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September 10, 2025Open Access

Fast Luminous Extragalactic Transients in the VLA Sky Survey: Implications for the Rates of Accretion-induced Collapse Events, Fast Blue Optical Transients and Gamma Ray Burst Afterglows

Key Points

The study discovered five fast luminous extragalactic transients, highlighting their significance in astrophysical research.
Estimates suggest that the occurrence rate for fast blue optical transients is about less than 0.01% of local core-collapse supernova rates.
Analysis from the Very Large Array Sky Survey provides insights into the volumetric rates of different transient phenomena in the universe.
Findings may enable more precise understanding of energetic transients, calling for coordinated multi-wavelength follow-up efforts.

Abstract

Abstract Radio wavelengths offer a unique window into high-energy astrophysical phenomena that may be obscured or too rapidly evolving to be captured at other wavelengths. Leveraging data from the Very Large Array Sky Survey, we perform a systematic search for fast (characteristic timescales ≲3 yr), luminous ( L ≳ 10 28 erg s −1 Hz −1 ) transients in the nearby universe ( z ≤ 0.3). We report the discovery of five such transients, and classify them based on their synchrotron emission energetics and host galaxy properties. From this sample, we derive observational constraints on the volumetric rates of certain corresponding transient classes. We limit the rates of accretion-induced collapse of white dwarfs with dense circumstellar medium interaction (and those producing pulsar wind nebulae) at ≲ 1.1 0 − 0.90 + 2.60 % ( ≲ 0.2 0 − 0.10 + 5.80 %) of the local Type Ia supernova rate, respectively, broadly consistent with theoretical predictions. For AT2018cow-like radio-bright luminous fast blue optical transients (LFBOTs), we estimate a rare occurrence rate of ≲ 0.0 2 − 0.01 + 0.32 % of the local core-collapse supernova rate, which is at least an order of magnitude smaller than the estimates from optical searches, thus highlighting the rarity of radio-luminous LFBOTs. We constrain the local volumetric rates of long- and short-duration gamma-ray bursts (GRBs) to be ≲ 11.4 6 − 9.48 + 26.28 Gpc −3 yr −1 and ≲ 80.8 8 − 66.90 + 185.87 Gpc −3 yr −1 , respectively, consistent with constraints from high energy and gravitational wave observations. These estimates incorporate beaming corrections, with median detectable viewing angles derived from afterglow simulations of ∼0.4 and ∼0.3 radians for long- and short-duration GRBs. Our findings highlight the potential of radio surveys to uncover rare, energetic transients. We emphasize the critical role of coordinated multi-wavelength follow-up in fully characterizing these enigmatic events.

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