The RS CVn–type Star GT Mus Shows Most Energetic X-Ray Flares Throughout the 2010sRyo Sasaki

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dc.contributor.authorSasaki, Ryo
dc.contributor.authorTsuboi, Yohko
dc.contributor.authorIwakiri, Wataru
dc.contributor.authorNakahira, Satoshi
dc.contributor.authorMaeda, Yoshitomo
dc.contributor.authorGendreau, Keith
dc.contributor.authorCorcoran, Michael F.
dc.contributor.authorHamaguchi, Kenji
dc.contributor.authorArzoumanian, Zaven
dc.contributor.authorMarkwardt, Craig B.
dc.contributor.authorEnoto, Teruaki
dc.contributor.authorSato, Tatsuki
dc.contributor.authorKawai, Hiroki
dc.contributor.authorMihara, Tatehiro
dc.contributor.authorShidatsu, Megumi
dc.contributor.authorNegoro, Hitoshi
dc.contributor.authorSerino, Motoko
dc.date.accessioned2021-04-08T18:20:37Z
dc.date.available2021-04-08T18:20:37Z
dc.date.issued2021-03-23
dc.description.abstractWe report that the RS CVn–type star GT Mus (HR 4492, HD 101379+HD 101380) was the most active star in the X-ray sky in the last decade in terms of the scale of recurrent energetic flares. We detected 11 flares from GT Mus in 8 yr of observations with the Monitor of All-sky X-ray Image (MAXI) from 2009 August to 2017 August. The detected flare peak luminosities were 1–4 × 10³³ erg s⁻¹ in the 2.0–20.0 keV band for its distance of 109.6 pc. Our timing analysis showed long durations (τr + τd) of 2–6 days with long decay times (τd) of 1–4 days. The released energies during the decay phases of the flares in the 0.1–100 keV band were in the range of 1–11 × 10³⁸ erg, which are at the upper end of the observed stellar flare. The released energies during the whole duration were in the range of 2–13 × 10³⁸ erg in the same band. We carried out X-ray follow-up observations for one of the 11 flares with the Neutron star Interior Composition Explorer (NICER) on 2017 July 18 and found that the flare cooled quasi-statically. On the basis of a quasi-static cooling model, the flare loop length is derived to be 4 × 10¹² cm (or 60 R☉). The electron density is derived to be 1 × 10¹⁰ cm⁻³, which is consistent with the typical value of solar and stellar flares (10¹⁰⁻¹³ cm⁻³). The ratio of the cooling timescales between radiative (τrad) and conductive (τcond) cooling is estimated to be τrad ~ 0.1 τcond from the temperature; thus, radiative cooling was dominant in this flare.en_US
dc.description.sponsorshipThis research used MAXI data provided by RIKEN, JAXA, and the MAXI team. This work was supported by NASA through the NICER team and the Astrophysics Explorers Program. It used data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory. The authors thank Kazunari Shibata for useful discussions and comments on the cooling process. R.S. acknowledges financial support from the Junior Research Associate Program in RIKEN, JSPS Overseas Challenge Program for Young Researchers and Research Assistant Program in Chuo University. Y.T. acknowledges financial support from JSPS KAKENHI grant No. JP17K05392. W.I. acknowledges support from the Special Postdoctoral Researchers Program in RIKEN and JSPS KAKENHI grant No. JP16K17717. Y.M. gratefully acknowledges funding from the Tanaka Kikinzoku Memorial Foundation. M.S. acknowledges financial support from JSPS KAKENHI grant No. JP16K17672.en_US
dc.description.urihttps://iopscience.iop.org/article/10.3847/1538-4357/abde38/metaen_US
dc.format.extent13 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2tzw0-rlur
dc.identifier.citationRyo Sasaki, Yohko Tsuboi et al., The RS CVn–type Star GT Mus Shows Most Energetic X-Ray Flares Throughout the 2010s, ApJ 910 25, DOI https://doi.org/10.3847/1538-4357/abde38en_US
dc.identifier.urihttps://doi.org/10.3847/1538-4357/abde38
dc.identifier.urihttp://hdl.handle.net/11603/21304
dc.language.isoen_USen_US
dc.publisherIOPen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
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dc.rightsPublic Domain Mark 1.0*
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.titleThe RS CVn–type Star GT Mus Shows Most Energetic X-Ray Flares Throughout the 2010sRyo Sasakien_US
dc.typeTexten_US

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