发表机构
The CHARA Array of Georgia State University; University of Tartu; University of Michigan; University of Exeter（佐治亚州立大学CHARA阵列; 塔尔图大学; 密歇根大学; 埃克塞特大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用CHARA阵列观测，测得黄特超巨星仙后座V509的高温致密态，未发现显著CO波段延展及近红外亮伴星，其角直径17-21年无显著长期变化，未排除紫外光谱提出的B1 V型伴星。
AI 中文摘要
黄特超巨星是罕见的演化大质量恒星，通常被认为是后红超巨星天体，在动力学不稳定的黄演化空区附近或内部向蓝端演化。仙后座V509是一个典型例子：其光谱推断的有效温度从1980年代中期的约5000 K升至1990年代末期的约7900 K，此后在升温后状态中保持在该值附近。我们使用2023年CHARA阵列6台望远镜的同步观测数据，结合H波段的MIRC-X设备和K波段的MYSTIC设备，测量其光球直径、搜寻亮伴星并约束任何空间延展的CO大气。采用固定大气模型临边昏暗分布轮廓的干涉数据拟合，得到临边昏暗角直径为1.1840–1.1950 mas。尽管名义上比之前Palomar Testbed干涉仪的测量值小约5%，但该差异仅为1.8σ，表明在17–21年的时间内无显著长期变化。闭合相位与中心对称亮度分布一致，在采样角距范围内未检测到近红外亮伴星，其中值3σ极限为ΔH=5.28 mag、ΔK=6.48 mag。紫外光谱提出的B1 V型伴星预计位于这些极限之下，未被排除。CO第一泛音通道得到的CO与连续谱直径比的加权均值为1.011±0.004，低于采用的3σ探测阈值，未发现显著的CO波段角延展。因此，尽管仙后座V509保留了光谱可见的原子星周气体，但其呈高温且分子致密的状态。
英文摘要
Yellow hypergiants are rare, evolved massive stars generally interpreted as post-red-supergiant objects evolving blueward through or near the dynamically unstable Yellow Evolutionary Void. V509~Cassiopeiae is a remarkable example: its spectroscopically inferred effective temperature increased from approximately 5000~K in the mid-1980s to about 7900~K by the late 1990s and has since remained near this value during its post-heating state. We use simultaneous six-telescope CHARA observations obtained in 2023 with MIRC-X in the $H$ band and MYSTIC in the $K$ band to measure its photospheric diameter, search for a luminous companion, and constrain any spatially extended CO atmosphere. Interferometric data fitting with fixed atmosphere-model center-to-limb variation profiles yield limb-darkened angular diameters of $1.1840$--$1.1950$~mas. Although nominally about 5\% smaller than the previous Palomar Testbed Interferometer measurement, the difference is only $1.8σ$, indicating no significant secular change over 17--21~yr. The closure phases are consistent with a centrosymmetric brightness distribution, and no near-infrared-bright companion is detected over the sampled separations. The median $3σ$ limits are $ΔH=5.28$~mag and $ΔK=6.48$~mag. The B1~V companion proposed from ultraviolet spectroscopy is expected to lie below these limits and is not excluded. The CO first-overtone channels give a weighted mean CO-to-continuum diameter ratio of $1.011\pm0.004$, below the adopted $3σ$ detection criterion. We find no significant CO-band angular extension. V509~Cas is thus hot and molecularly compact despite retaining spectroscopically visible atomic circumstellar gas.
CommentsAccepted for publication in The Astrophysical Journal; 6 figures, 4 tables and 15 pages
