CO OBSERVATIONS OF THE CEPHEUS FLARE .2. GAMMA-RAYS FROM THE INTERSTELLAR GAS AND A POSSIBLE NEW COS-B SOURCE

The correlation between the distribution of the interstellar gas in the Cepheus Flare region (100° ≤; l ≤ 141°, 8° ≤ b ≤ 22°) and that of the diffuse gamma radiation originating in these nearby clouds has been studied in detail. A maximum-likelihood analysis has been applied to compare maps of the atomic and molecular gas tracers (H I and 12CO observations) to the COS B γ-ray data. This yields an estimate of the 70 MeV-5 GeV emissivity spectrum of the atomic gas which agrees with previous measurements in the local interstellar medium. The results imply a value of (2.3 ± 1.2) × 1020 mol cm-2 Km-1 s for the N(H2)/Wco ratio in the Cepheus molecular complex. The correlation study has revealed the presence of a significant (3.9 σ) pointlike excess which stands above the diffuse gamma radiation at l = 111°, b = 19°.8, with an error box 1°.8 in radius. The excess satisfies the statistical detection criterion of the COS B catalog of sources and possibly corresponds to a new, bright, and extremely soft γ-ray source. A tentative identification could be made with the radio galaxy 3C 427.1.