A Population Study of the Radio Emission of Fast Blue Optical Transients

Abstract

Despite the fact that the progenitor of fast blue optical transients (FBOTs) is still a subject of debate, FBOTs are sometimes suggested to originate from the core collapse of ultra-stripped stars and be powered by a spinning-down neutron star. Following this consideration, it is expected that the late-time evolution of the progenitor stars can leave important imprints in the circumstellar material (CSM) of FBOTs, due to the strong mass loss of the stars. The interaction of the FBOT ejecta with the CSM can drive a long-lasting shock to generate radio emission, which thus enables us to probe the CSM properties through radio observation although such observations are still rare. Within the framework of the magnetar-powered model, Liu et al. fitted the multi-band optical light curves of 40 FBOTs, and hence, the statistical distributions of the FBOT magnetar and ejecta parameters were obtained. Based on these FBOT population results, we investigate the dependence of the radio emission on the mass-loss rate of the progenitors and evaluate the detectability of radio emission from FBOTs with current and future telescopes. It is found that the distribution of the peak time and peak luminosity of the emission at 8.4 GHz are primarily in the regions of t peak,ν = 102.12±0.63 days and L peak,ν = 1028.73±0.83 erg s−1 Hz−1, respectively. A joint detection of the Zwicky Transient Facility and Very Large Array could achieve success in about 8.7% FBOTs of z ≤ 1. Furthermore, if considering a joint detection of the Chinese Space Station Telescope and the Square Kilometer Array, this rate of success could be increased to about 23.9%.

Late-time Hubble Space Telescope Observations of AT 2018cow. II. Evolution of a UV-bright Underlying Source 2–4 Yr Post-discovery

“…Over the past decade, a class of peculiar transients has been discovered with brightness similar to supernovae (SNe), but a much shorter timescale, often accompanied by persistent blue color, commonly termed Fast Blue Optical Transients (FBOTs; e.g., Drout et al 2014;Arcavi et al 2016;Tanaka et al 2016;Pursiainen et al 2018;Rest et al 2018;Tampo et al 2020;Wiseman et al 2020;Ho et al 2023). The much shorter timescale is incompatible with standard SN models powered by radioactive decay and hydrogen recombination (which serve to prolong light curves), and thus alternative models were proposed, most commonly involving power sources such as interaction between ejecta and circumstellar material (CSM; Ofek et al 2010;Shivvers et al 2016;Kleiser et al 2018;McDowell et al 2018;Rest et al 2018;Tolstov et al 2019;Wang et al 2019;Suzuki et al 2020;Wang & Li 2020;Karamehmetoglu et al 2021;Maeda & Moriya 2022;Margalit et al 2022;Margalit 2022;Khatami & Kasen 2023;Liu et al 2023;Mor et al 2023) and energy injection by central engines such as neutron stars (NSs; Yu et al 2015;Hotokezaka et al 2017;Whitesides et al 2017;Liu et al 2022;Wang & Gan 2022) or black holes (BHs; Kashiyama & Quataert 2015;Rest et al 2018;Kawana et al 2020;Kremer et al 2021;Tsuna et al 2021;Fujibayashi et al 2022).…”

Late-time Hubble Space Telescope Observations of AT 2018cow. I. Further Constraints on the Fading Prompt Emission and Thermal Properties 50–60 days Post-discovery

“…As a result, a variety of alternative scenarios have been proposed to explain the characteristics of FBOTs, some of which involve interactions with circumstellar material (CSM; Ofek et al 2010;Shivvers et al 2016;Kleiser et al 2018b;McDowell et al 2018;Rest et al 2018;Tolstov et al 2019;Wang et al 2019;Suzuki et al 2020;Wang & Li 2020;Karamehmetoglu et al 2021;Maeda & Moriya 2022;Margalit et al 2022;Margalit 2022;Khatami & Kasen 2023;Liu et al 2023;Mor et al 2023), energy injection by a central engine such as a neutron star (NS; Yu et al 2015;Hotokezaka et al 2017;Whitesides et al 2017;Liu et al 2022;Wang & Gan 2022) or a black hole (BH; Kashiyama & Quataert 2015;Rest et al 2018;Tsuna et al 2021;Fujibayashi et al 2022), tidal disruption events (TDEs; Kawana et al 2020;Kremer et al 2021), electron-capture supernovae (ECSNe; Moriya & Eldridge 2016), and SNe within extended envelopes (Brooks et al 2017;Kleiser et al 2018a).…”