Probing the Accretion Scheme of the Dipping X-ray Binary 4U 1915-05 with Suzaku
Probing the Accretion Scheme of the Dipping X-ray Binary 4U 1915-05 with Suzaku
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DOI：
10.1093/pasj/psu117
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发表时间：
2014-09
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影响因子：
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通讯作者：
Zhongli Zhang;K. Makishima;Soki Sakurai;M. Sasano;Ko Ono
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作者：
Zhongli Zhang;K. Makishima;Soki Sakurai;M. Sasano;Ko Ono
俯冲的低质量x射线双星4U 1915-05是由Suzaku于2007年11月8日观测到的，净曝光为39 ksec。XIS检测到的0.8-10 keV信号速率为9.84+\-0.01 cts/s， HXD-PIN检测到的12-45 keV信号速率为0.29+/-0.01 cts/s。在去除周期衰减和x射线爆发后，0.8 - 45kev连续谱被成功地描述为一个光学厚盘发射（盘内温度~ 0.7 keV）和一个中子星黑体发射（温度~ 1.3 keV），条件是黑体成分（也可能是盘发射）被显著化。这一成功的建模与观测结果中4U 1915-05处于高软态是一致的，这意味着它的宽带频谱可以用与许多处于软态的非倾斜低质量x射线双星相同的方案来解释。它的热光度（~ 0.02倍的Eddington极限）相对较低的软状态，但在一个公差范围内，如果考虑到距离和倾角的不确定性。与低倾角和中倾角双星相比，高倾角双星具有更强的复合效应，复合y参数更大。这表明，在软状态下，这些天体的复合日冕呈扁圆形（而不是球形），沿着吸积盘平面延伸，因为如果日冕是球形的，y参数将不依赖于倾角。
The dipping low-mass X-ray binary 4U 1915-05 was observed by Suzaku on 2007 November 8 for a net exposure of 39 ksec. It was detected by the XIS with a 0.8-10 keV signal rate of 9.84+\-0.01 cts/s per camera, and HXD-PIN with a 12-45 keV signal rate of 0.29+/-0.01 cts/s. After removing the periodic dips and an X-ray burst, the 0.8 - 45 keV continuum was successfully described by an optically thick disk emission with an inner-disk temperature ~ 0.7 keV and a neutron-star blackbody emission with a temperature ~ 1.3 keV, on condition that the blackbody component, or possibly the disk emission too, is significantly Comptonized. This successful modeling is consistent with 4U 1915-05 being in a high-soft state in this observation, and implies that its broadband spectrum can be interpreted in the same scheme as for many non-dipping Low-mass X-ray binaries in the soft state. Its bolometric luminosity (~ 0.02 times the Eddington limit) is relatively low for the soft state, but within a tolerance, if considering the distance and inclination uncertainties. As a high-inclination binary, this source exhibited stronger Comptonization effect, with a larger Comptonizing y-parameter, compared to low and medium inclination binaries. This suggests that the Comptonizing coronae of these objects in the soft state is in an oblate (rather than spherical) shape, extending along the accretion disk plane, because the y-parameter would not depend on the inclination if the corona were spherical.