类Sco X-1源性质的谱研究
Spectral Investigations of the nature of the Sco X-1 like sources
摘要：
利用扩展的吸积盘日冕模型，给出了基于Rossi-XTE观测的类Sco X-1 Z轨源Sco X-1、GX 349+2和GX 17+2的光谱研究结果。将所得结果与Cyg X-2、GX 340+0和GX 5-1等类Cyg X-2的结果进行了比较，并提出了Z径迹源的一般模型。在正常分支上，类天蝎座源和类天鹅座源的情况相似，结果表明在软顶和硬顶之间质量吸积率Mdot增加，而不是像标准观点那样在Z附近增加。在类天鹅源中，增加Mdot会导致中子星温度kT从~1 keV增加到~2 keV。在较低的kT，辐射压力是小的，但在较高的kT，发射的中子星的流量是几倍super-Eddington和高辐射压力破坏的内盘发射上正常和水平分支上观察到的相对论喷流。在类SCO源中，主要的物理差异是在Z轨道的所有部分上超过2 keV的高kT，这表明射流总是可能的，即使在耀斑分支上也是如此。类天鹅星源中的燃烧分支与中子星上的能量释放有关，这与不稳定的核燃烧一致。类SCO源非常不同，因为燃烧似乎是不稳定燃烧和Mdot增加的组合，这使得燃烧更强。对所有6个经典Z轨道源的15年或RXTE ASM数据的分析表明，在Sco类源中，耀斑的高速率和强度表明能量的持续释放加热了中子星，导致高kT。Sco X-1观测到的异常小的耀斑支持了这一点。GX 17+2是Cyg型和Sco型之间的过渡型。我们的研究结果不支持的建议，天鹅座或天蝎座的性质是由光度。
英文摘要：
We present results of spectral investigations of the Sco X-1 like Z-track sources Sco X-1, GX 349+2 and GX 17+2 based on Rossi-XTE observations using an extended accretion disk corona model. The results are compared with previous results for the Cyg X-2 like group: Cyg X-2, GX 340+0 and GX 5-1 and a general model for the Z-track sources proposed. On the normal branch, the Sco-like and Cyg-like sources are similar, the results indicating an increase of mass accretion rate Mdot between soft and hard apex, not as in the standard view that this increases around the Z. In the Cyg-like sources, increasing Mdot causes the neutron star temperature kT to increase from ~1 to ~2 keV. At the lower kT, the radiation pressure is small, but at the higher kT, the emitted flux of the neutron star is several times super-Eddington and the high radiation pressure disrupts the inner disk launching the relativistic jets observed on the upper normal and horizontal branches. In the Sco-like sources, the main physical difference is the high kT of more than 2 keV on all parts of the Z-track suggesting that jets are always possible, even on the flaring branch. The flaring branch in the Cyg-like sources is associated with release of energy on the neutron star consistent with unstable nuclear burning. The Sco-like sources are very different as flaring appears to be a combination of unstable burning and an increase of Mdot which makes flaring much stronger. Analysis of 15 years or RXTE ASM data on all 6 classic Z-track sources shows the high rate and strength of flaring in the Sco-like sources suggesting that continual release of energy heats the neutron star causing the high kT. A Sco X-1 observation with unusually little flaring supports this. GX 17+2 appears to be transitional between the Cyg and Sco-like types. Our results do not support the suggestion that Cyg or Sco-like nature is determined by luminosity.
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