DOI

https://doi.org/10.48717/kbm1-jd38

Project

RA006

Title

ToO proposal on a merging SMBH candidate

Abstract

J1430+2303 is a recently discovered SMBHB candidate that shows unique chirp signals in the optical continuum and is an excellent target for studying the imminent merger of SMBHBs. Our recent VLA observations show that the flux density at 15 GHz is 1.6 times higher than seven months ago, and the radio spectrum flattened in December 2022 compared to the steep spectrum before May 2022. The increased radio flux and the evolution of the spectrum may be related to outflows observed in the X-ray spectra or to a nascent jet that has evolved and interacted with the dense circumnuclear medium. VLBI images can morphologically distinguish between disk-wind and jet after the outflows reach a certain separation distance. We propose to use 4 epochs of 22 GHz eEVN or regular EVN observation within the next 6 months to identify the physical origin of the nascent outflow -- the accretion disk wind or the jet. First, high-resolution images will confirm whether the radio flux enhancement and spectrum changes observed by the VLA are related to the core. Second, multiple-epoch observations can measure or constrain the velocity of the nascent outflow, providing strong evidence to distinguish between the non-relativistic wind and relativistic jet.