（196256）2003 EH $_{1}$的物理观测，象限流星流的假定母体
Physical Observations of (196256) 2003 EH$_{1}$, Presumed Parent of the Quadrantid Meteoroid Stream
摘要：
近地小行星（196256）2003 EH 1被认为与象限仪座流星体流有动力学联系。我们提出的光度观测采取调查这个机构的物理特性，并探讨其可能的关系流。我们没有发现持续质量损失的证据。一个模型拟合的点状表面亮度轮廓在2.1 AU限制积分亮度的分数贡献近核彗差$\leq$ 2.5%。假设一个典型的彗星核的半径等于（$\it p_{\rm R}$ =0.04），我们发现，有效的核半径为$r_e$ = 2.0 $\pm$ 0.2公里。时间分辨的${\it R}$波段测光可以用一个具有12.650 $\pm$ 0.033 hr旋转周期的双峰光变曲线来拟合。光变曲线的范围，$Δm_{\rm R}$ = 0.44 $\pm$ 0.01 mag，表示一个细长的形状，其轴比$\sim$ 1.5投射到天空平面上。这颗小行星的颜色比太阳略红，与C型小行星相当。由不存在分辨的彗差而设定的质量损失速率的极限是$\lesssim$ 2.5 $\times$ 10 $^{-2}$ kg ${\rm s^{-1}}$，对应于可能升华水冰$f_A$ $\lesssim$ 10 $^{-4}$的表面部分的上限。即使在象限仪星流200-500年的动力学年龄上持续下去，2003 EH 1的总质量损失也太小，不足以提供报告的流质量（$10^{13}$ kg），这意味着该流有另一个母体，或者2003 EH 1的质量损失是偶发的。
英文摘要：
The near-Earth asteroid (196256) 2003 EH1 has been suggested to have a dynamical association with the Quadrantid meteoroid stream. We present photometric observations taken to investigate the physical character of this body and to explore its possible relation to the stream. We find no evidence for on-going mass-loss. A model fitted to the point-like surface brightness profile at 2.1 AU limits the fractional contribution to the integrated brightness by near-nucleus coma to $\leq$ 2.5 %. Assuming an albedo equal to those typical of cometary nuclei ($\it p_{\rm R}$=0.04), we find that the effective nucleus radius is $r_e$ = 2.0$\pm$0.2 km. Time-resolved ${\it R}$-band photometry can be fitted by a two-peaked lightcurve having a rotational period of 12.650$\pm$0.033 hr. The range of the lightcurve, $Δm_{\rm R}$= 0.44 $\pm$ 0 .01 mag, is indicative of an elongated shape having an axis ratio $\sim$1.5 projected into the plane of the sky. The asteroid shows colors slightly redder than the Sun, being comparable with those of C-type asteroids. The limit to the mass loss rate set by the absence of resolved coma is $\lesssim$ 2.5$\times$ 10$^{-2}$ kg ${\rm s^{-1}}$, corresponding to an upper limit on the fraction of the surface that could be sublimating water ice $f_A$ $\lesssim$ 10$^{-4}$. Even if sustained over the 200-500 yr dynamical age of the Quadrantid stream, the total mass loss from 2003 EH1 would be too small to supply the reported stream mass ($10^{13}$ kg), implying either that the stream has another parent or that mass loss from 2003 EH1 is episodic.
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