用Subaru Hyper Suprime-Cam观测28P/诺伊明彗星的冲日效应
Opposition effect of comet 28P/Neujmin observed with Subaru Hyper Suprime-Cam
浏览论文内容
中文总结 AI 辅助
本研究用斯巴鲁HSC在日心距超10天文单位处观测28P彗核，证实其小相位角下的冲日增亮，发现其相干后向散射贡献大于C、D型小行星，表面结构或与二者不同。
中文摘要 AI 辅助
我们对28P/诺伊明彗星的彗核进行了观测研究，观测时的日心距离超过10天文单位，此时彗发污染已被有效最小化。观测使用8.2米斯巴鲁望远镜上的Hyper Suprime-Cam（HSC），在g、r和y波段开展。测得的颜色g-r=0.67±0.17，r-y=0.41±0.19，由此得到的光谱指数S'=8.8±4.2%/100 nm，与D型小行星的光谱指数相当。结合相位角α=0.334°的新观测数据与此前的观测结果，我们确定了28P彗核的相位函数，并证实其在小相位角下存在冲日增亮现象。推导得到的冲日效应振幅取决于所采用的相位系数，而由于多回归相位曲线中潜在的系统效应，该相位系数存在不确定性。不过，即便采用保守假设，28P的冲日效应也表明，其相干后向散射的贡献大于C型和D型小行星的典型值。斯巴鲁HSC的观测结果显示，尽管28P彗核的颜色与D型小行星相似，但其表面微观结构可能与C型和D型小行星不同。未来需开展覆盖从近冲日到大相位角的宽相位角范围的单次回归观测，并结合偏振测量，这对明确确定彗星核冲日效应的物理机制至关重要。
英文摘要
We present an observational study of the nucleus of comet 28P/Neujmin at a heliocentric distance exceeding 10 au, where coma contamination is effectively minimized. Observations were conducted in the $g$, $r$, and $y$ bands with the Hyper Suprime-Cam (HSC) on the 8.2-m Subaru Telescope. The measured colors, $g - r = 0.67\pm0.17$ and $r - y = 0.41\pm0.19$, yield a spectral index of $S' = 8.8\pm4.2\%/100$ nm, comparable to that of D-type asteroids. By incorporating new observational data at a phase angle $α= 0.334^{\circ}$ with previous observations, we determined the phase function for the nucleus of 28P and confirmed an opposition surge at small phase angles. The derived opposition effect amplitude depends on the adopted phase coefficient, which is uncertain due to potential systematic effects in multi-apparition phase curves. Nevertheless, even under conservative assumptions, the opposition effect of 28P suggests a larger coherent backscattering contribution than is typical for C- and D-type asteroids. The Subaru HSC observations suggest that, although the nucleus color resembles that of D-type asteroids, the surface microstructure of comet 28P's nucleus likely differs from those of C- and D-type asteroids. Future single-apparition observations covering a wide phase angle range from near-opposition to larger angles, combined with polarimetric measurements, will be essential to definitively establish the physical mechanisms responsible for the opposition effects of cometary nuclei.
