Light and colour variations of Mira variables in the Small Magellanic Cloud. Issue 1 (21st October 2020)

• Record Type: Journal Article
• Authors: Ita, Yoshifusa; Menzies, John W; Whitelock, Patricia A; Matsunaga, Noriyuki; Takayama, Masaki; Nakada, Yoshikazu; Tanabé, Toshihiko; Feast, Michael W; Nagayama, Takahiro
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 500:Issue 1(2021)
• Page Start: 82
• Page End: 100
• Publication Date: 2020-10-21
• Subjects: stars: AGB and post-AGB -- stars: carbon -- stars: late-type -- infrared: stars; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa3251
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The goal of this paper is to characterize the light variation properties of Mira variables in the Small Magellanic Cloud. We have investigated a combined optical and near-infrared multi-epoch data set of Mira variables based on our monitoring data obtained over 15 yr. Bolometric correction relations are formulated for various near-infrared colours. We find that the same bolometric correction equation holds for both the bolometricly brightest and faintest pulsation phases. Period–bolometric magnitude relations and period–colour relations were derived using time-averaged values. Phase lags between bolometric phase and optical and near-infrared phases were detected from the O-rich (the surface C/O number ratio is below unity) Mira variables, while no significant systematic lags were observed in most of the C-rich (the C/O ratio is over unity) ones. Some Miras show colour phase inversions, e.g. H – K s at its bluest while J – H and J – K s are at their reddest values at about the bolometricly brightest phase. Their occurrence conditions were studied but no clear direct or indirect trigger was found. A large NIR colour change unassociated with stellar pulsation was observed in Miras with long secondary periods, and its possible explanation is described.