{"case":{"id":"OS-0033","title":"A hidden source in NGC 4945 that has flared in the infrared every 5.4 years: three outbursts with a sudden rise","hook":"Found blind by Oddsky's search for repeating infrared sources in nearby galaxies (hunt H-0013): WISE sees cycles peaking in 2011, 2016-17 and 2022, and Spitzer caught the 2016 rise, a jump of 25x in under half a year. Nothing is catalogued at the position. Next peak expected around 2027.5.","status":"reproduced","target":{"name":"NGC 4945 periodic IR source","ra":196.41592,"dec":-49.42001,"aliases":[]},"summary":"An infrared source in the dusty edge-on starburst galaxy NGC 4945 (3.8 Mpc) that brightens sharply every 5.4 years: WISE saw cycles in 2011, 2016-17 and 2022, and Spitzer caught the 2016 rise. Each swing is about 3e5 L_sun, with no optical counterpart. Most likely a massive binary forming dust at each close approach; an extreme dusty pulsating star is the alternative. Next peak expected around 2027.5. Found blind by Oddsky hunt H-0013.","claims":[{"id":"C1","text":"WISE (unWISE neo11 difference photometry, H-0012/H-0013): three cycles peaking 2011.27, 2016.71 and 2022.14, a period of 5.43 yr (WISE) and 5.37 yr (joint WISE + Spitzer fit), with a sawtooth shape: fast rise (about 8% of the period), slower decline, short minimum (hunts/H-0013/README.md).","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"},{"id":"C2","text":"Spitzer/IRAC warm mission 2012-2019 tracks two cycles: from +22 to +505 (3.6 um) / +748 uJy (4.5 um) between 2016.34 and 2016.78, a rise in under 0.45 yr; a single 2007.6 [4.5] epoch fits the decline of a 2005.9 cycle.","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"},{"id":"C3","text":"Peak-to-trough W2 amplitude about 3e5 L_sun at 3.8 Mpc. The light-curve shape test favours a flat-minimum outburst train over a sinusoid (Z_joint = +83). Luminous dusty long-period variables reach P = 1,000-2,500 d and nu L_nu(4.5 um) of order 1e5-5e5 L_sun (Karambelkar et al. 2019, SPIRITS), so pulsation is not excluded by luminosity alone.","tag":"computed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"},{"id":"C4","text":"No optical or near-infrared counterpart: nothing in Gaia DR3 or HST at the position, in the dust lane of an edge-on starburst; a Galactic foreground star (b = +13 deg) is implausible with no Gaia source and P = 5.4 yr.","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"},{"id":"C5","text":"Not reported (2026-11-02): ADS full text for the coordinates and for the host with variability terms finds nothing on this source; nothing in TNS, SIMBAD, Gaia DR3, AllWISE or the Spitzer SEIP catalogue at the position; the SPIRITS catalogue of luminous long-period variables (Karambelkar et al. 2019) does not cover this galaxy.","tag":"observed","calls":[],"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"}],"hypotheses":[{"id":"H1","klass":"dust_formation","statement":"A massive colliding-wind binary forming dust at each periastron every 5.4 yr, deeply embedded in NGC 4945.","supports":["C1","C2","C3","C4"],"conflicts":[],"would_falsify":"An infrared spectrum with silicate or SiC features (AGB dust), or no brightening in 2026.8-2028.3.","status":"live","confidence":0.5,"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"},{"id":"H2","klass":"pulsation","statement":"An extremely luminous dusty long-period variable (super-AGB star or red supergiant with extreme mass loss).","supports":["C1","C3"],"conflicts":["C2"],"would_falsify":"Already strained by the fast rise and flat minimum, which pulsators do not show.","status":"live","confidence":0.35,"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"},{"id":"H3","klass":"artifact_instrumental","statement":"A WISE or Spitzer artefact.","supports":[],"conflicts":["C1","C2"],"would_falsify":"Two observatories see the same cycles at one position.","status":"live","confidence":0.03,"author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00"}],"predictions":[],"literature":[],"hunt":"H-0013","featured":false,"created_at":"2026-11-02T21:36:38+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":"2026-11-02T21:36:38+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":"2026-11-02T21:36:38+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K3","tool":"add_claim","args":{"id":"C3","tag":"computed"},"digest":"a8e3dde17ac83cf1","digest10":"a8e3dde17ac83cf1","author":"claude-opus-5.5","at":"2026-11-02T21:36:38+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":"2026-11-02T21:36:38+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K5","tool":"add_claim","args":{"id":"C5","tag":"observed"},"digest":"0bcef7dd6aaf715f","digest10":"0bcef7dd6aaf715f","author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K6","tool":"add_hypothesis","args":{"id":"H1","klass":"dust_formation"},"digest":"a3afdee2a580e9e9","digest10":"a3afdee2a580e9e9","author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K7","tool":"add_hypothesis","args":{"id":"H2","klass":"pulsation"},"digest":"3c8ab29249da19db","digest10":"3c8ab29249da19db","author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00","oddsky":"0.3.1","platform":"darwin-arm64"},{"id":"K8","tool":"add_hypothesis","args":{"id":"H3","klass":"artifact_instrumental"},"digest":"98cd99168b0a91ec","digest10":"98cd99168b0a91ec","author":"claude-opus-5.5","at":"2026-11-02T21:36:38+00:00","oddsky":"0.3.1","platform":"darwin-arm64"}],"investigations":[],"reviews":[]}