Markus Janson

Context . Unbiased surveys of large stellar samples are the prime means through which the prevalence of exoplanets can be derived, and crucial constraints to planet formation models can be set. Direct imaging (DI) is ideally positioned to probe the outer regions (5–300 au) of planetary systems, providing complementary information to techniques such as transits and radial velocities. Aims . We present the full sample of the SpHere INfrared survey for Exoplanets (SHINE), the second largest DI campaign to date. SHINE observed 460 stars between 2015 and 2023 thanks to the guaranteed time observations (GTO) allocated by ESO to the SPHERE consortium at VLT. The goal of this paper is to homogeneously derive the stellar properties of the targets and to define a subsample of young single hosts to be used as a starting point for the final statistical analysis of the survey. Methods . Stellar ages were determined based on kinematic indicators (such as the membership to young moving groups), age diagnostics (lithium abundance, rotation, and activity), and isochrone fitting. A thorough vetting for binarity was undertaken combining astrometric, spectroscopic, and imaging data. Results . A subsample of 333 stars, covering a large extent of stellar ages and masses, was constructed. Selection criteria, global features, as well as the properties of individual stars are reported and discussed.

Context. Observations of helium emission lines from classical T Tauri stars at high resolution ( R _λ > 10 000) offer great potential, showing distinct profile characteristics that help probe regions within the accretion geometry untapped by hydrogen lines. Parallel studies in the planetary-mass regime have not been explored. Aims. We investigate helium line emission from the nearby (47 pc), wide orbit (∼84 au), ∼13 M _Jup , accreting circumbinary companion Delorme 1 (AB)b and analyse the resolved profile characteristics to infer clues to line origin. Methods. We obtained high signal-to-noise spectra of the target over 33 exposures with VLT/UVES over near-ultraviolet to optical wavelengths at high resolution ( R _λ ~ 50 000). We studied the helium line profiles in the spectra and compared them to helium emission recorded from both accreting and non-accreting young stellar objects. Results. We detected seven neutral helium (He I ) lines λλ3890, 4027, 4473, 4923, 5017, 5877, 6680 at high confidence (> 5σ), with notable flux variation between epochs. The line profiles of He I λλ5877,4923,4473,4027 show clear asymmetry, with a narrow component at ∼0 kms ⁻¹ and a broad component redshifted by ∼15 kms ⁻¹ . The accretion luminosity (1.3 _−0.7 ^+1.6 × 10 ⁻⁵ L _⊙ ) and mass accretion rate (0.7 _−0.4 ^+0.9 × 10 ⁻⁸ M _Jup yr ⁻¹ ) obtained from median He I line luminosities using empirical scaling relations from stars are comparable but slightly higher than from the target’s ultraviolet excess emission. Conclusions. The protoplanet Delorme 1 (AB)b exhibits asymmetric He I lines similar to classical T Tauri stars, but with much smaller widths for the narrow and broad components. The triplet-singlet line ratio, a strong correlation with ultraviolet excess and the near-zero, redshifted velocities obtained for the narrow component suggest that it originates within the post-shock region, close to the planet surface. The persistent redshift of the broad component, its line width, and velocity correlation with the narrow component imply an origin within the shock structure, closer to the shock front. Emission seems to be dominated by accretion based on the obtained accretion luminosities, but a contribution from chromospheric activity may be present.

We present the discovery of a low-mass companion located at ρ ∼ 0 . ″ 85 ( r _proj ≈ 62 au) from the early type 1.3 Gyr old star HIP 53005 using direct-imaging data from the Subaru and Keck Telescopes and astrometry from the Hipparcos–Gaia Catalog of Accelerations. The companion, HIP 53005 C, is a component of a multiple system also including a ≈ 12 . ″ 4 separation M-dwarf companion inducing a negligible proper motion acceleration. HIP 53005 C’s position on color–magnitude diagrams, the fit of its spectral energy distribution to atmosphere models, and its location on an empirical mass-magnitude diagram all suggest that it lies at the M/L transition and near the hydrogen-burning limit (∼80 M _Jup ). However, our orbital fitting combining direct-imaging relative astrometry with proper motion acceleration favors a much higher dynamical mass of ∼185 M _Jup . An additional unseen, more closely orbiting companion below the detection limit (at ρ ≲ 0 . ″ 2 )) may explain this discrepancy. Alternatively, HIP 53005C could be a low-mass binary like Gliese 229Bab, making this system an intriguing laboratory for studying multiple star formation.

VHS 1256 b was the first planetary-mass companion to be observed with the James Webb Space Telescope’s Mid-Infrared Instrument (JWST/MIRI) using the Medium-Resolution Spectrometer (MRS). The MRS provides high-quality integral-field spectral data in the mid-infrared (IR) wavelengths from 4.9–18 μ m. This data set serves as a testbed for applying cross-correlation techniques to characterize exoplanet atmospheres. We implement the so-called molecular mapping approach, which consists of performing a spectral cross-correlation between each spectral pixel and atmospheric model templates. We compare these results with those obtained from cross-correlation of the extracted spectrum. Using a self-consistent Exo-REM atmospheric model grid, we constrain the temperature, surface gravity, C/O ratio, and metallicity, finding values consistent with those obtained from other analysis methods. We detect CO (S/N ∼ 25) and H ₂ O (S/N ∼ 76), with tentative detections of NH ₃ and CH ₄ (S/N ∼ 3). We test cross-correlation to measure trace-species abundances and isotopic ratios. We measure a volume mixing ratio (VMR) of [ NH 3 ] = − 5.7 3 − 0.14 + 0.15 and an isotopic ratio 12 C / 13 C = 77 . 8 − 10 + 13 , both consistent with free-chemistry retrievals. The derived NH ₃ VMR, combined with the measured temperature and radius, is consistent with VHS 1256 b having a mass above the deuterium-burning limit. These results demonstrate the diagnostic power of mid-IR spectroscopy and highlight cross-correlation as a robust method for characterizing directly imaged exoplanets, even in future higher-contrast regimes where spectral extraction becomes challenging. Future MIRI MRS observations across a wider range of temperatures and masses will further expand our understanding of planetary atmospheric chemistry.

Discovered almost ten years ago, the giant planet 51 Eridani b is one of the least separated (≈0.2″) and faintest ( J ≈ 19.74 mag) directly imaged exoplanets known to date. Its atmospheric properties have been thoroughly investigated through low- and medium-resolution spectroscopic observations, enabling the robust characterization of the planet’s bulk parameters. However, the planet’s intrinsically high contrast renders high-resolution spectroscopic observations difficult, despite their potential to yield key measurements essential for a more comprehensive characterization. This study sought to constrain the planet’s radial velocity, enabling a full 3D orbital solution when integrated with previous measurements. We obtained four high-contrast, high-resolution ( R ≈ 140 000) spectroscopic datasets of the planet, collected over a two-year interval with the HiRISE visitor instrument at the VLT to derive the planet’s radial velocity. Using self-consistent models of atmosphere, we were able to derive the radial velocity of the planet at each of the four epochs. These radial-velocity measurements were then used in combination with all existing relative astrometry in order to constrain the orbit of the planet. Our radial velocity measurements allowed us to break the degeneracy along the line of sight, making the unambiguous interpretation of the phase curve of the companion possible. We further constrained the orbital parameters, and particularly the eccentricity, for which we derive e = 0.55 ^+0.03 _−0.07 . The relatively high eccentricity indicates that the system has experienced dynamical interactions induced by an external perturber. We place constraints on the mass and semimajor axis of a hypothetical, unseen outer planet capable of producing the observed high eccentricities.

Context . Accretion processes in the planetary-mass regime are still poorly constrained, yet they strongly impact the formation and evolution of planets and the composition of circumplanetary disks. Aims . We investigate the resolved Balmer hydrogen emission-line profiles and their variability timescales in the ∼13 M _Jup , 30−45 Myr-old companion Delorme 1 (AB)b to derive constraints on the accretion mechanism at play. Methods . With VLT/UVES, we collected 31 new epochs of high-resolution optical (330–680 nm) spectra of the companion at R = 50 000, probing variability on timescales of hours to years. We study the companion’s H i emission line shape and flux variability and compare them to two proposed line origins: magnetospheric accretion funnel and localized accretion shock. Results . We detect H i Balmer lines from H α up to H10 (6564–3799 Å), as well as the UV continuum excess – signs of ongoing accretion. All lines and UV excess are variable. The H i lines can be decomposed into two static components that vary only by their flux. The broader component in velocity correlates strongly with the UV excess, and its profile is qualitatively reproduced by magnetospheric accretion funnel models but clearly not by shock models. With strong relative variability, this broad component almost entirely explains the variability in the shape of the line profiles. The second, narrower component correlates less with the UV excess and is best reproduced by shock-emission models. Its strong absolute variability makes it responsible for most of the line flux variability. Overall, the lines have low relative flux variability on hourly timescales, but up to ∼100% on weekly timescales and beyond, a behavior similar to T Tauri stars. Conclusions . The properties of the broad component of the H i lines strongly support magnetospheric accretion. The narrow component could be due to an accretion shock as well as chromospheric activity. Higher-cadence observations could search for rotational modulations to constrain the object’s rotational period and the exact geometry of the accretion flow.

Teegarden’s Star is one of the most promising targets for the first observations of LIFE as a nontransiting rocky planet with similar bulk properties to the Earth and a relatively quiescent M dwarf host star. We use LIFEsim, a software developed by the LIFE team based in ETH Zurich, along with thermal emission maps obtained from a suite of three-dimensional global climate model simulations, to explore the sensitivity of LIFE to the observation geometry. We find that 3 days of observation in broad band would be enough to disentangle the hemispheres of the planet with a 1 σ or 3 σ confidence level with a baseline or optimistic scenario, respectively. Doing the same for a fast rotator in the habitable zone of a G-class star would be prohibitively challenging. Given enough observation time, the sensitivity of LIFE may allow some spatial resolution of Teegarden’s Star b to be achieved, which may directly link to the presence of water clouds and therefore an active hydrology.

The ELT will provide groundbreaking science across a wide range of areas, including small habitable-zone exoplanets; however, true Earth analogs in the habitable zones of Sun-like stars are generally beyond the reach even of the ELT, due to the extreme contrast ratio and small angular separation between the planet and star. Here, we note that the combination of ELT and a space-based starshade would provide the contrast needed to observe potentially tens of Earth analogs, as well as other planets. This would yield the scientific basis needed for addressing central scientific questions regarding the frequency and distribution of habitability and life in the Universe. The huge aperture of ELT, combined with a contrast otherwise only reachable in space, opens up scientific avenues that are unmatched by any other existing or foreseen facility. ESO could conceivably collaborate with ESA (and others) to facilitate a starshade mission suitable for synergy with the ELT, as well as to prepare the ELT instrumentation in order to maximize its potential for synergy with a starshade.

We present the OASIS survey program discovery of a substellar companion orbiting the young A1V star HIP 71618, detected using precision astrometry from Gaia and Hipparcos and high-contrast imaging with SCExAO/CHARIS and Keck/NIRC2. Atmospheric modeling favors a spectral type of M5–M8 and a temperature of ∼2700 ± 100 K. Dynamical modeling constrains HIP 71618 B’s mass to be 60 − 21 + 27 M _Jup or 65 − 29 + 54 M _Jup , depending on the adopted companion mass prior. It has a nearly-edge-on 11 au orbit with high eccentricity. HIP 71618 B will be located within the Roman Coronagraph’s dark-hole region during the instrument’s technological demonstration phase. A high-signal-to-noise-ratio detection of HIP 71618 B at 575 nm would demonstrate a 5 σ contrast of 10 ⁻⁷ or better. The system is also located within or very close to the Roman Coronagraph’s Continuous Viewing Zone—near multiple candidate reference stars for dark-hole digging—and its primary is bright ( V ≈ 5). The suitability of HIP 71618 as a potential Roman Coronagraph target for demonstrating the instrument’s core requirement (TTR5) should motivate the timely deep vetting of candidate reference stars.

We present the discovery of a superjovian planet around the young A5 star HIP 54515, detected using precision astrometry from the Hipparcos Gaia Catalogue of Accelerations and high-contrast imaging with SCExAO/CHARIS from the recently commenced OASIS program. SCExAO/CHARIS detects HIP 54515 b in five epochs 0 . ″ 145–0 . ″ 192 from the star (∼3–4 λ / D at 1.65 μ m), exhibiting clockwise orbital motion. HIP 54515 b lies near the M/L transition with a luminosity of log( L / L _⊙ ) ∼−3.52 ± 0.03. Dynamical modeling constrains its mass and mass ratio to be 17.7 − 4.9 + 7.6 M _Jup and 0.0090 − 0.0024 + 0.0036 and favors a ∼25 au semimajor axis. HIP 54515 b adds to a growing list of superjovian planets with moderate eccentricities ( e ≈ 0.4). Now, the third planet discovered from surveys combining high-contrast extreme adaptive optics imaging with precision astrometry, HIP 54515 b, should help improve empirical constraints on the luminosity evolution and eccentricity distribution of the most massive planets. It may also provide a key technical test of the Roman Space Telescope Coronagraph Instrument’s performance in the low stellar flux, small angular separation limit, and a demonstration of its ability to yield constrainable planet spectral properties.