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Dust Echoes from Luminous Fast Blue Optical Transients

Metzger, BD and Perley, DA (2023) Dust Echoes from Luminous Fast Blue Optical Transients. Astrophysical Journal, 944 (1). ISSN 0004-637X

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Open Access URL: https://doi.org/10.3847/1538-4357/acae89 (Published version)


Luminous fast blue optical transients (LFBOTs) such as AT2018cow form a rare class of engine-powered explosions of uncertain origin. A hallmark feature of these events is radio/millimeter synchrotron emission powered by the interaction of fast ≳0.1c ejecta and dense circumstellar material (CSM) extending to large radii ≳1016 cm surrounding the progenitor. Assuming this CSM to be an outflow from the progenitor, we show that dust grains up to ∼1 μm in size can form in the outflow in the years before the explosion. This dusty CSM would attenuate the transient’s ultraviolet emission prior to peak light, before being destroyed by the rising luminosity, reddening the premaximum colors (consistent with the premaximum red-to-blue color evolution of the LFBOT candidate MUSSES2020J). Reradiation by the dust before being destroyed generates a near-infrared (NIR) “echo” of luminosity ∼1041-1042 erg s−1 lasting weeks, which is detectable over the transient’s rapidly fading blue continuum. We show that this dust echo is compatible with the previously unexplained NIR excess observed in AT2018cow. The gradual decay of the early NIR light curve can result from CSM, which is concentrated in a wide-angle equatorial outflow or torus, consistent with the highly aspherical geometry of AT2018cow’s ejecta. Premaximum optical/UV and NIR follow-up of LFBOTs provide a new probe of their CSM environments and place additional constraints on their progenitors.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
SWORD Depositor: A Symplectic
Date Deposited: 15 Mar 2023 13:14
Last Modified: 15 Mar 2023 13:14
DOI or ID number: 10.3847/1538-4357/acae89
URI: https://researchonline.ljmu.ac.uk/id/eprint/19101
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