JWST spectroscopy of SN 2010da/NGC 300 ULX-1: a surviving star hidden by dust

Beasor, ER ORCID: 0000-0003-4666-4606, Lau, R, Smith, N, Walton, DJ, Heida, M and Davies, B (2026) JWST spectroscopy of SN 2010da/NGC 300 ULX-1: a surviving star hidden by dust. Monthly Notices of the Royal Astronomical Society, 550 (2). ISSN 0035-8711

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Abstract

We present new James Webb Space Telescope ((Formula presented) ) NIRSpec and MIRI integral-field spectroscopy of the remarkable system SN 2010da/NGC 300 ULX-1, the only known ultraluminous X-ray source powered by a neutron star with a supergiant donor. Our new data, taken in 2024 November, reveal that the optical and near-infrared counterpart has dramatically faded since 2018 and no longer exhibits molecular absorption features characteristic of a red supergiant. Instead, the spectral energy distribution (SED) shows the donor has returned to its pre-outburst appearance, and is dominated by infrared continuum consistent with an optically thick warm ((Formula presented) 900 K) dust shell. The bolometric luminosity indicates the presence of a surviving luminous source with (Formula presented) = 4.11(Formula presented) 0.02. Radiative transfer modelling of the mid-infrared SED reveals a broad emission feature peaking near (Formula presented) 11 μm, best reproduced by silicon carbide (SiC) dust grains, a composition typically associated with carbon-rich evolved stars. We rule out a failed supernova scenario, which would predict a large drop in luminosity and continued fading. Given the association of SiC dust with asymptotic giant branch (AGB) stars, we suggest the donor star may be an AGB star that has survived and is now heavily enshrouded – having returned to a dust-obscured state following a transient post-outburst phase in which the system appeared as a red supergiant. We propose a revised evolutionary timeline in which the 2010 outburst initiated sustained super-Eddington accretion and temporarily altered the circumstellar environment. These observations provide rare insight into eruptive mass-loss, dust formation, and binary interaction in a unique system.

Item Type:	Article
Uncontrolled Keywords:	supergiants; stars: neutron; X-rays: binaries; transients: supernovae; 5109 Space Sciences; 51 Physical Sciences; 5101 Astronomical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Date of acceptance:	1 June 2026
Date of first compliant Open Access:	15 September 2026
Date Deposited:	15 Sep 2026 13:14
Last Modified:	15 Sep 2026 13:14
DOI or ID number:	10.1093/mnras/stag1077
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29431

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