LMC S63: a historical reappraisal of the outburst behaviour of a deeply eclipsing Magellanic symbiotic star

TL;DR

This study reexamines the historical outburst behavior of the eclipsing Magellanic symbiotic star LMC S63, revealing its orbital period, outburst history, and properties of its red giant companion over a century.

Contribution

It provides the first detailed analysis of LMC S63's outburst history, orbital characteristics, and the nature of its red giant companion, including bi-periodic pulsations and carbon enhancement.

Findings

LMC S63 has an orbital period of 1050 days.

Evidence suggests a second Z-And type outburst in its history.

The red giant is carbon-enhanced with C/O~1.2.

Abstract

We present an analysis of multi-epoch low-resolution spectrophotometry, complemented by the light curves provided by massive photometric surveys spanning over 100 years, of the symbiotic binary LMC S63. We showed that it is an eclipsing binary with the orbital period of 1050d. We also found evidence of outbursts in history of the white dwarf. If it was a Z-And type outburst, as is most likely, it would be a second such outburst recorded in the Magellanic Cloud symbiotic system. We confirmed that the red giant is enhanced in carbon, and estimated C/O~1.2 by fitting a model atmosphere to the SALT spectrum. We also found bi-periodic pulsations of the red giant, and demonstrated that it is similar to other carbon variables with confirmed bi-periodicity.