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Measurements

FLITS reports measurements from the current prepared session state.

Core outputs

The measurement workflow can report:

  • fluence in Jy ms, when an SEFD is available
  • peak flux density in Jy, when an SEFD is available
  • event duration in ms
  • spectral extent in MHz
  • peak-bin topocentric/source-header TOA (toa_peak_topo_mjd)
  • infinite-frequency topocentric TOA (toa_inf_topo_mjd) when FLITS knows the dedispersion reference frequency
  • barycentric infinite-frequency TDB TOA (toa_inf_bary_mjd_tdb) when source position, observatory location, and time-scale metadata are complete
  • one-dimensional Gaussian fits for selected burst regions

Calibration note

Flux and fluence require calibration information. If FLITS can identify a known observing setup, it may provide a default SEFD. Otherwise use the generic preset or specify an SEFD explicitly.

Without an SEFD, FLITS can still report selection- and timing-related outputs, but not calibrated flux-density values.

Provenance matters

Measurements depend on:

  • the event window
  • manual peaks, when they fall inside the selected event window
  • the off-pulse definition
  • the selected spectral extent
  • the applied channel mask
  • the current DM and reduced analysis state
  • timing metadata: source position, observatory location, time scale, time reference frame, and dedispersion reference frequency

Interpret exported values together with the stored provenance, not as context-free numbers.

TOA Timing Chain

FLITS V1 still uses a peak-bin estimator for TOA. The primary value is the time of the strongest event-window bin, or a manual peak only when that manual peak is inside the current event window. toa_topo_mjd and mjd_at_peak are retained as compatibility aliases for toa_peak_topo_mjd.

The infinite-frequency correction subtracts the cold-plasma dispersion delay from the finite dedispersion reference frequency to infinity:

delay_ms = 1000 * DM / (2.41e-4) * reference_frequency_mhz^-2

This value is reported as dispersion_to_infinite_frequency_ms. The correction is only applied when FLITS can identify a trustworthy reference frequency. For ordinary FLITS integer-bin dedispersion this is the highest channel frequency. Public CHIME catalog waterfalls are treated conservatively: their public file format does not by itself prove the reference frequency, so FLITS leaves the infinite-frequency TOA unavailable unless stronger metadata are supplied.

The barycentric value uses Astropy Time, EarthLocation, and SkyCoord to add the Solar-System barycentric light-travel-time correction to the infinite- frequency topocentric TOA, then reports the result in TDB. It requires:

  • source RA and Dec in ICRS decimal degrees
  • a complete observatory longitude, latitude, and height
  • a supported input time scale: UTC, TDB, TT, or TAI
  • topocentric input times

If a header says the data are already barycentric or pulsarcentric, FLITS does not apply another barycentric correction. The measurement payload records toa_status and toa_status_reason so exports show whether the chain stopped at the peak-bin value, reached infinite-frequency topocentric timing, or reached barycentric TDB timing.

These corrected TOAs are useful for consistent reporting, but they are still resolution-limited because the V1 estimator is the selected time bin, not a centroid, template, or likelihood-model TOA with a formal statistical uncertainty.

Event duration versus burst width

The event duration is the manually selected event-window span. It is useful session metadata, but it is not automatically the same thing as a model-independent burst-duration estimate or the same thing as a fitted component width.