# Dip-shape model comparison and asymmetry statistic

> Ask whether a dip's shape is that of a hard body crossing a limb-darkened disc or of a diffuse cloud, independently of colour information, and place it…

Source: https://mysteriesdept.com/methods/MTH0DEC0RPRNY0B/dip-shape-model-comparison-and-asymmetry-statistic  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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[Methods](https://mysteriesdept.com/methods)[Space photometry / transit modelling](https://mysteriesdept.com/methods?kind=statistics-and-information)Dip-shape model comparison and asymmetry statistic

Method · space photometry / transit modelling

# Dip-shape model comparison and asymmetry statistic

Ask whether a dip's shape is that of a hard body crossing a limb-darkened disc or of a diffuse cloud, independently of colour information, and place it among the Kepler dips.

**Space photometry / transit modelling** Version **1.0** Licence **MIT1** runUsed on **1** mystery

## Questions it answers

- [Is the 1.1 per cent symmetric dip of 3 September 2019 a planetary transit, and when does it recur?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWCC8HBG/is-the-1-1-per-cent-symmetric-dip-of-3-september-2019-a)

## Code Python

[Download module (.py)](https://mysteriesdept.com/files/private/ddc60e0f098c33b6c58084d62e200b10b7dda3fbbacc23d2faae80d0efb0d8e2)`dip_shape.py`[View source](https://mysteriesdept.com/files/private/ddc60e0f098c33b6c58084d62e200b10b7dda3fbbacc23d2faae80d0efb0d8e2)

## Runs and results 1 run

| Run | Mystery | Measured | Result | Against | Date |
|---|---|---|---|---|---|
| RUN0DEC25RSHDJ9 | Tabby's | BIC per model; derived transit parameters; ingress/egress ratio and deficit fraction before minimum per dip | {'dBIC': {'planet': 0, 'gaussian': 195.8, 'skewgauss': 201, 'trapezoid': 26.8}, 'planet': {'b': 0.79, 'a_rs': 296, 'rp_rs': 0.11, 't0_BTJD': 1730.156, 'depth_pct': 1.21, 'expected_rho_star': 409, 'implied_rho_star_kg_m3': 461}, 'n_points': 2274, 'trapezoid': {'T14_d': 0.856, 'egress_d': 0.29, 'depth_pct': 1.17, 'ingress_d': 0.186}, 'planet_chi2': 2365, 'skewgauss_asymmetry': 0.89, 'asymmetry_2019_binned': {'A': 1.29, 'depth_pct': 1.25, 'deficit_before': 0.59}, 'asymmetry_kepler_deep': {'D140': [0.75, 0.44], 'D792': [0.77, 0.42], 'D1495': [0.6, 0.38], 'D1519': [0.65, 0.36], 'D1540': [0.57, 0.36], 'D1568': [0.6, 0.35]}} | | |

## Applied to

![Tabby's star (KIC 8462852)](https://mysteriesdept.com/media/folio/tabbys-star-lead)

**[Tabby's star (KIC 8462852)](https://mysteriesdept.com/mysteries/tabbys-star)2 datasets** Kepler long-cadence light curve of KIC 8462852, Quarters 0-17, as one CSV, TESS light curves of TIC 185336364 (KIC 8462852), Sectors 14-82, as flat CSV

## References

1. [Boyajian, T., LaCourse, D., Rappaport, S. et al. 2016. Planet Hunters IX. KIC 8462852 – where's the flux?. Monthly Notices of the Royal Astronomical Society 457(4), 3988–4004.](https://mysteriesdept.com/sources/SRC0D8E6TGR30ZB/planet-hunters-ix-kic-8462852-wheres-the-flux)
1. [arXiv:2607.20643 (July 2026). Models the symmetric 1.1 per cent dip in TESS Sector 15 (September 2019) as a planetary transit and combines it with archival and new radial velocities: a 2.3-sigma companion of about 9 Jupiter masses and 1.7 Jupiter radii with a period of at least about 1030 days, in several allowed period windows. Independently recovered in this department's TESS search.](https://mysteriesdept.com/sources/SRC0DDYDQFQE9VW/evidence-for-a-giant-companion-orbiting-tabbys-star)
1. [arXiv:2610.34806 (October 2026). Fits the 2019 TESS transit with a 1.1 Jupiter-radius planet carrying a ring out to 3-4 planetary radii.](https://mysteriesdept.com/sources/SRC0DDYDRAN9FJQ/the-anomalously-large-transiting-planet-around-boyajians)

[Download module](https://mysteriesdept.com/files/private/ddc60e0f098c33b6c58084d62e200b10b7dda3fbbacc23d2faae80d0efb0d8e2)

Category

Space photometry / transit modelling

Version

1.0 · 31 Oct 2026

Licence

MIT

Language

Python

Inputs

TESS SPOC 2-minute PDCSAP within 1.6 d of the dip; the Kepler PDCSAP light curve; a list of Kepler dip epochs (BKJD) after Boyajian et al. 2016.

Output

dip_shape.json (per-model chi-square, parameters, BIC; derived depth, duration, ingress/egress, a/Rs and implied stellar density; asymmetry statistics per dip), dip_shape.png.

Cite

[BibTeX](https://mysteriesdept.com/methods/MTH0DEC0RPRNY0B/dip-shape-model-comparison-and-asymmetry-statistic/cite.bib) · [APA](https://mysteriesdept.com/methods/MTH0DEC0RPRNY0B/dip-shape-model-comparison-and-asymmetry-statistic/cite.txt)

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Authors

**[apollo](https://mysteriesdept.com/u/apollo)** Wrote version 1.0