论文标题
搜索与哈勃太空望远镜的亨德斯集群中七个白色矮人大约的巨型行星
Search for giant planets around seven white dwarfs in the Hyades cluster with the Hubble Space Telescope
论文作者
论文摘要
在恒星群集环境中仅确定了少量的系外行星。我们使用哈勃太空望远镜（HST）及其NICMOS仪器进行了高角度分辨率的直接成像搜索，用于在轨道上的自露的巨型行星，约有7个白色矮人在625 Myr附近（45 PC）Hyades Hyades Hyades群集中。在F110W和F160W过滤器中使用NIC1获得观察结果，并包含两个HST滚动角以促进角度差成像。搜索差异图像以寻找伴侣候选物，并计算出径向平均的对比曲线。尽管我们达到了> 0.5 arcsec的角度分离的最低质量检测极限，但没有发现七个白矮人中的任何一个行星质量伴侣，其初始主要序列质量> 2.8 msun。与进化模型的比较，根据一个模型产生5至7个木星质量的检测极限，根据另一个模型在9至12 MJUP之间，在物理分离处，对应于初始的半轴轴> 5至8a.u。 （即，在与宿主恒星的红色和渐近巨型分支阶段相关的群众损失事件之前）。这项研究提供了进一步的证据，表明最初是浓密的聚类环境（包括O-和B型恒星）可能不利于形成巨大的室外磁盘的形成，并且它们转化为巨型行星（M> 6 MJUP和A> 6 A.U.）。这与G型巨人和K型巨头周围的系外星群的径向速度调查一致，后者在恒星周围没有比3毫秒更大的恒星周围的行星。
Only a small number of exoplanets has been identified in stellar cluster environments. We initiated a high angular resolution direct imaging search using the Hubble Space Telescope (HST) and its NICMOS instrument for self-luminous giant planets in orbit around seven white dwarfs in the 625 Myr old nearby (45 pc) Hyades cluster. The observations were obtained with NIC1 in the F110W and F160W filters, and encompass two HST roll angles to facilitate angular differential imaging. The difference images were searched for companion candidates, and radially averaged contrast curves were computed. Though we achieve the lowest mass detection limits yet for angular separations >0.5 arcsec, no planetary mass companion to any of the seven white dwarfs, whose initial main sequence masses were >2.8 Msun, was found. Comparison with evolutionary models yields detection limits of 5 to 7 Jupiter masses according to one model, and between 9 and 12 Mjup according to another model, at physical separations corresponding to initial semimajor axis of >5 to 8 A.U. (i.e., before the mass loss events associated with the red and asymptotic giant branch phase of the host star). The study provides further evidence that initially dense cluster environments, which included O- and B-type stars, might not be highly conducive to the formation of massive circumstellar disks, and their transformation into giant planets (with m>6 Mjup and a>6 A.U.). This is in agreement with radial velocity surveys for exoplanets around G- and K-type giants, which did not find any planets around stars more massive than about 3 Msun.
