Observations of Orbiting Hot Spots around Scalarized Reissner-Nordstr\"om Black Holes

Abstract

This paper investigates the observational signatures of hot spots orbiting scalarized Reissner-Nordstr\"om black holes, which have been reported to possess multiple photon spheres. In contrast to the single-photon sphere case, hot spots orbiting black holes with two photon spheres produce additional image tracks in time integrated images capturing a complete orbit of hot spots. Notably, these newly observed patterns manifest as a distinct second-highest peak in temporal magnitudes when observed at low inclination angles. These findings offer promising observational probes for distinguishing black holes with multiple photon spheres from their single-photon sphere counterparts.