Photometric Investigation for Mira Variable with OGLE and ZTF.

JiaYu Ou^1*, Chow-Choong Ngeow¹

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

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

Nowadays , there are a lot of time-series sky survey datasets at which techniques of machine learning can be used for classification of variable stars. In our work, we are interested in Mira variables (hereafter Mira). Mira variables are AGB pulsating stars that exhibit large cyclical variation spanning 100 to 1500 days. Mira variables can be divided into O-rich and C-rich Miras. We have collected confirmed Miras light curve data in LMC and SMC from the OGLE database. Applying the random forest algorithm to the I-band light curves for the Miras in Magellanic Clouds, we have classified these Miras into regular Miras and non-regular Miras, at which the non-regular Miras exhibit a long term variation in addition to their primary pulsation periods. Our results confirm that the period-luminosity relation at maximum light has a smaller dispersion, but this only occurs on the regular oxygen-rich (O-rich) Miras which we recommend to be applied in future distance scale work. We have also collected multi-band photometry for these Miras to perform a spectral-energy-distribution (SED) fitting with stellar and dust components, showing that a large fraction of dust is clearly presence for the non-regular Miras. According to our results, we believe that the periodic long-term variations seen on the non-regular Miras might due to the presence of dust. 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, CRTS, ASAS-SN, PTF and ZTF data taken from 2009 to 2021. Based on the combined light curve and SEDs, we found that this Mira could exhibit a long secondary variation, hence we classified [HBS 2006] 40671 as a non-regular Mira. We have also collected more Miras in M33 to confirm their period-luminosity relations using both PTF and ZTF data.

Keywords: Variables, AGB stars, Period-luminosity relations