Chandra observations of coronal emission from the early G supergiants α and β Aquarii

We report Chandra detections of coronal X-rays from the early G supergiants alpha Aquarii ( HD 209750: G2 Ib) and beta Aquarii (HD 204867: G0 Ib). Previous ROSAT observations of these archetypical " hybrid chromosphere" stars were inconclusive, in the case of alpha Aqr owing to a 38' mispointing, and for beta Aqr because of a small positional discrepancy of the apparent source. The Chandra High Resolution Camera (HRC-I), with its superior spatial resolution and sensitivity, has obtained a positive detection of a Aqr and recovered faint emission at the location of b Aqr, now well separated from the stronger source to the southeast that dominated the earlier ROSAT image. The coronal L-X/ L-C (IV) luminosity ratios of both supergiants are extremely depressed relative to early G main-sequence stars, continuing the " X-ray deficiency syndrome" originally identified in late F/early G luminosity class III giants of the Hertzsprung gap.