The connection between starspots and superflares: a case study of two stars

Abstract

How do the characteristics of starspots influence the triggering of stellar flares? Here we investigate the activity of two K-type stars, similar in every way from mass to rotation periods and planetary systems. Both stars exhibit about a hundred spots, however, Kepler-411 produced 65 superflares, while Kepler-210 presented none. The spots of both stars were characterized using the planetary transit mapping technique, which yields the intensity, temperature, and radius of starspots. The average radius was $(17\pm 7)\times 10^3$ km and $(58\pm 23)\times 10^3$ km, while the intensity ratio with respect to the photosphere was $(0.35\pm 0.24)$ $I_c$ and $(0.64\pm 0.15)$ $I_c$, and the temperature was $(3800\pm 700)$ K and $(4180\pm 240)$ K for spots of Kepler-411 and Kepler-210, respectively. Therefore, spots on the star with no superflares, Kepler-210, are mostly larger, less dark, and warmer than those on the flaring star, Kepler-411. This may indicate magnetic fields with smaller magnitude and complexity of the spots on Kepler-210 when compared to those on Kepler-411. Thus, starspot area appears not to be the main culprit of superflares triggering. Perhaps the magnetic complexity of active regions is more important.

arXiv comment5 pages,4 Figures

References in corpus (22)

• Kepler Mission Design, Realized Photometric Performance, and Early Science
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• Flare-productive active regions
• Starspots, spin-orbit misalignment, and active latitudes in the HAT-P-11 exoplanetary system
• Statistical properties of superflares on solar-type stars based on 1-min cadence data
• Superflares on Solar-Type Stars Observed with Kepler II. Photometric Variability of Superflare-Generating Stars : A Signature of Stellar Rotation and Starspots
• White-light flares on cool stars in the Kepler Quarter 1 Data
• Are superflares on solar analogues caused by extra-solar planets?
• Influence of Stellar Multiplicity On Planet Formation. I. Evidence of Suppressed Planet Formation Due to Stellar Companions Within 20 AU and Validation of Four Planets From the Kepler Multiple Planet Candidates
• The Starspots of HAT-P-11: Evidence for a Solar-like Dynamo
• Properties of starspots on CoRoT-2
• The connection between stellar activity cycles and magnetic field topology
• Differential rotation in K, G, F and A stars
• Starspot activity and superflares on solar-type stars
• Kepler-411: a four-planet system with an active host star
• Kepler-210: An active star with at least two planets
• Activity and rotation of Kepler-17
• Temporal Evolution of Spatially-Resolved Individual Star Spots on a Planet-Hosting Solar-type Star: Kepler 17
• TESS observations of southern ultra fast rotating low mass stars
• Stellar Magnetic Activity and "Butterfly Diagram" of Kepler-63
• Kepler-411 Differential Rotation from Three Transiting Planets
• The Puzzling Story of Flare Inactive Ultra Fast Rotating M dwarfs. I. Exploring their Magnetic Fields

Cited by in corpus (2)

• Temporal Variation of Flare Occurrence Rates via the Spot Evolution on the Sun and Solar-type Stars
• Characterisation of starspot structure and differential rotation of Kepler-411