Detection of narrow "laser" lines masked by spatially inhomogeneous broadening in radiation emitted from stellar atmospheres

Methods for detection of narrow spectral lines in the radiation emitted by a distant source, masked by a spatially inhomogeneous frequency shift, are considered. An analysis is made of the possibility of using, in principle, the Brown–Twiss correlation method and of the optical heterodyne method with independent heterodynes for this purpose. The normalized mutual correlation function is calculated in the plane of two receivers used to investigate a distant source characterized by a spatially inhomogeneous broadening of the spectrum. Estimates are given of the signal/noise ratio for both methods when applied to sources in the form of "laser" regions in a stellar atmosphere in the case of a strong rotation-induced spatial broadening of the spectrum.