Bright Long Secondary Period Stars for Follow-up Observations

Abstract

Long secondary period (LSP) variable stars are a subclass of long-period variables (LPV) that exhibit additional long-term variability alongside pulsations. Despite being observed in over 30% of LPVs, the reason behind the LSP phenomenon is still debated. The most favoured explanation, supported by recent growing evidence, is binarity, where the pulsating giant star has a substellar-mass companion. To further test this hypothesis, it is important to identify bright LSP variables, for which high-quality spectroscopic and interferometric observations can be obtained more easily. Motivated by the absence of a catalog of bright nearby LSPs, we searched the All Sky Automated Survey (ASAS) data in the $V$-band magnitude range 5.5-14 mag, and for declinations $< +28^\circ$. The resulting catalog contains 23 LSPs, 13 of which are new discoveries. We compare our catalog with the LSP lists available in the literature.