The peculiar ejecta of the nova V1425 Aquilae

TL;DR

This study presents optical observations of nova V1425 Aquilae 23 years post-eruption, revealing two distinct ejecta components with different velocities and compositions, and estimates its distance at approximately 3.3 kpc.

Contribution

It provides detailed characterization of the ejecta structure and composition of V1425 Aquilae long after eruption, highlighting the presence of two distinct ejecta components and their possible origins.

Findings

Ejecta consist of two components with different velocities and compositions.

The high-velocity component is asymmetrically located southwest of the binary.

Distance to the nova is estimated at approximately 3.3 kpc.

Abstract

Many important details of the mechanisms underlying the ejection of material during a (classical) nova eruption are still not understood. Here we present optical spectroscopy and narrow-band images of the nova V1425 Aql, 23 years after the nova eruption. We find that the ejecta consist of two significantly different components. The first resembles what is commonly seen in novae, that is, a symmetric distribution centred on the position of the underlying cataclysmic binary and presenting both allowed (hydrogen and helium) and forbidden ([OIII] and [NII]) transitions. The second one, on the other hand, consists of material travelling at an approximately three times higher velocity that is not visible in the allowed transitions, presents a significantly different [NII] - [OIII] ratio, and is located at approximately 2.3 arcsec to the southwest of the position of the binary. Comparing the velocities and spatial extensions of the two ejecta, we find that both originated in the same nova eruption. We explore possible extrinsic and intrinsic mechanisms for the asymmetry of the high-velocity material in the form of asymmetrically distributed interstellar material and magnetic accretion, respectively, but find the available data to be inconclusive. From the expansion parallax, we derive a distance for the nova of 3.3(3) kpc.