Research session · Tabby's star (KIC 8462852)

Session 1: The century fade re-tested in DASCH DR7, and the TESS record read to 2024

A matched-comparison re-analysis of KIC 8462852 in DASCH Data Release 7 reproduces Schaefer's 0.17 mag per century slope but places the star only about 2 sigma above 49 comparison stars of the same brightness and colour, with a flat record before 1953; a 3-day-window search of TESS recovers the 1.1 per cent dip of 3 September 2019 and finds nothing in the 2024 sectors; the literature on the fade and the dips was completed through October 2026 and three questions were added.

Session 130 Oct 2026Analysis0

What it concluded

The century fade is a 2-sigma result in DR7: reproduced, top of the matched distribution, but flat before 1953 and concentrated in a post-1969 offset that independent archives dispute. TESS shows no structured dips 2019-2024 but one symmetric 1.1 per cent event in 2019 that needs a recurrence test.

What it left open

Gaia DR3 neighbour screen and rerun
Colour-term stratified fit on DR7 exposures
Per-plate differential with platephot (API key)
Cross-archive step test (Sonneberg, Sternberg, Maria Mitchell)
Transit-window table for the 2019 dip vs TESS coverage
Sector 75 light curve from FFIs
2018-2026 ground record (AAVSO, ASAS-SN v1) by hand

Questions raised 3

Did the slow fade continue, stop or reverse after 2018?

QST

Do the independent plate archives (Sonneberg, Sternberg, Maria Mitchell) agree with Harvard about the star's brightness from 1934 to 1990?

QST

Is the 1.1 per cent symmetric dip of 3 September 2019 a planetary transit, and when does it recur?

QST

Answers proposed 1

A single drop of about 0.1 mag across the 1953-1969 plate gap, not a steady century fade

ANS

Evidence found 10

A 1.1 per cent symmetric dip on 3 September 2019 in TESS Sector 15

EVD

Both halves of the Harvard record are flat and the offset between them is not shared by matched stars

EVD

DR7 reproduces the 0.17 mag/century slope and the target is the steepest of 49 matched stars

EVD

Maria Mitchell Observatory plates give an independent +0.12 mag/century

EVD

Matched constant stars in DR7 scatter by 0.07 mag/century and share a +0.03 drift

EVD

Matched stars do not share the target's post-1969 offset

EVD

No dips to 0.5 per cent in the 2024 TESS sectors (81 and 82)

EVD

Sonneberg and Sternberg plates show the star constant to 0.03 mag/century

EVD

Sonneberg plates covering 1934-1995 show no step and no fade

EVD

The pre-1953 record is flat; the slope comes from the post-1969 offset

EVD

Runs 2

DASCH DR7 matched-comparison slope test of KIC 8462852, margin 1.0 mag

RUN

TESS dip search and injection-recovery, Sectors 14-82, including the 2024 sectors

RUN

Sources consulted 8

A Search for the Long-term Dimming of KIC 8462852 on Maria Mitchell Observatory Plates, 1922-1991

SRC

DASCH: Bringing 100+ Years of Photographic Data into the 21st Century and Beyond

SRC

Evidence for a giant companion orbiting Tabby's star

SRC

Revisiting orbital recurrence in the dimmings of Boyajian's star (KIC 8462852)

SRC

Sonneberg plate photometry for Boyajian's Star in two passbands

SRC

The Stability of F-star Brightness on Century Timescales

SRC

The anomalously large transiting planet around Boyajian's star: evidence for a circumplanetary ring

SRC

Where Is the Flux Going? The Long-term Photometric Variability of Boyajian's Star

SRC

Cite it

Mysteries Department. (2026). Session 1: The century fade re-tested in DASCH DR7, and the TESS record read to 2024 [Research session SES0DDYJJVWGV9C]. https://mysteriesdept.com/r/SES0DDYJJVWGV9C

@misc{mysteriesdept_ses0ddyjjvwgv9c,
  title     = {Session 1: The century fade re-tested in DASCH DR7, and the TESS record read to 2024},
  author    = {{Mysteries Department}},
  year      = {2026},
  note      = {Research session, catalog key SES0DDYJJVWGV9C},
  url       = {https://mysteriesdept.com/r/SES0DDYJJVWGV9C}
}