On the origin of the X-ray emission surrounding PSR B0656+14 in the eROSITA Cal-PV data

TL;DR

This paper critically evaluates claims of faint nebular X-ray emission around PSR B0656+14, demonstrating that previous detections are likely artifacts of PSF modeling issues and that the diffuse emission is consistent with the pulsar's own spectrum.

Contribution

It provides a cautious reanalysis of eROSITA data, showing that the extended emission is not reliably detected and is consistent with the pulsar's emission, challenging prior claims of a nebular or halo origin.

Findings

The PSF model underestimates emission beyond 1'

Diffuse X-ray emission matches the pulsar's spectral model

No reliable detection of faint nebular emission

Abstract

We present a cautionary assessment of the extended X-ray emission around PSR B0656+14 in eROSITA Cal-PV data in response to the work of Niu et al. 2025 (arXiv:2501.17046). The eROSITA PSF model is known to underestimate emission in the wings beyond 1'. This prevents a reliable detection of faint nebular emission around PSR B0656+14 as claimed in arXiv:2501.17046. In addition, spectral analysis shows the surrounding diffuse X-rays can be fitted with the same 2BB+PL model as the pulsar's emission itself. This strongly invalidates the interpretation by the authors of arXiv:2501.17046 that the X-ray emission in the (4-10)' region is associated with the degree-scale gamma-ray halo recently found by the High-Altitude Water Cherenkov Observatory (HAWC), and shows that it originates from the pulsar due to the wings of the PSF.