SN 2018bsz: Significant Dust Formation in a Nearby Superluminous Supernova

Chen, TW, Brennan, SJ, Wesson, R, Fraser, M, Schweyer, T, Inserra, C, Schulze, S, Nicholl, M, Anderson, JP, Hsiao, EY, Jerkstrand, A, Kankare, E, Kool, EC, Kravtsov, T, Kuncarayakti, H, Leloudas, G, Li, CJ, Matsuura, M, Pursiainen, M, Roy, R et al (2026) SN 2018bsz: Significant Dust Formation in a Nearby Superluminous Supernova. The Astrophysical Journal, 1009 (2). ISSN 0004-637X

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Abstract

We investigate the thermal emission and the extinction from dust associated with the nearby (z = 0.0267) superluminous supernova (SLSN) 2018bsz. Our dataset combines daily cadence, simultaneous optical and near-infrared (NIR) coverage up to ∼100 days with late-time (+ 1.7 yr) mid-infrared (MIR) observations. At 230 days after the light-curve peak, the supernova (SN) is not detected in the optical, but shows a surprisingly strong NIR excess, with r − J > 3 mag and r − Ks > 5 mag. The temporal evolution of the infrared (IR) light curve allows us to assess whether the MIR emission originates from newly formed dust, either in the SN ejecta or in a postshock circumstellar shell, or instead from an IR echo produced by preexisting circumstellar or interstellar dust heated by the SN radiation. Our radiative-transfer modeling shows that the circumstellar and interstellar echo scenarios cannot simultaneously reproduce the observed IR luminosity and its temporal evolution, and we therefore disfavor these interpretations. In contrast, a scenario in which new dust forms in the SN ejecta at epochs ≳200 days provides a self-consistent explanation for the evolution of the SN flux. We can fit the spectral energy distribution well at +230 days with 5 × 10−4 M⊙ of carbon dust, increasing over the following several hundred days to 10−2 M⊙ by +535 days. SN 2018bsz is the first SLSN showing evidence for dust formation within the SN ejecta, and appears to form 10 times more dust than normal core-collapse supernovae (SNe) at similar epochs. Together with their preference for low-mass, low-metallicity host galaxies, we suggest that superluminous SNe may be a significant contributor to dust formation in the early Universe.

Item Type:	Article
Uncontrolled Keywords:	5109 Space Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); 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:	IOP Publishing
Date of acceptance:	24 July 2026
Date of first compliant Open Access:	22 October 2026
Date Deposited:	22 Oct 2026 12:58
Last Modified:	22 Oct 2026 12:58
DOI or ID number:	10.3847/1538-4357/ae91e7
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29730

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