Super-hard X-Ray Emission from eta Carinae Observed with Suzaku - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado

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Abstract: We present the Suzaku results of eta Carinae in the 5-50 keV range conductedtwice around the apastron in 2005 August for 50 ks and in 2006 February for 20ks. The X-ray Imaging Spectrometer XIS produced hard 5-12 keV bandspectra, resolving K shell lines from highly ionized Fe and Ni. The Hard X-rayDetector yielded a significant detection in the super-hard 15-50 keV band,which is uncontaminated by near-by sources. We constrained the temperature ofthe optically-thin thermal plasma emission dominant in the hard band as 3-4keV using the K-shell line features with the XIS. We found significant excessemission above the thermal emission in the super-hard band with the PIN,confirming the previous INTEGRAL ISGRI report. The entire 5-50 keV spectrawere fitted by a combination of a thermal plasma model plus a flat power-law ora very hot thermal bremsstrahlung model for the excess emission. No significantchange of the excess emission was found at different epochs within thesystematic and statistical uncertainties and no flare-like flux amplificationwas seen in the hard band, indicating that the excess emission is a steadyphenomenon. We argue that the super-hard emission is attributable to theinverse Compton of stellar UV photons by non-thermal electrons or to thethermal bremsstrahlung of very hot plasma, and not to the bremsstrahlung bynon-thermal electrons colliding with cold ambient matter.

Autor: Akiko Sekiguchi, Masahiro Tsujimoto, Shunji Kitamoto, Manabu Ishida, Kenji Hamaguchi, Hideyuki Mori, Yohko Tsuboi


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