Stellar Parameters and Magnetic Activity of Eruptive Variable Stars Based on TESS Light Curves and the LAMOST Spectral Survey

Abstract Eruptive variable stars are an important type of variable stars. We investigate the chromospheric activity and white-light flare properties of International Variable Star Index (VSX)-selected eruptive stars by combining LAMOST DR10 low-resolution spectroscopy with TESS 2 minute cadence flare measurements. The LAMOST spectroscopic parent sample contains 3099 unique VSX-selected eruptive-star targets with 9132 low-resolution spectra, and the quality-controlled H α subset contains 2913 unique targets and 8259 spectra. The adopted TESS flare catalog contains 6665 flare events from 453 TESS Input Catalog (TIC) targets, among which 6621 flare events from 450 TIC targets have successful VSX matches. The final statistical sample is treated as a magnetic-activity-dominated eruptive-star population, with RS CVn systems analyzed separately from other main-sequence eruptive stars. The H α equivalent widths used in this work are independently measured from LAMOST spectra, and the excess H α emission and normalized activity index are used to compare chromospheric activity across spectral type. The H α activity indicators show a clear temperature dependence, with cooler stars generally displaying stronger and more broadly distributed chromospheric emission, whereas earlier-type bins require cautious interpretation. Multiepoch LAMOST spectra reveal H α variability in both RS CVn systems and other main-sequence eruptive stars, although the variability indicators show substantial scatter. The TESS flare population is dominated by short-duration and low-to-moderate-amplitude events, with higher-energy flares forming a sparser extension.