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标题：Surprises in the simultaneous X-ray and optical monitoring of π Aquarii ★
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作者：Yaël Nazé ; Gregor Rauw ; Myron Smith 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：632
页码：1-11
DOI：10.1051/0004-6361/201936307
语种：English
出版社：EDP Sciences
摘要：To help constrain the origin of the peculiar X-ray emission ofγCas stars, we conducted a simultaneous optical and X-ray monitoring ofπAqr in 2018. At that time, the star appeared optically bright and active, with a very strong Hαemission. Our monitoring covers three 84 d orbital cycles, allowing us to probe phase-locked variations as well as longer-term changes. In the new optical data, the radial velocity variations seem to span a smaller range than previously reported, which might indicate possible biases. The X-ray emission is variable, but without any obvious correlation with orbital phase or Hαline strength. Furthermore, the average X-ray flux and the relative range of flux variations are similar to those recorded in previous data, although the latter data were taken when the star was less bright and its disk had nearly entirely disappeared. Only the local absorption component in the X-ray spectrum appears to have strengthened in the new data. This absence of large changes in X-ray properties despite dramatic disk changes appears at odds with previous observations of otherγCas stars. It also constrains scenarios proposed to explain theγCas phenomenon.
关键词：Key wordsenstars: early-typestars: emission-line, Bestars: massiveX-rays: starssupernovae: generalstars: individual: π Aqr