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标题：Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2 ★
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作者：I. Pillitteri ; L. Fossati ; N. Castro Rodriguez 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：610
DOI：10.1051/0004-6361/201732078
语种：English
出版社：EDP Sciences
摘要：Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them (~10%) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V starρOph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyze spectra ofρOph A obtained with the FORS2 spectrograph at ESO Very Large Telescope (VLT) at two epochs, and detect a longitudinal component of the magnetic field of the order of ~500 G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters ofρOph A and further constrained its age. We conclude thatρOph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.
关键词：Keywordsenstars: activitystars: early-typestars: magnetic fieldpulsars: individual: ρ Ophiuchi A