Suzaku observations of the hard X-ray spectrum of Vela Jr

TL;DR

Suzaku observations of Vela Jr. reveal a consistent, featureless hard X-ray spectrum from 2 to 22 keV, challenging simple one-zone synchrotron models with exponential cutoff.

Contribution

This study provides the first detailed broad-band X-ray spectral analysis of Vela Jr., showing the spectrum is well fitted by a power-law or broken power-law without a cutoff, questioning standard emission models.

Findings

Hard X-ray emission detected in the TeV region.

X-ray spectrum fits a power-law with photon index ~3.15.

Spectrum shows no evidence of a spectral cutoff.

Abstract

We report the results of Suzaku observations of the young supernova remnant, Vela Jr.\ (RX J0852.0$-$4622), which is known to emit synchrotron X-rays, as well as TeV gamma-rays. Utilizing 39 Suzaku mapping observation data from Vela Jr., a significant hard X-ray emission is detected with the hard X-ray detector (HXD) from the north-west TeV-emitting region. The X-ray spectrum is well reproduced by a single power-law model with the photon index of 3.15$^{+1.18}_{-1.14}$ in the 12--22 keV band. Compiling this with the soft X-ray spectrum simultaneously observed with the X-ray imaging spectrometer (XIS) onboard Suzaku, we find that the wide-band X-ray spectrum in the 2--22 keV band is reproduced with a single power-law or concave broken power-law model, which are statistically consistent with each other. Whichever the model of a single or broken power-law is appropriate, clearly the spectrum has no rolloff structure. Applying this result to the method introduced in \citet{yama2014}, we find that one-zone synchrotron model with electron spectrum having a power-law plus exponential cutoff may not be applicable to Vela Jr.