Tomohisa Kawashima

In 2026, the Event Horizon Telescope (EHT) carried out the first time-lapse monitoring campaign comprising a series of 18 observations of the 6.1 6 − 0.57 + 0.71 × 1 0 9 M ⊙ black hole at the center of M87 with a cadence of approximately twice per week over a few months, matched to the expected dynamical timescale. Here we present a first-look image from the campaign, reconstructed from a single four-minute scan obtained on 2026 April 3. The resulting image displays the now-familiar asymmetric ring morphology first revealed by the 2017 EHT observations and subsequently confirmed by observations obtained in 2018 and 2021. While representing only a very small subset of the full program, this image demonstrates a significant advance in the operational capabilities of the EHT. Through improvements in array operations, data transport and processing, the collaboration has reduced the interval between observation and imaging to only a few months, establishing the EHT as a facility capable of routinely undertaking time-domain studies of the dynamic universe at extremely high resolutions of ∼20 μ as.

Relativistic jets are among the most energetic phenomena in the Universe and influence galaxy evolution through energetic feedback, yet the physical connection between accretion flows and jet launching remains unresolved. Jet production is widely attributed to the Blandford–Znajek mechanism, which extracts black hole rotational energy via large-scale magnetic fields sustained by an accretion flow. Although this mechanism is observationally well supported for hot, geometrically thick accretion flows, highly accreting environments with strong jets present a paradox, as they are typically dominated by cold, geometrically thin disks incapable of sustaining large-scale magnetic fields. Here, we report coordinated X-ray microcalorimeter spectroscopy achieved by X-ray Imaging and Spectroscopy Mission (XRISM) and millimeter–radio interferometric observations by Global Millimeter Very Long Baseline Interferometry (VLBI) Array (GMVA), Very Long Baseline Array (VLBA), and East Asian VLBI Network (EAVN) of the broad-line radio galaxy 3C 120. High-resolution X-ray spectroscopy reveals a relativistically broadened Fe K α line, indicating that the cold, geometrically thin disk is truncated at ∼20 R _g ( R _g is the gravitational radius), with the inner region replaced by a hot, geometrically thick flow. Concurrently, radio imaging indicates that jet profile extrapolation toward the black hole horizon yields a radius comparable to or even narrower than the disk truncation radius. These results demonstrate that, even at high accretion rates, jet launching is linked to a hot inner flow, possibly via the Blandford–Znajek process, providing evidence for a universal disk–jet connection via geometric transition.

The 2021 Event Horizon Telescope observations resolve the innermost jet region of the blazar 3C 279 with unprecedented detail. The reconstructed images consistently reveal a compact core elongated nearly orthogonal to the large-scale jet axis. This rarely observed morphology recurs across multiple epochs and from 22–230 GHz and is therefore intrinsic rather than an imaging artifact. Geometric model fitting identifies several components with apparent speeds up to β _app ∼ 10, requiring bulk Lorentz factors Γ ≳ 10.3 and constraining viewing angles to extremely small values (≲1°). Rest-frame brightness temperatures are systematically low ( T _B ∼ 10 ⁹ –10 ¹⁰ K), consistent with optically thin emission at 230 GHz. These results suggest that the jet bends toward the observer on sub-parsec scales, producing strong relativistic beaming. Possible drivers of the observed jet bending and temporal evolution include the jet’s interaction with the interstellar medium, kink or Kelvin-Helmholtz instabilities, magnetic reconnection near the horizon, or binary-induced precession. However, the current temporal coverage of VLBI data remains insufficient to distinguish between these mechanisms. Continued multifrequency VLBI monitoring will be essential to constraining the dynamics and geometry of the jet base in 3C 279.

Event Horizon Telescope (EHT) images of the supermassive black hole M87* depict an asymmetric ring of emission. General relativistic magnetohydrodynamic (GRMHD) models of M87* and its accretion disk predict that the amplitude and location of the ring’s peak brightness asymmetry should fluctuate due to turbulence in the source plasma. We compare the observed distribution of brightness asymmetry amplitudes to the simulated distribution in GRMHD models, across varying black hole spin a _* . We show that, for strongly magnetized (MAD) models, three epochs of EHT data marginally disfavor ∣ a _* ∣ ≲ 0.2. This is consistent with the Blandford–Znajek model for M87’s jet, which predicts that M87* should have nonzero spin. We show quantitatively how future observations could improve spin constraints and discuss how improved spin constraints could distinguish between differing jet-launching mechanisms and black hole growth scenarios.

We present an in-depth analysis of the transverse oscillations in the M87 jet, as identified in our previous study, which reported oscillatory patterns with a characteristic period of ∼1 yr in the edge-brightened jet structure extending up to 12 mas from the core. This work is based on high-cadence KaVA 22 GHz observations conducted from 2013 December to 2016 June. By analyzing the transverse velocity profiles and the spatial evolution of the oscillations, we find that the oscillations propagate downstream along the jet, with a wavelength of ∼9–10 mas. A single-mode sinusoidal wave model applied to the ridgelines successfully reproduces the observed transverse oscillations and yields superluminal wave speeds of ∼2.7–2.9 c , consistent with the bulk jet velocity in this region. These findings suggest that the transverse oscillations may be interpreted either as transverse MHD waves—possibly excited by jet precession, nutation, or quasiperiodic magnetic flux eruptions near the central engine—or as manifestations of jet instabilities, such as current-driven instabilities. Further investigation is required to distinguish between these scenarios and to clarify the dominant physical mechanism.

In Very-Long Baseline Interferometric arrays, nearly co-located stations probe the largest scales and typically cannot resolve the observed source. In the absence of large-scale structure, closure phases constructed with these stations are zero and, since they are independent of station-based errors, they can be used to probe data issues. Here, we show with an expansion about co-located stations, how these trivial closure phases become non-zero with brightness distribution on smaller scales than their short baseline would suggest. When applied to sources that are made up of a bright compact and large-scale diffuse component, the trivial closure phases directly measure the centroid relative to the compact source and higher-order image moments. We present a technique to measure these image moments with minimal model assumptions and validate it on synthetic Event Horizon Telescope (EHT) data. We then apply this technique to 2017 and 2018 EHT observations of M87* and find a weak preference for extended emission in the direction of the large-scale jet. We also apply it to 2021 EHT data and measure the source centroid about 1 mas northwest of the compact ring, consistent with the jet observed at lower frequencies.

Relativistic jets from supermassive black holes are expected to be magnetically launched and guided, with magnetic energy systematically converted to bulk kinetic energy throughout an extended acceleration–collimation zone (ACZ). A key prediction of magnetohydrodynamic (MHD) models is a transition from poloidally dominated fields near the engine to toroidally dominated fields downstream, yet direct tests within the ACZ are hampered by weak polarization and strong Faraday rotation. We report quasi-simultaneous, high-sensitivity, multifrequency very long baseline interferometric polarimetry of M87 spanning 1.4–24.4 GHz. We present high-fidelity, Faraday-rotation-corrected maps of intrinsic linear polarization that continuously resolve the ACZ in the deprojected distance range of ∼9.0 × 10 ³ to ∼3.6 × 10 ⁵ gravitational radii from the black hole. The maps reveal pronounced north–south asymmetries in fractional linear polarization and electric vector position angle (EVPA), peaking in the inner ACZ at a projected distance of ∼20 mas along the jet and remaining prominent out to ∼100 mas. These signatures are best reproduced by models with a large-scale ordered helical field that retains a substantial poloidal component—contrary to the rapid toroidal dominance expected under steady ideal MHD. This tension implies ongoing magnetic dissipation that limits toroidal buildup over the ACZ. The handedness of the helix provides an independent constraint on the BH’s spin direction, supporting a spin vector oriented away from the observer, consistent with the orientation inferred from horizon-scale imaging. Farther downstream, the asymmetries diminish, and the EVPA and fractional polarization distributions become more symmetric; we tentatively interpret this as evolution toward a more poloidally dominated configuration, while noting current sensitivity and dynamic range limits.