Possible Association of Two Stellar Bowshocks with Unidentified Fermi Sources

TL;DR

This study investigates whether the bowshocks of two runaway stars are the sources of specific unidentified Fermi gamma-ray signals, suggesting a novel class of gamma-ray emitting stellar bowshock sources.

Contribution

The paper presents the first potential identification of stellar bowshocks as gamma-ray sources through multi-wavelength analysis and modeling of Fermi data.

Findings

Bowshocks of Lambda Cephei and LS 2355 are coincident with unidentified Fermi sources.

Inverse Compton emission models fit the Fermi data well for both stars.

Gamma-ray emission from these bowshocks could be the first of their kind detected.

Abstract

The bowshocks of runaway stars had been theoretically proposed as gamma-ray sources. However, this hypothesis has not been confirmed by observations up to date. In this paper, we present two runaway stars (Lambda Cephei and LS 2355) whose bowshocks are coincident with the unidentified Fermi gamma-ray sources 3FLG J2210.1+5925 and 3FGL J1128.7-6232, respectively. After performing a cross-correlation between different catalogues at distinct wavelengths, we found that these bowshocks are the most peculiar objects in the Fermi position ellipses. Then, we computed the inverse Compton emission and fitted the Fermi data in order to test the viability of both runaway stars as potential counterparts of the two high-energy sources. We obtained very reasonable values for the fitted parameters of both stars. We also evaluated the possibility for the source 3FGL J1128.7-6232, which is positionally coincident with an HII region, to be the result of background cosmic-rays protons interacting with the matter of the cloud, as well as the probability of a pure chance association. We conclude that the gamma rays from these Fermi sources might be produced in the bowshocks of the considered runaway stars. In such a case, these would be the first sources of this class ever detected at gamma rays.