Discovery of X-ray Emission from the Galactic Supernova Remnant G32.8-0.1 with Suzaku

TL;DR

This study presents the first detailed X-ray analysis of supernova remnant G32.8-0.1 using Suzaku, revealing complex thermal and non-thermal emission features, and identifies a potential new supergiant fast X-ray transient within it.

Contribution

First dedicated Suzaku X-ray study of G32.8-0.1, detecting full-shell emission and analyzing its thermal and non-thermal components, along with identifying a new variable X-ray source.

Findings

Detection of X-ray emission from the entire SNR shell.

Identification of both low-temperature thermal and high-temperature or non-thermal components.

Discovery of a variable, heavily absorbed X-ray source possibly being a supergiant fast X-ray transient.

Abstract

We present the first dedicated X-ray study of the supernova remnant (SNR) G32.8-0.1 (Kes 78) with Suzaku. X-ray emission from the whole SNR shell has been detected for the first time. The X-ray morphology is well correlated with the emission from the radio shell, while anti-correlated with the molecular cloud found in the SNR field. The X-ray spectrum shows not only conventional low-temperature (kT ~ 0.6 keV) thermal emission in a non-equilibrium ionization state, but also a very high temperature (kT ~ 3.4 keV) component with a very low ionization timescale (~ 2.7e9 cm^{-3}s), or a hard non-thermal component with a photon index Gamma~2.3. The average density of the low-temperature plasma is rather low, of the order of 10^{-3}--10^{-2} cm^{-3}, implying that this SNR is expanding into a low-density cavity. We discuss the X-ray emission of the SNR, also detected in TeV with H.E.S.S., together with multi-wavelength studies of the remnant and other gamma-ray emitting SNRs, such as W28 and RCW 86. Analysis of a time-variable source, 2XMM J185114.3-000004, found in the northern part of the SNR, is also reported for the first time. Rapid time variability and a heavily absorbed hard X-ray spectrum suggest that this source could be a new supergiant fast X-ray transient.