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LISA is a space-based gravitational wave detector set to launch in the mid-2030s 📅. It is designed to capture low-frequency gravitational waves. Unlike LIGO, which detects the final merger of a compact binary, LISA would capture the evolution of the system as the objects grow closer together. ⏳ 2/10

In this paper, we considered a binary similar to GW150914 – binary black holes of ~36 and ~29 solar masses. If LISA had been observing, it would’ve detected this system years before ground detectors did! BUT, we placed the binary in orbit around a supermassive black hole of 10^8 solar masses. 👀 3/10

Stellar mass black holes in active galactic nuclei end up in circularized orbits very close to the central supermassive black hole. If two form a binary while orbiting that close, the gravitational waves emitted experience intense gravitational lensing! 🔎 4/10

The main effects that we consider on the lensing of the gravitational wave signal are: 🔹Frequency shifts from orbital motion 🔹Redshifting due to the gravitational well 🔹Magnification near the SMBH Each shaping what LISA will detect! 🌠 5/10

18/2/25, 10:21 pm0 reposts5 likes

We ran relativistic simulations to calculate the redshift and magnification at any point in the BBH's orbit. Then, we used those results to approximate the characteristic strain and frequency – giving us a better idea of how these signals would be detected by LISA. 👂 6/10

Unlike mergers that occur in a vacuum, where the evolution of the frequency smoothly increases, here it oscillates as the binary moves towards and away from us in its orbit. 🌊 🚨 We have a problem: These oscillations prevent the signals from building up, making them hard to detect! 7/10

But there is hope! 🌟 At two points in the orbit, the rate of change of the frequency slows down and magnification is greater than zero. Causing the signal to rise above LISA’s sensitivity curve! 📈 This effect depends on the orbital radius around the SMBH and the inclination of the AGN disk. 8/10