Evolution of Hen 3-1357, the Stingray Nebula

The spectroscopic evolution of Hen\,3-1357, the Stingray Nebula, is presented by analysing data from 1990 to 2021. High resolution obtained in 2021 with South African Large Telescope Resolution Spectrograph and 2009 European Southern Observatory-Very UVES spectrograph are used determine physical conditions chemical abundances nebula. From comparison these different epochs it found that intensity highly-ionized emission lines has been decreasing time, while low-ionization increasing, confirming nebula recombining, lowering its excitation class, as a consequence changes central star which 2002 had an effective temperature 60,000 K then getting colder. present about 40,000 K. It suggested suffered late thermal pulse returning AGB phase. nebular chemistry Hen\,3-1357 indicates all elements, except He Ne, sub solar abundances. values predicted stellar nucleosynthesis models at end phase, shows initial mass lower than 1.5 M$_{\odot}$. We estimated ADF(O$^{+2}$) be between 2.6 3.5.