α TrA Junior

Abstract

The ``hybrid chromosphere'' star α Trianguli Australis (K2 Ib-IIa) displays atypical coronal properties for its class: elevated soft X-ray emission, flare outbursts, and a superhot (T~10 MK) spectrum. The Wide Field Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST) now has found a faint object close to the red supergiant, 0.4" nearly due south and about 1% its intensity in the F160BW ultraviolet filter, consistent with a G0 dwarf. Potentially, the ``young sun'' companion to the massive primary could completely dominate the coronal luminosity. The X-ray centroid in a contemporaneous Chandra High-Resolution Camera (HRC) pointing is offset in the direction of the faint UV secondary, but measurements of the radio counterpart of a serendipitous X-ray source 12" southeast (SE) of α TrA, obtained with the Australia Telescope Compact Array (ATCA), suggest a conflicting offset.