Occultation Step Candidates

Find discrete sampled flux-drop candidates at a supplied threshold; two steps are not by themselves evidence for an occulted binary.

Description

A sampled fractional flux drop can nominate an occultation step.

A sampled fractional flux drop can nominate an occultation step. Its time is the later sample's time, so cadence limits timing precision and two candidates alone do not establish a binary source.^[1]

Find discrete sampled flux-drop candidates at a supplied threshold; two steps are not by themselves evidence for an occulted binary.

When to use Occultation Step Candidates

Use this tool to find discrete sampled flux-drop candidates at a supplied threshold; two steps are not by themselves evidence for an occulted binary.

Prepare the source, detector or coordinate measurements. Confirm frame, epoch, angular units, axis directions and the stated RA proper-motion convention before entering values.

How to use Occultation Step Candidates and understand its results

Prepare the source, detector or coordinate measurements. Confirm frame, epoch, angular units, axis directions and the stated RA proper-motion convention before entering values.
Enter sampleTimesSeconds, fluxes, minimumFractionalDrop using the field table and calculation rules, then run the tool.
Read stepTimesSeconds, stepCount, twoStepCandidate. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
sampleTimesSeconds	Sample times seconds	list of number	Required
fluxes	Fluxes	list of number	Required
minimumFractionalDrop	Minimum fractional drop	number	Required

Enter aligned nonempty increasing times in seconds and strictly positive fluxes, plus a drop threshold in (0,1]. The tool checks adjacent samples, returns qualifying later-sample times and their count, and sets twoStepCandidate only for exactly two candidates. No candidates is a successful outcome.

Paired lists must be nonempty and have equal lengths. Sequences checked for increasing order must be nonempty and strictly increasing; additional calculation rules may require more samples.

drop_i=(flux_(i−1)−flux_i)/flux_(i−1); candidate if drop_i≥threshold

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
stepTimesSeconds	Step times seconds	list of number
stepCount	Step count	number
twoStepCandidate	Two step candidate	boolean

json

{
  "input": {
    "sampleTimesSeconds": [
      0,
      1,
      2,
      3,
      4
    ],
    "fluxes": [
      100,
      100,
      70,
      70,
      40
    ],
    "minimumFractionalDrop": 0.2
  },
  "output": {
    "stepTimesSeconds": [
      2,
      4
    ],
    "stepCount": 2,
    "twoStepCandidate": true
  }
}

Limitations and assumptions

No denoising, significance calculation, event interpolation or occultation model is applied. Zero flux is an input error in this implementation, and instrumental/noise steps can also qualify.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Occultation Stellar Angular Diameter: Estimate diameter from a central occultation-edge crossing and shadow speed, then angular size; diffraction, integration smearing and noncentral chords are excluded. For a complementary task, use Iterative Astrometric Sigma Clip: Iteratively clip residuals using recalculated sample standard deviation, retaining original indices and a bounded iteration count.

References

Occultation Step Candidates — tool.io

Similar or alternative tools

Occultation Stellar Angular Diameter
Estimate diameter from a central occultation-edge crossing and shadow speed, then angular size; diffraction, integration smearing and noncentral chords are excluded.
Iterative Astrometric Sigma Clip
Iteratively clip residuals using recalculated sample standard deviation, retaining original indices and a bounded iteration count.