Observations of V404 Cygni, an X-ray transient containing a black hole of nine solar masses and a companion star, show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates at least ten times lower than previously thought, suggesting that the accretion rate is not the critical parameter for inducing inner-disk instabilities.
- Mariko Kimura
- Keisuke Isogai
- Makoto Uemura
