7Be in the outburst of the ONe nova V6595 Sgr

TL;DR

This study detected 7Be in the outburst spectra of the ONe nova V6595 Sgr, providing insights into isotope abundance and nova classification, with implications for nucleosynthesis in different nova types.

Contribution

First detection of 7Be in an ONe nova, measuring its abundance and comparing it to CO novae, expanding understanding of isotope production in nova outbursts.

Findings

7Be detected with N(7Be)/N(H) ~ 7.4 x 10^{-6}

7Be abundance is about half of typical nova values

Nova classified as ONe type based on emission lines

Abstract

We report the search for 7Be isotope in the outbursts of the classical nova V6595 Sgr by means of high resolution UVES observations taken at the ESO VLT in April 2021, about two weeks after discovery and under difficult circumstances due to the pandemic. Narrow absorption components with velocities at about -2620 and -2820 km/s, superposed on broader and shallow absorption, are observed in the outburst spectra for the 7BeII 313.0583, 313.1228 nm doublet resonance lines, as well as in several other elements such as CaII, FeI, MgI, NaI, HI but LiI. Using CaII K line as a reference element, we infer N(7Be)/N(H) ~ 7.4 x 10^{-6}, or ~ 9.8 x 10^{-6} when the 7Be decay is taken into account. The 7Be abundance is about half of the value most frequently measured in novae. The possible presence of over-ionization in the layers where 7Be is detected is also discussed. Observations taken at the Telescopio Nazionale Galileo (TNG) in La Palma 91 days after discovery showed prominent emission lines of Oxygen and Neon which allow to classify the nova as ONe type. Therefore, although 7Be is expected to be higher in CO novae, it is found at comparable levels in both nova types.