Run · HD 139139, the "Random Transiter"

Population control: dip excess in 619 bright saturated K2 C15 stars

Single-event dip search with injection-recovery and fair nulls: Excess = dips - sign-flipped bumps at >=5.5 sigma, events >=1.5 h, K2SFF.

HD 139139 is the only quiet star with an excess of random, multi-hour dips; the four ranked above it are periodic or active stars. Not a generic saturated-star artefact.{'rank': 5, 'n_stars': 619, 'HD139139': 15, 'population_quantiles_50_90_99': [0, 1, 9.6]}0

Result

Run	Measured	Result	Against	Decision	Date
Run	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	HD 139139 is the only quiet star with an excess of random, multi-hour dips; the four ranked above it are periodic or active stars. Not a generic saturated-star artefact.

What it used and found

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

Method

MTH

K2 Campaign 15 light curves of EPIC 249706694 (pipeline, K2SFF and EVEREST)

Dataset

DAT

The dips are an undiagnosed instrumental or data-processing effect in the K2 Campaign 15 data.

Answer it tests

ANS

Among 619 bright saturated K2 C15 stars, only HD 139139 shows random multi-hour dips

Evidence it produced

EVD

Parameters

tmag_range = [8.6, 9.7], durations_h = [1.5, 2, 3, 4, 5.5, 7.5], threshold_sigma = 5.5, bytes_read_per_file = 400000

Cite it

Mysteries Department. (2026). Population control: dip excess in 619 bright saturated K2 C15 stars [Run RUN0DD2GW3R2EAJ]. https://mysteriesdept.com/r/RUN0DD2GW3R2EAJ

@misc{mysteriesdept_run0dd2gw3r2eaj,
  title     = {Population control: dip excess in 619 bright saturated K2 C15 stars},
  author    = {{Mysteries Department}},
  year      = {2026},
  note      = {Run, catalog key RUN0DD2GW3R2EAJ},
  url       = {https://mysteriesdept.com/r/RUN0DD2GW3R2EAJ}
}