Hubble Space Telescope WFPC2 Observations of the Binary Fraction among Pre-Main-Sequence Cluster Stars in Orion
Hubble Space Telescope WFPC2 Observations of the Binary Fraction among Pre-Main-Sequence Cluster Stars in Orion
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哈勃太空望远镜 WFPC2 对猎户座前主序星团中双星部分的观测
DOI：
10.1086/303718
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
A. Ghez
中科院分区：
文献类型：
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作者：
D. Padgett;S. Strom;A. Ghez
我们基于哈勃太空望远镜 (HST) 广域行星相机 2 (WFPC2) 观测，对与 NGC 2024、NGC 2068 和 NGC 2071（距离 = 460 pc）相关的致密（平均恒星间隔 ~0.05 pc）嵌入星团的光学可见（IHST < 19 mag）成员的双星频率进行了估计。在 99 个目标中，有 15 个被发现是双星，预计线性间隔为 138-1050 天文单位 (0.″3 < θ < 2.″3)。在此分离范围内，所得多重分数为 15/99 或 0.15 ± 0.04，而太阳邻域 G 和 K 星观测到的可比值分别为 0.11 和 0.09。我们还检查了 O'Dell 和 Wen 获得的梯形星团的档案 F547M WFPC2 图像，发现对于 VHST < 17 的恒星，在分离范围 138-828 AU 中，二元频率为 7/50 或 0.14 ± 0.05。我们的结果与 Reipurth 和 Zinnecker 最近根据观测确定的 0.16 ± 0.03 值非常吻合。 238 颗前主序 (PMS) 恒星位于附近 (d ~ 150 pc) 低密度（平均恒星间隔 ~0.3 pc）恒星形成区域，其间隔范围相当。我们的结果表明，具有相同分离度的 PMS 双星比主序双星多。此外，我们没有发现任何证据表明在相对密集的星团中形成的双星的比例与低密度恒星形成区域的特征不同。
We present estimates of the binary frequency for optically visible (IHST < 19 mag) members of the dense (mean star separation ~0.05 pc) embedded stellar clusters associated with NGC 2024, NGC 2068, and NGC 2071 (distance = 460 pc) based on Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations. Of 99 targets, 15 are found to be double stars with projected linear separations of 138-1050 AU (0.″3 < θ < 2.″3). The resulting multiplicity fraction is 15/99 or 0.15 ± 0.04 in this separation range, while the comparable values observed for solar neighborhood G and K stars are 0.11 and 0.09, respectively. We also examined the archival F547M WFPC2 images of the Trapezium cluster obtained by O'Dell & Wen and found a binary frequency of 7/50 or 0.14 ± 0.05 in the separation range 138-828 AU for stars with VHST < 17. Our results compare well with the value of 0.16 ± 0.03 determined recently by Reipurth & Zinnecker from observations of 238 pre-main-sequence (PMS) stars in nearby (d ~ 150 pc) low-density (mean star separation ~0.3 pc) star-forming regions over comparable separation ranges. Our results suggest an excess of PMS binaries over main-sequence binaries with the same separations. In addition, we find no evidence that the fraction of binaries formed in relatively dense clusters differs from that characterizing low-density star-forming regions.