Spectrophotometry of a Flare on EQ Pegasi A

Volume 54 number 1 (2026)

Download this article (pdf)

Robert K. Buchheim

8731 E Lost Gold Circle, Gold Canyon, AZ 85118; Bob@RKBuchheim.org

Abstract

Time-series B-band and TESS photometry is combined with time-series spectroscopy to characterize the brightness profile and the development of spectral features of a large flare on EQ Peg A. At its peak, the flare increased the star’s brightness by 1.2 magnitudes in B-band, and it released ≈ 3.2 × 10^32 erg in B-band. Photometrically, the flare showed a typical “fast rise, exponential decay” shape, with FWHM ≈ 1.7 minutes. Time-series spectroscopy shows that the Balmer emission lines remain strong for a much longer time (FWHM ≈ 11 to 15 min, depending on the line), taking about 3.5 hours to return to their pre-flare strength. The continuum slope of the flare spectrum indicates a peak temperature of TFlare = 14,000 K ± 2000 K (averaged over a 5-minute exposure). The photometric color index (B-TESS) indicates a peak color temperature of T(B-TESS) ≈ 11,800 K.