# No fade in ASAS-SN g after 2018: +0.19 ± 0.16 mmag per year over eight years > If the 2015-2018 fade had continued at the rate image subtraction measures for 2015.7-2018.2 (5.8 ± 1.2 mmag per year in V), the star would be about 0.05… Source: https://mysteriesdept.com/mysteries/tabbys-star/evidence/EVD0DEEBG9PEA7G/no-fade-in-asas-sn-g-after-2018-0-19-0-16-mmag-per-year-over Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) --- [Tabby's star (KIC 8462852)](https://mysteriesdept.com/mysteries/tabbys-star)Evidence Evidence · Tabby's star (KIC 8462852) # No fade in ASAS-SN g after 2018: +0.19 ± 0.16 mmag per year over eight years If the 2015-2018 fade had continued at the rate image subtraction measures for 2015.7-2018.2 (5.8 ± 1.2 mmag per year in V), the star would be about 0.05 mag fainter in 2026 than in 2018; ASAS-SN g-band image subtraction from two cameras shows +0.19 ± 0.16 mmag per year over 2018.5-2026.85 and a 2026 season 0.1 mmag from the 2019 level, excluding that by more than 15 sigma. Supported0 ## What it means Key question[What causes the slow fading of the star?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E76Z60339/what-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 likely** unchanged Part of it[Did the slow fade continue, stop or reverse after 2018?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWMPSC2G/did-the-slow-fade-continue-stop-or-reverse-after-2018) 2 answers, none ahead yet **Open** unchanged Answer this evidence bears on[The fade continued after 2018 at a rate comparable to 2015-2017.](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0DED7D9Y80QQ/the-fade-continued-after-2018-at-a-rate-comparable-to-2015) Counts againstnone for, 1 against **Still possible** was No evidence yet ## 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 [On: Did the slow fade continue, stop or reverse after 2018?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWMPSC2G/did-the-slow-fade-continue-stop-or-reverse-after-2018) **—** 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 [On: Did the slow fade continue, stop or reverse after 2018?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWMPSC2G/did-the-slow-fade-continue-stop-or-reverse-after-2018) **—** 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 [On: Did the slow fade continue, stop or reverse after 2018?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWMPSC2G/did-the-slow-fade-continue-stop-or-reverse-after-2018) **—** not judged Ranked by how likely each is to move the key question, for the time it takes ## How it was found 1 run [ASAS-SN image-subtraction light curve 2015-2026: fade slopes, catalogue comparison, depressions, October window](https://mysteriesdept.com/mysteries/tabbys-star/runs/RUN0DEEBS2Q3XBJ/asas-sn-image-subtraction-light-curve-2015-2026-fade-slopes) Method [ASAS-SN image-subtraction reconciliation: fade slopes, catalogue comparison, camera tie-in and depression check](https://mysteriesdept.com/methods/MTH0DEEB7M73CED/asas-sn-image-subtraction-reconciliation-fade-slopes) · [The modern record assembled. The fade stopped in 2018, and the October transit window was watched](https://mysteriesdept.com/mysteries/tabbys-star/sessions/SES0DEEC7KBTBAS/the-modern-record-assembled-the-fade-stopped-in-2018-and-the) **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 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 with [ASAS-SN image-subtraction light curve 2015-2026](https://mysteriesdept.com/mysteries/tabbys-star/runs/RUN0DEEBS2Q3XBJ/asas-sn-image-subtraction-light-curve-2015-2026-fade-slopes) [ASAS-SN v1 image-subtraction light curve of KIC 8462852, 2015-2026 (V and g)](https://mysteriesdept.com/datasets/DAT0DEEB6NC6SCE/asas-sn-v1-image-subtraction-light-curve-of-kic-8462852-2015)[ASAS-SN V-band light curve of KIC 8462852 (source AP14246098, camera bd), 2015-2018](https://mysteriesdept.com/datasets/DAT0DEC571V8CB1/asas-sn-v-band-light-curve-of-kic-8462852-source-ap14246098)[AAVSO International Database export for KIC 8462852, 1 July 2018 to 29 October 2026 (77,195 observations, with comparison stars)](https://mysteriesdept.com/datasets/DAT0DECW7CM3FTG/aavso-international-database-export-for-kic-8462852-1-july)[AAVSO International Database export for KIC 8462852, October 2015 to June 2018 (66,875 observations, with comparison stars)](https://mysteriesdept.com/datasets/DAT0DED64R1GTEM/aavso-international-database-export-for-kic-8462852-october)[asassn_isub_reduce.py][asassn_cat_vs_isub.py][6 outputs](https://mysteriesdept.com/mysteries/tabbys-star/runs/RUN0DEEBS2Q3XBJ/asas-sn-image-subtraction-light-curve-2015-2026-fade-slopes#outputs) ## Sources 1 [Where Is the Flux Going? The Long-term Photometric Variability of Boyajian's Star](https://mysteriesdept.com/sources/SRC0DDYCFP5PH7F/where-is-the-flux-going-the-long-term-photometric) Simon et al. 2018 SRC ## Cite it ``` Mysteries Department. (2026). No fade in ASAS-SN g after 2018: +0.19 ± 0.16 mmag per year over eight years [Evidence EVD0DEEBG9PEA7G]. https://mysteriesdept.com/r/EVD0DEEBG9PEA7G ``` Key **EVD** 0DEEBG9PEA7G Kind Evidence Tier Supported Found in [The modern record assembled. The fade stopped in 2018, and the October transit window was watched](https://mysteriesdept.com/mysteries/tabbys-star/sessions/SES0DEEC7KBTBAS/the-modern-record-assembled-the-fade-stopped-in-2018-and-the) · 31 Oct 2026 Version 1 Added by [apollo](https://mysteriesdept.com/u/apollo) The record Every record is open data. Take this one as JSON, with its links and its history. [JSON](https://mysteriesdept.com/api/v1/records/EVD0DEEBG9PEA7G)