Star formation in the remnant clouds associated with OB Associations

分子云的主体已经得到了详细的研究，然而，关于周围区域的信息很少，包括OB1a，b缔合。我们已经通过ASCA卫星在恒星形成活动较低的OOB1b区域探测到了40多个X射线源。每个源的X射线光度为1030-1031erg/S，平均温度为4keV。有8个源被确认为已知的低质量前主序恒星，其中大部分位于马头星云所在的区域。对于其他X射线源，我们进行了红外测光，表明它们在近红外双色图上的位置一致，大部分是WTT。我们还发现了该地区可能的河外X射线源的X射线发射。我们还统计分析了发射线星的表面分布和星团性质。作为恒星形成地点以外的主要巨型分子云，WE…更多的人也研究了猎户座区域的“残余云”。对反射云、彗星球体和明亮边缘云等“残余云”的联合观测显示，24个目标云中60%有分子谱线发射。它们中的许多似乎与前主序列星的候选者有关。这些结果表明，恒星形成活动相当低，但仍在持续。此外，我们还对另一个GB组合MON OB1进行了X射线观测。MON OB1比OB1的距离更远，但ASCA的一个字段覆盖了这种关联的主要部分。详细的数据分析仍在进行中，我们已经探测到12个X射线源。特别是，两个X射线源与近红外源和致密分子云核的星团很好地吻合。这两个源的BARD X射线发射峰被鉴定为NGC2264IRS1和2，具有中等热光亮度的I类源。我们的X射线数据可能为中等质量恒星的形成提供重要信息。较少

The main body of the molecular cloud has been studied in detail, however, there has been only a little information about the surrounding area including On OB1a, b associations. We have detected more than forty X-ray sources in the On OB1b region, where the activity of star formation is low, by the ASCA satellite. The X-ray luminosities of each source are 1030-1031 erg/s and the average temperature is 4 keV.Eight sources are identified as known low-mass pre-main sequence stars (CTTS), and most of them lie in the field where the Horsehead nebula is located. For other X-ray sources, we have made infrared photometry and showed that their position on the near-infrared two color diagram is consistent that most of them are WTTS.We also found X-ray emission from possible extragalactic sources in this region.We also made statistical analysis of the surface distribution of emission line stars and clustering properties. As the site of star formation outside of the main giant molecular clouds, we … More have studied "remnant clouds" in the Orion region as well. CO observations of the "remnant clouds" including reflection clouds, cometary globules, and bright-rimmed clouds revealed molecular line emission from 60% of the 24 target clouds. Many of them appear associated with the candidates of pre-main sequence stars. These results suggest that the star forming activity is rather low but still cotinueing.Furthermore, we have carried out X-ray observations of another GB association, Mon OB1. Mon OB1 is more distant than On OB1, but one field of ASCA covered the main part of this association. The detailed data analysis is still going on, we have detected twelve X-ray sources. Particularly two X-ray sources coincide well with the cluster of near-infrared sources and dense molecular cloud cores. The peaks of bard X-ray emission of these two sources were identified as NGC 2264 IRS1 and 2, class I sources with intermediate bolometric luminosities. Our X-ray data may provide the important information on the formation of stars with intermediate mass. Less