Cool Stars 14 - Submitted Abstract # 331
This version created on 05 October 2006

Alpha TrA Junior


Thomas Ayres, University of Colorado (CASA)
Alexander Brown, University of Colorado (CASA)
Graham Harper, University of Colorado (CASA)

For a long time it has been proposed that the anomalous properties of
the so-called "hybrid chromosphere" star Alpha Trianguli Australis (K2
II)--particularly its elevated coronal X-ray emission and frequent
flaring--could best be explained by an unseen hyperactive G dwarf
companion (which would share the youthful evolutionary age [about 50
Myr] of the massive primary).  Recently, a series of Hubble WFPC2
exposures finally have recovered the "young sun" (hence "Junior") of
the red supergiant.  The solar blind F160BW filter was exploited to
accentuate the relative brightness of a warm companion, which
otherwise would be more than 8 magnitudes fainter in the V band.  The
companion is about 0.4 arcsec nearly due S of the primary, at a
position angle of 162 degrees (measured E from N).  The secondary is
about 1% the intensity of the primary in the UV filter, as would be
predicted for a G0  spectrum.  Although a G dwarf of that age could
completely dominate the soft X-ray emission, it would have little
influence on the FUV spectrum.  

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