VLBA确定到附近恒星形成区的距离VII。独角兽R2
VLBA determination of the distance to nearby star-forming regions VII. Monoceros R2
摘要：
我们提出了一系列的16个甚长基线阵列（VLBA）的高角分辨率观测的一个星团的怀疑低质量的年轻恒星在麒麟座R2地区。四个紧凑和高度可变的无线电源被检测到，其中三个在一个时代，第四个共七次。后一个源的方向是先前已知的\UCHII \区域VLA~1，它的射电性质类似于磁活跃星的射电性质;我们将其称为VLA~1 $^\star$。我们将其在天球上的位移建模为自行和三角视差的组合。使用均匀自行获得的拟合产生视差$\varpi$ = 1.10 $\pm$ 0.18 mas，但具有相当高的拟合后色散。如果包括加速度项（可能是由于未检测到的伴随物），则拟合的质量显著提高，并且视差的最佳估计变为$\varpi$ = 1.12 $\pm$ 0.05 mas。拟合加速度的大小表明轨道周期为十年。测量的视差对应于距离$d$ = 893 $^{+44}_{-40}$ pc，与先前的间接测定非常一致。
英文摘要：
We present a series of sixteen Very Long Baseline Array (VLBA) high angular resolution observations of a cluster of suspected low-mass young stars in the Monoceros R2 region. Four compact and highly variable radio sources are detected; three of them in only one epoch, the fourth one a total of seven times. This latter source is seen in the direction to the previously known \UCHII\ region VLA~1, and has radio properties that resemble those of magnetically active stars; we shall call it VLA~1$^\star$. We model its displacement on the celestial sphere as a combination of proper motion and trigonometric parallax. The fit obtained using a uniform proper motion yields a parallax $\varpi$ = 1.10 $\pm$ 0.18 mas, but with a fairly high post-fit dispersion. If acceleration terms (probably due to an undetected companion) are included, the quality of the fit improves dramatically, and the best estimate of the parallax becomes $\varpi$ = 1.12 $\pm$ 0.05 mas. The magnitude of the fitted acceleration suggest an orbital period of order a decade. The measured parallax corresponds to a distance $d$ = 893$^{+44}_{-40}$ pc, in very good agreement with previous, indirect, determinations.
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。
