Search for Soft X-ray Flashes at Fireball Phase of Classical/Recurrent Novae using MAXI/GSC data

TL;DR

This study searched for precursive soft X-ray flashes in classical and recurrent novae using MAXI/GSC data but found no significant signals, providing upper limits that constrain models of massive white dwarf populations.

Contribution

Developed a PSF-fit tool for flux measurement and applied it to a five-year dataset to search for precursive X-ray flashes in novae, setting new upper limits.

Findings

No precursive SXFs detected above 3 sigma significance.

Established upper limits for X-ray luminosity of novae.

Constraints on the population of massive white dwarfs in binary systems.

Abstract

We searched for precursive soft X-ray flashes (SXFs) associated with optically-discovered classical or recurrent novae in the data of five-years all-sky observations with Gas Slit Camera (GSC) of the Monitor of All-sky X-ray Image (MAXI). We first developed a tool to measure fluxes of point sources by fitting the event distribution with the model that incorporates the point-spread function (PSF-fit) to minimize the potential contamination from nearby sources. Then we applied the PSF-fit tool to 40 classical/recurrent novae that were discovered in optical observations from 2009 August to 2014 August. We found no precursive SXFs with significance above $3 \sigma$ level in the energy range of 2$-$4 keV between $t_{d}-10$d and $t_{d}$, where $t_{d}$ is the date when each nova was discovered. We obtained the upper limits for the bolometric luminosity of SXFs, and compared them with the theoretical prediction and that observed for MAXI J0158$-$744. This result could constrain the population of massive white dwarfs with a mass of roughly 1.40 solar mass, or larger, in binary systems.