Jumping the energetics queue: Modulation of pulsar signals by extraterrestrial civilizations

•ETI may modify the radio emission of pulsars to use them as beacons.•We provide a few examples of modulation mechanisms.•We provide observational signatures that astronomers can search for.

It has been speculated that technological civilizations evolve along an energy consumption scale first formulated by Kardashev, ranging from human-like civilizations that consume energy at a rate of ∼10191019 erg s−1 to hypothetical highly advanced civilizations that can consume ∼10441044 erg s−1. Since the transmission power of a beacon a civilization can build depends on the energy it possesses, to make it bright enough to be seen across the Galaxy would require high technological advancement. In this paper, we discuss the possibility of a civilization using naturally-occurring radio transmitters – specifically, radio pulsars – to overcome the Kardashev limit of their developmental stage and transmit super-Kardashev power. This is achieved by the use of a modulator situated around a pulsar, that modulates the pulsar signal, encoding information onto its natural emission. We discuss a simple modulation model using pulse nulling and considerations for detecting such a signal. We find that a pulsar with a nulling modulator will exhibit an excess of thermal emission peaking in the ultraviolet during its null phases, revealing the existence of a modulator.