GS2023+338: a new class of X-ray transient source?
GS2023+338: a new class of X-ray transient source?
复制标题
GS2023 338：一类新的X射线瞬变源？
作者：
S. Kitamoto;H. Tsunemi;S. Miyamoto;K. Yamashita;Seiko Mizobuchi;M. Nakagawa;T. Dotani;F. Makino
瞬态X射线源通常被认为是由包含黑洞或中子星的吸积双星系统组成1 -5。瞬态X射线辐射被认为是由于情节质量转移到紧凑的星星;如果是这样，瞬态源应该提供信息的质量吸积机制。1989年5月21日，Ginga 7号卫星上的全天观测仪6（ASM）在天鹅座8发现了一个不寻常的明亮X射线瞬态源，GS 2023 +338。ASM和大面积计数器9（LAC）也在Ginga上，此后一直在监测源。在这里，我们报告的光变曲线和光谱演变所观察到的ASM和LAC。从5月21日至6月1日，强度在几秒到几天的时间尺度上变化高达500倍10。随后，快速变化持续存在，而较慢的变化消失了。光谱数据符合幂律模型，光子指数为0.0至-2.5，吸收柱密度为1021.7-1022.8 H原子cm−2。这种不寻常的行为还有待解释。
TRANSIENT X-ray sources are generally considered to comprise accreting binary systems containing either a black hole or a neutron star1–5. The transient X-ray emission is thought to result from episodic mass transfer to the compact star; if this is so, transient sources should provide information on the mass-accretion mechanism. On 21 May 1989, the All-Sky Monitor6 (ASM) onboard the satellite Ginga7 discovered an unusual bright X-ray transient source, GS2023+338, in the constellation of Cygnus8. The ASM and Large-Area Counters9 (LAC), also on Ginga, have since monitored the source. Here we report the light curves and spectral evolution observed by the ASM and LAC. From 21 May to 1 June, the intensity varied by up to a factor of 500 on timescales from a few seconds to a few days10. Subsequently the rapid variations persisted, whereas slower ones disappeared. The spectral data fit a power-law model with a photon index of 0.0 to –2.5 and an absorption column density of 1021.7–1022.8 H atoms cm−2. This unusual behaviour remains to be explained.