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Abstract Dust associated with various stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether supernovae play an important role in dust production. We report evidence of dust formation in the cold, dense shell behind the ejecta–circumstellar medium (CSM) interaction in the Type Ia-CSM supernova (SN) 2018evt three years after the explosion, characterized by a rise in mid-infrared emission accompanied by an accelerated decline in the optical radiation of the SN. Such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the Hα emission line. Our model suggests enhanced CSM dust concentration at increasing distances from the SN as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. By the time of the last mid-infrared observations at day +1,041, a total amount of 1.2 ± 0.2 × 10−2 M⊙of new dust has been formed by SN 2018evt, making SN 2018evt one of the most prolific dust factories among supernovae with evidence of dust formation. The unprecedented witness of the intense production procedure of dust may shed light on the perceptions of dust formation in cosmic history.
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Deep late-time observations of the supernova impostors SN 1954J and SN 1961V
ABSTRACT SN 1954J in NGC 2403 and SN 1961V in NGC 1058 were two luminous transients whose definitive classification as either non-terminal eruptions or supernovae remains elusive. A critical question is whether a surviving star can be significantly obscured by dust formed from material ejected during the transient. We use three lines of argument to show that the candidate surviving stars are not significantly optically extinct (τ ≲ 1) by dust formed in the transients. First, we use SED fits to new HST optical and near-IR photometry. Secondly, neither source is becoming brighter as required by absorption from an expanding shell of ejected material. Thirdly, the ejecta masses implied by the Hα luminosities are too low to produce significant dust absorption. The latter two arguments hold independent of the dust properties. The Hα fluxes should also be declining with time as t−3, and this seems not to be observed. As a result, it seems unlikely that recently formed dust can be responsible for the present faintness of the sources compared to their progenitors, although this can be verified with the James Webb Space Telescope. This leaves three possibilities: (1) the survivors were misidentified; (2) they are intrinsically less luminous; (3) SN 1954J and SN 1961V were true supernovae.
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- Award ID(s):
- 1814440
- PAR ID:
- 10164180
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 489
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 1986 to 1994
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/stz2282
