Gamma-ray follow-up studies on eta Carinae ( K. Reitberger et al.)

Vol. 544
In section 7. Stellar structure and evolution

Gamma-ray follow-up studies on eta Carinae

The study reports the first secure GeV spectrum and variability study of the extremely massive Galactic binary system eta Carina. The star is already well known for its misbehavior throughout the electromagnetic spectrum but not previously at such high energy. The authors used Fermi/LAT data above 0.1 GeV, establishing the source variability relative to two nearby (constant emission) pulsars in the same field. The integrated VHE flux decreases with increasing orbital separation of the five-year period binary and the spectrum is strongly (and statistically significantly) variable above 1 GeV; there appear to be two components with a minimum at around 10 GeV. The behavior is similar to that observed for Galactic microquasars (e.g. LSI +61^o303) but in this case there is no signature of a compact object for the companion of the hypermassive LBV primary.