发表机构
Centre for Astrophysics Research, University of Hertfordshire; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC); Joint ALMA Observatory（赫特福德大学天体物理研究中心; 欧洲航天局（ESA）欧洲空间研究与技术中心（ESTEC）; ALMA联合观测站）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本工作通过VLBA多历元巡天探测猎户座星云团射电源，发现非热辐射高度间歇，约9%源高变，并证实射电与X射线光度遵循Güdel-Benz关系。
AI 中文摘要
我们展示了一项对猎户座星云团（ONC）中射电源的多历元甚长基线阵列（VLBA）巡天，更新了探测统计并研究了历元间的变异性。该数据集包含八个C波段（4-8 GHz）历元，针对先前在甚大阵列深度巡天中识别出的575个射电源。VLBA观测实现了毫角秒量级的分辨率，并且仅对高亮温度敏感，这意味着只观测到非热辐射。我们探测到226个独特的射电源，对应探测比例为39%。大多数源（约83%）仅被探测到一次，表明与年轻恒星天体（YSOs）相关的非热辐射具有高度间歇性。为了量化变异性，我们使用了每个历元的峰值流量密度和变异性因子（VF），其定义为最大与最小流量之比。我们识别出21个源（约占探测源的9%）表现出高变异性，定义为流量密度至少变化五倍。我们与COUP钱德拉巡天进行交叉匹配以将源识别为YSOs。我们为约56%的探测源找到了COUP对应体。剩余群体不能仅用变异性或背景污染来解释，表明存在一类没有X射线对应体的射电探测YSOs。我们发现射电与X射线光度之间存在清晰的相关性，与Güdel-Benz关系一致，该关系是磁活动恒星的非热射电与热X射线发射之间的经验关系。
英文摘要
We present a multi-epoch Very Long Baseline Array (VLBA) survey of radio sources in the Orion Nebula Cluster (ONC), updating the detection statistics and investigating inter-epoch variability. The dataset comprises eight C-band (4-8 GHz) epochs targeting 575 radio sources previously identified in deep Very Large Array surveys. VLBA observations result in resolutions of milliarcseconds and are only sensitive to high brightness temperatures meaning only non-thermal emission is observed. We detect 226 unique radio sources corresponding to a detection fraction of 39 per cent. The majority of sources (~83 per cent) are detected only once indicating that non-thermal emission associated with Young Stellar Objects (YSOs) is highly intermittent. To quantify variability, we use per-epoch peak flux densities and the variability factor (VF) defined as the ratio between the maximum and minimum fluxes. We identify 21 sources (~9 per cent of detected sources) that exhibit high variability defined as a change of flux density by at least a factor of five. We crossmatch with the COUP Chandra survey to identify sources as YSOs. We identify COUP counterparts for ~56 per cent of the detected sources. The remaining population cannot be explained solely by variability or background contamination, suggesting a population of radio detected YSOs without X-ray counterparts. We find a clear correlation between radio and X-ray luminosities consistent with the Güdel-Benz relation, the empirical relation between non-thermal radio and thermal X-ray emission for magnetically active stars.
Comments31 pages, 7 main figures, 2 figures in appendices
