Sebastian F. Hoenig

Detections of protoplanets are rare and protoplanetary disk features mischaracterized as planets are common. PDS 70 is one of only two stars known to host multiple confirmed protoplanets, PDS 70 b and c, and repeat detections of a third point-like source in the system suggest the presence of third inner planet. However, previous observations of this third source are insufficient to distinguish whether it is a planet or a concentrated dust clump in Keplerian motion. Our observations with VLTI/GRAVITY+ did not re-detect this point-like source, suggesting that it is, in fact, a dust clump and not a planet. These observations demonstrate how the angular resolving power of VLTI/GRAVITY+ can be used to distinguish between protoplanets and protoplanetary disk features.

Context. High-precision astrometric observations at the microarcsecond level require a consistent relativistic framework for modelling both the dynamics of test particles and the propagation of light in gravitational fields. Aims. We aim to formulate the post-Newtonian (PN) expansion in the test body limit in a manner that yields simple and broadly applicable expressions for the motion of massive and massless particles in generic, spherically symmetric spacetimes. In particular, we intend to formulate it such that the formalism suits the modelling of observations of stars orbiting the Galactic centre (GC). Methods. We employed the PN expansion scheme to derive equations of motion for test particles and applied a perturbative solution method to solve the boundary value problem of identifying the geodesic connecting a given emitter–observer pair. Results are validated against numerical integration of the photon geodesic equation. Results. We derive the PN equations of motion for test particles in a generic, spherically symmetric spacetime. We derive analytical expressions for the apparent position of stars as measured by an observer on Earth and show the importance of this formalism for the GC science case. We compare our results with other approaches taken in the literature and discuss its implications for the modelling of orbital motion around Sgr A*. Conclusions. The proposed framework is well suited for the analysis of astrometric observations of stars orbiting the GC with microarcsecond accuracy. In this context, measurements performed with the GRAVITY+ instrument at the Very Large Telescope Interferometer can be used to place constraints on metric theories of gravity through the combined modelling of stellar dynamics and relativistic light propagation near Sgr A*.

This Letter presents JWST MIRI/Medium-Resolution Spectrometer (MRS) observations of the central r ≈ 40–240 pc regions of five active galactic nuclei (AGN) spanning a wide range of luminosities (log L _bol /erg s ⁻¹ ≈ 39.8–43.8). Combining multiphase diagnostics from polycyclic aromatic hydrocarbons (PAHs), molecular hydrogen (H ₂ ), and ionized gas at spatial scales of ∼4–24 pc, this study presents a spatially resolved investigation into the effects of the two distinct AGN feedback modes—radiative and kinetic—on the surrounding medium. The results indicate that these two feedback modes, associated with AGN irradiation and shock processing, respectively, collectively drive the relative suppression of PAH emission in the nuclear regions of the targets studied here. Moreover, the coexistence of these two AGN feedback modes, especially the shock processing associated with either jets or outflows, in the central regions of AGN naturally explains both the bimodal distribution of PAH band ratios observed in the targets studied here and the seemingly disparate results reported in the literature. Although based on a limited sample, these findings provide new insights into calibrating star formation rates from PAH emission in AGN and, more importantly, lay the groundwork for a practical framework to diagnose and quantify AGN feedback in the JWST era.

We utilize James Webb Space Telescope/Mid Infrared Instrument (JWST/MIRI) Integral Field Unit observations from the Galaxy Activity, Torus and Outflow Survey to investigate the diverse range of ionized outflow rates of obscured active galactic nuclei (AGN) with similar bolometric luminosity and explore potential associations with AGN feedback. We explore spatial correlations between ionized emission potentially associated with fast shocks ([Fe II ] _{5.34 μ m} ) and the excitation of H ₂ . We further constrain our investigation to the inner 400 pc (the nuclear and circumnuclear regions r < 200 pc), and estimate the excitation temperature and column density of H ₂ assuming local thermodynamic equilibrium and using the S(1)–S(8) rotational H ₂ emission lines visible to JWST/MIRI spectroscopy. We report the molecular gas temperature of the deprojected 400 pc nuclear region to correlate with the ionized mass outflow rate. We also observe a stronger degree of spatial correlation between [Fe II ] _{5.34 μ m} emission and H ₂ gas temperature. We observe regions of enhanced [Fe II ] _{5.34 μ m} /[Ar II ] _{6.99 μ m} spatially coincident with the ionization cones of objects with higher ionized outflow rates and [Fe II ] _{5.34 μ m} /[Ar II ] _{6.99 μ m} in the deprojected 400 pc nuclear region to scale positively with both the ionized outflow rate and the estimated molecular gas temperature. We do not observe the estimated jet cavity power within the central 400 pc as strongly correlated with the ionized mass outflow rate or molecular gas temperature of the nuclear region. We take the preceding observations to suggest a higher degree of interaction between AGN outflows and the circumnuclear disk.

WISPIT 2 is a nearby young star with a multiringed disk that was recently confirmed to host a ∼4.9 M _Jup gas giant planet embedded in a large (60 au) gap at a radial separation of 57 au from the host star. We confirm and characterize a second, close-in planet in the WISPIT 2 system using a combination of new Very Large Telescope/SPHERE H -band dual-polarization imaging and VLTI/GRAVITY K -band interferometric observations of the WISPIT 2 system. The GRAVITY detection is consistent with a point-like source while its extracted K -band spectrum shows CO band-head absorption at 2.3 μ m and a continuum shape consistent with a young giant planet. From the GRAVITY data, we extract a medium resolution K -band spectrum of the companion and fit atmospheric model grids using the species tool with nested sampling to constrain its effective temperature, radius, and luminosity. We infer T _eff of 1500–2600 K, a radius of 0.91–2.2 R _Jup , and a luminosity of (−3.47)–(−3.63). Comparison with evolutionary tracks implies a mass range of 8–12 M _Jup , approximately twice as massive as the previously confirmed WISPIT 2b. The astrometry rules out a background source and marginally detects orbital motion of WISPIT 2 c, which needs further follow-up observations for confirmation. WISPIT 2 now becomes an analog to PDS 70, offering a second laboratory for studying the formation and early evolution of a multiplanet system within its natal disk.

This Letter presents an analysis of the infrared (∼3–28 μ m) spectra extracted from the nuclear ( r < 150 pc) regions of four low-luminosity active galactic nuclei (AGN), observed by JWST NIRSpec/integral field unit and MIRI/Medium Resolution Spectroscopy as an extension of the Galaxy Activity, Torus, and Outflow Survey. We find that, compared to higher-luminosity AGN, these low-luminosity AGN exhibit distinct properties in their emission of ionized gas, polycyclic aromatic hydrocarbons (PAHs), and molecular hydrogen (H ₂ ). Specifically, the low-luminosity AGN exhibit relatively weak high ionization potential lines (e.g., [Ne V ] and [O IV ]), and the line ratios suggest that fast radiative shocks (with v _s of ∼100s km s ⁻¹ ) are the primary excitation source of ionized gas therein. Under the low-excitation conditions of their nuclear regions, these low-luminosity AGN generally exhibit a higher fraction of PAHs with large size ( N _C ≳ 200), reflecting the preferential destruction of smaller PAH molecules by AGN feedback. Furthermore, the H ₂ transitions in these low-luminosity AGN are not fully thermalized, with slow, plausibly jet-driven molecular shocks (with v _s ≤ 10 km s ⁻¹ ) likely being the extra excitation source. Taken together with results from the literature, these findings indicate that feedback operates in both low- and high-luminosity AGN, although its impact varies with AGN luminosity. In particular, systematic variations in PAH band ratios are found across AGN, demonstrating the differing influence of feedback in AGN of varying luminosities and highlighting the potential of PAH band ratios as diagnostics for distinguishing kinetic- and radiative-mode AGN feedback.

We present the first near-infrared interferometric data of a QSO at z = 4. The K -band observations were performed with GRAVITY+ on the VLTI using all four UTs, detecting a differential phase signal that traces the spatially resolved kinematics for both the H β and H γ lines in the broad-line region (BLR). We fit the two lines simultaneously with an updated model that includes distinct rotating and conical outflowing components. For the best-fit model, more than 80% of the H I line emission from the BLR originates in an outflow with a velocity up to 10 ⁴ km s ⁻¹ . This is oriented so that our line of sight is along an edge of the conical structure, which produces the prominent blue wing on the line profile. A combination of anisotropic line emission and mid-plane opacity leads to the single-sided phase signal. The model is able to qualitatively match both the outflowing C IV line profile and the systemic O I fluorescent emission. The black hole mass of 8 × 10 ⁸ M _⊙ that we derive is the highest redshift black hole mass measurement to date obtained directly from BLR dynamics. It is an order of magnitude lower than that inferred from various single epoch scaling relations, and it implies that the accretion is highly super-Eddington. With reference to recent simulations, the data suggest that this QSO is emitting close to its radiative limit in a regime where strong outflows are expected around a polar conical region.

Type-2 quasars (QSO2s) are active galactic nuclei (AGN) seen through a significant amount of dust and gas that obscures the central supermassive black hole and the broad line region. Despite this, recent mid-infrared spectra of the central 0.5–1.1 kpc of five QSO2s at z ∼ 0.1, obtained with the MRS module of JWST/MIRI, revealed 9.7, 18, and 23 μm silicate features in emission in two of them. This indicates that the high angular resolution of JWST/MIRI now allows us to peer into their nuclear region, exposing some of the directly illuminated dusty clouds that produce silicate emission. To test this, we fit the nuclear mid-infrared spectrum of the QSO2 with the strongest silicate features, J1010, with two different sets of torus models implemented in an updated version of the Bayesian tool BayesClumpy . These are the CLUMPY and the CAT3D-WIND models. The CAT3D-WIND model is preferred by the observations based on the marginal likelihood and fit residuals, although the two torus models successfully reproduce the spectrum by means of intermediate covering factors (C _T = 0.45± ^0.26 _−0.18 and C _T = 0.66± ^0.16 _−0.17 for the CLUMPY and CAT3D-WIND models) and low inclinations ( i = 50°± ^8° _9° and i = 13°± ^7° _6° ). Indeed, four of the five QSO2s with JWST/MIRI observations, including J1010, are in the blowout or “forbidden” region of the Eddington ratio-column density diagram, indicating that they are actively clearing gas and dust from their nuclear regions, leading to reduced covering factors. This is in contrast with Seyfert 2 galaxies observed with JWST, which are in the “permitted” regions of the diagram and show 9.7 μm silicate features in absorption. This supports a scenario where the more luminous the AGN and the higher their Eddington ratio, the lower the torus covering factor, driven by radiation pressure on dusty gas.

Context . This study presents the first application of high-precision astrometry to search for exomoons around substellar companions, as this field remains largely unexplored. Aims . We investigate whether the orbital motion of the companion HD 206893 B exhibits astrometric residuals consistent with the gravitational influence of an exomoon or binary planet. Methods . Using the VLTI/GRAVITY instrument, we monitored the astrometric positions of HD 206893 B and c on short (days to months) and long (yearly) timescales. This enabled us to isolate potential residual wobbles in the motion of component B attributable to an orbiting moon. Results . Our analysis reveals tentative astrometric residuals in the HD 206893 B orbit. If interpreted as an exomoon signature, these residuals correspond to a candidate (HD 206893 B I) with an orbital period of approximately 0.76 years and a mass of ~0.4 Jupiter masses. However, the origin of these residuals remains ambiguous and could be due to systematics. Complementing the astrometry, our analysis of GRAVITY R = 4000 spectroscopy for HD 206893 B confirms a clear detection of water, but no CO was found using cross-correlation. We also found that AF Lep b, and β Pic b are the best short-term candidates to look for moons with GRAVITY+. Conclusions . Our observations demonstrate the transformative potential of high-precision astrometry in the search for exomoons and proves the feasibility of the technique to detect moons with masses lower than Jupiter and potentially down to less than Neptune in optimistic cases. Crucially, further high-precision astrometric observations with VLTI/GRAVITY are essential to verify the reality and nature of this signal and apply this technique to a range of planetary systems.

Active galactic nuclei (AGNs), star formation (SF), and galaxy interactions can drive turbulence in the gas of the interstellar medium (ISM), which, in turn, plays a role in SF taking place within galaxies. The impact on molecular gas is of particular importance, as it serves as the primary fuel for SF. Our goal is to investigate the origin of turbulence and the emission of molecular gas, as well as low-and-intermediate-ionisation gas, in the inner few kpc of both AGN hosts and star-forming galaxies (SFGs). We used archival JWST MIRI/MRS observations of a sample consisting of 54 galaxies at z < 0.1. We present flux measurements for the H ₂ S(5) λ 6.9091 μm, [Ar II ] λ 6.9853 μm, [Fe II ] λ 5.3403 μm, and [Ar III ] λ 8.9914 μm emission lines along with velocity dispersion estimated by the W ₈₀ parameter. For galaxies with coronal line emission, we included measurements of the [Mg V ] λ 5.6098 μm line. We compared the line ratios to photoionisation and shock models to explore the origin of the gas emission. AGNs exhibit broader emission lines than SFGs, with the largest velocity dispersions observed in radio-strong (RS) AGNs. The H ₂ gas is less turbulent compared to ionised gas, while coronal gas presents higher velocity dispersions. The W ₈₀ values for the ionised gas show a decrease when going from the nucleus out to radii of approximately 0.5–1 kpc, followed by an outward increase up to 2–3 kpc. In contrast, the H ₂ line widths generally display increasing profiles with distance from the center. Correlations between the W ₈₀ parameter and line ratios such as H ₂ S(5)/[Ar II ] and [Fe II ]/[Ar II ] indicate that the most turbulent gas is associated with shocks, enhancing H ₂ and [Fe II ] emissions. Based on the observed line ratios and velocity dispersions, the [Fe II ] emission is consistent with predictions of fast shock models, while the H ₂ emission is likely associated with molecules formed in the post-shock region. We speculate that these shocked gas regions are produced by AGN outflows and jet-cloud interactions in AGN-dominated sources; whereas in SFGs, they might be created through stellar winds and mergers. This shock-induced gas heating may be an important mechanism of AGN (or stellar) feedback, preventing the gas from cooling and forming new stars.