Mira variables time series analysis from OGLE to ZTF.

JiaYu Ou^1*, Chow Choong Ngeow¹

¹Graduate Institute of Astronomy, National Central University, Taoyuan, Taiwan

* Presenter:JiaYu Ou, email:m1039004@gm.astro.ncu.edu.tw

Mira variables are asymptotic giant branch pulsating stars that exhibit large cyclical variation spanning 100 to 700 days, but in some extreme cases the variations can go beyond 1500 days. Mira variables can be divided into O-rich and C-rich Miras. We collected confirmed 2015 Mira stars light curve data in LMC and SMC in OGLE database. Based on light curve we found Miras can also be divided into regular Miras and multi-periodic Miras. We used python package Feature analysis for time series (FATs) to extract the light curve features, then we used these features to separate out the regular Miras and multi-periodic Miras using machine learning techniques. Light curves of the multi-periodic Miras can be de-composed to a short pulsation period and a long secondary variation. We then applied our results to [HBS 2006] 40671, a confirmed long period Mira found in M33. Using observed light curves from Hartmann et al (2006) data, Barsukova et al. (2011) found a period of 665 day for this Mira. In addition to Hartmann's data (2005~2006), we also collected LOT( Lulin Observatory) data, CRTS (Catalina Real-time Transient Survey) data, ASAS-SN data,  PTF (Palomar Transient Factory) and ZTF (Zwicky Transient Facility) data taken from 2009 to 2018. Combining all datasets that spanned ~13 years we can refine the period of this Mira. Based on the combined light curve, we found that this Mira could exhibit a long secondary variation, hence we classified [HBS 2006] 40671 as a multi-periodic Mira. In this work, we also present our latest investigation on the period refinement of this Mira.

Keywords: AGB stars, Long period variable