# Single-event dip search with injection-recovery and fair nulls

> Test whether HD 139139's 2017 dips recur in later photometry, and whether dips like them are common in other bright K2 stars. Run 3 times on the site…

Source: https://mysteriesdept.com/methods/MTH0DD2FEM3PXJB/single-event-dip-search-with-injection-recovery-and-fair  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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[Methods](https://mysteriesdept.com/methods)[Astronomy: time-series photometry](https://mysteriesdept.com/methods?kind=statistics-and-information)Single-event dip search with injection-recovery and fair nulls

Method · astronomy: time-series photometry

# Single-event dip search with injection-recovery and fair nulls

Test whether HD 139139's 2017 dips recur in later photometry, and whether dips like them are common in other bright K2 stars.

**Astronomy: time-series photometry** Version **1.0** Licence **MIT3** runsUsed on **1** mystery

## Questions it answers

- [Are the 28 dips real changes in starlight, or an instrumental effect?](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79RZW80KRQ/are-the-28-dips-real-changes-in-starlight-or-an-instrumental)
- [Do the dips still occur?](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79S0KP69RV/do-the-dips-still-occur)

## Code Python

[Download module (.py)](https://mysteriesdept.com/files/private/597e9be6c9dfa3ab55e819a2224212c6ddf3f96082a45cda46156b2ef2625df9)`dips.py`[View source](https://mysteriesdept.com/files/private/597e9be6c9dfa3ab55e819a2224212c6ddf3f96082a45cda46156b2ef2625df9)

## Runs and results 3 runs

| Run | Mystery | Measured | Result | Against | Date |
|---|---|---|---|---|---|
| RUN0DD2GVJ41GHK | HD | Dips vs sign-flipped bumps at >=5.5 sigma; published dips recovered | {'EVEREST': [19, 4], 'K2SFF_all': [23, 12], 'K2SFF_ge1.5h': [21, 6], 'recovered_K2SFF': 22, 'recovered_EVEREST': 17} | Sign-flipped search with symmetric outlier handling | |
| RUN0DD2GVRRESBS | HD | Per-dip completeness and expected detections at the K2 rate (>=4.5 sigma); detections in real data | {'candidate': {'btjd': 3778.5485, 'depth_ppm': 507, 'duration_h': 2.24, 'depth_err_ppm': 105}, 'expected_A': 0.44, 'expected_B': 0.7, 'completeness_A': 0.094, 'completeness_B': 0.149, 'fap_independent': '0.5-2%', 'real_detections': 1} | Noise-only false alarms at >=4.5 sigma: 0.014 per 13.5 d (circular-shift null) · independent check with white and phase-randomised nulls gives FAP 0.6-1.6% for the candidate | |
| RUN0DD2GW3R2EAJ | HD | Excess = dips - sign-flipped bumps at >=5.5 sigma, events >=1.5 h, K2SFF | {'rank': 5, 'n_stars': 619, 'HD139139': 15, 'population_quantiles_50_90_99': [0, 1, 9.6]} | The same statistic across 619 stars of Tmag 8.6-9.7 in C15 | |

## Applied to

![HD 139139, the "Random Transiter"](https://mysteriesdept.com/media/folio/hd-139139-random-transiter-lead)

**[HD 139139, the "Random Transiter"](https://mysteriesdept.com/mysteries/hd-139139-random-transiter)3 datasets** K2 Campaign 15 light curves of EPIC 249706694 (pipeline, K2SFF and EVEREST), TESS Sector 91 full-frame-image light curves at the position of HD 139139 (2025), Table of the 28 transit-like events (times, durations, depths)

## References

1. [Rappaport, S., Vanderburg, A., Kristiansen, M. et al. 2019. The Random Transiter – EPIC 249706694/HD 139139. Monthly Notices of the Royal Astronomical Society 488(2), 2455–2465.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)
1. [Alonso, R., Hoyer, S., Deleuil, M. et al. 2023. No random transits in CHEOPS observations of HD 139139. Astronomy & Astrophysics 680, A78.](https://mysteriesdept.com/sources/SRC0D79RXE47SN4/no-random-transits-in-cheops-observations-of-hd-139139)

[Download module](https://mysteriesdept.com/files/private/597e9be6c9dfa3ab55e819a2224212c6ddf3f96082a45cda46156b2ef2625df9)

Category

Astronomy: time-series photometry

Version

1.0 · 29 Oct 2026

Licence

MIT

Language

Python

Inputs

A light curve (time, flux, quality); the 27 non-suspect dips of Rappaport et al. 2019 Table 1 for injection.

Output

Dip candidates with time, duration, depth and significance; completeness by depth and duration; expected detections at the K2 rate; false-alarm counts.

Cite

[BibTeX](https://mysteriesdept.com/methods/MTH0DD2FEM3PXJB/single-event-dip-search-with-injection-recovery-and-fair/cite.bib) · [APA](https://mysteriesdept.com/methods/MTH0DD2FEM3PXJB/single-event-dip-search-with-injection-recovery-and-fair/cite.txt)

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Authors

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