Magnetic activities on active solar-type stars

Abstract

Indian Institute of Astrophysics, II Block Koramangala, Bangalore 560034, India We present results obtained from the studies of magnetic activities on four solar-type stars (F-type star KIC 6791060, K-type star LO Peg, and two M-type planet-hosting stars K2–33 and EPIC 211901114) by using optical observations from several ground- and space-based telescopes. In this study, we investigate magnetic activities such as spot-topographic evolution and flaring events in these stars. We compare the results obtained from this study with that of the Sun. In the surface temperature maps, one active longitude has been detected in KIC 6791060, whereas in each of the other three cases two active longitudes are seen. The spottedness was found to vary in the range of 0.07–0.44%, 9–26%, 3.6–4.2%, and 4.5–5.3% for KIC 6791060, LO Peg, K2–33, and EPIC 211901114, respectively. Several flaring events have been identified in each star. An increasing trend in flaring frequency per stellar rotation has been found in the stars with change in spectral type from F to M. These findings indicate the increase in magnetic activities with the spectral type of stars. This can be explained due to increasing the ratio of the thickness of the convection zone to the radiation zone from F-type star to the M-type stars.

Investigation of very low mass binaries using VLT/NaCo

“…Low mass stars with partially or fully convective envelops show a high level of magnetic activities (see Pandey & Karmakar, 2015;Patel et al, 2016;Savanov et al, 2016Savanov et al, , 2019Karmakar, 2019Karmakar, , 2021Karmakar et al, 2016Karmakar et al, , 2017Karmakar et al, , 2022Karmakar et al, , 2023. Recent studies have shown the magnetic activities also increase for the later spectral types (e.g., Savanov et al, 2018;Karmakar et al, 2019). Typically, the stars with a mass range of 0.075-0.6 M are called very low mass stars (VLMs).…”