Non-detection in a Fermi/LAT observation of AXP 4U 0142+61: magnetars?

TL;DR

This paper discusses how the non-detection of AXP 4U 0142+61 by Fermi/LAT supports the accretion model over the magnetar model for explaining AXPs and SGRs, proposing future observations to test these theories.

Contribution

It suggests that Fermi/LAT non-detections can differentiate between magnetar and accretion models for AXPs and SGRs, favoring the accretion model based on recent observations.

Findings

Fermi/LAT non-detection favors the accretion model.

Future observations of other AXPs are recommended.

Non-detection can distinguish between competing models.

Abstract

Significant research in compact stars is currently focused on two kinds of enigmatic sources: anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs). Although AXPs and SGRs are popularly thought to be magnetars, other models (e.g. the accretion model) to understand the observations can still not be ruled out. It is worth noting that a non-detection in a Fermi/LAT observation of AXP 4U 0142+61 has been reported recently by Sasmaz Mus & Gogus. We propose here that Fermi/LAT observations may distinguish between the magnetar model and the accretion model for AXPs and SGRs. We explain how this null observation of AXP 4U 0142+61 favors the accretion model. Future Fermi/LAT observations of AXP 1E 1547.0-5408 and AXP 1E 1048.1-5937 are highly recommended.