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{High dispersion spectroscopy of solar-type superflare stars with Subaru/HDS†

Published online by Cambridge University Press:  09 September 2016

Yuta Notsu ,
Satoshi Honda ,
Hiroyuki Maehara ,
Shota Notsu ,
Takuya Shibayama ,
Daisaku Nogami  and
Kazunari Shibata
Yuta Notsu*
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, Japan, 606-8502
Satoshi Honda
Affiliation:
Center for Astronomy, University of Hyogo, 407-2, Nishigaichi, Sayo-cho, Sayo, Hyogo, Japan, 679-5313
Hiroyuki Maehara
Affiliation:
Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, 3037-5 Honjo, Kamogata, Asakuchi, Okayama, Japan, 719-0232
Shota Notsu
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, Japan, 606-8502
Takuya Shibayama
Affiliation:
Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan, 464-8601
Daisaku Nogami
Affiliation:
Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, Japan, 606-8502
Kazunari Shibata
Affiliation:
Kwasan and Hida Observatories, Kyoto University, Yamashina-ku, Kyoto, Japan, 607-8471
*
*email: ynotsu@kwasan.kyoto-u.ac.jp
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Abstract

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We carried out spectroscopic observations with Subaru/HDS of 50 solar-type superflare stars found from Kepler data. More than half (34 stars) of the target stars show no evidence of the binary system, and we confirmed atmospheric parameters of these stars are roughly in the range of solar-type stars.

We then conducted the detailed analyses for these 34 stars. First, the value of the “v sin i” (projected rotational velocity) measured from spectroscopic results is consistent with the rotational velocity estimated from the brightness variation. Second, there is a correlation between the amplitude of the brightness variation and the intensity of Ca II IR triplet line. All the targets expected to have large starspots because of their large amplitude of the brightness variation show high chromospheric activities compared with the Sun. These results support that the brightness variation of superflare stars is explained by the rotation of a star with large starspots.

Keywords

stars:activitystars:flarestars:rotationstars:solar-typestars:starspots
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S320: Solar and Stellar Flares and their Effects on Planets , August 2015 , pp. 138 - 143
Copyright
Copyright © International Astronomical Union 2016 

Footnotes

†

This study is based on observational data collected with Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

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