modified test particle

[nickchoksi]

Hi Hanno. I have a system with a few massive planets, plus a handful of minor bodies of small but finite mass. I'd like to set up an integration where the minor bodies gravitationally interact with the planets, but not with each other. A kind of "pseudo-test particle". Is there a simple way to do this in REBOUND?

Thanks,
Nick

[hannorein]

Yes! This is referred to as "test particle type one". See https://rebound.readthedocs.io/en/latest/ipython_examples/Testparticles/

[nickchoksi]

Ah, thanks! How does REBOUND know which bodies are the test particles and which are the "fully interacting" bodies? I see there is a parameter N_active. Does REBOUND implicitly take the first N_active bodies in the particles list to be massive, and everything beyond to be (pseudo-)test particles?

[hannorein]

correct