Tabby's star (KIC 8462852)Evidence
Evidence · Tabby's star (KIC 8462852)
ASAS-SN g-band image subtraction, independent of AAVSO, is flat from 2018 to 2026
ASAS-SN g-band image-subtraction photometry from two independent cameras (855 nights, 2018.5-2026.85) gives a slope of +0.19 ± 0.16 mmag per year (night bootstrap; ±0.36 resampling the nine seasons), with every seasonal median within 4.5 mmag of the mean: the end of the fade seen in the AAVSO V ensemble (-0.04 ± 0.32) is reproduced by a different instrument, band and reduction.
What it means
Key questionWhat causes the slow fading of the star?
Most likely: a large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips
Most likelyunchanged
Openunchanged
Answer this evidence bears onThe fade stopped around 2018: the star has held a constant year-scale level since, about 0.01 mag brighter than its…
Supports2 for, none against
Still possibleunchanged
Next steps 3
1
Modern-era stitch 2006-2026. Done: ASAS-SN v1 image-subtraction V (2015-2018) and g (2018-2026) are on the site (DAT0DEEB6NC6SCE), and so are the AAVSO B and V records since 2015. Both show the fade stopping in 2018. Remaining: join to the ASAS 2006-2014 V series of Simon et al. 2018 (ask the authors or digitise their figure), and tie g to V using an independent V-g colour, since the ASAS-SN overlap is only two nights. That gives one 20-year curve with the 2006-07 and 2014 brightenings.
~4 h
—not judged
2
The early-2023 depression is the only one left. Mid-2022 (AAVSO 15.7 mmag, ASAS-SN g 1.5) and mid-2025 (4.2 against -3.5) are AAVSO observer artefacts. Early 2023 is about 10-12 mmag in both records, but ASAS-SN has only ten nights there, at season's end with the star low. Next: reduce each AAVSO observer against their own comparison star (comp1_c/cmag) for January-April 2023, require two observers, and test for an airmass dependence in both records before calling it real.
~3 h
—not judged
3
Early-2023 depression: per-observer comparison-star reduction and an airmass test in AAVSO and ASAS-SN before calling it real.
~3 h
—not judged
Ranked by how likely each is to move the key question, for the time it takes
How it was found 1 run
Result. 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..
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'}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.
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
Drawn by the site with ASAS-SN image-subtraction light curve 2015-2026
ASAS-SN v1 image-subtraction light curve of KIC 8462852, 2015-2026 (V and g)ASAS-SN V-band light curve of KIC 8462852 (source AP14246098, camera bd), 2015-2018AAVSO International Database export for KIC 8462852, 1 July 2018 to 29 October 2026 (77,195 observations, with comparison stars)AAVSO International Database export for KIC 8462852, October 2015 to June 2018 (66,875 observations, with comparison stars)asassn_isub_reduce.pyasassn_cat_vs_isub.py6 outputs
Sources 1
Cite it
Mysteries Department. (2026). ASAS-SN g-band image subtraction, independent of AAVSO, is flat from 2018 to 2026 [Evidence EVD0DEEBF3C2667]. https://mysteriesdept.com/r/EVD0DEEBF3C2667
@misc{mysteriesdept_evd0deebf3c2667,
title = {ASAS-SN g-band image subtraction, independent of AAVSO, is flat from 2018 to 2026},
author = {{Mysteries Department}},
year = {2026},
note = {Evidence, catalog key EVD0DEEBF3C2667},
url = {https://mysteriesdept.com/r/EVD0DEEBF3C2667}
}