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Tabby's star (KIC 8462852)Research sessionsSession 4
Research session 4 · Tabby's star (KIC 8462852)

A fourth plate archive and a twenty-year light curve

The public historical data not yet used were brought in: the APPLAUSE DR4 plate archive (Hamburg and Bamberg, 1915-1981) and the full ASAS 2006-2017 table hidden in the arXiv source of Simon et al. 2018. APPLAUSE was reduced against the same comparison stars as DASCH. ASAS was joined to ASAS-SN and AAVSO to make one V light curve from 2006 to 2026.

Session 42 Nov 2026Data gathering and confirmatory2 runs4 evidence2 figures
Session 3 · The modern record assembled. The fade stopped in 2018, and the October transit window was watchedLatest session · all 4

Going in the sweep before the work

What changed since Session 331 Oct 2026, 16:19 → 26 Oct 2026, 11:58
0datasets added
0sources added
0news stories matched
0duplicates or retired records
STEP

In brief

  1. APPLAUSE plates show the star about 0.15 mag fainter after 1969 than before 1953, beyond 95 per cent of matched comparison stars and with the same sign as Harvard. The shape is flat-step-flat, but at about 1.4 sigma, with era and equipment confounded, it is suggestive only. If real, the drop happened by about 1955.
  2. On one scale from 2006 to 2026, the star's two fading episodes (2011-2013, 2015-2018) coincide with its two dip episodes. It recovered after each, and has been flat through the dip-free years since 2019. That points to one dust supply behind both, and argues against a monotonic relaxation.
What this changes: The century-fade question gains a second archive supporting a single 1950s drop (suggestive) and evidence against a steady fade. The slow-fade question gains a dip-fade link that favours diffuse dust and counts against a planet-engulfment relaxation.

What movedNo question changed standing

Most likelyunchanged
Openunchanged
No evidence yetunchanged

What's next1 step set · 1 done · ranked

1
Request Maria Mitchell per-plate data
Could shiftFair odds~5 h
On: Did the star fade over the twentieth century?
16score
Details

Ask Castelaz (Brevard College; APDA at PARI) for the per-plate magnitudes of the 835 Maria Mitchell plates, or the digitised cut-outs, and re-reduce them against the DASCH and APPLAUSE matched stars, testing for a 1950-1970 step.

Done this session
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.
On: Did the slow fade continue, stop or reverse after 2018?

Next steps live on their questions, where anyone can take one up. Ranked by how likely each is to move a key question, for the time it takes.

What was done

  1. APPLAUSE access. The archive's TAP service is reachable from the workspace but cancels statements after about 5 seconds. Cone searches and some plate queries time out. Lookups by Gaia ID are indexed, so the DASCH comparison sample (target, 64 matched, 120 control) was given Gaia DR3 IDs from the Session 2 screen, and every detection of those stars was fetched by ID in cached batches. The result is 16,639 detections on 718 plates. 45 of the stars are covered (DAT0DFQ1389EQ9V). The archive's own paper is now a source [@enke2024applause].

  2. APPLAUSE reduction (MTH0DFQ1D4C7MWE, RUN0DFQ2HNJMYAC). Three versions were tried before one could be trusted:

    • Per-telescope zero points gave a spurious +0.29 step, because comparison-star zero points included plates without the target.
    • Per-system zero points (telescope, filter, emulsion) are blind to change between systems by construction.
    • APPLAUSE's own Gaia residual exists only for its calibration stars, of which the target is one.

    The adopted version rebuilds the archive's synthetic magnitude, RP + colour term × (BP − RP), from Gaia DR3 for every star. Each star then has one zero point, and the target is ranked against the comparison stars on the same plates. Step +0.154 mag, null 0.01 ± 0.10, 5th percentile. The step holds at +0.13 to +0.18 across comparison sets and cuts (EVD0DFQ1YQEBVM8), and the record is flat within each era (EVD0DFQ249YD49D). Within single telescopes the checks disagree, and no system spans the change.

Figure 1

APPLAUSE puts the star 0.15 mag fainter from 1955 on, beyond 95% of matched comparison stars

Step after 1969 minus before 1953 (mag; positive = fainter): KIC 8462852 under each analysis choice, and the comparison-star null

00.050.10.150.2magall compsmatched onlycontrol onlyerr < 0.25err < 0.5classifier > 0.9per-system zero pointscomparison starsp 0.05p 0.08p 0.04p 0.03p 0.07p 0.03blind to era change±0.10
00.050.10.150.2magall compsmatched onlycontrol onlyerr < 0.25err < 0.5classifier …per-system …comparison …
step
p is the fraction of comparison stars with a step at least as large. The per-system version cannot see a change between telescopes or emulsions, and every change of era in APPLAUSE is one.
Drawn by the site

  1. ASAS table. The journal shows only a stub, but the arXiv source of Simon et al. carries all 496 ASAS V points, 2006-2017 [@simon2018where]. They are on the site as DAT0DFQ146NH581.

  2. Twenty-year stitch (MTH0DFQ1DSTJHRR, RUN0DFQ2NQVEE44). ASAS is tied to ASAS-SN V over 2015-2017 (offset -3 mmag), AAVSO to ASAS-SN V over 2015.7-2018.9, and ASAS-SN g to AAVSO over 2018-2026 (season rms 4 mmag). The star faded 47 ± 5 mmag from the 2010 to the 2013 season and recovered 34 ± 7 by 2015. It faded about 10 mmag to 2018 and has been flat since. Both fades overlap dip episodes (EVD0DFQ24NXSGHG). The recovery is against a one-way relaxation after swallowing a planet (EVD0DFQ25HE60E9).

Figure 2

Two fades in twenty years, each while the star was dipping

Seasonal median V relative to 2007 (mmag; positive = fainter)

-1001020304050mmag200720092010201120122013201420152016201720182020202220242026D800D15002017 dips
-1001020304050mmag200720092010201120122013201420152016201720182020202220242026
seasonal median
ASAS to 2015, ASAS-SN V 2015-2018, AAVSO V from 2019; ASAS seasonal errors 3-9 mmag.
Drawn by the site
  1. Not public. Sonneberg's plates are digitised but not served, so the per-plate magnitudes must be requested from Hippke et al. or the observatory. The Maria Mitchell plates sit in the APDA archive at PARI, and the per-plate table must be requested from Castelaz.
Runs 2
RunMeasuredResultAgainstDecision
APPLAUSE DR4: the 1950s-1970s step tested against matched comparison stars on 151 plates · 1 figureMedian differential after 1969 minus before 1953 (mag), ranked among comparison starsDASCH_DR7_step +0.09 (about 2 sigma vs matched stars) · Sonneberg_Hippke2017 constant to 0.03-0.04 mag/century · Enke2024_APPLAUSE_global no decade-scale variationSuggestive support for a single drop. The step is the same sign as DASCH and larger, and lies beyond 95% of comparison stars in every comparison set and cut. It is not decisive: the honest error is ±0.10 mag, every change of era is also a change of telescope or emulsion, the within-telescope checks split, and per-system zero points erase it by construction. If real, the drop happened by about 1955.
The 2006-2026 V light curve on one scale: two fading episodes, both during dip episodes · 1 figureSeasonal median V on the ASAS-SN V scale (mmag relative to the 2007 season)Simon2018 brightenings 2007 and 2014, fade 6.3 mmag/yr 2015-2017 · Montet2016_Kepler about 3% fade 2009-2013Two fading episodes (2011-2013 and 2015-2018) coincide with the two dip episodes (Kepler Q8 and Q16-17; 2017). Recovery followed each. The star has held flat through the dip-free years 2019-2026. Suggestive of one dust supply behind both the dips and the slow changes. The recovery is against a monotonic relaxation.
Answers proposed 2
MTH
MTH
Answers taken up again 3
QST
QST
QST
Evidence found 4
EVD
EVD
EVD
EVD
Used: datasets 2
DAT
DAT
Used: sources 1
SRC
Consulted: sources 1
SRC
Produced: datasets 2
DAT
DAT

Cite it

Mysteries Department. (2026). Session 4: A fourth plate archive and a twenty-year light curve [Research session SES0DFQ3P4VQQSX]. https://mysteriesdept.com/mysteries/tabbys-star/sessions/SES0DFQ3P4VQQSX/session-4-a-fourth-plate-archive-and-a-twenty-year-light
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