Suzaku X-Ray Imaging and Spectroscopy of Cassiopeia A
Maeda, Yoshitomo; Ishida, Manabu; Petre, Robert; Fukazawa, Yasushi; Kamae, Tsuneyoshi; Kodaka, Natsuki; Kokubun, Motohide; Takahashi, Tadayuki; Terada, Yukikatsu; Hughes, John P.; Ezoe, Yuichiro; Matsumoto, Hironori; Vink, Jacco; Kouzu, Tomomi; Bamba, Aya; Uchiyama, Yasunobu; Tamagawa, Toru; Tsuboi, Yohko; Tsunemi, Hiroshi; Kosugi, Hiroko; Tamura, Keisuke; Okada, Shunsaku; Nakamura, Ryoko; Miyata, Emi; Holt, Stephen S.; Hiraga, Junko; Helder, Eveline A.; Someya, Kentaro; Totsuka, Kohta
Japan, United States, Netherlands
Abstract
Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were carried out. K-shell transition lines from highly ionized ions of various elements were detected, including Chromium (Cr-Kα at 5.61 keV). The X-ray continuum spectra were modeled in the 3.4-40 keV band, summed over the entire remnant, and were fitted with a simplest combination of the thermal bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits with this assumption indicate that the continuum emission is likely to be dominated by non-thermal emission with a cut-off energy at >1 keV. The thermal-to-nonthermal fraction of the continuum flux in the 4-10 keV band is best estimated as ∼0.1. Non-thermal-dominated continuum images in the 4-14 keV band were made. The peak of the non-thermal X-rays appears at the western part. The peak position of the TeV γ-rays measured with HEGRA and MAGIC is also shifted at the western part with the 1-sigma confidence. Since the location of the X-ray continuum emission was known to be presumably identified with the reverse shock region, the possible keV-TeV correlations give a hint that the accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements in the reverse shock region.