Measurements

FLITS reports measurements from the current prepared session state.

The Prepare tab groups selection readiness, headline measurements, timing details, and uncertainty flags. These values come from the GBT guided workflow; its absolute TOA fields are not part of the validated reference calculation.

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.

Uncertainties, and what FLITS will not claim

Every reported quantity carries its own uncertainty and its own classification of what that uncertainty means. FLITS distinguishes two cases, and refuses to blur them:

Classification	Meaning
formal_1sigma	The statistical term and the systematic terms it needs were both available, and are combined in quadrature. This is a complete 1-sigma uncertainty.
statistical_only	Only the statistical (radiometer-noise) term is known. The systematic contribution is missing, so the stated value is a lower bound on the true uncertainty.

For flux-like quantities the systematic term that matters is the fractional uncertainty on the SEFD. Supply it as sefd_fractional_uncertainty when opening the session:

session = BurstSession.from_file(
    "burst.fil",
    dm=527.65,
    sefd_jy=10.0,
    sefd_fractional_uncertainty=0.1,  # 10% SEFD uncertainty
)

Without it, FLITS still reports a fluence — the statistical part is real and useful for relative comparisons — but marks it not publishable and records why. A fluence quoted from a statistical_only result understates its uncertainty, often by a large factor, because SEFD uncertainty typically dominates.

Each quantity also records the basis of its uncertainty in words: which noise reference was used, and which terms were combined. That text is carried into exports, so a number in a table can be traced back to how it was derived without rerunning anything.

Distance-dependent quantities behave the same way: isotropic energy needs distance_fractional_uncertainty before it is reported as a formal uncertainty.

Check the flags before quoting a number

measurement_flags records what was missing or suspect — missing_sefd, missing_sefd_fractional_uncertainty, edge_clipped and others. They are the fastest way to see whether a value is ready to use.

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.

Width methods normally run the configured off-pulse Monte Carlo uncertainty trials. Large population pipelines that calibrate uncertainties end-to-end can set WidthAnalysisSettings(uncertainty_trials=0) to compute the width values without this per-burst bootstrap. Such results carry the uncertainty_disabled quality flag and do not report a width uncertainty.