Single-harmonic search for extreme mass-ratio inspirals

Extreme mass-ratio inspirals (EMRIs) are one of the key sources of gravitational waves for space-based detectors such as the Laser Interferometer Space Antenna. However, their detection remains a major data analysis challenge due to the signals’ complexity and length. We present a semicoherent, time-frequency search strategy for detecting EMRI harmonics without relying on full waveform templates. We perform an injection and search campaign of single mildly eccentric equatorial EMRIs in stationary Gaussian noise. The detection statistic is constructed solely from the EMRI frequency evolution, which is modeled phenomenologically using a singular value decomposition basis. The pipeline and the detection statistic are implemented in time frequency, enabling efficient searches over one year of data in approximately one hour on a single graphic processing unit. The search pipeline achieves 94% detection probability at SNR ¼ 30 for a false-alarm probability of 10−2, recovering the frequency evolution of the dominant harmonic within 1% relative error. By mapping the EMRI parameters consistent with the recovered frequency evolution, we show that the semicoherent detection statistic enables a subpercent precision estimation of the EMRI intrinsic parameters. These results establish a computationally efficient framework for constructing EMRI proposals for the LISA global fit.