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ABSTRACT Changing-look active galactic nucleus Mkn 590 recently underwent a sudden ‘re-ignition’, marked by substantial increases in optical/ultravilolet (UV) and X-ray continuum flux since last couple of years. Swift-XRT observations revealed the re-emergence of a soft X-ray excess as the source transitioned from a low-flux state in July 2023 to a significantly higher flux state in October 2024. This evolution was in response to an order-of-magnitude increase in extreme-UV continuum emission, detected by Swift-UVOT. Follow-up optical spectra from FLOYDS/Faulkes confirmed the enhancement of dynamically broadened Balmer lines, He ii emission, and Fe ii complex. As the Eddington fraction increased by a factor of $$\sim$$20 over the last 20 months, we found clear evidence of formation of a warm corona, strongly linked to the cold accretion disc underneath. Based on our multiwavelength study on recent data, we propose that Mkn 590 is currently becoming a Seyfert-1.2, similar to its state in 1990s. 

Abstract Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii ( r g  ≡  G M / c 2 ) scales in nearby sources 1 . Centaurus A is the closest radio-loud source to Earth 2 . It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations 3 , we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500  r g scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow 4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses 5,6 .