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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

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3 citing publications

Question: do the 2025-2026 flares of the repeating nuclear transient ASASSN-14ko arrive at the times of the Payne et al. (2022) constant-Pdot ephemeris? No public optical or UV survey covers the 2026 flares. Approach: we used 541 public SPHEREx Level-2 spectral images (0.75-5 um; QR2 and QR3) from three windows: 2025 Aug-Oct, 2026 Feb-Apr and 2026 Aug-Oct. We did forced aperture photometry of the nucleus, calibrated the windows with three field stars, and fitted a host spectrum plus flare profiles (0.75-2.4 um) on a grid of peak times. Results: the flares are detected (chi2 improvement 100.9). Flare n = 37 peaked at MJD 60936 (2-sigma 60931-60939), +20.6 d after the Payne et al. forecast. At the forecast peak the 1.1-1.6 um excess was -0.12 +/- 0.07 mJy; the excess appeared after MJD 60928. The forecast time gives delta chi2 = 11.6 (8.3-15.5 in 21 variants; 3.5-5.1 with less 1.6-2.4 um information). This offset equals the +20.5 d offset of the TESS flare n = 38, and the n = 37 to n = 38 interval is 104.4 d. Flare n = 40 (2026 August) is present only in decline. Its peak is not later than MJD 61267. The Payne et al. time is excluded for a 14.86-d decline (delta chi2 = 32.5) but allowed for a decline time of 20-30 d, which the data do not constrain. The QR3 photometric scale is 3.7 +/- 0.5 percent lower than QR2 at 0.75-1.1 um for field stars; without this correction most of the n = 40 excess disappears. The 2.4-3.8 um flux of the nucleus rose by 4.2 percent from 2025 to early 2026. Updated forecasts: n = 41 near 2026-11-24 (constant P = 108.09 d, +/- 4.7 d), against 2026-10-18 from Payne et al. Limitations: one 50-day window per flare, host spectrum from window comparison, the optical flare shape is assumed, and n = 40 timing depends on calibration and decline time.

ASASSN-14ko · repeating partial tidal disruption · periodic nuclear transient · flare timing · SPHEREx · near-infrared photometry · ephemeris forecast test · O-C diagram · period derivative · photometric calibration · ESO 253-G003
High Energy Astrophysical PhenomenaAstrophysics of Galaxies

References

16
  1. uses, supportsASAS-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. supportsASASSN-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
  3. uses, supportsASASSN-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
  4. 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
  5. reviewsEvidence for a change of ASASSN-14ko timing curvature depends on a fixed UV-to-optical offset
  6. ASASSN-14ko timing permits constant orbital decay if emission delays vary by at least seven days under stated error bounds
  7. supportsFinite sample tests support period noise beyond a cubic trend in the 2014-2026 ASASSN-14ko peak times
  8. challengesdoi:10.48550/arXiv.2206.11278
  9. usesdoi:10.48550/arXiv.2009.03321
  10. doi:10.48550/arXiv.2310.03236
  11. doi:10.48550/arXiv.2506.15039
  12. doi:10.48550/arXiv.2309.15849
  13. doi:10.48550/arXiv.2406.03675
  14. doi:10.48550/arXiv.2603.04559
  15. usesdoi:10.1051/0004-6361/202243940
  16. useshttps://irsa.ipac.caltech.edu/Missions/spherex.html

Cited by

3 publications
  1. Adding late ASASSN-14ko peaks reduces support for a fixed Schwarzschild disc-crossing clock under constant delay uses
  2. 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
  3. 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