# Second real TESS target: KELT-11 b, sector 9 Status: real public-data analysis record for human verification. This is not a detection, a discovery, or a timing result for publication. - Task: `jdp-tess-second-target` - Record generated (UTC): `2026-10-24T18:39:37Z` - Target: KELT-11 b (TIC 55092869), sector 9 - Docket position: 15 - TESS magnitude recorded in the docket: 7.3212 - Ephemeris reference: Mounzer et al. 2022 (2022), https://ui.adsabs.harvard.edu/abs/2022A&A...668A...1M/abstract - Machine-readable record: `research/tess-timing/data/second-target-run/analysis.json` - Folded table: `research/tess-timing/data/second-target-run/folded_lightcurve.csv` - Control record: `research/tess-timing/data/sector56-control-run/analysis.json` ## Why this target and sector The first real acquisition walked the committed docket, skipped rows below the 7.0 saturation guard, and stopped at docket position 14, HD 209458 b (TIC 420814525), sector 56. This run continues the same walk from the next row. Row 15 is KELT-11 b. Its first recorded sector, sector 9, returned one SPOC 120 s light curve and one SPOC target pixel file from the same observation, so the walk stopped there. Sector 9 is not the sector that the docket flags as postdating the ephemeris. The docket marks sectors 62, 89, and 100 for that one-sided date comparison. Sector 9 predates the 2022 reference year. This run therefore makes no sector-novelty claim and does not use sector 9 as evidence that the published ephemeris omitted an observation. ## Data provenance | Product | Filename | Bytes | SHA-256 | Source URL | | --- | --- | ---: | --- | --- | | lightcurve | `tess2019058134432-s0009-0000000055092869-0139-s_lc.fits` | 1,848,960 | `5b3be4a757da818466ee92fca8dad3bb3558191e9df98c01a9ad6044ccc1582d` | | | target-pixel-file | `tess2019058134432-s0009-0000000055092869-0139-s_tp.fits` | 52,562,880 | `e140ac21aa7b7ba9439f31da20b138301e49cc00e555a52ca2856e33822be0f9` | | Both FITS primary headers report TICID 55092869 and SECTOR 9. The files were downloaded by `research/tess-timing/scripts/fetch_products.py --download` through `scripts/acquire_second_target.py`, copied without editing or recompression, and hashed again after the copy. The acquisition record is `research/tess-timing/data/real-run-2/acquisition.json`. The control uses the committed sector 56 products: - `research/tess-timing/data/real-run/tpf.fits` SHA-256 `2b5bd6ee4747cfe0c5405c869b871064fd74e4b5f0521c4e6be9fdc2b5c96030` - `research/tess-timing/data/real-run/lightcurve.fits` SHA-256 `1b76b4a4b73e24954fa6e29a7e28a174685113ecdbad1bf10ef0e7b766ce99e9` ## Method The same stages and settings are applied to both targets. The only inputs that differ are the two target-sector product pairs and their published ephemerides. | Stage | Setting | Value | | --- | --- | --- | | Aperture | Threshold fraction of peak excess | 0.05 | | Aperture | Annulus radii (pixels) | 2.0 to 3.5 | | Aperture | Pairing tolerance | 60 s | | Quality | Mask value | 175 (bits 1, 2, 4, 8, 32, 128) | | Detrend | Running-median window | 1001 cadences | | Detrend | Sigma clip | 3.0 sigma, 3 iterations | | Detrend | In-transit mask | none | | Fit | Transit window | +/-0.5 d around the predicted epoch | | Fit | Period | fixed from the published ephemeris | | Fit | Limb darkening | u1 = 0.0, u2 = 0.0 (fixed method setting) | | Fit | Impact parameter | 0.0 (fixed method setting) | | Fit | Dilution | 0.0 (fixed method setting) | | Fold | Phase window | +/-0.6 d | | Fold | Bin width | 0.5 h | The full-sector fit path in `tess_timing.pipeline.run_target` is not used. One transit model applied to a whole sector would treat the other transits as outliers, and the transit-model integration makes that fit slow. The fit here is a single-transit fit at the predicted epoch. The published period and ephemeris choose the window, so the fitted mid-transit time is not an independent detection or a period measurement. ## Aperture and common-mask results | Quantity | KELT-11 b sector 9 | HD 209458 b sector 56 (control) | | --- | ---: | ---: | | Aperture pixels | 9 | 14 | | Annulus pixels | 27 | 23 | | Target pixel file cadences | 18,187 | 20,079 | | Aperture cadences retained | 16,923 | 19,612 | | Light-curve cadences retained | 15,783 | 18,792 | | Common-mask cadences | 15,783 | 18,792 | | SAP difference RMS (ppm) | 1619.6 | 790.6 | | PDCSAP difference RMS (ppm) | 2261.2 | 1019.4 | | SAP Pearson r | 0.822089 | 0.961576 | | PDCSAP Pearson r | 0.279758 | 0.933892 | The aperture series is a threshold aperture on the target pixel file, not a reimplementation of the SPOC pipeline. The difference RMS is a diagnostic on one common quality mask. ## Detrending results | Quantity | KELT-11 b sector 9 | HD 209458 b sector 56 (control) | | --- | ---: | ---: | | Input cadences | 15,783 | 18,792 | | Trend defined | 8,559 | 14,774 | | Trend undefined | 7,224 | 4,018 | | Clipped | 427 | 932 | | Long gaps | 7 | 4 | | Robust residual scatter (ppm) | 806.4 | 464.3 | | Trend span (ppm) | 8968.9 | 3168.4 | | Median aperture error (ppm) | 1.1e+04 | 8314.9 | | Raw flux scatter (ppm) | 2456.9 | 3156.6 | Both runs use the same 1001-cadence window and no in-transit mask. The KELT-11 b series has 7 long gaps recorded by the detrending step and a larger undefined fraction than sector 56. The trend is a running median, not a physical model. ## Single-transit fit | Quantity | KELT-11 b sector 9 | HD 209458 b sector 56 (control) | | --- | ---: | ---: | | Fit-window cadences | 703 | 720 | | Predicted epoch BTJD | 1553.813559 | 2840.878897 | | Fitted mid-transit BTJD | 1553.816219 | 2840.878747 | | Fitted mid-transit uncertainty (s) | 80.3 | 2.3 | | Offset from prediction (s) | 229.8 | -13.0 | | Offset in reported sigma | 2.86 | -5.62 | | Radius ratio | 0.04461 | 0.12318 | | First-to-fourth contact duration (h) | 7.053 | 2.879 | | Baseline offset | 3.012668e-04 | -1.068063e-05 | | Jitter | 1.06144829e-05 | 8.68813109e-06 | | RMS (ppm) | 694.6 | 586.0 | | Chi-square per degree of freedom | 0.004307 | 0.004640 | | In-transit cadences | 211 | 86 | | Converged | yes | yes | The radius ratio and duration are conditional on zero limb darkening, a central impact parameter, and the fixed published period. No published depth or duration was checked in this task, so the fitted shape is not compared with the source paper. The model depth implied by the radius ratio is 1989.8 ppm before any dilution correction. ## Binned depth and folded curve - Fold window: +/-0.6 d around the fitted mid-transit. - Bin width: 0.5 h; non-empty bins: 48. - In-transit bins: 14; out-of-transit bins: 5. - Binned depth: 1653.0 +/- 1575.8 ppm (out-of-transit minus in-transit weighted mean). - The uncertainty is a quadrature sum of weighted-mean errors and does not include correlated noise. It is not a published depth measurement. - The binned depth is 1.05 times its quoted uncertainty. The model fit uses all 703 cadences in the window and returns a smaller formal uncertainty, so the binned value and the fit are not independent estimates of the same quantity. ![Phase-folded KELT-11 b and HD 209458 b](figures/second-target-fold.svg) ## Comparison with sector 56 The same stages run on both targets and both single-transit fits converge. The differences are in data volume, sampling, and aperture behaviour. Sector 9 has fewer retained cadences, more long gaps, and a larger undefined trend fraction than sector 56. The KELT-11 b transit is longer and shallower, so its fitted mid-transit uncertainty is larger. The threshold aperture also agrees less well with the mission SAP series on KELT-11 b than on HD 209458 b (Pearson r 0.822 versus 0.962), and the PDCSAP agreement is much weaker (0.280 versus 0.934). The 9-pixel aperture on this evolved star is a weaker match to the mission reduction, and the difference is a diagnostic rather than a validation of either reduction. The HD 209458 b control fit returns a mid-transit time 13.0 s from the published prediction with a reported uncertainty of 2.3 s, an offset of -5.62 reported sigma. The KELT-11 b fit returns a time 229.8 s from the prediction with a reported uncertainty of 80.3 s, an offset of +2.86 reported sigma. That is too large to read as a clean consistency check. The formal least-squares uncertainty is therefore not sufficient on its own as an external error calibration. The KELT-11 b offset should be read the same way. Possible causes include an underestimated error budget, the published ephemeris uncertainty, and the backward extrapolation of a 2022 ephemeris to 2019 data. This run does not separate them. ## Honest limits - No transit is claimed. Both targets are known planets and the ephemerides are published. - No period, ephemeris, or transit timing variation is measured. The period is fixed and one transit is fitted. - No sector-novelty claim is made. KELT-11 b sector 9 predates the 2022 ephemeris reference year. - No contamination ratio, nearby-source count, crowding correction, or false-positive analysis is performed. - Limb darkening, impact parameter, and dilution are fixed at zero. These are method settings, not measured stellar parameters. - The aperture uncertainties are conservative relative to the observed scatter, and the reported fit uncertainties come from a covariance scaled by the reduced chi-square. They are not a full error budget. - The control fit is offset from its published prediction by 5.6 reported sigma, so the formal uncertainties are not sufficient on their own as an external calibration. - The fit uses the extracted aperture uncertainty, not SAP_FLUX_ERR or PDCSAP_FLUX_ERR. The mission uncertainties are used only for validation and do not enter the fitted parameters. - The detrending window is pre-declared at 1001 cadences. A different window would change the trend and the fitted parameters. - The full-sector fit path was not used; the fit is a single-transit fit selected by the published ephemeris. - The data are a MAST snapshot from the acquisition date. Product bytes and availability can change. - The KELT-11 b and HD 209458 b fits do not replace the published ephemerides and are not independent confirmations. ## Reproduction ``` python research/tess-timing/scripts/acquire_second_target.py --dry-run python research/tess-timing/scripts/acquire_second_target.py python research/tess-timing/scripts/second_target_analysis.py python -m pytest research/tess-timing/tests/test_second_target.py -q ``` The acquisition command contacts MAST. The analysis command is offline. ## Software | Component | Version | | --- | --- | | Python | 3.12.1 | | NumPy | 1.26.4 | | tess_timing | 0.1.0 | Generated by `research/tess-timing/scripts/second_target_analysis.py` from the committed product files and acquisition records. The acquisition step is the only step that uses the network.