In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with the Very Large Array. Because of its radio brightness (νF ν ≈ 6×10 39 erg s −1 ), this transient likely represents a secondary black hole in orbit around the AGN. Using Chandra ACIS observations from 2015 to 2017, we have looked for an X-ray counterpart to Cygnus A-2. The separation of 0.42 arcsec means that Cygnus A-2 can not be spatially resolved, but by comparing the data with simulated marx data, we put an upper limit to the 2-10 keV X-ray luminosity of Cygnus A-2 of 1 × 10 43 erg s −1 . Using the Fundamental Plane for accreting black holes, we find that our upper limit to the X-ray flux of Cygnus A-2 in 2015-2017 disfavours the interpretation of Cygnus A-2 as a steadily accreting black hole. We suggest instead that Cygnus A-2 is the radio afterglow of a tidal disruption event (TDE), and that a peak in the 2-10 keV luminosity of the nuclear region in 2013, when it was observed by Swift and NuSTAR, is X-ray emission from the TDE. A TDE could naturally explain the X-ray light curve of the nuclear region, as well as the appearance of a short-lived, fast, and ionized outflow previously detected in the 2013 NuSTAR spectrum. Both the radio and X-ray luminosities fall in between typical luminosities for 'thermal' and 'jetted' TDE types, suggesting that Cygnus A-2 would be unlike previously seen TDE's.

We present a spectral analysis of the lobes and X-ray jets of Cygnus A, using more than 2 Ms of Chandra observations. The X-ray jets are misaligned with the radio jets and significantly wider. We detect non-thermal emission components in both lobes and jets. For the eastern lobe and jet, we find 1 keV flux densities of 71 +10 −10 nJy and 24 +4 −4 nJy, and photon indices of 1.72 +0.03 −0.03 and 1.64 +0.04 −0.04 respectively. For the western lobe and jet, we find flux densities of 50 +12 −13 nJy and 13 +5 −5 nJy, and photon indices of 1.97 +0.23 −0.10 and 1.86 +0.18 −0.12 respectively. Using these results, we modeled the electron energy distributions of the lobes as broken power laws with age breaks. We find that a significant population of non-radiating particles is required to account for the total pressure of the eastern lobe. In the western lobe, no such population is required and the low energy cutoff to the electron distribution there needs to be raised to obtain pressures consistent with observations. This discrepancy is a consequence of the differing X-ray photon indices, which may indicate that the turnover in the inverse-Compton spectrum of the western lobe is at lower energies than in the eastern lobe. We modeled the emission from both jets as inverse-Compton emission. There is a narrow region of parameter space for which the X-ray jet can be a relic of an earlier active phase, although lack of knowledge about the jet's electron distribution and particle content makes the modelling uncertain.

We use new and archival Chandra observations of Cygnus A, totalling ∼1.9 Ms, to investigate the distribution and temperature structure of gas lying within the projected extent of the cocoon shock and exhibiting a rib-like structure. We confirm that the Xrays are dominated by thermal emission with an average temperature of around 4 keV, and have discovered an asymmetry in the temperature gradient, with the southwestern part of the gas cooler than the rest by up to 2 keV. Pressure estimates suggest that the gas is a coherent structure of single origin located inside the cocoon, with a mass of roughly 2 × 10 10 M . We conclude that the gas is debris resulting from disintegration of the cool core of the Cygnus A cluster after the passage of the jet during the early stages of the current epoch of activity. The 4 keV gas now lies on the central inside surface of the hotter cocoon rim. The temperature gradient could result from an offset between the centre of the cluster core and the Cygnus A host galaxy at the switch-on of current radio activity.