Period evolution of repeating transients in galactic nuclei

Itai Linial, Eliot Quataert

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Wide-field surveys have recently detected recurring optical and X-ray sources near galactic nuclei, with period spanning hours to years. These phenomena could result from repeated partial tidal disruptions of stars by supermassive black holes (SMBHs) or by interaction between star and SMBH-accretion discs. We study the physical processes that produce period changes in such sources, highlighting the key role of the interaction between the orbiting star and the accretion disc. We focus on ASASSN-14ko - a repeatedly flaring optical source with a mean period and a detected period decay (Payne et al. 2022). We argue that the system's is most compatible with true orbital decay produced by hydrodynamical drag as a star passes through the accretion disc on an inclined orbit, twice per orbit. The star is likely a sun-like star whose envelope is somewhat inflated, possibly due to tidal heating. Star-disc interaction inevitably leads to drag-induced stripping of mass from the star, which may be the dominant component in powering the observed flares. We discuss ASASSN-14ko's possible formation history and observational tests of our interpretation of the measured. Our results imply that partial tidal disruption events manifesting as repeating nuclear transients cannot be modelled without accounting for the cumulative impact of tidal heating over many orbits. We discuss the implications of our results for other repeating transients, and predict that the recurrence time of quasi-periodic eruptions is expected to decay at a rate of the order of.

Original languageEnglish (US)
Pages (from-to)4317-4329
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume527
Issue number2
DOIs
StatePublished - Jan 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • accretion, accretion discs
  • galaxies: nuclei
  • transients: tidal disruption events

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