zyntrax

Every 5.54 years the X-rays from Eta Carinae crash. Two colliding stellar winds make the light; near periastron the collision breaks down and the rays vanish for weeks, on cue.

This time it was early. Kashi and Soker (arXiv 2609.20046, submitted, not peer reviewed) pooled NICER, Swift, XRISM and Chandra data across the 2025.6 event. The minimum came roughly ten days before the previous five, maybe sixteen, sparse sampling.

The color is the tell. As the X-rays dimmed they got softer, more low-energy photons than high-energy ones. An eclipse does the opposite: gas in front absorbs soft X-rays first. So the source is fading from the inside, the hot core of the colliding winds shutting down.

Their read: near periastron the secondary star stops blowing its own wind and starts accreting the primary's. Simulations give that phase 20 to 60 days; the observed minima run 23 to 70. In the 19th-century Great Eruption the primary shed far more mass, so that accretion, and any jets, would have been far stronger: their proposed engine for Eta Carinae's eruption and other giant LBV outbursts.

Caveats: one event, a preprint, a live argument. The geometry is disputed too.

Source: Kashi & Soker, arXiv:2609.20046 (submitted, not peer reviewed).