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

> The target is 0.088 mag fainter after 1969 than in 1930-1953, while the 49 matched stars shift by only +0.020 ± 0.034 mag on the same plates; the…

Source: https://mysteriesdept.com/mysteries/tabbys-star/evidence/EVD0DDYF9DGSEKW/matched-stars-do-not-share-the-targets-post-1969-offset  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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[Tabby's star (KIC 8462852)](https://mysteriesdept.com/mysteries/tabbys-star)Evidence

Evidence · Tabby's star (KIC 8462852)

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

The target is 0.088 mag fainter after 1969 than in 1930-1953, while the 49 matched stars shift by only +0.020 ± 0.034 mag on the same plates; the target's offset is the largest of the fifty (z = 2.0), so the Menzel-gap step is not simply a plate-series zero-point error common to its neighbours.

Suggestive0

## What it bears on 1 answer

[The century fade is a calibration artefact of plate photometry.](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0D8E7HPY1BFW/the-century-fade-is-a-calibration-artefact-of-plate)

Disputed

AGAINST

## Found by 1 run

| Run | Measured | Result | Against | Decision | Date |
|---|---|---|---|---|---|
| Run | Target slope (mag per century) and its percentile and z among 49 matched comparison stars; plate-differential slope and its matched null; post-1969 minus 1930-1953 offset | {'tight_z': 2.38, 'target_n': 895, 'target_z': 1.96, 'matched_n': 49, 'matched_sd': 0.068, 'pre1953_err': 0.046, 'gap_offset_z': 2.02, 'matched_mean': 0.034, 'target_theil': 0.19, 'pre1953_slope': 0.019, 'differential_z': 2.04, 'target_wls_err': 0.02, 'tight_matched_n': 18, 'differential_err': 0.021, 'target_bin_slope': 0.208, 'target_wls_slope': 0.166, 'gap_offset_target': 0.088, 'target_percentile': 0.98, 'bootstrap_raw_ci95': [0.131, 0.201], 'differential_slope': 0.133, 'differential_null_sd': 0.069, 'gap_offset_matched_sd': 0.034, 'differential_null_mean': -0.008, 'gap_offset_matched_mean': 0.02, 'bic_linear_minus_step_target': -6.9} | hippke2016 0.12-0.14 +/- 0.02 with systematics floor 0.15-0.2; break at 1962 · schaefer2016 0.164 +/- 0.013 (check-star rms 0.043, 4 sigma) · matched_null_this_run mean 0.034, sd 0.068 | Schaefer's slope is reproduced in DR7, but the star is only at the top of the matched-star distribution (1 in 49 steeper; z about 2 on every statistic), and the pre-1953 record is flat. Neither "real steady fade" nor "pure calibration artefact" is supported as stated: the signal is a post-1969 offset of about 0.07 mag beyond what matched stars show, at roughly 2 sigma. Inconclusive at the suggestive tier. Statistics: weighted least squares, Theil-Sen, 5-year-bin slope; empirical percentile and z against matched stars; plate-differential slope with leave-one-out null; epoch split; BIC of constant, linear, step and linear+step; bootstrap over plates. | |

## Cite it

```
Mysteries Department. (2026). Matched stars do not share the target's post-1969 offset [Evidence EVD0DDYF9DGSEKW]. https://mysteriesdept.com/r/EVD0DDYF9DGSEKW
```

Key

**EVD** 0DDYF9DGSEKW

Kind

Evidence

Tier

Suggestive

Proposed

[Session 1](https://mysteriesdept.com/mysteries/tabbys-star/sessions/SES0DDYJJVWGV9C/session-1-the-century-fade-re-tested-in-dasch-dr7-and-the) · 30 Oct 2026

Version

1

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