India’s AstroSat and NASA’s space observatories collaborate to solve black hole mystery

An important astronomical phenomenon has emerged, revealing powerful interactions between a massive black hole and its surrounding environment. Researchers from NASA and India’s ISRO have used multiple space observatories, including Chandra, Hubble Space Telescope (HST), Neutron Star Interior Composition Explorer (NICER), Swift observatory and India’s AstroSat, to observe the aftermath of a star’s destruction by a black hole. The study has uncovered important connections between previously unconnected cosmic phenomena.

Tidal disruption events and their consequences
In 2019, astronomers detected the destruction of a star that had gotten too close to a black hole, causing what is known as a tidal disruption event (TDE). The remains of the star created an expanding debris disk, which over time began to interact with another orbiting star or possibly a smaller black hole. This interaction has produced regular bursts of X-rays, occurring about every 48 hours when the orbiting star collides with the debris disk, the Indian Space Research Organisation (ISRO) said in a press release. Matt Nicholl, an astronomer at Queen’s University Belfast, commented that this scenario is similar to a diver entering a pool, which produces splashes with each entry.

Linking TDEs and quasi-periodic eruptions

Previous studies had identified various tidal disruption events, but the connection between TDEs and a newly recognized class of cosmic phenomena called quasi-periodic eruptions (QPEs) remained speculative. Co-author Dheeraj Pasham, affiliated with the Massachusetts Institute of Technology, noted the importance of this discovery in linking these events.

Observational successes with AstroSat
The TDE, named AT2019qiz, was initially observed at the Zwicky Transient Facility of Palomar Observatory. Follow-up studies with NASA observatories revealed that the debris disk had expanded significantly, so that any orbiting object with a period of a week could collide with it. The researchers, including Gulab Dewangan of the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune, acknowledged the unique capabilities of AstroSat in contributing to this research.

Implications for future research
The findings suggest that researchers should allow time for the debris disk to dissipate sufficiently before observing outbursts. This information could aid in the search for additional QPEs associated with tidal disruptions, potentially enhancing our understanding of the environment around supermassive black holes.