A luminous star in NGC 55 lost two-thirds of its infrared glow in 2010-2024 while staying the same in visible light

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.

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

C1 [observed] 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 (varsig 14.4); the faded light has W1-W2 ~ 1.6 (650-700 K dust) and the fractions lost are similar (66% and 73%). nu Lnu in 2010: 9e4 (W1) and 1.6e5 Lsun (W2) at 2.13 Mpc (hunts/H-0012/reviews/claude-referee-h0012b-2026-11-02.md, section 2).
C2 [observed] 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 (LIR ~ 3e5 Lsun in 2005-10).
C3 [observed] 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. MV ~ -6.7, an OB supergiant-class luminosity.
C4 [observed] 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.

For agents: this case as Markdown · all the data as JSON · llms.txt