arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1502.03443astro-ph.HE
收藏

蓝致密矮星系VII Zw 403中X射线双星到硬超亮态的跃迁

Transition of an X-ray binary to the hard ultraluminous state in the blue compact dwarf galaxy VII Zw 403

Matthew Brorby, Philip Kaaret, Hua Feng

摘要:

我们研究了VII Zw 403的X射线谱,这是一个邻近的低金属量蓝矮星系。该星系被观测到包含一个X射线源,很可能是一个高质量X射线双星(HMXB),在0.3-8 keV能量范围内的光度为1.3- 23 x10^38 erg·s^-1。朱雀星的一项新观测显示,它的亮度达到了1.7 × 10^40 erg s^-1 [0.3 ~ 8 keV],高出了7 ~ 130倍。从高通量状态的光谱是硬的,最好的磁盘加康普顿化模型描述,并表现出在5千电子伏以上的能量曲率。这与许多高质量的超铝X射线源光谱是一致的,这些光谱被解释为恒星质量黑洞(StMBH)以超爱丁顿速率吸积。然而,这与另一个低金属量BCD中的HMXB I Zw 18相反,它在高通量下呈现出软光谱,类似于银河系黑洞双星,并被解释为可能的中等质量黑洞。确定BCD中HMXB的光谱特性对再电离时代的模型具有重要意义。据认为,早期宇宙中X射线加热的主要成分是第一个星系中的HMXB。早期的星系是小的,缺乏金属,恒星形成的星系与大的H I质量分数-属性共享的本地BCD我们今天看到的。了解早期宇宙类似星系(如BCD)中HMXB的光谱演化是估计其在再电离时期对星系际介质加热贡献的重要一步。BCD中仅有的两个光谱学研究的HMXB的性质之间的强烈对比促使对低金属丰度环境中更大样本的HMXB进行进一步研究,以正确估计早期宇宙中的X射线加热。

英文摘要:

We examine the X-ray spectra of VII Zw 403, a nearby low-metallicity blue compact dwarf (BCD) galaxy. The galaxy has been observed to contain an X-ray source, likely a high mass X-ray binary (HMXB), with a luminosity of 1.3-23x10^38 erg s^-1 in the 0.3-8 keV energy range. A new Suzaku observation shows a transition to a luminosity of 1.7x10^40 erg s^-1 [0.3-8 keV], higher by a factor of 7-130. The spectra from the high flux state are hard, best described by a disk plus Comptonization model, and exhibit curvature at energies above 5 keV. This is consistent with many high-quality ultraluminous X-ray source spectra which have been interpreted as stellar mass black holes (StMBH) accreting at super-Eddington rates. However, this lies in contrast to another HMXB in a low-metallicity BCD, I Zw 18, that exhibits a soft spectrum at high flux, similar to Galactic black hole binaries and has been interpreted as a possible intermediate mass black hole. Determining the spectral properties of HMXBs in BCDs has important implications for models of the Epoch of Reionization. It is thought that the main component of X-ray heating in the early universe was dominated by HMXBs within the first galaxies. Early galaxies were small, metal-deficient, star forming galaxies with large H I mass fractions --- properties shared by local BCDs we see today. Understanding the spectral evolution of HMXBs in early universe analogue galaxies, such as BCDs, is an important step in estimating their contribution to the heating of the intergalactic medium during the Epoch of Reionization. The strong contrast between the properties of the only two spectroscopically studied HMXBs within BCDs motivates further study on larger samples of HMXBs in low metallicity environments in order to properly estimate the X-ray heating in the early universe.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑