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Pipeline Overview

QuickLook produces a 9-panel diagnostic figure. This page explains what each panel shows and how the pipeline works.

Pipeline steps

Target name
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1. Resolve target (ExoFOP-TESS -> TIC ID, coordinates, known ephemeris)
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2. Download light curve (MAST via lightkurve)
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3. Sigma-clip outliers from raw light curve
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4. Flatten/detrend (wotan biweight filter by default)
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5. Generalized Lomb-Scargle periodogram (stellar rotation)
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6. Transit Least Squares search (planet/companion detection)
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7. Download target pixel file (TPF)
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8. Query Gaia catalog for nearby sources
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9. Generate 9-panel diagnostic figure

The 9-panel figure

Top row -- Stellar variability

Panel 1: Raw light curve

The raw PDCSAP (or SAP) flux from the TESS pipeline, shown in blue. The red line is the best-fit trend from the detrending step (wotan biweight filter). This panel reveals stellar variability, systematics, and any obvious transit-like dips.

Panel 2: Lomb-Scargle periodogram

The Generalized Lomb-Scargle (GLS) periodogram of the raw light curve (with known transits masked). The peak corresponds to the stellar rotation period. High peaks indicate active or variable stars. The periodogram method can be changed to standard Lomb-Scargle (ls) or Box Least Squares (bls).

Panel 3: Phase-folded rotation

The raw light curve folded at the peak GLS period, showing the rotational modulation pattern. A clean sinusoidal shape suggests starspots rotating in and out of view.

Middle row -- Transit detection

Panel 4: Flattened light curve

The raw light curve divided by the trend (panel 1), producing a normalized, detrended light curve centered on 1.0. Red markers highlight data points inside detected transits (from the TLS search in panel 5). This panel is where transits are most visible.

Panel 5: TLS periodogram

The Transit Least Squares periodogram, which searches for periodic box-shaped (transit-like) dips. The y-axis is the Signal Detection Efficiency (SDE). The peak period is the best-fit orbital period. An SDE above ~8 is generally considered a significant detection.

Panel 6: Archival image + Gaia overlay

The TESS aperture (blue polygon) overlaid on an archival sky survey image (DSS by default). Orange and red circles show nearby Gaia sources, scaled by brightness. This panel helps identify:

  • Blended neighbors that could be the true source of the signal
  • Background eclipsing binaries contaminating the aperture
  • Crowded fields where photometric dilution is significant

Bottom row -- Transit characterization

Panel 7: Phase-folded transit (odd/even)

The flattened light curve folded at the TLS best-fit period and zoomed around the transit. Odd transits (red) and even transits (blue) are shown separately. The black line is the best-fit transit model. If odd and even depths differ significantly, the signal is likely an eclipsing binary rather than a planet.

Panel 8: Secondary eclipse check

The phase-folded light curve centered at phase 0.5 (halfway between transits). A dip here indicates a secondary eclipse, which is a strong sign of a self-luminous companion (eclipsing binary or high-albedo brown dwarf). The dashed horizontal line shows the primary transit depth for reference.

Panel 9: Summary panel

A text summary with:

  • Target identifiers (TIC, TOI, Gaia ID, coordinates)
  • Stellar parameters from ExoFOP (radius, mass, Teff)
  • TLS results (period, depth, duration, SDE)
  • Derived companion parameters (radius ratio, estimated radius)
  • SIMBAD object classification
  • Pipeline metadata (sector, cadence, runtime)

Detrending methods

QuickLook uses wotan for detrending. The default is biweight, but any wotan method can be used:

Method Description Best for
biweight Tukey's biweight (robust) General use (default)
cosine Cosine filtering Smooth trends
median Sliding median Simple systematics
mean Sliding mean Simple systematics
gp Gaussian process Complex variability (slow for short cadence)

Warning

GP flattening (--flatten_method gp) is not recommended for short-cadence data (exposure time <= 120s) due to computational cost.

Output files

When -save is used, QuickLook produces:

File Description
TARGET_sSECTOR_FLUX_CADENCE.png The 9-panel diagnostic figure
TARGET_sSECTOR_FLUX_CADENCE_tls.h5 HDF5 file with full TLS results

Example: WASP-21_s56_pdcsap_sc.png and WASP-21_s56_pdcsap_sc_tls.h5

The HDF5 file contains the TLS periodogram, best-fit parameters, stellar parameters, and metadata. Use read_tls to extract a summary CSV from a directory of these files.