Time-domain analysis of multiwaveband flares from AD Leonis

Abstract

Radio bursts of magnetically active stars reveal the intensity and activity of the stellar magnetic field. They may also be related to the planets around the stars. We monitored a radio-active star, AD Leonis, 3000 seconds per day for 17 days in November 2020, and 5000 seconds per day for 5 days in July 2023 with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Based on the simultaneous flux increases in Stokes I and Stokes V, one left-hand circular polarized radio burst is identified. The $\sim 50~{{\%}}$ degree of circular polarization indicates the burst being originated from non-thermal radiation related to the stellar magnetic field. Combining the newly discovered burst with previous observations of radio and X-ray bursts from AD Leonis, we did a periodicity analysis for the 49 bursts in total. No periodicity with confidence level >3σ is found, while a candidate period of 3.04 days at ≈2σ confidence level is presented and discussed. Results of recent FAST observations and the periodicity analysis suggest a more compact campaign of observation toward this source, from which a more optimistic result of period search could be achieved.