The Distance of 4 kpc to the SNR CTB 109/AXP 1E 2259+586 system

TL;DR

This paper revises the distance to the supernova remnant CTB 109 and its associated pulsar using HI and CO spectral analysis, establishing it at approximately 4 kpc, which impacts understanding of its explosion energy.

Contribution

The study provides a revised distance estimate for CTB 109 using spectral absorption features, clarifying its position within the Perseus arm and its physical properties.

Findings

Distance to CTB 109 is approximately 4 kpc.

The molecular cloud is on the far side of the Perseus arm velocity reversal.

The revised distance implies a normal explosion energy for the SNR.

Abstract

We suggest a revised distance to the supernova remnant (SNR) G109.1-1.0 (CTB 109) and its associated anomalous X-ray pulsar (AXP) 1E 2259+586 by analyzing 21cm HI-line and 12CO-line spectra of CTB 109, HII region Sh 152, and the adjacent molecular cloud complex. CTB 109 has been established to be interacting with a large molecular cloud (recession velocity at v=-55 km s^-1). The highest radial velocities of absorption features towards CTB 109 (-56 km s^-1) and Sh 152 (-65 km s^-1) are larger than the recombination line velocity (-50 km s^-1) of Sh 152 demonstrating the velocity reversal within the Perseus arm. The molecular cloud has cold HI column density large enough to produce HI self-absorption (HISA) and HI narrow self-absorption (HINSA) if it was at the near side of the velocity reversal. Absence of both HISA and HINSA indicates that the cloud is at the far side of the velocity reversal within the Perseus Arm, so we obtain a distance for CTB 109 of 4+/-0.8 kpc. The new distance still leads to a normal explosion energy for CTB 109/AXP 1E 2259+586.