Neutron-capture element abundances in the planetary nebula NGC 5315 from deep optical and near-infrared spectrophotometry★†

Abstract

We analyze the chemical composition of the planetary nebula (PN) NGC 5315,\nthrough high-resolution (R = 40000) optical spectroscopy with UVES at the Very\nLarge Telescope, and medium-resolution (R = 4800) near-infrared spectroscopy\nwith FIRE at Magellan Baade Telescope, covering a wide spectral range from 0.31\nto 2.50 micron. The main aim of this work is to investigate neutron (n)-capture\nelement abundances to study the operation of the slow n-capture ("s-process")\nin the AGB progenitor of NGC 5315. We detect more than 700 emission lines,\nincluding ions of the n-capture elements Se, Kr, Xe, and possibly Br. We\ncompute physical conditions from a large number of diagnostic line ratios, and\nderive ionic abundances for species with available atomic data. The total\nabundances are computed using recent ionization correction factors (ICFs) or by\nsumming ionic abundances. Total abundances of common elements are in good\nagreement with previous work on this object. Based on our abundance analysis of\nNGC 5315, including the lack of s-process enrichment, we speculate that the\nmost probable scenario is that the progenitor star is in a binary system as\nhinted at by radial velocity studies, and interactions with its companion\ntruncated the AGB before s-process enrichment could occur. However there are\nother two possible scenarios for its evolution, that cannot be ruled out: i)\nthe progenitor is a low-mass single star that did not undergo third dredge-up;\nii) the progenitor star of NGC 5315 had an initial mass of 4--6 solar masses,\nand any s-process enhancements were heavily diluted by the massive envelope\nduring the AGB phase.\n