GeV γ-ray emission in the star-forming region S140

Abstract

We report the detection of a GeV γ-ray source in the S140 HII region using 17.75 years of Fermi-LAT data, with a source-detection significance of ~32.1σ in the 0.1-500 GeV energy band. The emission is significantly extended (AIC evidence ratio above 1 GeV is 2x10^9) and is therefore designated as 4FGL J2220.8+6319e. The γ-ray emission coincides spatially with a molecular cloud that hosts the massive young stellar object S140 IRS1. Its spectrum is best fitted by a log-parabolic spectrum (TS_cur(LP) = 104.1) and can be reproduced by both hadronic and leptonic models. The jet driven by S140 IRS1 offers a viable particle acceleration site, yielding injection timescales and maximum particle energies consistent with theoretical expectations, whereas stellar winds are energetically disfavored.

Accepted for publication in ApJ