The spectral evolution and ejecta of recurrent nova U Sco in the 2010 outburst

TL;DR

This study presents comprehensive spectroscopic and X-ray observations of the 2010 outburst of recurrent nova U Sco, revealing the evolution of ejecta, the formation of a nebular spectrum, and detailed modeling of ejecta heterogeneity.

Contribution

It provides the first detailed analysis of nebular spectrum formation in recurrent novae and models the ejecta's heterogeneity using photoionization techniques.

Findings

Detection of a hot X-ray source 52 days post-outburst

Observation of nebular spectrum formation in recurrent novae

Ejecta mass estimated at around 3 x 10^-6 solar masses

Abstract

Synoptic spectroscopic observations of the U Sco 2010 outburst from maximum light to quiescence as well as a contemporaneous X-ray observation are presented and analyzed. The X-ray spectrum 52 days after outburst indicates a hot source (kTbb ~ 70 eV). . Narrow line components from the irradiated companion atmosphere were observed in hydrogen and helium optical recombination lines. The formation of a nebular spectrum is seen for the first time in this class of recurrent novae, allowing a detailed study of the ejecta using photoionization models. Unusual [OIII] auroral-to-nebular line ratios were found and possible scenarios of their origin are discussed. The modeling of the emission line spectrum suggests a highly heterogeneous ejecta with mass around or above 3 x 10-6 Msun