Discovery of Spectral Transitions from Two Ultraluminous Compact X-Ray Sources in IC 342
Discovery of Spectral Transitions from Two Ultraluminous Compact X-Ray Sources in IC 342
复制标题
DOI：
10.1086/318903
复制
发表时间：
2000-11
期刊：
影响因子：
--
通讯作者：
A. Kubota;T. Mizuno;K. Makishima;Y. Fukazawa;J. Kotoku;T. Ohnishi;M. Tashiro
中科院分区：
文献类型：
--
作者：
A. Kubota;T. Mizuno;K. Makishima;Y. Fukazawa;J. Kotoku;T. Ohnishi;M. Tashiro
Two ASCA observations were made of two ultraluminous compact X-ray sources (ULXs) in the spiral galaxy IC 342. In the 1993 observation, source 2 showed a 0.5-10 keV luminosity of 6 × 1039 ergs s-1 (assuming a distance of 4.0 Mpc) and a hard power-law spectrum of photon index ~1.4. As already reported, source 1 was ~3 times brighter on that occasion and exhibited a soft spectrum represented by a multicolor disk model with an inner-disk temperature of ~1.8 keV. The second observation, made in 2000 February, revealed that source 1 had made a transition into a hard spectral state, while source 2 made a transition into a soft spectral state. The ULXs are therefore inferred to exhibit two distinct spectral states, and they sometimes make transitions between them. These results significantly reinforce the scenario that describes ULXs as mass-accreting black holes.
