{"case":{"id":"OS-0032","title":"A luminous star in NGC 55 lost two-thirds of its infrared glow in 2010-2024 while staying the same in visible light","hook":"Found by Oddsky's failed-supernova search (hunt H-0012 v2), but not a failed supernova: the mid-infrared light faded threefold over 14 years while Hubble shows the blue, luminous star unchanged. Its dust is clearing.","status":"reproduced","target":{"name":"NGC 55 fading dusty star","ra":3.80788,"dec":-39.2148,"aliases":[]},"summary":"A luminous, blue star in the nearby galaxy NGC 55 (2.1 Mpc) whose mid-infrared light was steady from 2005 to 2010 and then faded threefold by 2024, while Hubble shows the star itself unchanged. Most likely a massive star's dust disk or shell dissipating. It is also a warning case for failed-supernova searches: an infrared 'vanishing' source that is not a vanishing star. Found by Oddsky hunt H-0012.","claims":[{"id":"C1","text":"WISE (unWISE neo11, absolute PSF flux): a smooth, decelerating fade with no recovery, W1 740 to 251 uJy and W2 1,675 to 456 uJy from 2010.4 to 2024.4 (var_sig 14.4); the faded light has W1-W2 ~ 1.6 (650-700 K dust) and the fractions lost are similar (66% and 73%). nu L_nu in 2010: 9e4 (W1) and 1.6e5 L_sun (W2) at 2.13 Mpc (hunts/H-0012/reviews/claude-referee-h0012b-2026-11-02.md, section 2).","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00"},{"id":"C2","text":"Spitzer 2005: [4.5] = 1,727 uJy, equal to W2 in mid-2010 within 3%, so the source was steady for 4.5 yr before fading; the IRAC SED rises to 8 um (L_IR >~ 3e5 L_sun in 2005-10).","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00"},{"id":"C3","text":"Optical counterpart Gaia DR3 4997972666905659392, 0.20\" away: G = 20.18, BP-RP = 0.14. HST F814W 21.20 (2007) and 21.10 (2024): constant to ~0.1 mag while the mid-infrared fell threefold. M_V ~ -6.7, an OB supergiant-class luminosity.","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00"},{"id":"C4","text":"Not reported: no ADS full-text match for the coordinates; nothing in SIMBAD within 4\" or TNS within 30\"; NGC 55 was not observed by SPIRITS.","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00"}],"hypotheses":[{"id":"H1","klass":"dust_formation","statement":"A dusty massive star (sgB[e], LBV or WR dust-maker) whose circumstellar dust, in a disk or a shell seen through a gap, is dissipating after an earlier dust-forming episode.","supports":["C1","C2","C3","C4"],"conflicts":[],"would_falsify":"An optical spectrum showing a quasar redshift, or no B[e]/LBV/WR emission lines.","status":"live","confidence":0.7,"author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00"},{"id":"H2","klass":"artifact_blend","statement":"A background AGN behind NGC 55, coincident with the blue star.","supports":["C2"],"conflicts":["C3"],"would_falsify":"A stellar optical spectrum at NGC 55's velocity; the blue point source steady to 0.1 mag for 17 years and ~700 K dust (not 1,200-1,500 K) already disfavour it.","status":"live","confidence":0.2,"author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00"}],"predictions":[],"literature":[],"hunt":"H-0012","featured":false,"created_at":"2026-11-02T19:15:16+00:00"},"series":{},"context":{},"provenance":{},"skeptic":null,"ledger":[{"id":"K1","tool":"add_claim","args":{"id":"C1","tag":"observed"},"digest":"47420e4be8ce39a8","digest10":"47420e4be8ce39a8","author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K2","tool":"add_claim","args":{"id":"C2","tag":"observed"},"digest":"810fe66681869023","digest10":"810fe66681869023","author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K3","tool":"add_claim","args":{"id":"C3","tag":"observed"},"digest":"a8e3dde17ac83cf1","digest10":"a8e3dde17ac83cf1","author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K4","tool":"add_claim","args":{"id":"C4","tag":"observed"},"digest":"a75fcb10446e9d88","digest10":"a75fcb10446e9d88","author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K5","tool":"add_hypothesis","args":{"id":"H1","klass":"dust_formation"},"digest":"a3afdee2a580e9e9","digest10":"a3afdee2a580e9e9","author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K6","tool":"add_hypothesis","args":{"id":"H2","klass":"artifact_blend"},"digest":"3c8ab29249da19db","digest10":"3c8ab29249da19db","author":"claude-opus-5.5","at":"2026-11-02T19:15:16+00:00","oddsky":"0.3.1","platform":"darwin-arm64"}],"investigations":[],"reviews":[]}