SPHEREx QR2 detects the 0.75–5 µm excess of 47 of 78 clean MO26 white dwarfs with G < 17, and of all 22 with a WISE-predicted S ≥ 10; background sources cause the 2 excesses in 56 clean controls

We used SPHEREx Quick Release 2 spectral images (0.75–5.0 µm, 2025–2026) to test the infrared excesses in the list of Murillo-Ojeda et al. (2026, MO26) of white dwarfs within 100 pc. We did forced PSF photometry at the Gaia DR3 position, and we fitted the Gaia neighbours at the same time. We divided the flux by a Montreal photosphere model, and we calibrated the ratio with 30 clean DA controls. The controls are 100 random white dwarfs (G < 17) from the Gaia 100 pc catalogue that are not in MO26. Version 2 analyses 289 of the 293 targets with G < 17. It adds a pre-registered sensitivity test and a post-hoc blend check. For targets without a blend or PSF problem, SPHEREx finds an excess (S_max ≥ 5) in 47 of 78 MO26 white dwarfs (29 of 36 at G < 16.1, 18 of 42 at G ≥ 16.1) and in 2 of 56 controls. For each target, we calculated the SPHEREx significance that the WISE excess predicts (S_pred). All 22 targets with S_pred ≥ 10 have S_max ≥ 5 (median S_max/S_pred 1.08). All 15 targets with no excess have S_pred ≤ 3.2. Thus, SPHEREx does not refute any MO26 excess, but it cannot test most of the faint excesses. Background sources cause the two control excesses: a red source 1.8 arcsec from CBS 204 (Spitzer IRAC, Legacy Surveys) and a galaxy 6 arcsec from GALEX 2668675296612320268 (Legacy Surveys DR10, AllWISE position). A blend check with CatWISE2020, Legacy Surveys DR10, Pan-STARRS1 and VHS passes 40 of the 47 MO26 excesses. It finds a galaxy near 5 of them, for example Ton S 193 (as Farihi et al. 2010 found) and 2MASS J15500449+2200356 (S_max 23.3). Five excesses with no reference other than MO26 pass the blend check: L 454-9, L 221-49, SDSS J172945.16+020818.4, HS 0507+0434A and G 84-26. A blackbody fits better than a cool companion for 41 of the 47 excess spectra. For 33 of them, a companion is not necessary (median blackbody temperature 1159 K). The pre-registered comparison of the 3.4 µm flux with WISE finds a change in 2 targets. WD J2100+2122 is 40 % fainter than in 2024, after its 2023 outburst. The change of 2MASS J15500449+2200356 comes from the galaxy blend. WD 0145+234 is 22 % above AllWISE. Limitations: the SPHEREx pixels are 6.2 arcsec, and the blend check cannot find sources closer than about 2 arcsec. The QR2 calibration can change. The blend check and some rules are post hoc. We give the code, the photometry, the catalogue replies and the reproduction steps.

white dwarfs · infrared excess · debris disks · SPHEREx · WISE · NEOWISE · Spitzer IRAC · forced PSF photometry · false positives · source blending · mid-infrared variability · planetary debris · Gaia DR3 · CBS 204 · WD J2100+2122 · LAWD 84 · WD 0145+234 · 100 pc sample · sensitivity test · Legacy Surveys