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Guided Workflow: GBT Burst

This walkthrough follows a single GBT-L burst from loading through preparation, measurements, width comparison, DM optimization, temporal diagnostics, fitting, and export.

The example file is a SIGPROC filterbank from DIAG_FRB20240114A:

blc_s_guppi_60385_53711_DIAG_FRB20240114A_0057_1673.964_1675.753_b32_I0_D527_851_F256D_K_t30_d1.fil

The filename records D527_851, but this cutout is already dedispersed. Load it with DM = 0 in FLITS. Use the DM tab later only as a local residual/refinement diagnostic around zero.

1. Download the tutorial burst

mkdir -p tutorial-data
curl -L -o tutorial-data/flits-tutorial-gbt-frb20240114a-v1.fil \
  https://github.com/DirkKuiper/flits/releases/download/tutorial-data-v1/flits-tutorial-gbt-frb20240114a-v1.fil

For development checkouts that already have the ignored local data directory, the source file is:

data/GBT-L/blc_s_guppi_60385_53711_DIAG_FRB20240114A_0057_1673.964_1675.753_b32_I0_D527_851_F256D_K_t30_d1.fil

2. Start FLITS

flits --data-dir ./tutorial-data --host 127.0.0.1 --port 8123

Open http://127.0.0.1:8123.

In the loader:

  1. Select flits-tutorial-gbt-frb20240114a-v1.fil.
  2. Enter 0 for DM.
  3. Leave the preset on the detected GBT setting.
  4. Load the session.

Expected first-session checks:

  • 256 channels
  • full time span of about 423 ms
  • native sample time of 10.24 us
  • default plotted time bins reduced by x32, or 327.68 us
  • GBT calibration preset with 10 Jy SEFD
  • the bright burst is near 240 ms

Loaded GBT burst in the FLITS aligned viewer.

3. Prepare the burst

Use the Prepare controls to focus the analysis state before interpreting any numbers.

Set:

  • event window: 235 to 250 ms
  • off-pulse windows: 221 to 233 ms, and 248 to 259 ms
  • spectral window: 1300 to 1750 MHz
  • masks: optionally click 'Auto Mask' once

4. Compute measurements

Click Compute after the event, off-pulse, and spectral windows are set.

The exact values can shift slightly with selection quantization, but the result should be close to:

Quantity Expected value
Peak S/N ~36.5
Integrated event S/N ~93.4
Fluence ~5.4 Jy ms
Peak flux density ~0.95 Jy
Peak topocentric TOA ~60385.62166196854 MJD
Infinite-frequency topocentric TOA ~60385.62166196854 MJD
Barycentric TDB TOA ~60385.61773505590 MJD

Because the session DM is 0, the infinite-frequency correction is 0 ms and the peak and infinite-frequency topocentric TOAs are the same. The expected measurement flags are calibrated, acf, and missing_distance; the distance flag is normal unless you provide a distance or redshift.

Measurement summary for the prepared GBT burst.

5. Run a local DM sweep

Open the DM tab and run a DMphase sweep with:

  • center DM: 0
  • half range: 10.0
  • step: 0.5
  • metric: DMphase

Expected checks:

  • best DM near 5.41 pc cm^-3
  • sampled best DM near 5.5 pc cm^-3
  • fit status: dmphase_weighted_polyfit
  • residual status: ok

DMphase sweep and residual diagnostics for the prepared burst.

6. Export the session for reproducibility

Use Save Session in the sidebar after the event window, off-pulse windows, spectral window, mask state, measurements, and DM sweep are where you want them.

The saved JSON snapshot stores the interactive session state, not just the final values. FLITS writes it into a snapshots/ folder next to the source data so the analysis can be reopened later from Saved Sessions and inspected from the same crop, selection, masking, calibration, notes, and analysis state. Use Download JSON only when you need a portable copy outside the snapshot library.

Session panel with save, JSON, and saved-session controls.