypothetical companion stars at arcsecond
separations from the primary. Chandra's unprecedented spatial resolution allows
to pinpoint the location of the X-ray emission in the same targets. Finally,
with IR spectroscopy of the A/B-type stars still detected with Chandra we search
for temperature sensitive features indicating the existence of even closer cool
companions. Even with this multi-fold strategy we are likely to miss the closest
of the possible companions, but a study of the X-ray properties can provide
further information on the nature of the emitters.