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Paper: Large X-ray Flares from B-Type Stars, HD261902 and HD47777, in NGC2264 Observed with CHANDRA
Volume: 361, Active OB-Stars: Laboratories For Stellar and Circumstellar Physics
Page: 533
Authors: Yanagida, T.; Ezoe, Y.; Kawaharada, M.; Kokubun, M.; Makishima, K.
Abstract: The 100 ksec Chandra ACIS-I archival data of high mass star forming region (SFR) NGC 2264 were analyzed, and 285 X-ray sources were detected, with their luminosities ranging 5&3215;1028 ∼ 1032 erg s−1. Among them, two B type stars, HD 261902 (B8) and HD 47777 (B3), showed clear flare like time variations on a typical time scale of ∼ 5 hours, both peak X-ray luminosities reaching ∼ 1032 erg/s. In both cases, the time averaged flare spectra can be described by emission model involving two temperatures. The two stars are thus too X-ray luminous for their intermediate mass range, and the flare-like variation is inconsistent with the general lack of magnetic activities in normal B-type stars. These results suggest that some young B-type stars form magnetically active binaries, and can be regarded as much younger analogues of Algol.
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