The Distance to the S147 Supernova Remnant

TL;DR

This study accurately determines the distance to the S147 supernova remnant by combining Gaia data with spectroscopic observations, resulting in a precise measurement that aligns with pulsar and binary companion distances.

Contribution

The paper introduces a method using high velocity CaII and NaI absorption lines in stellar spectra to measure SNR distances with improved accuracy over previous estimates.

Findings

Median distance to S147 is 1.37 kpc with small uncertainties.

Distance measurement aligns with pulsar and binary companion distances.

High velocity absorption lines correlate with SNR emission flux.

Abstract

In the absence of a parallax distance to a pulsar or a surviving binary in a supernova remnant (SNR), distances to Galactic SNRs are generally very uncertain. However, by combining Gaia data with wide field, multi-fiber echelle spectroscopy, it is now possible to obtain accurate distances to many SNRs with limited extinction by searching for the appearance of high velocity CaII or NaI absorption lines in hot stars as a function of distance. We demonstrate this for the SNR S147 using the spectra of 259 luminous, blue stars. We obtain a median distance of 1.37 kpc (1.30 to 1.47 kpc at 90% confidence) that is consistent with the median parallax distance to the pulsar of 1.46 kpc (1.12 to 2.10 kpc at 90% confidence), but with significantly smaller uncertainties. Our distance is also consistent with the distance to the candidate unbound binary companion in this SNR, HD37424. The presence of high velocity absorption lines is correlated with the emission line flux of the SNR but not with the radio flux.