An 11-star calibration gives 0.9–1.8% flux offsets for TYC 8241-2652-1 at 4.2–5.0 µm in three SPHEREx QR2 periods in 2025–2026

We test whether warm dust emission returned at TYC 8241-2652-1 after its large 2008–2010 decrease. Earlier NEOWISE data showed a low state through 2024. We extract public SPHEREx QR2 pixels for the target and 11 field stars. We selected the field stars before we read the new fluxes. Four common wavelength bins use 59 target measurements. Their centers span 4.273–4.818 micrometers. We compare an approximate old continuum with the new fluxes after a correction from the field stars. The offsets are +1.07% in June–July 2025, +1.80% in January–February 2026, and +0.94% in June 2026. The full-period offset is +1.27%. Its conditional two sided 95% calibration range is -0.39% to +2.96%. This range assumes normal source residuals with the same distribution for the target and controls. The target is outside the controls' old W1-W2 color range. The control residuals also depend on that color. Thus, these ranges do not give unconditional dust limits. The planned short wavelength color test has no common usable bins. Other extractions and old references also give small offsets. The usable samples do not show a return of the old 450 K dust model. That model would add about 136% flux at 4.6 micrometers if the star kept its old level. The four-bin period test ends on June 28, 2026. A July 17 point at 4.986 micrometers is preserved outside that statistic. We publish 4,341 cutouts, source replies and hashes, all results, figures, and code for an offline check. Cold dust and events between usable samples remain outside the test.

TYC 8241-2652-1 · SPHEREx · QR2 · NEOWISE · warm dust · debris disks · infrared variability · forced photometry · calibration · public data