arXiv subjects

M. Vioque

Publications and source records attributed to M. Vioque.

At least 19 recordsLinked to original sources

arXiv2026

An analysis of the Herbig star population and their protoplanetary disks within 1 kpc

Herbig stars are intermediate mass pre-main sequence stars of 1.5 to $\sim15$~M$_\odot$ and are in between low and high-mass star formation. This work provides a catalog of all 243 known bona-fide Herbig stars with clear infrared excess and in many cases accretion signatures within 1~kpc. It contains archival, recalibrated, and newly derived stellar parameters, accretion rate properties, and disk dust mass measurements. We derive the latter by using newly obtained millimeter photometry and literature values. We find that 50\% of Herbig dust disks are more massive than 10~M$_\oplus$, while this is only true for 20\% and 5\% of the T~Tauri disks in Lupus and Upper~Scorpius respectively. Furthermore, the Herbig disk dust mass distribution is bimodal, it consists of a high and low disk mass population with a mean dust mass of 21~M$_\oplus$ and 0.45~M$_\oplus$ respectively. We find that the catalog is near complete for within 300~pc, however, this decreases to 24\% out to 1~kpc. We observe a flat relation for Herbig disks due to objects with short disk lifetimes, caused by a combination of low disk masses and high accretion rates. Furthermore, we find the peak of the occurrence rate of massive (>10~M$_\oplus$) disks to occur at $\sim$1-2~M$_\odot$ stars, coinciding with the peak in occurrence rate of giant exoplanets. The small number of Herbig stars with low accretion rates ($<10^{-8}$~M$_\odot$~yr$^{-1}$) or low disk dust masses ($\lesssim1$~M$_\oplus$), combined with the lack of an age dependence in the disk dust mass distribution, suggests that the observed Herbig star population represents the surviving disk-hosting phase in the optically visible late stages of intermediate-mass star formation. We argue that this is either due to the formation of deep dust traps in these disks or replenishment by late-infall, or a combination of the two.

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arXiv2026

ESO User Support and Observation Preparation for VLTI Science Operations

We present recent enhancements to VLTI observing capabilities from a user-oriented perspective, together with new developments in ESO's Observation Handling Tools and end-to-end operations model for VLTI. Key upgrades include GRAVITY+ Coud\'e guiding with laser guide stars at the UTs, improved limiting magnitudes for GRAVITY and MATISSE, and a new MATISSE narrow-field off-axis mode, all supported by a streamlined, uniform template structure. Phase 2 tools now enable finding-chart generation and the selection of Coud\'e guide stars and fringe-tracker targets, and will soon offer expanded preparation features and uv-coverage visualisation. We summarise usage statistics for snapshot, astrometric, imaging, and time-series observations, outline VLTI scheduling considerations, and present new video tutorials. Starting in 2026, an archive data stream of reduced GRAVITY dispersed visibilities has become available. Complementary community engagement in VLTI operations continues to grow. We close by identifying operational lessons for future interferometric facilities, including the importance of an end-to-end data-flow and user-support model, flexible scheduling, high-level observation-preparation tools, and coordinated community support to keep complex interferometric facilities usable by a broad community.

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arXiv2026

ESOFinder: an LLM-powered tool to help users navigate ESO documentation

The large amount and diversity of documentation available for users of the European Southern Observatory (ESO), spanning the full observing lifecycle from proposal preparation and observation planning to data reduction and archival access, makes it increasingly challenging for the astronomical community to efficiently find relevant information. To address this, we have developed ESOFinder, an in-house chatbot powered by Large Language Models (LLMs) and Retrieval Augmented Generation (RAG). ESOFinder integrates public information from instrument manuals, phase 1/2/3 documentation, data reduction pipeline manuals, the ESO Knowledge Base, and key web resources (spanning more than 3500 links and over 100 manuals) to provide concise, context-aware, and reference-linked answers to user queries about proposal or observation preparation, data retrieval, and data processing. Built on open-source LLMs, running on a local server, ESOFinder ensures data privacy, transparency, and complete control over the knowledge base. Its multi-step architecture allows verification of retrieved documents and generated answers, reducing the risk of hallucinations and improving the reliability of responses compared to commercial tools. The current version of ESOFinder is being tested internally at ESO to evaluate its performance, assess its integration with internal workflows, and identify limitations in coverage and accuracy. These tests will guide further improvements, including the incorporation of additional documentation, and enhanced retrieval strategies. Ultimately, ESOFinder aims to become an interface for users to navigate ESO's complex documentation ecosystem and to support both staff and community astronomers in their daily tasks.

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arXiv2026

X-Shooter survey of disk accretion in Upper Scorpius II. A lack of correlation between accretion rates and disk properties

The evolution of protoplanetary discs is intertwined with the process of planet formation, growth and migration. Studies of nearby star forming regions of different ages and properties provide the necessary information needed to understand the processes dictating their evolution. This paper presents the results of a spectroscopic study of the stellar and accretion properties of a large sample of 127 stars with protoplanetary discs in the Upper Scorpius region with disc dust masses inferred from ALMA continuum measurements. The accretion luminosity is derived from the excess UV continuum emission with respect to the photospheric and chromospheric one self-consistently with the stellar spectral types, extinction and luminosity, using FRAPPE. We apply a new method to evaluate upper limits to the accretion luminosity. In ~50% of cases we evaluate upper limits on the accretion luminosity, either because the S/N of the data is insufficient or because the measured value of the accretion luminosity is below the estimate of the emission due to chromospheric activity. The results show that the mass accretion rate has a weak correlation with the stellar mass, while no correlation is observed with disc properties such as dust mass or gas disc radius. The dispersion is larger than what is found in younger star forming regions such as Lupus and Cham. I, and suggests a fading of the correlations with age. We find no evidence that membership to Upper Scorpius sub-groups, nor the properties of known binary or transition discs can explain the origin of this dispersion. The lack of correlation and large dispersion of accretion rates challenge the current expectations of evolutionary models. The observed properties point to a decoupling of the inner and outer disc by the age of Upper Scorpius and a fading of the relations observed in younger star forming regions.

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arXiv2026

Lithium and the evolution of intermediate-mass T Tauri and Herbig stars. Rotation, accretion, and planets

(Abridged) We contribute to our understanding of the evolution of young intermediate-mass stars by providing a comprehensive analysis of their lithium (Li) content. A sample of 71 intermediate-mass T Tauri (IMTT) and Herbig stars within the mass range 1.5 -- 3.5 M$_{\odot}$ was carefully selected for the analysis. Metallicities, rotational velocities, and accretion rates were obtained from spectra. The curves of growth for stars hotter than 8000 K were built to infer the Li abundances, which were interpreted considering standard models of stellar interiors and non-standard processes affecting Li depletion. Li is generally less strongly depleted in intermediate-mass stars than in their lower-mass counterparts, as expected from standard evolution models. However, Li abundances significantly below the cosmic value are observed in 25 -- 30$\%$ of intermediate-mass stars. It is also unexpected that the results show no significant difference between the 1.5 --2.5 M$_{\odot}$ and 2.5 -- 3.5 M$_{\odot}$ subsamples. Evidence is provided showing that disk-locking works in young intermediate-mass stars. This constitutes independent support for the hypothesis that magnetospheric accretion scenario operates in these sources. We found that disk-locking is effective for a timescale that is about twice shorter than for lower-mass stars, before magnetospheres reduce their sizes during the transition from the IMTT to the Herbig regime. This contraction of the magnetosphere can explain the increase in rotation by a factor of about 3 and in accretion by a factor of about 4 that is observed during this transition. We propose a complex scenario linking rotation, accretion, and the surface Li abundance. Finally, we tentatively suggest that the known relation between the presence of planets and Li depletion might also be present in intermediate-mass main sequence (MS) stars and might originate in the pre-MS.

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arXiv2025

Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake. How do Planetary Systems Form?

The detection and characterization of protoplanets in protoplanetary disks around young stars is emerging as a transformative field that will redefine our understanding of how planetary systems form. While current facilities have revealed the diversity of mature exoplanets and the complex structures of disks, we still lack the crucial observational link between them: a statistically meaningful census of planets caught in the act of formation. This white paper argues that such a breakthrough requires access to the nearest and most informative star-forming regions, roughly half of which are poorly accessible or entirely unreachable from Cerro Armazones. Although the ELT alone will strongly impact our knowledge of planet formation, its location prevents Europe from fully exploiting the necessary parameter space. A 30-40 m telescope in the northern hemisphere is therefore essential for obtaining diffraction-limited imaging of protoplanets and disks across the entire sky, enabling robust demographics, exploiting synergies with ngVLA, Gaia, and other facilities covering the north, and ensuring that Europe remains at the forefront of the planet-formation revolution in the coming decades.

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arXiv2025

Star formation and accretion rates within 500 pc as traced by Gaia DR3 XP spectra

Accretion rates from protoplanetary disks onto forming stars are a key ingredient in star formation and protoplanetary disk evolution. Extensive efforts surveying individual star forming regions with spectroscopy and narrow-band photometry have been performed to derive accretion rates on large populations of young stellar objects (YSOs). We use Gaia DR3 XP spectra to perform the first all-sky homogeneous analysis of YSO accretion within 500 pc. We characterise the H$\alpha$ line emission of YSOs by using the H$\alpha$ pseudo-equivalent widths and XP spectra from Gaia DR3. We derive accretion luminosities, mass accretion rates and stellar parameters for 145 975 candidate YSO H$\alpha$ emitters all-sky. We describe filtering strategies to select specific sub-samples of YSOs from this catalogue. We identify a large population of low-accreting YSO candidates untraced by previous surveys. The population of low accreting YSOs is mostly spatially dispersed, away from star forming regions or more clustered environments of star formation. Many YSOs appear disconnected from young populations, reminiscent of 'Peter Pan' YSOs. We find $L_{acc}\propto L_\star^{1.41\pm0.02}$ and $\dot M_{acc}\propto M_\star^{2.4\pm0.1}$ for the purest all-sky sample of YSO candidates. By fitting an exponential to the fraction of accreting stars in clusters of different ages in the Sco-Cen complex, we obtain an accretion timescale of 2.7$\pm$0.4 Myr. The percentage of accretors found by fitting a power-law is 70% at 2 Myr and 2.8% at 10 Myr. With this new catalogue of H$\alpha$ emitters we significantly increase the number of YSO candidates with accretion rate estimations in the local neighbourhood. This allows us to study accretion timescales and the spatial and physical properties of YSO accretion from a large, all-sky, and homogeneous sample for the first time. [abridged]

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arXiv2024

Intermediate mass T Tauri disk masses and a comparison to their Herbig disk descendants

The precursors of Herbig stars are called Intermediate Mass T Tauri (IMTT) stars, which have spectral types later than F, but stellar masses between 1.5 and 5 M_\odot, and will eventually become Herbig stars with spectral types of A and B. ALMA Band 6 and 7 archival data are obtained for 34 IMTT disks with continuum observations, 32 of which have at least 12CO, 13CO, or C18O observations although most of them at quite shallow integrations. The disk integrated flux together with a stellar luminosity scaled disk temperature are used to obtain a total disk dust mass by assuming optically thin emission. Using thermochemical Dust And LInes (DALI) models from previous work, we additionally obtain gas masses of 10/35 of the IMTT disks based on the CO isotopologues. The IMTT disks in this study have the same dust mass and radius distributions as Herbig disks. The dust mass of the IMTT disks is higher compared to that of the T Tauri disks, as is also found for the Herbig disks. No differences in dust mass are found for group I versus group II disks, in contrast to Herbig disks. The disks for which a gas mass could be determined show similar high mass disks as for the Herbig disks. Comparing the disk dust and gas mass distributions to the mass distribution of exoplanets shows that there also is not enough dust mass in disks around intermediate mass stars to form the massive exoplanets. On the other hand there is more than enough gas to form the atmospheres of exoplanets. We conclude that the sampled IMTT disk population is almost indistinguishable compared to Herbig disks, as their disk masses are the same, even though these are younger objects. Based on this, we conclude that planet formation is already well on its way in these objects, and thus planet formation should start early on in the lifetime of Herbig disks.

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arXiv2024

Gas, not dust: Migration of TESS/Gaia hot Jupiters possibly halted by the magnetospheres of protoplanetary disks

(Abridged) The presence of short-period (< 10 days) planets around main sequence (MS) stars has been associated either with the dust-destruction region or with the magnetospheric gas-truncation radius in the protoplanetary disks that surround them during the pre-MS phase. However, previous analyses have only considered low-mass FGK stars, making it difficult to disentangle the two scenarios. This exploratory study is aimed at testing whether it is the inner dust or gas disk driving the location of short-period, giant planets. By combining TESS and Gaia DR3 data, we identified a sample of 47 intermediate-mass (1.5-3 M$_{\odot}$) MS stars hosting confirmed and firm candidate hot Jupiters. We compared their orbits with the rough position of the inner dust and gas disks, which are well separated around their Herbig stars precursors. We also made a comparison with the orbits of confirmed hot Jupiters around a similarly extracted TESS/Gaia sample of low-mass sources (0.5-1.5 M$_{\odot}$). Our results suggest that the inner gas (and not the dust) disk limits the innermost orbits of hot Jupiters around intermediate-mass stars. These findings also provide tentative support to previous works that have claimed this is indeed the case for low-mass sources. We propose that hot Jupiters could be explained via a combination of the core-accretion paradigm and migration up to the gas-truncation radius, which may be responsible for halting inward migration regardless of the stellar mass regime. Larger samples of intermediate-mass stars with hot Jupiters are necessary to confirm our hypothesis, which implies that massive Herbig stars without magnetospheres (> 3-4 M$_{\odot}$) may be the most efficient in swallowing their newborn planets.

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arXiv2024

The AstraLux-TESS high-spatial resolution imaging survey. Search for stellar companions of 215 planet candidates from TESS

Chance-aligned sources or blended companions can cause false positives in planetary transit detections or simply bias the determination of the candidate properties. In the era of high-precision space-based photometers, the need for high-spatial resolution images has demonstrated to be critical for validating and confirming transit signals. This already applied to the Kepler mission, it is now applicable to the TESS survey and will be critical for PLATO. We present the results of the AstraLux-TESS survey, a catalog of high-spatial resolution images obtained with the AstraLux instrument (Calar Alto) in the context of the TESS Follow-up Observing Program. We use the lucky-imaging technique to obtain high-spatial resolution images from planet candidate hosts included mostly in two relevant regimes: exoplanet candidates belonging to the level-one requirement of the TESS mission (planets with radii $R<4~R_{\oplus}$), and candidates around intermediate-mass stars. Among the 185 planet host candidate stars observed, we found 13 (7%) to be accompanied by additional sources within 2.2 arcsec separation. Among them, six are not associated to sources in the Gaia DR3 catalog, thus contaminating the TESS light curve. We provide upper limits and probabilities to the possible existence of field contaminants through the sensitivity limits of our images. Among the isolated hosts, we can discard hazardous companions (bright enough to mimic a planetary transit signals) for all their planets. The results from this catalog are key for the statistical validation of small planets (prime targets of the TESS mission) and planets around intermediate-mass stars in the main-sequence. These two populations of planets are hard to confirm with the radial velocity technique. Our results also demonstrate the importance of this type of follow-up observations for future transit missions like PLATO, even in the Gaia era.

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arXiv2024

High-resolution ALMA observations of compact discs in the wide-binary system Sz 65 and Sz 66

Substructures in disc density are ubiquitous in the bright extended discs that are observed with high resolution. These substructures are intimately linked to the physical mechanisms driving planet formation and disc evolution. Surveys of star-forming regions find that most discs are in fact compact, less luminous, and do not exhibit these same substructures. It remains unclear whether compact discs also have similar substructures or if they are featureless. This suggests that different planet formation and disc evolution mechanisms operate in these discs. We investigated evidence of substructure within two compact discs around the stars Sz 65 and Sz 66 using high angular resolution observations with ALMA at 1.3 mm. The two stars form a wide-binary system with 6.36 arcsec separation. The continuum observations achieve a synthesised beam major axis of 0.026 arcsec, equivalent to about 4.0 au, enabling a search for substructure on these spatial scales and a characterisation of the gas and dust disc sizes with high precision. We analysed the data in the image plane through an analysis of reconstructed images, as well as in the uv plane by modelling the visibilities and by an analysis of the 12CO emission line. Comparisons were made with high-resolution observations of compact discs and radially extended discs. We find evidence of substructure in the dust distribution of Sz 65, namely a shallow gap centred at approximately 20 au, with an emission ring exterior to it. Ninety percent of the measured continuum flux is found within 27 au, and the distance for 12CO is 142 au. The observations show that Sz 66 is very compact: 90 per cent of the continuum flux is contained within 16 au, and 48 au for the gas. While the overall prevalence and diversity of substructure in compact discs relative to larger discs is yet to be determined, we find evidence that substructures can exist in compact discs.

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arXiv2022

Relation between metallicities and spectral energy distributions of Herbig Ae/Be stars. A potential link with planet formation

(Abridged) The stellar metallicity, [M/H], may have important implications for planet formation. In particular, Kama et al. proposed that the deficit of refractory elements in the surfaces of some Herbig Ae/Be stars (HAeBes) may be linked to the presence of disk cavities likely caused by Jovian planets that trap the metal-rich content. This work aims to provide a robust test on the previous proposal by analyzing the largest sample of HAeBes with homogeneously derived [M/H] values, stellar, and circumstellar properties. [M/H] values of 67 HAeBes were derived based on observed spectra and Kurucz synthetic models. Statistical analyses were carried out aiming to test the potential relation between [M/H] and the group I sources from the spectral energy distribution (SED) classification by Meeus et al., associated to the presence of cavities potentially carved by giant planets. Our study robustly confirms that group I sources tend to have a lower [M/H] than that of group II HAeBes. A similar analysis involving SED-based transitional disks does not reveal such a relation, indicating that not all processes capable of creating dust holes have an effect on the stellar abundances. We also show that the observed [M/H] differences are not driven by environmental effects. Finally, group I sources tend to have stronger (sub-) mm continuum emission presumably related to the presence of giant planets. Indeed, literature results indicate that disk substructures probably associated to their presence are up to ten times more frequent in group I HAeBes. We provide indirect evidences suggesting that giant planets are more frequent around group I/low [M/H] stars than around the rest of the HAeBes. However, the direct test requires multiple detections of forming planets in their disks, so far limited to the candidate around the metal depleted ([M/H] = -0.35 +- 0.25) group I HAeBe star AB Aur.

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arXiv2022

Gaia EDR3 comparative study of protoplanetary disk fractions in young stellar clusters

(Abridged) The lifetime of protoplanetary disks around young stars limits the timescale when planets form. A disk dissipation timescale < 10 Myr was inferred from surveys providing the fraction of stars with disks in young stellar clusters with different ages. However, most previous surveys focused on the compact region within ~ 2 pc from the clusters' centers, for which the disk fraction information considering the outer part is practically absent. We aim to test if disk fraction estimates change when inferred from an extended region around the clusters' centers. Gaia EDR3 data and a best-suited, Virtual Observatory (VO)-based tool -Clusterix-, are used to identify member stars for a representative sample of 19 young clusters considering two concentric fields of view (FOV) with radii ~ 20 pc and ~ 2 pc. Our analysis reveals that the inner disk fractions inferred from the compact and the extended regions are equal within ~ 10%, which does not support a previous hypothesis proposing that disk fractions should be significantly larger considering extended regions. A list of member and disk stars in each cluster is provided and stored in a VO-compliant archive. Averaged values and plots characterizing the whole clusters are also provided, including HR diagrams based on Gaia colors and absolute magnitudes. Our results cover the largest fields ever probed when dealing with disk fractions for all clusters analysed, and imply that their complete characterization requires the use of wide FOVs. The resulting database is a benchmark for future detailed studies of young clusters, whose disk fractions must be accurately determined by using multi-wavelength analysis potentially combined with data from coming Gaia releases.

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arXiv2021

The first interferometric survey in the K-band of massive YSOs. On the hot dust, ionised gas, and binarity at au scales

Circumstellar discs are essential for high mass star formation, while multiplicity, in particular binarity, appears to be an inevitable outcome since the vast majority of massive stars (> 8 Msun) are found in binaries (up to 100%). We constrain the sizes of the dust and ionised gas (Brgamma) emission of the innermost regions towards a sample of six MYSOs, and provide high-mass binary statistics of young stars at 2-300 au scales using VLTI (GRAVITY, AMBER) observations. We determine the inner radius of the dust emission and place MYSOs with K-band measurements in a size-luminosity diagram for the first time, and compare our findings to T Tauris and Herbig AeBes. We also compare the observed K-band sizes to the sublimation radius predicted by three different disc scenarios. Lastly, we apply binary geometries to trace close binarity among MYSOs. The inner sizes of MYSOs, Herbig AeBe and T Tauri stars appear to follow a universal trend at which the sizes scale with the square-root of the stellar luminosity. The Brgamma emission originates from somewhat smaller and co-planar area compared to the 2.2 {\mu}m continuum emission. We discuss this new finding with respect to disc-wind or jet origin. Finally, we report an MYSO binary fraction of 17-25% at milli-arcsecond separations (2-300 au). The size-luminosity diagram indicates that the inner regions of discs around young stars scale with luminosity independently of the stellar mass. At the targeted scales (2-300 au), the MYSO binary fraction is lower than what was previously reported for the more evolved main sequence massive stars, which, if further confirmed, could implicate the predictions from massive binary formation theories. Lastly, we spatially resolve the crucial star/disc interface in a sample of MYSOs, showing that au-scale discs are prominent in high-mass star formation and similar to their low-mass equivalents.

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arXiv2021

K-band GRAVITY/VLTI interferometry of "extreme" Herbig Be stars. The size-luminosity relation revisited

(Abridged:) It has been hypothesized that the location of Herbig Ae/Be stars (HAeBes) within the empirical relation between the inner disk radius (r$_{in}$), inferred from K-band interferometry, and the stellar luminosity (L$_*$), is related to the presence of the innermost gas, the disk-to-star accretion mechanism, the dust disk properties inferred from the spectral energy distributions (SEDs), or a combination of these effects. This work aims to test whether the previously proposed hypotheses do, in fact, serve as a general explanation for the distribution of HAeBes in the size-luminosity diagram. GRAVITY/VLTI spectro-interferometric observations at $\sim $2.2 $ \mu$m have been obtained for five HBes representing two extreme cases concerning the presence of innermost gas and accretion modes. V590 Mon, PDS 281, and HD 94509 show no excess in the near-ultraviolet, Balmer region of the spectra ($\Delta$D$_B$), indicative of a negligible amount of inner gas and disk-to-star accretion, whereas DG Cir and HD 141926 show such strong $\Delta$D$_B$ values that cannot be reproduced from magnetospheric accretion, but probably come from the alternative boundary layer mechanism. Additional data for these and all HAeBes resolved through K-band interferometry have been compiled from the literature and updated using Gaia EDR3 distances, almost doubling previous samples used to analyze the size-luminosity relation. We find no general trend linking the presence of gas inside the dust destruction radius or the accretion mechanism with the location of HAeBes in the size-luminosity diagram. Underlying trends are present and must be taken into account when interpreting the size-luminosity correlation. Still, it is argued that the size-luminosity correlation is most likely to be physically relevant in spite of the previous statistical warning concerning dependencies on distance.

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arXiv2021

First detection of a disk free of volatile elements around a young A-type star: A sign of collisions between rocky planets?

Aims. We present the first detailed analysis of the astrophysical parameters of the poorly studied Sco-Cen member HD 152384 and its circumstellar environment. Methods. We analyze newly obtained optical-near-IR XSHOOTER spectra, as well as archival TESS data, of HD 152384. In addition, we use literature photometric data to construct a detailed spectral energy distribution (SED) of the star. Results. The photospheric absorption lines in the spectrum of HD 152384 are characteristic of a A0 V star, for which we derive a stellar mass of 2.1 +/- 0.1 M_sun and a stellar age > 4.5 Myr. Superimposed on the photospheric absorption, the optical spectrum also displays double-peaked emission lines of Ca II, Fe I, Mg I and Si I, typical of circumstellar disks. Notably, all Hydrogen and Helium lines appear strictly in absorption. A toy model shows that the observed emission line profiles can be reproduced by emission from a compact (radius < 0.3 au) disk seen at an inclination of ~24 degrees. Further evidence for the presence of circumstellar material comes from the detection of a moderate infrared excess in the SED, similar to those found in extreme debris disk systems. Conclusions. We conclude that HD 152384 is surrounded by a tenuous circumstellar disk which, although rich in refractory elements, is highly depleted of volatile elements. To the best of our knowledge such a disk is unique within the group of young stars. However, it is reminiscent of the disks seen in some white dwarfs, which have been attributed to the disruption of rocky planets. We suggest that the disk around HD 152384 may have a similar origin and may be due to collisions in a newly formed planetary system.

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arXiv2021

Homogeneous study of Herbig Ae/Be stars from spectral energy distributions and Gaia EDR3

(Abridged) Herbig Ae/Be stars (HAeBes) have so far been studied based on relatively small samples that are scattered throughout the sky. Their fundamental stellar and circumstellar parameters and statistical properties were derived with heterogeneous approaches before Gaia. Our main goal is to contribute to the study of HAeBes from the largest sample of such sources to date, for which stellar and circumstellar properties have been determined homogeneously from the analysis of the spectral energy distributions (SEDs) and Gaia EDR3 parallaxes and photometry. Multiwavelength photometry was compiled for 209 bona fide HAeBes for which Gaia EDR3 distances were estimated. Using the Virtual Observatory SED Analyser (VOSA), photospheric models were fit to the optical SEDs to derive stellar parameters, and the excesses at infrared (IR) and longer wavelengths were characterized to derive several circumstellar properties. The stellar temperature, luminosity, radius, mass, and age were derived for each star based on optical photometry. In addition, their IR SEDs were classified according to two different schemes, and their mass accretion rates, disk masses, and the sizes of the inner dust holes were also estimated uniformly. The initial mass function fits the stellar mass distribution of the sample within 2 < M_star/M_sun < 12. In this aspect, the sample is therefore representative of the HAeBe regime and can be used for statistical purposes when it is taken into account that the boundaries are not well probed. A statistical analysis was carried out mainly focused on the different circumstellar properties of Herbig Ae (HAe) and Be (HBe) stars. The complete dataset is available online through a Virtual Observatory-compliant archive, representing the most recent reference for statistical studies on the HAeBe regime.

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arXiv2020

Planet formation in intermediate-separation binary systems

We report the first characterisation of the individual discs in the intermediate separation binary systems KK Oph and HD 144668 at millimetre wavelengths. In both systems the circum-primary and the circum-secondary discs are detected in the millimetre continuum emission, but not in $^{13}$CO nor C$^{18}$O lines. Even though the disc structure is only marginally resolved, we find indications of large-scale asymmetries in the outer regions of the primary discs, most likely due to perturbation by the companion. The derived dust masses are firmly above debris disc level for all stars. The primaries have about three times more dust in their discs than the secondaries. In the case of HD 144668 the opacity spectral index of the primary and secondary differ by the large margin of 0.69 which may be a consequence of the secondary disc being more compact. Upper limits on the gas masses imply less than 0.1 M$_{\textrm{jup}}$ in any of these discs, meaning that giant planets can no longer form in them. Considering that there have been no massive gas discs identified to date in intermediate separation binaries (i.e., binaries at a few hundred au separation), this opens space for speculation whether their binarity causes the removal of gas, with tidal interaction truncating the discs and hence shortening the accretion timescale. More systematic studies in this respect are sorely needed.

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