2004/02/13 by Roberto Viotti, R. F. Viotti, L. A. Antonelli +2
Physics and Astronomy · #Absorption (acoustics) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Atomic physics #Electron #Galaxy #Gamma-ray bursts and supernovae #Line (geometry) #Luminosity #Nuclear physics #Optics #Photon #Physics #Radiation #Spectral line #Thermal #astro-ph
paper · pdf · doi:10.1051/0004-6361:20040113
published as Astron.Astrophys. 420 (2004) 527-532 · 7 pages, 6 figures, accepted for publication in Astronomy and Astrophysics
arxiv created 2004/02/13 · openalex publication_date 2004/05/28 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report on the June 2000 long (100 ks) BeppoSAX exposure that unveiled a new very high energy component of the X-ray spectrum of η Car above 10 keV extending to at least 50 keV. We find that the 2–150 keV spectrum is best reproduced by a thermal + non-thermal model. The thermal component dominates the 2–10 keV spectral range with kTh = 5.5 ± 0.3 keV and log NHh = 22.68 ± 0.01. The spectrum displays a prominent iron emission line centred at 6.70 keV. Its equivalent width of 0.94 keV, if produced by the thermal source, gives a slightly sub-solar iron abundance ([Fe/H] = -0.15 ± 0.02). The high energy tail above 10 keV is best fitted by a power law with a photon index of 2.42 ± 0.04. The integrated 13–150 keV luminosity of ~12 is comparable to that of the 2–10 keV thermal component (19 ). The present result can be explained, in the η Car binary star scenario, by Comptonisation of low frequency radiation by high energy electrons, probably generated in the colliding wind shock front, or in instabilities in the wind of the S Dor primary star. It is possible that the high energy tail had largely weakened near the minimum of the 5.53 yr cycle. Probably, the thermal component has a longer recovery time like that of the highest excitation optical emission lines. Both features can be associated with the large absorption measured by BeppoSAX at phase 0.05.