arXiv subjects

Roy van Boekel

Publications and source records attributed to Roy van Boekel.

At least 19 recordsLinked to original sources

arXiv2026

METIS high-contrast imaging simulations: From instrument modelling to science readiness

The Mid-infrared Extremely Large Telescope (ELT) Imager and Spectrograph (METIS) instrument, expected to see first light in early 2030, aims to detect and characterise exoplanets and circumstellar disks through high- contrast imaging (HCI) and spectroscopy. The High-contrast End-to-End Performance Simulator (HEEPS), initially developed to support the design of the METIS HCI modes, has evolved into a crucial tool for the METIS science team to prepare and optimize observations. HEEPS is an open-source Python-based software with a modular architecture, integrating the wavefront Fresnel propagation package PROPER, and HCI image processing with the Vortex Image Processing (VIP) package. Though designed for METIS, its modularity has been applied to other HCI instruments as well. This work presents recent updates to HEEPS, including modelling of the final METIS pupil and Lyot stops, revised quasi-static non-common path aberrations (NCPA) and Talbot effect simulations informed by as-built optical surface errors, and updated METIS Single Conjugated Adaptive Optics (SCAO) simulations. We also discuss advancements in NCPA control strategies focusing on framerate, latency and sensing performance optimization, particularly for mitigating water vapor seeing effects using the asymmetric Lyot wavefront sensor (ALF) algorithm. With these refinements, we present a comprehensive grid of HCI performance simulations for METIS, covering a range of magnitudes in the L, M, and N-bands, and several HCI observing modes. These simulations produce updated 5-sigma sensitivity contrast curves and mock HCI observations, providing key insights on HCI performance for instrument optimization and science observation planning. Our results underscore the key role of end-to-end simulations in bridging instrumental design and scientific readiness in the ELT era.

astro-ph.IM↗

arXiv2026

Maximising the mid-infrared high-contrast performance of ELT/METIS despite water vapour seeing

The Mid-infrared ELT Imager and Spectrograph (METIS) will be equipped with a SCAO system delivering Strehl ratios above 90% at L band (3.5 - 4.1 um) and close to 99% at N band (8 - 13 um) on bright stars. Yet, the actual wavefront quality seen by the METIS coronagraphic modules used for high-contrast imaging will be significantly affected by water vapour seeing, which add a strong chromatic component to dry air seeing in the mid-infrared. We analysed two years of VLTI/GRAVITY fringe tracker archives to assess the variability of differential water vapour column density at millisecond timescales on ELT scales. Our analysis suggests that water vapour seeing will add a median wavefront error of about 175 nm rms at N band, consisting mostly of low-order aberrations, with around 150 nm rms of tip-tilt errors. If not corrected, this effect would degrade the achievable sensitivity limits in terms of contrast by more than two magnitudes. To mitigate this effect, we plan to deploy a focal-plane wavefront sensing and control algorithm based on an asymmetric pupil using a deep learning approach. After briefly discussing the practical impacts of focal-plane wavefront control in METIS, we compare the expected high-contrast imaging performance with and without focal-plane wavefront control.

astro-ph.IM↗

arXiv2026

Charge migration characterization in the METIS H2RG detectors

The Mid-infrared ELT Imager and Spectrograph (METIS) is one of the first-light instruments of the Extremely Large Telescope (ELT). For the L and M band, the instrument makes use of Teledyne's H2RG detectors, known to be affected by charge migration, also known as the brighter-fatter effect (BFE). In the H2RG detectors this manifests as photo-electrons moving from a central bright pixel to neighboring pixels as the depletion region of the central pixel shrinks with accumulated charge. Due to its effect of `blurring' information, it especially affects direct imaging, transit, and high-resolution spectroscopy applications. We aim to characterize its effect in the METIS H2RG detectors, such that we can remove it without losing information.

astro-ph.IM↗

arXiv2026

Detectability of resolved hydrogen lines from the accretion shock at gas giants and their CPDs

Fewer gas giants have been caught in their accretion phase than mature ones are known. Extremely Large Telescope (ELT) instruments will have a higher sensitivity and a smaller inner working angle than tools up to now, which should increase search yields. We examine what METIS, the first-generation ELT spectrograph with R=1e5, can reveal about accreting gas giants. We focus on the accessible hydrogen recombination lines, mainly Brackett alpha and Pfund-series lines. Our approach is general but we take PDS70b as a fiducial case. It is similar to WISPIT2b. To calculate high-resolution line profiles, we combine a semianalytical multi-D description of the flow onto an accreting planet and its circumplanetary disc (CPD) with local non-LTE shock-emission models. We assume the limiting scenario of no extinction, appropriate for gas giants in gaps, and negligible contribution from magnetospheric accretion. We use simulated detector sensitivities to compute needed observing times. Both the planet- and the CPD-surface shocks contribute to the line, which has a Gaussian core but wider, asymmetrical wings. The line is much narrower than the free-fall velocity, and in fact has a nearly constant FWHM=30--40 km/s at low densities. For our fiducial accretion rate onto PDS70b, the Br-a line peak excess is as strong as the photospheric continuum, modulated mostly by H2O features. At Br-a, already the continuum of PDS 70 b yields a per-bin S/N=12 in 4h. With ProDiMo, we estimate the CPD not to hinder the detection of the line emission. The peak excess should require only 10 min to reach S/N=3. For pure shock emission, the line shape is barely sensitive to the planetary or system parameters. A complex profile would indicate that magnetospheric accretion contributes significantly. The high spectral resolution of METIS will help reveal line shapes even of faint accretors with great fidelity.

astro-ph.EP↗

arXiv2026

STARSFLUX: an all-sky catalogue of absolute spectro-photometric calibrators from 0.3 to 30 $μ$m

Obtaining accurate fluxes for faint sources from the ground at near- and mid-infrared wavelengths is challenging because of rapidly varying atmospheric absorption, and is often limited by the lack of a nearby spectro-photometric calibrator. We present the STellar Absolute Reference Spectroscopic Flux Library (STARSFLUX), an all-sky catalogue of 64,484 calibrator spectra spanning 0.3--30 $μ$m, based on the Mid-infrared stellar Diameters and Fluxes compilation Catalogue (MDFC). STARSFLUX combines Gaia DR3 stellar parameters, multi-band photometry from space- and ground-based surveys, and synthetic NewEra PHOENIX atmosphere models. For each star, we fit the observed SED with an interpolated model spectrum, angular diameter, and extinction to produce an absolutely flux-calibrated spectrum. The derived angular diameters can also be used to calibrate interferometric observations. We validate the catalogue using three independent tests. First, STARSFLUX angular radii agree closely with Gaia DR3 radii, with a median $|ΔR|/R_{\rm Gaia,DR3} \simeq 4.8$ per cent. Second, integrated L-band (2.8--4.2 $μ$m) fluxes for 12 stars in common with the Cohen infrared standards agree with Cohen values with a mean absolute percentage difference of $4.7 \pm 2.6$ per cent. Third, comparison with Gaia DR3 BP/RP spectra shows that the near-UV/visible/near-IR absolute spectro-photometric fluxes agree to approximately 3 per cent. The FITS spectra are available at https://home.strw.leidenuniv.nl/~gamez/ and will be submitted to VizieR.

astro-ph.SR↗

arXiv2025

MINDS. Anatomy of a water-rich, inclined, brown dwarf disk: lack of abundant hydrocarbons

2MASS J04381486+2611399 (or J0438) is one of the few young brown dwarfs (BD) with a highly inclined ($i\!\sim\!70^\circ$) disk. Here we report results from JWST-MIRI MRS, HST-ACS and ALMA Band 7 observations. Despite its late spectral type (M7.25), the spectrum of J0438 resembles those of inner disks around earlier-type stars (K1-M5, T Tauri stars), with a volatile reservoir lacking hydrocarbons (except for acetylene, C$_2$H$_2$) and dominated by water. Other identified species are H$_2$, CO$_2$, HCN, [Ar$^{+}$], and [Ne$^{+}$]. The dominance of water over hydrocarbons is driven by multiple factors such as disk dynamics, young disk age, low accretion rate and possible inner disk clearing. J0438 appears highly dynamic, showing a seesaw-like variability and extended emission in H$_2 \,\,\, S$(1), $S$(3), $S$(5), [Ne$^{+}$] and CO ($J=3-2$). Interestingly, the CO emission reaches up to 400 au from the brown dwarf, suggesting ongoing infalling/outflowing activity impacting the disk chemistry. These observations underscore the combined power of MIRI, HST and ALMA in characterizing the chemical diversity and dynamics of brown dwarf disks.

astro-ph.EP↗

arXiv2025

Multi dust species inner rim in magnetized protoplanetary disks

The inner regions of protoplanetary disks, within ten astronomical units, are where terrestrial planets are born. By developing a new class of multi-dust radiative magnetized inner rim models, we can gain valuable insights into the conditions during planet formation. Our goal is twofold: to study the influence of highly refractory dust species on the inner rim shape and to determine how the magnetic field affects the inner disk structure. The resulting temperature and density structures are analyzed and compared to observations. The comparison focuses on a median SED of Herbig stars and interferometric constraints from the H, K, and N-band of three Herbig-type star-disk systems: HD 100546, HD 163296, and HD 169142. We investigate 1) the influence of a large-scale magnetic field on the inner disk structure and 2) the effect of having the four most important dust species (corundum, iron, forsterite, and enstatite) shaping the rim. We use frequency-dependent irradiation and the effect of accretion heating. With the Optool package, we obtain frequency-dependent opacities for each dust grain family and calculate the corresponding temperature-dependent Planck and Rosseland opacities. Our models with multiple dust species show a smoother and radially more extended inner rim. Strongly magnetized disks show a substantial increase in the emission flux between the L and N-bands. Weakly magnetized disk models with large-scale vertical magnetic fields < 0.3 Gauss at 1 au best fit with NIR interferometric observations. Our model comparison supports the existence of moderate magnetic fields ($β$ > $10^4$), which could still drive a magnetic wind in the inner disk. Our results show that multi-dust models, including magnetic fields, still lack NIR emission, especially in the H-band. One potential solution might be a heated gas disk or evaporating objects like planetesimals close to the star.

astro-ph.EP↗

arXiv2025

XUE. JWST spectroscopy of externally irradiated disks around young intermediate-mass stars

Most young stars and therefore planetary systems form in high-mass star forming regions and are exposed to ultraviolet radiation, affecting the protoplanetary disk. These regions are located at large distances and only now with JWST become accessible to study the inner disks surrounding young stars. We present the eXtreme UV Environments (XUE) program, which provides the first detailed characterization of the physical and chemical properties of the inner disks around young intermediate-mass stars exposed to external irradiation from nearby massive stars. We present high signal to noise MIRI-MRS spectroscopy of 12 disks located in three sub-clusters of the high-mass star-forming region NGC 6357. Based on their mid-infrared spectral energy distribution, we classify the XUE sources into Group I and II based on the Meeus scheme. We analyze their molecular emission features, and compare their spectral indices and 10 $μ$m silicate emission profiles to those of nearby Herbig and intermediate T Tauri disks. Despite being more massive, the XUE stars host disks with molecular richness comparable to isolated T Tauri systems. The 10 $μ$m silicate features show lower F$_{11.3}$/F$_{9.8}$ ratios at a given F$_{\mathrm{peak}}$, but current uncertainties prevent conclusions about their inner disk properties. Most disks display water emission from the inner disk, suggesting that even in these extreme environments rocky planets can form in the presence of water. The absence of strong line fluxes and other irradiation signatures suggests that the XUE disks have been truncated by external UV photons. However, this truncation does not appear to significantly impact the chemical richness of their inner regions. These findings indicate that even in extreme environments, IMTT disks can retain the ingredients necessary for rocky planet formation.

astro-ph.SR↗

arXiv2025

Evidence for an accretion bridge in the DX Cha circumbinary system from VLTI/MATISSE observations

DX Cha (HD 104237) is a spectroscopic binary consisting of a Herbig A7.5Ve-A8Ve primary star and a K3-type companion. Here we report on new $3.55$ micrometer interferometric observations of this source with the Multi Aperture Mid-Infrared Spectroscopic Experiment (MATISSE) at the Very Large Telescope Interferometer (VLTI). To model the four MATISSE observations obtained between 2020 and 2023, we constructed a time-dependent interferometric model of the system, using the oimodeler software. The model consists of an asymmetric ring and two point sources on a Keplerian orbit. Our best-fit model consists of a circumbinary ring with a diameter of $0.86$ au ($8.1$ mas), featuring a strong azimuthal asymmetry. We found that the position angle of the asymmetry changes tens of degrees between the MATISSE epochs. The ring is relatively narrow, with a full width at half maximum (FWHM) of $\sim$$0.13$ au ($1.23$ mas). The presence of circumstellar dust emission so close to the binary is unexpected, as previous hydrodynamic simulations predicted an inner disk cavity with a diameter of $\sim$$4$ au ($\sim$$37.5$ mas). Thus, we argue that the narrow envelope of material we detected is probably not a gravitationally stable circumbinary ring, but may be part of tidal accretion streamers channeling material from the inner edge of the disk toward the stars.

astro-ph.SR↗

arXiv2024

Characterization of a Longwave HgCdTe GeoSnap Detector

New longwave HgCdTe detectors are critical to upcoming plans for ground-based infrared astronomy. These detectors, with fast-readouts and deep well-depths, will be key components of extremely large telescope instruments and therefore must be well understood prior to deployment. We analyze one such HgCdTe detector, a Teledyne Imaging Sensors GeoSnap, at the University of Michigan. We find that the properties of the GeoSnap are consistent with expectations from analysis of past devices. The GeoSnap has a well-depth of 2.75 million electrons per pixel, a read noise of 360 e-/pix, and a dark current of 330,000 e-/s/pix at 45 K. The device experiences 1/f noise which can be mitigated relative to half-well shot noise with modest frequency image differencing. The GeoSnap's quantum efficiency is calculated to be 79.7 +- 8.3 % at 10.6 microns. Although the GeoSnap's bad pixel fraction, on the order of 3%, is consistent with other GeoSnap devices, close to a third of the bad pixels in this detector are clustered in a series of 31 "leopard" spots spread across the detector plane. We report these properties and identify additional analyses that will be performed on future GeoSnap detectors.

astro-ph.IM↗

arXiv2024

METIS high-contrast imaging: from final design to manufacturing and testing

The Mid-infrared ELT Imager and Spectrograph (METIS) is one of the first-generation scientific instruments for the ELT, built under the supervision of ESO by a consortium of research institutes across and beyond Europe. Designed to cover the 3 to 13 $μ$m wavelength range, METIS had its final design reviewed in Fall 2022, and has then entered in earnest its manufacture, assembly, integration, and test (MAIT) phase. Here, we present the final design of the METIS high-contrast imaging (HCI) modes. We detail the implementation of the two main coronagraphic solutions selected for METIS, namely the vortex coronagraph and the apodizing phase plate, including their combination with the high-resolution integral field spectrograph of METIS, and briefly describe their respective backup plans (Lyot coronagraph and shaped pupil plate). We then describe the status of the MAIT phase for HCI modes, including a review of the final design of individual components such as the vortex phase masks, the grayscale ring apodizer, and the apodizing phase plates, as well as a description of their on-going performance tests and of our plans for system-level integration and tests. Using end-to-end simulations, we predict the performance that will be reached on sky by the METIS HCI modes in presence of various environmental and instrumental disturbances, including non-common path aberrations and water vapor seeing, and discuss our strategy to mitigate these various effects. We finally illustrate with mock observations and data processing that METIS should be capable of directly imaging temperate rocky planets around the nearest stars.

astro-ph.IM↗

arXiv2023

XUE. Molecular inventory in the inner region of an extremely irradiated Protoplanetary Disk

We present the first results of the eXtreme UV Environments (XUE) James Webb Space Telescope (JWST) program, that focuses on the characterization of planet forming disks in massive star forming regions. These regions are likely representative of the environment in which most planetary systems formed. Understanding the impact of environment on planet formation is critical in order to gain insights into the diversity of the observed exoplanet populations. XUE targets 15 disks in three areas of NGC 6357, which hosts numerous massive OB stars, among which some of the most massive stars in our Galaxy. Thanks to JWST we can, for the first time, study the effect of external irradiation on the inner ($< 10$ au), terrestrial-planet forming regions of proto-planetary disks. In this study, we report on the detection of abundant water, CO, CO$_2$, HCN and C$_2$H$_2$ in the inner few au of XUE 1, a highly irradiated disk in NGC 6357. In addition, small, partially crystalline silicate dust is present at the disk surface. The derived column densities, the oxygen-dominated gas-phase chemistry, and the presence of silicate dust are surprisingly similar to those found in inner disks located in nearby, relatively isolated low-mass star-forming regions. Our findings imply that the inner regions of highly irradiated disks can retain similar physical and chemical conditions as disks in low-mass star-forming regions, thus broadening the range of environments with similar conditions for inner disk rocky planet formation to the most extreme star-forming regions in our Galaxy.

astro-ph.SR↗

arXiv2023

Thermal Emission from the hot Jupiter WASP-103b in J and Ks Bands

Hot Jupiters, particularly those with temperature higher than 2000 K are the best sample of planets that allow in-depth characterization of their atmospheres. We present here a thermal emission study of the ultra hot Jupiter WASP-103 b observed in two secondary eclipses with CFHT/WIRCam in J and Ks bands. By means of high precision differential photometry, we determine eclipse depths in J and Ks to an accuracy of 220 and 270 ppm, which are combined with the published HST/WFC3 and Spitzer data to retrieve a joint constraints on the properties of WASP-103 b dayside atmosphere. We find that the atmosphere is best fit with a thermal inversion layer included. The equilibrium chemistry retrieval indicates an enhanced C/O (1.35$^{+0.14}_{-0.17}$) and a super metallicity with [Fe/H]$=2.19^{+0.51}_{-0.63}$ composition. Given the near-solar metallicity of WASP-103 of [Fe/H]=0.06, this planet seems to be $\sim$100 more abundant than its host star. The free chemistry retrieval analysis yields a large abundance of FeH, H$^{-}$, CO$_2$ and CH$_4$. Additional data of better accuracy from future observations of JWST should provide better constraint of the atmospheric properties of WASP-103b.

astro-ph.EP↗

arXiv2023

Spatially resolving polycyclic aromatic hydrocarbons in Herbig Ae disks with VISIR-NEAR at the VLT

We use the long-slit spectroscopy mode of the VISIR-NEAR experiment to perform diffraction-limited observations of eight nearby Herbig Ae protoplanetary disks. We extract spectra for various locations along the slit with a spectral resolution of R = 300 and perform a compositional fit at each spatial location using spectral templates of silicates and the four PAH bands. This yields the intensity vs. location profiles of each species. Results. We could obtain spatially-resolved intensity profiles of the PAH emission features in the N-band for five objects (AB Aurigae, HD 97048, HD 100546, HD 163296, and HD 169142). We observe two kinds of PAH emission geometry in our sample: centrally-peaked (HD 97048) and ring-like (AB Aurigae, HD 100546, HD 163296, and potentially HD 169142). Comparing the spatial PAH emission profiles with near-infrared scattered light images, we find a strong correlation in the disk sub-structure but a difference in radial intensity decay rate. The PAH emission shows a less steep decline with distance from the star. Finally, we find a correlation between the presence of (sub-) micron-sized silicate grains leading to the depletion of PAH emission within the inner regions of the disks. In this work, we find the following: (1) PAH emission traces the extent of Herbig Ae disks to a considerable radial distance. (2) The correlation between silicate emission within the inner regions of disks and the depletion of PAH emission can result from dust-mixing and PAH coagulation mechanisms and competition over UV photons. (3) For all objects in our sample, PAHs undergo stochastic heating across the entire spatial extent of the disk and are not saturated. (4) The difference in radial intensity decay rates between the PAHs and scattered-light profiles may be attributed to shadowing and dust-settling effects, which affect the scattering grains more than the PAHs.

astro-ph.EP↗

arXiv2023

The ESO's Extremely Large Telescope Working Groups

Since 2005 ESO has been working with its community and industry to develop an extremely large optical/infrared telescope. ESO's Extremely Large Telescope, or ELT for short, is a revolutionary ground-based telescope that will have a 39-metre main mirror and will be the largest visible and infrared light telescope in the world. To address specific topics that are needed for the science operations and calibrations of the telescope, thirteen specific working groups were created to coordinate the effort between ESO, the instrument consortia, and the wider community. We describe here the goals of these working groups as well as their achievements so far.

astro-ph.IM↗

arXiv2023

Forbidden emission lines in protostellar outflows and jets with MUSE

Forbidden emission lines in protoplanetary disks are a key diagnostic in studies of the evolution of the disk and the host star. We report spatially resolved emission lines, [OI] 6300, 6363, [NII] 6548, 6583, H$α$, and [SII] 6716, 6730 Angstrom that are believed to be associated with jets and magnetically driven winds in the inner disks. Observations were carried out with the optical integral field spectrograph of the Multi Unit Spectroscopic Explorer (MUSE), at the Very Large Telescope (VLT). With a resolution of 0.025 X 0.025 arcsec$^{2}$, we aim to derive the position angle of the outflow/jet (PA$_{outflow/jet}$) that is connected with the inner disk. The forbidden emission lines analyzed here have their origin at the inner parts of the protoplanetary disk. From the maximum intensity emission along the outflow/jet in DL Tau, CI Tau, DS Tau, IP Tau, and IM Lup, we were able to reliably measure the PA$_{outflow/jet}$ for most of the identified lines. We found that our estimates agree with PA$_{dust}$ for most of the disks. These estimates depend on the signal-to-noise level and the collimation of the outflow (jet). The outflows/jets in CIDA 9, GO Tau, and GW Lup are too compact for a PA$_{outflow/jet}$ to be estimated. Based on our kinematics analysis, we confirm that DL Tau and CI Tau host a strong outflow/jet with line-of-sight velocities much greater than 100 km s$^{-1}$, whereas DS Tau, IP Tau, and IM Lup velocities are lower and their structures encompass low-velocity components to be more associated with winds. Our estimates for the mass-loss rate, $\dot{M}_{loss}$, range between (1.1-6.5)X10$^{-7}$-10$^{-8}$ $M_{\odot}$ yr$^{-1}$ for the disk-outflow/jet systems analyzed here. The outflow/jet systems analyzed here are aligned within around 1 degree between the inner and outer disk. Further observations are needed to confirm a potential misalignment in IM Lup.

astro-ph.SR↗

arXiv2022

Impact of water vapor seeing on mid-infrared high-contrast imaging at ELT scale

The high-speed variability of the local water vapor content in the Earth atmosphere is a significant contributor to ground-based wavefront quality throughout the infrared domain. Unlike dry air, water vapor is highly chromatic, especially in the mid-infrared. This means that adaptive optics correction in the visible or near-infrared domain does not necessarily ensure a high wavefront quality at longer wavelengths. Here, we use literature measurements of water vapor seeing, and more recent infrared interferometric data from the Very Large Telescope Interferometer (VLTI), to evaluate the wavefront quality that will be delivered to the METIS mid-infrared camera and spectrograph for the Extremely Large Telescope (ELT), operating from 3 to 13 μm, after single-conjugate adaptive optics correction in the near-infrared. We discuss how the additional wavefront error due to water vapor seeing is expected to dominate the wavefront quality budget at N band (8-13 μm), and therefore to drive the performance of mid-infrared high-contrast imaging modes at ELT scale. Then we present how the METIS team is planning to mitigate the effect of water vapor seeing using focal-plane wavefront sensing techniques, and show with end-to-end simulations by how much the high-contrast imaging performance can be improved.

astro-ph.IM↗

arXiv2022

Detection of Na and K in the atmosphere of the hot Jupiter HAT-P-1b with P200/DBSP

We present a new optical transmission spectrum of the hot Jupiter HAT-P-1b based on two transits observed with the Double Spectrograph (DBSP) on the Palomar 200-inch (P200) telescope. The DBSP transmission spectrum, covering a wavelength range from 3250 to 10007 Å, is consistent with that observed with the Hubble Space Telescope (HST), but the former has a finer spectral resolution. The DBSP spectrum alone reveals the presence of a pressure broadened line wing for Na, the line cores for both Na and K, and tentative evidence for H$_2$O. We obtain consistent results from the spectral retrieval analyses performed on the DBSP-only dataset and the DBSP, HST, and Spitzer combined dataset. Our retrievals suggest a mostly clear atmosphere for HAT-P-1b, with a cloud coverage of $22^{+5}_{-3}$% that is dominated by enhanced haze. We derive subsolar abundances for Na, K, and C, and subsolar-to-solar for O. Future observations with James Webb Space Telescope and ground-based high-resolution spectrographs should be able to not only confirm the presence of these species but also stringently constrain the formation and migration pathways for HAT-P-1b.

astro-ph.EP↗