title: Observational evidence for enhanced magnetic activity of superflare stars.
abstract: Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares.
authors.affiliation: Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, Denmark.|Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
authors.forename: Christoffer
authors.initials: C
authors.lastname: Karoff
authors.affiliation: Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, Denmark.
authors.forename: Mads Faurschou
authors.initials: MF
authors.lastname: Knudsen
authors.affiliation: Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussel, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: De Cat
authors.affiliation: INAF-Osservatorio Astrofisico di Catania, via S.Sofia 78, 95123 Catania, Italy.
authors.forename: Alfio
authors.initials: A
authors.lastname: Bonanno
authors.affiliation: Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, Denmark.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Fogtmann-Schulz
authors.affiliation: Department of Astronomy, Beijing Normal University, 19 Avenue Xinjiekouwai, Beijing 100875, China.
authors.forename: Jianning
authors.initials: J
authors.lastname: Fu
authors.affiliation: INAF-Osservatorio Astrofisico di Catania, via S.Sofia 78, 95123 Catania, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Frasca
authors.affiliation: Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, Denmark.
authors.forename: Fadil
authors.initials: F
authors.lastname: Inceoglu
authors.affiliation: AMS, 14C Dating Centre, Department of Physics, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Nanjing Institute of Astronomical Optics and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Nanjing Institute of Astronomical Optics and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042, China.
authors.forename: Yonghui
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Nanjing Institute of Astronomical Optics and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042, China.
authors.forename: Yuefei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China.
authors.forename: Jianrong
authors.initials: J
authors.lastname: Shi
authors.affiliation: Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang