Run · Tabby's star (KIC 8462852)

ASAS-SN image-subtraction light curve 2015-2026: fade slopes, catalogue comparison, depressions, October window

ASAS-SN image-subtraction reconciliation: fade slopes, catalogue comparison, camera tie-in and depression check: Least-squares slope of nightly medians (mmag/yr), night and season bootstrap.

Fade stopped by 2018, confirmed independently of AAVSO. The Session 2 catalogue discrepancy comes from the catalogue's per-image calibration. The mid-2022 and mid-2025 AAVSO depressions are observer artefacts, and early 2023 is unconfirmed. ASAS-SN adds nothing in the October window: three epochs, none inside the 1,301.44-1,301.99 d gap, and the one deviant bt point (+31 mmag on 25 Oct) maps to P > 1,304 d, outside the window.{'cat_minus_isub': '-2.68 ± 0.88', 'g_2018.5_2026.85': '+0.19 ± 0.16 (±0.36 season)', 'catalogue_V_same_nights': '+3.10 ± 1.49', 'isub_V_2015.7_2018.2_same_nights': '+5.78 ± 1.23'}0

Result

Run	Measured	Result	Against	Decision	Date
Run	Least-squares slope of nightly medians (mmag/yr), night and season bootstrap	{'cat_minus_isub': '-2.68 ± 0.88', 'g_2018.5_2026.85': '+0.19 ± 0.16 (±0.36 season)', 'catalogue_V_same_nights': '+3.10 ± 1.49', 'isub_V_2015.7_2018.2_same_nights': '+5.78 ± 1.23'}	AAVSO_V_2015.7_2018.2 +8.5 ± 2.6 · AAVSO_V_2018.5_2026.8 -0.04 ± 0.32 · Simon_et_al_2015_2017 +6.3 ± 1.4	Fade stopped by 2018, confirmed independently of AAVSO. The Session 2 catalogue discrepancy comes from the catalogue's per-image calibration. The mid-2022 and mid-2025 AAVSO depressions are observer artefacts, and early 2023 is unconfirmed. ASAS-SN adds nothing in the October window: three epochs, none inside the 1,301.44-1,301.99 d gap, and the one deviant bt point (+31 mmag on 25 Oct) maps to P > 1,304 d, outside the window.

What it used and found

ASAS-SN image-subtraction reconciliation: fade slopes, catalogue comparison, camera tie-in and depression check

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

ASAS-SN V-band light curve of KIC 8462852 (source AP14246098, camera bd), 2015-2018

Dataset

DAT

ASAS-SN v1 image-subtraction light curve of KIC 8462852, 2015-2026 (V and g)

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

ASAS-SN g-band image subtraction, independent of AAVSO, is flat from 2018 to 2026

Evidence it produced

EVD

Image subtraction reproduces Simon et al.'s 2015-2018 fade; the public ASAS-SN catalogue flattens it

Evidence it produced

EVD

No fade in ASAS-SN g after 2018: +0.19 ± 0.16 mmag per year over eight years

Evidence it produced

EVD

Figures 1

Figure 1

The star faded in V until 2018, then held flat in g for eight years

ASAS-SN image-subtraction seasonal medians relative to the first season of each band (mmag; positive = fainter)

seasonal median

Seasons are labelled by the year they end. V is camera bd. g combines cameras bD and bt, tied together to 0.5 mmag. The two bands overlap on only two nights, so their zero points are set separately.

Drawn by the site

Parameters

clip = 5 MAD from 31-night running median, transit = {'T0_BJD': 2458730.164, 'depth_mag': 0.012, 'duration_d': 0.85}, bins_days = 30, period_grid = [1299, 1305, 0.01], running_bins = 13

Cite it

Mysteries Department. (2026). ASAS-SN image-subtraction light curve 2015-2026: fade slopes, catalogue comparison, depressions, October window [Run RUN0DEEBS2Q3XBJ]. https://mysteriesdept.com/r/RUN0DEEBS2Q3XBJ

@misc{mysteriesdept_run0deebs2q3xbj,
  title     = {ASAS-SN image-subtraction light curve 2015-2026: fade slopes, catalogue comparison, depressions, October window},
  author    = {{Mysteries Department}},
  year      = {2026},
  note      = {Run, catalog key RUN0DEEBS2Q3XBJ},
  url       = {https://mysteriesdept.com/r/RUN0DEEBS2Q3XBJ}
}