Distance to the SNR CTB 109/AXP 1E 2259+586 by HI absorption and self-absorption

TL;DR

This paper refines the distance to SNR CTB 109 and its associated AXP 1E 2259+586 using HI and CO spectral analysis, revealing the cloud's position within the Perseus arm and confirming a typical supernova explosion energy.

Contribution

The study introduces a revised distance estimate for CTB 109 based on HI self-absorption analysis, clarifying its position in the Perseus arm and implications for its explosion energy.

Findings

Distance to CTB 109 is 4±0.8 kpc.

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

The explosion energy of CTB 109/AXP 1E 2259+586 is typical for supernovae.

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.