# Recombining Plasma & Gamma-ray Emission in the Mixed-morphology Supernova Remnant 3C 400.2

## TL;DR

This study reveals recombining plasma and gamma-ray emission in supernova remnant 3C 400.2, indicating complex plasma states and high-energy processes involving ejecta and interstellar material.

## Contribution

First detection of recombining plasma in 3C 400.2 and identification of gamma-ray emission, including a new extended gamma-ray source near the remnant.

## Key findings

- Recombining plasma detected in NE and SE regions with ejecta origin.
- Gamma-ray emission observed at ~5σ level from 3C 400.2.
- New extended gamma-ray source identified near the SNR.

## Abstract

3C 400.2 belongs to the mixed morphology supernova remnant class, showing center-filled X-ray and shell-like radio morphology. We present a study of 3C 400.2 with archival Suzaku and Fermi-LAT observations. We find recombining plasma (RP) in the Suzaku spectra of north-east and south-east regions. The spectra of these regions are well described by two-component thermal plasma models: The hard component is in RP, while the soft component is in collisional ionization equilibrium (CIE) conditions. The RP has enhanced abundances indicating that the X-ray emission has an ejecta origin, while the CIE has solar abundances associated with the interstellar material. The X-ray spectra of north-west and south-west regions are best fitted by a two-component thermal plasma model: an ionizing and a CIE plasma. We have detected GeV gamma-ray emission from 3C 400.2 at the level of $\sim$5$\sigma$ assuming a point-like source model with a power-law (PL) type spectrum. We have also detected a new GeV source at the level of $\sim$13$\sigma$ assuming a Gaussian extension model with a PL type spectrum in the neighborhood of the SNR. We report the analysis results of 3C 400.2 and the new extended gamma-ray source and discuss the nature of gamma-ray emission of 3C 400.2 in the context of existing NANTEN CO data, DRAO HI data, and the Suzaku X-ray analysis results.