AAVSO: American Association of Variable Star Observers

Identification of Bimodal Period and Long Secondary Period Carbon Red Giants Misclassified as “Miscellaneous” in VSX (Abstract)

Volume 49 number 1 (2021)

Kristine Larsen
Geological Sciences Department, Central Connecticut State University; Larsen@ccsu.edu


(Abstract only) In a 2015 JAAVSO paper, Percy and Huang applied VStar analysis software to AAVSO visual observations of known carbon red giants in order to better determine the periodicities of these stars. In particular, they sought to separate false periodicities (due to alias and spurious periods) from truly biperiodic stars with two pulsation periods as well as long secondary period (LSP) stars. Previous work by this author and her students has determined that while pulsating red giants in general have sufficient irregularities and multiple periodicities to confound automated classification algorithms, for example those of ASAS (All-Sky Automated Survey) and ASAS-SN (All-Sky Automated Survey for Supernovae), VStar analysis can often identify improved periods and lead to the proper classification of these stars’ variability type. This project, motivated by the work of Percy and Huang, is a preliminary analysis of 250 spectral class C red giants with V-band variability that are classified as MISC in VSX (Variable Star Index) on the basis of their MISC classification in the “ASAS Catalogue of Variable Stars” (Pojmański 2002, Acta Astron., 52, 397). The goal is to better determine their periodicities, and in particular to identify biperiodic and LSP carbon red giants in order to improve the accuracy of their VSX citations.