Research note

Window QC on the sector 56 light curve

Cadence coverage, background, and centroid summaries for eight predicted transit windows in the HD 209458 b sector 56 light curve. Descriptive only.

The light curve for HD 209458 b, sector 56 has 20,079 input rows. After the quality mask and finite-value checks, 18,792 cadences remain. There are three gaps; the longest is 18,239.707002 s against a 180 s gap threshold, and those gaps contain 449 missing cadences.

This note looks at eight windows centred on predicted mid-transit times. Each window is centre - 0.5 d to centre + 0.5 d, inclusive. The half-width is a fixed diagnostic interval, not a fitted transit duration.

Coverage

All eight windows are full at 720 cadences except cycle 2323, which loses one cadence to the quality mask.

Background and centroid

The background is not flat across the sector. Median SAP_BKG in the eight windows ranges from 2,494.48 to 4,085.78 e-/s. The 5th to 95th percentile range is as small as 28.46 e-/s in cycle 2321 and as large as 1,933.81 e-/s in cycle 2320.

The centroid is stable at the quoted precision. Median MOM_CENTR1 is between 1,867.04 and 1,867.14 pixels, and median MOM_CENTR2 is between 357.56 and 357.62 pixels. Peak-to-peak scatter within a window is at most 0.027 pixels in either coordinate.

These are per-window summaries after the 175 quality mask. They are not calibrated astrophysical quantities and they are not a detrending model.

Limits

• The eight window centres are predicted mid-transit times read from the committed record. They are not measured transit times.
• No contamination ratio or nearby-source count is computed because no source catalogue is committed.
• No detrending, transit fit, folding, or timing measurement is performed.
• The record describes one target in one sector and does not establish data quality or a detectable transit.

Topics: light-curves, astronomy-methods, reproducibility