Run · Tabby's star (KIC 8462852)

AAVSO 2015-2026 ensemble reduction: seasonal levels and slopes by epoch

Observer-offset ensemble reduction of the AAVSO record: Seasonal median relative to 2019; least-squares slope in mmag per year within 2015.7-2018.2 and 2018.5-2026.9; changepoint BIC gain.

The 2015-2018 decline is real in the AAVSO ensemble at the published rate, and it did not continue: 2018.5-2026.8 is flat to 0.3 mmag per year. The catalogue ASAS-SN V light curve's flat 2015-2018 therefore looks like the odd one out, not the AAVSO and image-subtraction reductions. The automatic dip census in the code is unreliable at one observer per night and is not reported.{'B': {'n_obs': 31245, 'nights': 2680, 'observers': 17, 'slope_2015.7_2018.2': [2.41, 2.56], 'slope_2018.5_2026.9': [1.79, 0.45]}, 'V': {'n_obs': 80214, 'nights': 3117, 'seasonal': {'2015': -0.0037, '2016': 0.0024, '2017': 0.0132, '2018': 0.004, '2019': 0, '2020': 0.0025, '2021': 0.002, '2022': 0.0074, '2023': 0.001, '2024': -0.003, '2025': 0.006, '2026': 0.0009}, 'observers': 24, 'slope_2015.7_2018.2': [8.51, 2.58], 'slope_2018.5_2026.9': [-0.04, 0.32], 'changepoint_bic_gain': -3.2}}0

Result

Run	Measured	Result	Against	Decision	Date
Run	Seasonal median relative to 2019; least-squares slope in mmag per year within 2015.7-2018.2 and 2018.5-2026.9; changepoint BIC gain	{'B': {'n_obs': 31245, 'nights': 2680, 'observers': 17, 'slope_2015.7_2018.2': [2.41, 2.56], 'slope_2018.5_2026.9': [1.79, 0.45]}, 'V': {'n_obs': 80214, 'nights': 3117, 'seasonal': {'2015': -0.0037, '2016': 0.0024, '2017': 0.0132, '2018': 0.004, '2019': 0, '2020': 0.0025, '2021': 0.002, '2022': 0.0074, '2023': 0.001, '2024': -0.003, '2025': 0.006, '2026': 0.0009}, 'observers': 24, 'slope_2015.7_2018.2': [8.51, 2.58], 'slope_2018.5_2026.9': [-0.04, 0.32], 'changepoint_bic_gain': -3.2}}	simon2018 +6.3 +/- 1.4 mmag/yr (2015-2017, ASAS-SN bd) · schaefer2018 0.023 mag in B over 2015.75-2018.18 (about 9.6 mmag/yr), V 0.77 x B · asassn_catalogue_v1 -0.5 +/- 1.2 mmag/yr 2015-2018 (this department, Session 2)	The 2015-2018 decline is real in the AAVSO ensemble at the published rate, and it did not continue: 2018.5-2026.8 is flat to 0.3 mmag per year. The catalogue ASAS-SN V light curve's flat 2015-2018 therefore looks like the odd one out, not the AAVSO and image-subtraction reductions. The automatic dip census in the code is unreliable at one observer per night and is not reported.

What it used and found

Observer-offset ensemble reduction of the AAVSO record

Method

MTH

AAVSO International Database export for KIC 8462852, 1 July 2018 to 29 October 2026 (77,195 observations, with comparison stars)

Dataset

DAT

AAVSO International Database export for KIC 8462852, October 2015 to June 2018 (66,875 observations, with comparison stars)

Dataset

DAT

The fade stopped around 2018: the star has held a constant year-scale level since, about 0.01 mag brighter than its…

Answer it tests

ANS

AAVSO V: +8.5 mmag/yr fading to 2018, then flat to 0.3 mmag/yr for eight years

Evidence it produced

EVD

Parameters

bands = ['Johnson V', 'Johnson B'], uncertainty_max = 0.03, reference_season = [2019, 2020], running_median_nights = 31, min_nights_per_observer = 40

Cite it

Mysteries Department. (2026). AAVSO 2015-2026 ensemble reduction: seasonal levels and slopes by epoch [Run RUN0DED7WSPR1EN]. https://mysteriesdept.com/r/RUN0DED7WSPR1EN

@misc{mysteriesdept_run0ded7wspr1en,
  title     = {AAVSO 2015-2026 ensemble reduction: seasonal levels and slopes by epoch},
  author    = {{Mysteries Department}},
  year      = {2026},
  note      = {Run, catalog key RUN0DED7WSPR1EN},
  url       = {https://mysteriesdept.com/r/RUN0DED7WSPR1EN}
}