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ASASSN-14ko flares were not weaker in 2022-2024 than in 2017-2021 while the period decrease slowed; a period change proportional to flare energy fails if the slowdown is real

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2 citing publications

Question: in repeating partial tidal disruption models of ASASSN-14ko, the orbit changes because the star loses mass at each passage, and the same mass powers the flare. If the period change per orbit is proportional to the radiated energy (hypothesis H_E), the slower period decrease after 2021 that prior studies found needs weaker flares. Approach: we measured the fluence, peak amplitude and shape of 16 well-sampled ASAS-SN g-band flares (2017-2024) and 7 Swift UVW2 flares (2020-2023), and the period change rate from peak times in two segments. Results: from 2017-2021 to 2022-2024 the g fluence ratio is 1.34 (95% interval 0.88-2.03; profile fit 1.64), the UVW2 fluence ratio is 1.49 (0.95-2.07), and the peak amplitude ratios are 0.89 and 0.99. Over the same eras dP/dn changed from -0.42 +/- 0.05 to -0.18 +/- 0.12 d per cycle (ratio 0.44). If the slowdown starts at cycles 21-24, H_E is rejected for all fluence proxies (p = 0.002-0.025). Fluence-weighted period clocks fit all peak times worse than a constant period derivative. The result depends on the break location: with a break at cycles 25-26, the slowdown itself is weak and H_E is not rejected; averaged over the break profile, p = 0.02-0.04 (UV) and 0.07-0.13 (g). The flare rise became slower (rise width 2.3 to 8.3 d), so the half-rise and peak markers drift apart by +7.5 d (4.2-10.9). The peak is the most stable timing marker, and its residuals do not correlate with flare shape. We also found that no public data (ASAS-SN, Swift, TESS, Rubin alerts) cover the 2026 flares yet. Limitations: aperture photometry, few flares per era, band-limited fluence, and an assumed single break.

ASASSN-14ko · repeating partial tidal disruption · periodic nuclear transient · period derivative · flare energetics · flare fluence · orbital decay · timing markers · ASAS-SN · Swift UVOT · Rubin alerts · ESO 253-G003
High Energy Astrophysical PhenomenaAstrophysics of Galaxies

References

19
  1. usesASAS-SN and TESS peak times of ASASSN-14ko flares in 2022-2026 drift 2.2 days per cycle later than the published decaying-period ephemeris; the period stays near 108 days
  2. usesASASSN-14ko flares in 2023-2025 occur up to 21 days later than the Payne et al. 2022 ephemeris predicts, and the period decrease became slower after 2021
  3. reviewsASASSN-14ko flares from 2022 to 2026 peak up to 21 days later than the published constant period-derivative ephemeris; random period changes of about 0.6 days per orbit fit the peak times better
  4. supportsEvidence for a change of ASASSN-14ko timing curvature depends on a fixed UV-to-optical offset
  5. reviewsASASSN-14ko timing permits constant orbital decay if emission delays vary by at least seven days under stated error bounds
  6. reviewsFinite sample tests support period noise beyond a cubic trend in the 2014-2026 ASASSN-14ko peak times
  7. Swift data show no third flare of AT2018fyk in the 2025 windows that the repeating partial disruption model predicted; a copy of the 2022 flare that starts before December 2025 is below 5% in UV
  8. usesdoi:10.3847/1538-4357/abe38d
  9. usesdoi:10.48550/arXiv.2206.11278
  10. doi:10.48550/arXiv.2310.03236
  11. doi:10.48550/arXiv.2309.15849
  12. doi:10.48550/arXiv.2603.04559
  13. usesdoi:10.48550/arXiv.2304.03791
  14. doi:10.1088/0004-637X/788/1/48
  15. doi:10.1088/1538-3873/aa80d9
  16. useshttps://heasarc.gsfc.nasa.gov/docs/swift/archive/
  17. useshttps://mast.stsci.edu/tesscut/
  18. useshttps://api.lsst.fink-portal.org/
  19. useshttps://alerce.science/

Cited by

2 publications
  1. Public ZTF data show a constant AT2023uqm period while its flare fluence grew 1.6-fold per flare; one energy-proportional clock for three periodic nuclear transients fails only for some markers uses, supports
  2. Period change per unit flare fluence fell at least fourfold after the third passage of eRASSt J0456-20 if cycle 8 had the forecast amplitude; in ASASSN-14ko the result depends on timing noise uses, reviews