Microthermal Residuals from Directed Electromagnetic Emissions as a New Class of Technosignature

Highly collimated electromagnetic beams are a plausible medium for interstellar communication, particularly when enhanced by gravitational lensing. However, their directional nature makes them unlikely to be intercepted by unintended observers. This study examines the thermodynamic consequences of such beams interacting with the interstellar medium, proposing a new class of technosignature: residual thermal anisotropies induced by beam absorption in cold astrophysical structures—termed Bonaque traces. Simulations across a broad parameter space—wavelength, power, duration, divergence, and medium type—demonstrate that detectable temperature increments can arise under realistic physical conditions. The resulting residuals are broadband, spatially coherent, and potentially persistent over long scales. Observational detectability is found to be viable with current or archival far-infrared instrumentation, particularly in galactic cirrus and diffuse atomic clouds. This framework enables a shift in technosignature detection: from interception of active transmissions to identificaion of their physical imprint.