ASCA, RXTE, EUVE, and Optical Observations of the High Magnetic Field Cataclysmic Variable AR Ursae Majoris
ASCA, RXTE, EUVE, and Optical Observations of the High Magnetic Field Cataclysmic Variable AR Ursae Majoris
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DOI：
10.1086/307505
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发表时间：
1999-08
期刊：
影响因子：
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通讯作者：
P. Szkody;S. Vennes;G. Schmidt;R. Wagner;R. Fried;A. Shafter;E. Fierce
中科院分区：
文献类型：
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作者：
P. Szkody;S. Vennes;G. Schmidt;R. Wagner;R. Fried;A. Shafter;E. Fierce
在低状态下用 ASCA 观察到最高场极性 AR UMa，在高状态下用同步 EUVE、RXTE 和地面光学光度测量观察到。低态的边缘检测对硬 X 射线发射施加了限制，该限制比高态通量限制低 5 倍。高态 EUV 光变曲线在相位 0.9 处以峰值通量进行高度调制，但通量从未完全消失，这意味着在轨道上的任何时间都可以看到加热区域。明亮阶段的光谱表明温度为 265,000 K，而较暗阶段的温度较低，约为 215,000 K，并且在流倾角阶段光谱最热（320,000 K）。然而，黑体和标准恒星大气模型都无法很好地拟合数据。为了使 EUV 调制与偏振测量和光谱学得出的几何参数一致，白矮星上的主要加热区域必须从南磁极几何延伸，同时北极始终处于视野范围内。 The temperatures of the heated regions are typical of polars, but the projected areas are small, which could be due to the lack of a good view of the main pole at the low inclination of the system. RXTE 光变曲线显示轨道上没有调制，并且仅在硬 X 射线中进行了边缘检测，这意味着存在弱的轫致辐射分量，这对于最高磁场极地来说是典型的。在光学中，在相位 0.5 处达到峰值的低幅度正弦调制与受照射次级的起源一致。
The highest field polar AR UMa was observed with ASCA during a low state, and with simultaneous EUVE, RXTE, and ground-based optical photometry during a high state. The marginal detection at the low state places a limit on the hard X-ray emission, which is a factor of 5 below the high-state flux limit. The high-state EUV light curves are highly modulated with peak flux at phase 0.9, but the flux never entirely disappears, implying some view of a heated area at all times of the orbit. The spectra during bright phases suggest a temperature of 265,000 K while the fainter phases are cooler, ~215,000 K, and the spectrum is hottest (320,000 K) during the stream dip phases. However, neither a blackbody nor a standard stellar atmosphere model provides a good fit to the data. In order for the EUV modulation to be consistent with geometrical parameters derived from polarimetry and spectroscopy, the primary heated area on the white dwarf must be geometrically extended from the southern magnetic pole while the northern pole is constantly in view. The temperatures of the heated regions are typical of polars, but the projected areas are small, which could be due to the lack of a good view of the main pole at the low inclination of the system. The RXTE light curve shows no modulation over the orbit and only a marginal detection in hard X-rays, implying a weak bremsstrahlung component that is typical for the highest magnetic field polars. In the optical, a low-amplitude sinusoidal modulation peaking at phase 0.5 is consistent with an origin from the irradiated secondary.