Distance and Reddening of the Enigmatic Gamma-ray-Detected Nova V1324 Sco

TL;DR

This paper accurately determines the distance and reddening of nova V1324 Sco using optical spectroscopy, revealing it is more distant and luminous than previously thought, and suggests a main-sequence companion based on brightness modulations.

Contribution

It introduces a robust spectroscopic method for measuring distance and reddening of gamma-ray novae, improving accuracy over prior estimates.

Findings

Distance > 6.5 kpc, >40% greater than previous estimates

Higher gamma-ray luminosity than previously calculated

Main-sequence companion likely based on brightness modulations

Abstract

It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst. Despite using an unreliable method to determine its distance, previous work showed that nova V1324 Sco was the most gamma-ray luminous of all gamma-ray-detected novae. We present here a different, more robust, method to determine the reddening and distance to V1324 Sco using high-resolution optical spectroscopy. Using two independent methods we derived a reddening of E(B-V) = 1.16 +/- 0.12 and a distance rD > 6.5 kpc. This distance is >40% greater than previously estimated, meaning that V1324 Sco has an even higher gamma-ray luminosity than previously calculated. We also use periodic modulations in the brightness, interpreted as the orbital period, in conjunction with pre-outburst photometric limits to show that a main-sequence companion is strongly favored.