十颗超冷次矮星的三角投影
Trigonometric parallaxes of ten ultracool subdwarfs
摘要：
我们测量了十个超冷次矮星样本相对于许多背景星系的绝对三角视差和自行。这些观测是在西班牙Calar Alto的3.5米望远镜上用OMEGA 2000相机在H波段进行的，时间为3.5年。这是第一次直接对背景星系进行天体测量的简化。我们得到了绝对的平均误差在1和3 mas之间。有了六个全新的超冷（> sdM 7）次矮星，我们的基准超冷（> sdM 7）次矮星数量增加了一倍多。M_{K_s}与J-K_s图中的6颗恒星完全符合M7至L4的亚矮星序列模型，[M/H]在-1.0至-1.5之间，而4颗恒星符合M7至T6的中等低金属丰度（[M/H]=-0.5）。除了一个外，我们所有的天体都有很大的切向速度，在200到320公里/秒之间，这是典型的星系晕种群。我们的结果与最近对我们的三个目标的独立测量结果非常一致，并以更高的精度确认了先前测量的最近和最冷（T型）亚矮星2 MASS 0937+29的视差和绝对星等M_{K_s}。对于所有目标，我们还获得了相对于2 MASS标准的几个毫量级的红外J，H，K_s测光。
英文摘要：
We measured absolute trigonometric parallaxes and proper motions with respect to many background galaxies for a sample of ten ultracool subdwarfs. The observations were taken in the H-band with the OMEGA2000 camera at the 3.5m-telescope on Calar Alto, Spain during a time period of 3.5 years. For the first time, the reduction of the astrometric measurements was carried out directly with respect to background galaxies. We obtained absolute parallaxes with mean errors ranging between 1 and 3 mas. With six completely new parallaxes we more than doubled the number of benchmark ultracool (>sdM7) subdwarfs. Six stars in the M_{K_s} vs. J-K_s diagram fit perfectly to model subdwarf sequences from M7 to L4 with [M/H] between -1.0 and -1.5, whereas 4 are consistent with a moderately low metallicity ([M/H]=-0.5) from M7 to T6. All but one of our objects have large tangential velocities between 200 and 320 km/s typical of the Galactic halo population. Our results are in good agreement with recent independent measurements for three of our targets and confirm the previously measured parallax and absolute magnitude M_{K_s} of the nearest and coolest (T-type) subdwarf 2MASS 0937+29 with higher accuracy. For all targets, we also obtained infrared J,H,K_s photometry at a level of a few milli-magnitudes relative to 2MASS standards.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
