Unstable Phenomena in Stable Magnetospheres: Searching for Radio Flares from Magnetic OBA Stars Using VCSS

Abstract

Although the majority of hot magnetic stars have extremely stable, ∼kilogauss strength surface magnetic fields with simple topologies, a subset undergoes small-scale explosions due to centrifugal breakout. The resulting small-scale flares are typically below the sensitivity of current magnetospheric diagnostics and do not generate detectable transient signatures. However, a recently reported radio flare from the hot magnetic star CU Vir suggests that some of the most energetic events do reach detectable levels. Motivated by this, we searched for transient radio sources in the first two epochs of the VLITE Commensal Sky Survey at the positions of 761 hot magnetic stars. We report three detections. A false-association analysis shows a less-than-1% probability that the sources are imaging artifacts. We then examine the stellar parameters of the three stars to understand if they are likely to produce flares. We conclude that while at this stage, we cannot make a definitive association of the detections with the stars, the current data are consistent with the hypothesis that the flares originate in the stellar magnetospheres.