We have made an extensive survey of emission-line stars in the IC 1396 H II region to investigate the low-mass population of pre-main-sequence (PMS) stars. A total of 639 Hα emission-line stars were detected in an area of 4.2?deg2 and their i' photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H II region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the H II region. Based on the extinction estimated from the near-infrared color-color diagram, we have selected PMS star candidates associated with IC 1396. The age and mass were derived from the extinction-corrected color-magnitude diagram and theoretical PMS tracks. Most of our PMS candidates have ages of <3?Myr and masses of 0.2-0.6 M ☉. Although it appears that only a few stars were formed in the last 1?Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10?Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered the formation of many low-mass stars at the dense inhomogeneity in and around the H II region by a radiation-driven implosion.
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机译：我们已经对IC 1396 H II区域的发射线恒星进行了广泛的调查，以研究主序前（PMS）恒星的低质量种群。在4.2？deg2的区域内共检测到639个Hα发射线恒星，并对其i'光度进行了测量。它们的空间分布在象鼻小球（Rim A）附近和H II区边缘的亮边云（Rim B和SFO 37、38、39、41）和HD 206267附近显示了一些聚集体。 H II地区最令人兴奋的明星。基于根据近红外色图估计的消光，我们选择了与IC 1396相关的PMS星候选。年龄和质量是从消光校正后的色度图和理论PMS轨道得出的。我们大多数的PMS候选人的年龄小于3岁，质量为0.2-0.6 M☉。尽管看起来只有几个恒星形成在这颗恒星东部的最后一个1毫米，但我们的调查区域中各次区域之间的年龄差异从统计检验中还不清楚。我们的结果可能表明，大质量恒星是在低质量恒星持续形成10？Myr之后诞生的。令人兴奋的恒星的诞生可能是出生分子云中缓慢但连续的恒星形成的后期阶段。它可能通过辐射驱动的内爆在H II区域内及其周围的致密不均匀性中触发了许多低质量恒星的形成。
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