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NGC 777 provides an example of a phenomenon observed in some group-central ellipticals, in which the temperature profile shows a central peak, despite the short central cooling time of the intragroup medium. We use deep Chandra X-ray observations of the galaxy, supported by uGMRT 400 MHz radio imaging, to investigate the origin of this hot core. We confirm the centrally peaked temperature profile and find that the entropy and cooling time both monotonically decline to low values (2.62 ${}_{-0.18}^{+0.19}$ keV cm ^2 and ${71.3}_{-13.1}^{+12.8}$ Myr, respectively) in the central ∼700 pc. Faint diffuse radio emission surrounds the nuclear point source, with no clear jets or lobes but extending to ∼10 kpc on the northwest–southeast axis. This alignment and extent agree well with a previously identified filamentary H α + [N ii ] nebula. While cavities are not firmly detected, we see X-ray surface brightness decrements on the same axis at 10–20 kpc radii, which are consistent with the intragroup medium having been pushed aside by expanding radio lobes. Any such outburst must have occurred long enough ago for lobe emission to have faded below detectability. Cavities on this scale would be capable of balancing radiative cooling for at least ∼240 Myr. We consider possible causes of the centrally peaked temperature profile, including gravitational heating of gas as the halo relaxes after a period of active galactic nucleus jet activity, and heating by particles leaking from the remnant relativistic plasma of the old radio jets.

Recent observations of galaxy clusters and groups with misalignments between their central active galactic nucleus jets and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet–bubble connection in cooling cores, and the processes responsible for jet realignment. To investigate the frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and groups. Using Very Long Baseline Array radio data, we measure the parsec-scale position angle of the jets, and compare it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample and selected subsets, we consistently find that there is a 30%–38% chance to find a misalignment larger than ΔΨ = 45° when observing a cluster/group with a detected jet and at least one cavity. We determine that projection may account for an apparently large ΔΨ only in a fraction of objects (∼35%), and given that gas dynamical disturbances (such as sloshing) are found in both aligned and misaligned systems, we exclude environmental perturbation as the main driver of cavity–jet misalignment. Moreover, we find that large misalignments (up to ∼90°) are favored over smaller ones (45° ≤ ΔΨ ≤ 70°), and that the change in jet direction can occur on timescales between one and a few tens of Myr. We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we discuss several engine-based mechanisms that may cause these dramatic changes.