Stars on the Verge: Investigating Semiregular Light Variations and Changing Multiperiods of the Luminous Red Supergiant μ Cephei from over 175 yr of Photometry

Abstract μ Cephei is a 4th mag semi-regular variable M2Ia star. It is among the largest, most luminous red supergiants in our galactic neighborhood and a probable SN-II core-collapse progenitor. Analyses of ∼175 yr of photometry were conducted. The observations are mostly from the AAVSO database. Period analyses were conducted using the Period Analysis Software (Peranso-3) package. The CLEANest and Wavelet (WWZ) programs were utilized. Two dominant “periods” were found: P = 870 ± 50 days (∼2.39 yr) and a long period of ∼5300 ± 155 days (∼14.5 yr). The long period was prominent during the first ∼90 yr but weakened and was followed by multiple transitory periods ranging from ∼3000 to 4600 days. μ Cephei has interesting features including multiple periods, period-splitting, period-merging and period-decays.