First Detection of X-ray Variability of $\eta$ Carinae
Session 21 -- Stellar Spectroscopy, Atmospheres, Models, Intrinsic Variables, Theory, Part I
Display presentation, Tuesday, June 13, 1995, 9:20am - 6:30pm

## [21.04] First Detection of X-ray Variability of $\eta$ Carinae

M. F. Corcoran (LHEA/USRA), G. L. Rawley (ARC), J. H. Swank, R. Petre (LHEA), J. H. M. M. Schmitt (MPE)

Recent ROSAT Position Sensitive Proportional Counter (PSPC) observations for the first time unequivocally reveal the presence of a compact source of hard X-ray emission centered on the peculiar star $\eta$ Carinae. These observations also show a dramatic change in the hard-band ($E \ge$ 1.6 keV) counting rate by $\approx$ a factor of 2 in a 4-month interval. ROSAT High Resolution Imager (HRI) observations which span the PSPC observations also reveal a variable source of X-ray emission centered on $\eta$ Carinae. Thus strong variability which is a characteristic of $\eta$ Carinae in radio through IR and visible-band wavelengths is also observed at X-ray energies. The increase in hard X-ray emission could be the result of a tripling of the mass-loss rate in less than 4 months.