Original title: Prospects of electromagnetic follow-up of neutron star-black hole mergers in the LIGO-India era
Yogita Kumari, Kanchan Soni, Sanjit Mitra · September 2026
When a dead star called a neutron star crashes into a black hole, space ripples with gravitational waves. Sometimes this collision also creates a bright flash of light called a kilonovaA brief flash of light produced when two dense objects like a neutron star and a black hole merge.. However, spotting that light is hard because telescopes do not always know exactly where to point. Researchers tested how well a giant telescope called the Vera C. Rubin Observatory could spot these flashes once a new detector, LIGO-India, joins current wave detectors. Adding LIGO-India helps pinpoint the crash location much more accurately and keeps watch more often. This roughly doubles the number of light follow-ups and helps find events much farther away. The team also designed a custom strategy that adjusts camera exposure times for each crash. Over the next decade, this setup could catch a few of these joint events, helping scientists measure the expansion of our universe.
You are at a huge outdoor concert and someone sets off a firework. You hear the boom but have no idea where it was, so you cannot point your camera in time to photograph the flash. If a friend stands far away and hears it too, the two of you can roughly triangulate the spot and know where to aim. In this paper, the firework is the cosmic collision, the boom is the ripple in space, and the camera is the telescope; adding a detector in India is the second ear, and it doubles how often the telescope gets pointed the right way.
When a neutron star and a black hole merge, they can create a brief flash of light called a kilonova. Adding a new detector in India doubles how many of these flashes we can catch, giving us more chances to measure the expansion rate of the universe.
The abstract doesn't say, but it notes that only a subset of mergers produce detectable counterparts, and the predicted rates have large uncertainties. The results depend on the binary mass ratio, black hole spin, and neutron star equation of state.
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Prospects of electromagnetic follow-up of neutron star-black hole mergers in the LIGO-India era — Yogita Kumari, Kanchan Soni, Sanjit Mitra
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.