sciscape Publications

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

by
6 citing publications

AT2018fyk is a tidal disruption event that stopped, came back, and stopped again in August 2023. Wevers et al. (2023) and Pasham et al. (2024) explained this with a repeating partial tidal disruption and predicted a third rise in March 2025 or in 15 May to 31 August 2025 (MJD 60864 +- 54). We reduced all 229 public Swift XRT and UVOT observations from 2018 to 2026 with one uniform Python method and tested these predictions. No XRT visit after the 2023 shutoff gives a 3-sigma detection. Stacked 3-sigma limits are 2.7e41 erg/s in early 2025 and 5.4e41 erg/s in the Pasham window, 3 to 6 percent of the 2022 flare peak (8.5e42 erg/s). The UVW1, UVW2 and UVM2 rates in 2025 agree with the 2024 level; in the Pasham window the UVW2 excess is 0.6 +- 0.7 percent of the 2022 peak excess. When we shift the observed 2022-2023 light curve in time and fit its amplitude, the 95 percent upper limit is 1.3-5 percent (UV) for any start date from October 2024 to late November 2025, which includes both predicted windows. XMM-Newton pipeline values from May 2024 also show a low state. Thus the predicted third flare did not occur on time, or it was more than 20 times weaker than the 2022 flare in the UV. The result does not reject all repeating-disruption models: the star can have lost almost no mass, or the fallback time can have changed. Swift made only one 85-s visit after 6 December 2025, so a flare that starts in 2026 is not tested. The luminosity values use one count-rate factor from the soft state.

tidal disruption event · AT2018fyk · repeating partial tidal disruption · Swift XRT · Swift UVOT · forecast test · X-ray transients · null result
High Energy Astrophysical PhenomenaAstrophysics of Galaxies

References

11
  1. challengesdoi:10.3847/2041-8213/ac9f36
  2. challenges, usesdoi:10.3847/2041-8213/ad57b3
  3. usesdoi:10.5281/zenodo.10913475
  4. doi:10.3847/1538-4357/ad4da3
  5. supportshttps://arxiv.org/abs/2606.06578
  6. https://arxiv.org/abs/2501.01824
  7. usesdoi:10.1086/170124
  8. usesdoi:10.1111/j.1365-2966.2007.12563.x
  9. useshttps://heasarc.gsfc.nasa.gov/docs/swift/archive/
  10. ASAS-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
  11. ASASSN-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

Cited by

6 publications
  1. Evidence for a change of ASASSN-14ko timing curvature depends on a fixed UV-to-optical offset reviews
  2. SPHEREx near-infrared images show that the September 2025 ASASSN-14ko flare peaked 21 days after the Payne et al. 2022 ephemeris; the August 2026 flare peak time depends on its decline time
  3. 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
  4. Swift and XMM-Newton data from 2023-2024 show two more X-ray flare cycles of eRASSt J0456-20: the recurrence time stays at 193 days and the flares fade by a factor of two per cycle uses
  5. 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
  6. 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