C/2007 N3（鹿林）彗星的近冲photometry
Near opposition photometry of comet C/2007 N3 (Lulin)
摘要：
对彗星C/2007 N3（鹿林）的观测是在接近对冲的相位角（$1.7^{\circ}$ - $10^{\circ}$）进行的。在2009年2月24日至28日期间，使用安装在阿布山红外天文台1.2米望远镜上的光偏振计，在IHW蓝色和红色连续光谱以及$R$宽带中进行了光度观测。在所有频带中，对于上述相位角范围，检测到亮度随着相位角减小而显著线性增加。在IHW红（6840 nm）滤波器波段估算的相位系数（$β= 0.040\pm 0.001$ mag deg $^{-1}$）与波长无关。对于相位角$>1.7^{\circ}$，没有观察到非线性反向浪涌。在前面提到的范围内，亮度随着相位角的减小而线性增加，可以使用阴影隐藏模型来解释。彗星的颜色被发现是类似于太阳的颜色，表明颗粒大于$0.1μm$占主导地位。在相位角$\sim 6.5^\circ$处看到亮度下降约0.20等。
英文摘要：
Observations on comet C/2007 N3 (Lulin) were made at phase angles close to opposition ($1.7^{\circ}$ - $10^{\circ}$). Photometric observations were carried out during 2009 February 24-28, in the IHW blue and red continuum and $R$ broad band using photo-polarimeter mounted on the 1.2m telescope at Mt Abu IR Observatory. In all the bands, a significant linear increase in brightness with decreasing phase angle is detected for the above phase angle range. The phase coefficient ($β= 0.040\pm 0.001$ mag deg$^{-1}$ estimated in IHW red (6840Å) filter band) is found to be independent of wavelength. No non-linear opposition surge is observed for phase angle $>1.7^{\circ}$. The linear increase in brightness with decreasing phase angle in the range mentioned earlier can be explained using the shadow hiding model. The colour of the comet is found to be similar to the solar colour indicating the dominance of grains larger than $0.1μm$. A dip in the brightness of about 0.20 mag is seen at the phase angle $\sim 6.5^\circ$.
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