arXiv subjects

P. Ábrahám

Publications and source records attributed to P. Ábrahám.

At least 19 recordsLinked to original sources

arXiv2026

MINDS survey of silicates in T Tauri disks: Correlation between dust and gas

Context. Silicates are key constituents of planet-forming disks and major building blocks of rocky planets. Mid-infrared spectral features of micron-sized silicate grains trace grain growth, mineralogy, and disk chemistry. Aims. We characterized the dust mineralogy in T Tauri disks using James Webb Space Telescope (JWST)/Mid-Infrared Instrument (MIRI) observations and investigated the connections between the dust and molecular gas compositions. Methods. We analyzed JWST/MIRI spectra of 26 disks from the MIRI mid-Infrared Disk Survey (MINDS). Using our DustComp spectral decomposition tool, we inferred the mass fractions of individual dust species. The fits included Mg$_2$SiO$_4$ (forsterite), MgSiO$_3$ (enstatite), and SiO$_2$ (silica), together with amorphous silicates of corresponding stoichiometry. Results. Mg-rich (and Fe-poor) silicates reproduce the data well, with residuals typically within $\pm3\%$. Grain size distributions are skewed toward sizes larger than $2μ$m, indicating significant growth. The average dust composition is dominated by Mg$_2$SiO$_4$-stoichiometry grains ($\sim60\%$), followed by MgSiO$_3$ ($\sim30\%$) and SiO$_2$ ($\sim10\%$). Crystalline mass fractions are typically in the $5$-$24\%$ range, with a mean of $14\%$. Annealed silica is robustly detected in nine objects, with cristobalite as the main polymorph. We found a correlation between dust and molecular gas composition: disks with strong annealed silica features show stronger CO$_2$ emission, while forsterite-rich disks display stronger H$_2$O emission. Disks with annealed silica features may also have elevated gas-phase C/O ratios. Conclusions. The observed dust-gas correlation may provide the first indication that the molecular gas composition regulates the availability of dust species in the inner disk.

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arXiv2026

Unlocking the dynamics of Young Stellar Objects: Time-Domain Interferometry with six 4-m class telescopes

The dynamics of the inner regions of young stellar objects (YSOs) is driven by a variety of physical phenomena, from magnetospheres and accretion to the dust sublimation rim and inner disk flows. These inner environments evolve on timescales of hours to days, exactly when bursts, dips, and rapid structural changes carry the most valuable information about star and planet formations, but remain hardly reachable with current facilities. A better reactive infrastructure with six or more telescopes, combined with alerts from large time-domain surveys (e.g., at the era of LSST/Rubin type facilities), and equipped with instruments spanning from the V-band to the thermal infrared (N), would provide the instantaneous uv-coverage and spectral diagnostics needed to unambiguously interpret and image these events as they happen. Such a world's first time-domain interferometric observatory would enable qualitatively new science: directly linking optical and infrared variability to spatially resolved changes in magnetospheric accretion, inner-disk geometry, and dust and gas dynamics in the innermost astronomical unit. Crucially, connecting these processes to outer-scale unresolved information from JWST, ALMA, and the ELT would yield a complete tomography of the planet-forming region.

astro-ph.IM↗

arXiv2026

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) I: Motivation, sample, data reduction, and results overview

The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity, and that some belts contain CO gas, whose origin and implications are uncertain. Most of this progress, however, has been limited by low-resolution observations. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to constrain their detailed radial and vertical structure, and to characterise the gas content. We constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models. The first ARKS results are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits multiple dusty rings. For highly inclined belts, we found that non-Gaussian vertical distributions are common and are indicative of multiple dynamical populations. We also found that 10 of the 24 belts present asymmetries. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas rich systems. ARKS has revealed a great diversity of structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products.

astro-ph.EP↗

arXiv2025

Multi-band infrared imaging reveals dusty spiral arcs around the binary B[e] star 3 Puppis

3 Puppis is the brightest known B[e] star. Recent work classifies this A-type object as a supergiant, yet the impact of its binarity on the circumstellar environment (CE) remains hard to characterize. To resolve its dusty region at 5-10 mas, we obtained mid-IR interferometric observations with VLTI/MATISSE over 3-12 μm. Because the (u,v) coverage supports imaging, we introduce a statistical interferometric-imaging workflow based on MiRA to generate averaged images: this systematic approach enables the selection of an optimal set of reconstructions, improving the robustness and fidelity of the recovered features. We also use SPARCO, an independent tool well suited to bright central objects embedded in fainter extended emission. Images from both tools in the L, M, and N bands agree and reveal an asymmetric, elongated feature ~17 mas (~10 au at 631 pc) southeast of the star with ~20% density contrast. A second northwest asymmetry and a skewed inner rim are detected. Simple geometric modelling, guided by the MATISSE images, constrains the morphology, location, and flux of the CE and its asymmetries. The images are consistent with earlier VLTI measurements but expose a more complex CE with large-scale clumps in the southeast and northwest parts of the disc. Hydrodynamic modelling indicates that tidal spiral-wake perturbations from the central binary, dynamically excited at Lindblad resonances in the circumbinary disc, best explain the radial extent and curvature of the elongated structures seen in all bands.

astro-ph.SR↗

arXiv2025

An interferometric mid-infrared study of the eruptive star binary Z CMa with MATISSE/VLTI. I. Imaging the protoplanetary disks during the 2023 outburst

The mid-infrared (MIR) emitting regions of the individual protoplanetary disks in the binary system Z CMa are resolved by MATISSE/VLTI. The observations were obtained during a serendipitous large outburst of the HBe star that lasted more than 100 days, while the FUor companion is presumed to be in quiescence. The size of the MIR-emitting disk region of the more massive HBe star increases toward longer wavelengths from $<14$ mas at 3.5$μm$ to $\ll 50$ mas at 11.5$μm$ . The lack of substructures in the HBe disk might suggest that it is a continuous disk; however, this could be due to observational constraints. We also note a radial variation of the silicate absorption feature over the disk, where the optical depth increases inwards of $<$40~au radii. This contradicts the scenario of a carved, dusty cocoon surrounding the HBe star. In the case of the less massive FUor companion, the MIR-emitting region is much smaller with an angular size $\leq$15 mas (or else a physical radius $<9$ au) in all bands, suggesting a compact disk. Both disks are aligned within uncertainties, and their orientation agrees with that of the known jets. Furthermore, MATISSE data place the binary's separation at $117.88 \pm 0.73$ mas and a position angle of $139.16^o\,\pm\,0.29^o$ east of north. Our estimates for the orbital elements gave an eccentric orbit ($e\sim0.17$) with a moderate inclination ($i\sim 66$\degr). The derived total mass is $M_{\rm total} = 16.4^{+2.1}_{-2.3}$ M$_\odot$, while the period is approximately 950 years. Our MATISSE imaging of the Herbig disk during outburst indicates a temperature gradient for the disk, while imaging of the FUor companion's disk corroborates previous studies showing that FUor disks are rather compact in the MIR. We cannot infer any misalignment between the MATISSE results and earlier ALMA/JVLA data, nor can we infer any influence from the alleged flyby event.

astro-ph.SR↗

arXiv2025

PENELLOPE VII: Revisiting empirical relations to measure accretion luminosity

The accretion luminosity (Lacc) in young, low-mass stars is crucial for understanding stellar formation, but direct measurements are often hindered by limited spectral coverage and challenges in UV-excess modeling. Empirical relations linking Lacc to various accretion tracers are widely used to overcome these limitations. This work revisits these empirical relations using the PENELLOPE dataset, evaluating their applicability across different star-forming regions and to accreting young objects other than Classical T Tauri Stars (CTTSs). We analyzed the PENELLOPE VLT/X-Shooter dataset of 64 CTTSs, measuring fluxes of several accretion tracers and adopting the stellar and accretion parameters derived from PENELLOPE works. We supplemented our analysis with the ODYSSEUS HST data set, which covers a wider spectral range in NUV bands. We compared the Lacc values obtained in the PENELLOPE and ODYSSEUS surveys finding statistically consistent results. Our analysis confirms that existing empirical relations, previously derived for the Lupus sample, provide reliable Lacc estimates for CTTSs in several other star-forming regions. We revisit empirical relations for accretion tracers in our dataset, based on HST-fit, with coefficients which are consistent within 1sigma with XS-fit results for most lines. We also propose a method to estimate extinction using these relations and investigate the empirical relations for Brackett lines (Br8 to Br21). The Lacc vs Lline empirical relations can be successfully used for statistical studies of accretion on young forming objects in different star-forming regions. These relations also offer a promising approach to independently estimate extinction in CTTSs. We confirm that near-infrared lines (PaB and BrG) reliably trace Lacc in high accretors, making them valuable tools for probing accretion properties of high accreting young stars not accessible in the UVB.

astro-ph.SR↗

arXiv2025

The Outbursting YSOs Catalogue (OYCAT)

YSOs can display unpredictable and high-amplitude rises in brightness that can last from a few months to possibly over 100 years. These types of outbursts are explained by large changes in the mass accretion rate from the disk onto the central star. The outbursts support to a model of star formation (episodic accretion) where stars would spend most of their lifetimes accreting at low rates, and gain most of their mass through these short-lived accretion outbursts. The universality of episodic accretion, as well as its potential impact on stellar and planetary formation are still under debate. Improvement on the statistics of the members of the eruptive class is needed to better understand the episodic accretion phenomenon and its universality across different mass regimes and environments. In this paper we collect published information on the spectroscopic and photometric characteristics of 174 YSOs confirmed to belong to the eruptive variable class. We classify these objects into five different sub-classes (we find 49 FUor, 20 FUor-like, 16 EX Lupi-type, 81 Peculiar/V1647 Ori-like/MNors and 8 Periodic YSOs). The classification follows what has been done previously in the literature, and it is not an attempt to redefine these classes. In addition, we present a list of 18 embedded, and 6 massive YSOs, as additional categories of eruptive variable YSOs. Due to the complexity and/or faintness of these systems, it is hard to place them into the original classification scheme of this class of variable YSOs. Finally, we present a separate list of 355 candidate eruptive variable YSOs, which either lack spectroscopic information or the available spectroscopic data is not sufficient for an unambiguous classification. The online catalogue of confirmed and candidate eruptive YSOs will be maintained and updated in the future to serve as an important reference for the star formation community.

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arXiv2025

Time-resolved protoplanetary disk physics in DQ Tau with JWST

Accretion variability is ubiquitous in YSOs. While large outbursts may strongly affect the disk, the effects of moderate bursts are less understood. We aim to study the physical response of the disk around the eccentric binary system DQ Tau to its periodic accretion changes. We organized a multi-wavelength campaign centered on four JWST/MIRI spectra. We targeted three periastrons (high accretion state) and one apastron (quiescence). We used optical and near-infrared spectroscopy and photometry to measure how the accretion luminosity varies. We decomposed the multi-epoch SEDs into stellar, accretion, and rim components. We fitted the solid-state features using various opacity curves and the molecular features using slab models. We find the inner disk of DQ Tau to be highly dynamic. The temperature, luminosity, and location of the inner dust rim vary in response to the movement of stars and the L_acc variations. This causes variable shadowing of the outer disk, leading to an anti-correlation between the rim temperature and the strength of the silicate feature. The dust mineralogy remains constant, dominated by large amorphous olivine and pyroxene grains, with smaller fractions of crystalline forsterite. The excitation of CO (1550-2260 K), HCN (880-980 K), and hot H2O (740-860 K) molecules as well as the luminosity of the [NeII] line correlate with the accretion rate, while the warm (650 K) and cold (170-200 K) H2O components are mostly constant. CO emission, originating from a hot (>1500 K) region likely within the dust sublimation radius, is most sensitive to L_acc changes. In comparison with other T Tauri disks, DQ Tau is highly C-poor and displays moderately inefficient pebble drift. We conclude that even moderate accretion rate changes affect the thermal structure in the planet-forming disk regions on short timescales, providing a crucial benchmark for understanding disk evolution.

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arXiv2025

Discovery of carbon monoxide emission from five debris disks around young A-type stars

Over the past fifteen years, surveys mainly at millimeter wavelengths have led to the discovery of $\sim$20 gas-bearing debris disks, most of them surrounding young intermediate-mass stars. Exploring the properties and origin of this gas could be fundamental to better understanding the transition between the protoplanetary and debris disk phases, the evolution of icy planetesimal belts, and the formation of planetary atmospheres. To expand the list of known CO-bearing debris disks and to improve our knowledge of the environmental conditions under which they can form, we targeted twelve dust-rich debris disks around young ($<$50 Myr) intermediate-mass stars. Using the ALMA 12-m Array we performed millimeter continuum and CO line observations to search for dust and gas and to measure their quantity and spatial distribution. We discovered CO gas in five disks. Two of them have a low CO content of a few times 10$^{-5}$ M$_\oplus$, similar to that of $β$ Pic. The other three disks, however, are CO-rich with $M_\mathrm{CO}>10^{-3}$ M$_\oplus$. By combining our results with those of other studies we concluded, in agreement with previous findings, that the detection rate of CO gas is significantly higher for disks around stars with $6.5~L_\odot<L_*<21.9~L_\odot$ ($\sim$A8$-$A0 spectral type) than for disks around less luminous stars ($0.18~L_\odot<L_*<6.4~L_\odot$, K7$-$A9). A comparison of the measured CO masses and the estimated mass loss rates of solids in disks with low CO content ($<$10$^{-4}$ M$_\oplus$) suggests that collisions may play a role in CO gas production in such systems. Interestingly, however, the estimated mass loss rates of CO-rich debris disks are not higher than those of systems with low CO content. In light of this finding, we speculate on what could lead to the formation of CO-rich debris disks.

astro-ph.EP↗

arXiv2025

Time-dependent response of protoplanetary disk temperature to an FU Ori-type luminosity outburst

Context. The most prominent cases of young star variability are accretion outbursts in FU Ori-type systems. The high power of such outbursts causes dramatic changes in the physical and chemical structure of a surrounding protoplanetary disk. As characteristic thermal timescales in the disk are comparable to the duration of the outburst, the response of its thermal structure is inherently time dependent. Aims. We analyzed how the disk thermal structure evolves under the substantial-yet transient-eating of the outburst. To cover different possible physical mechanisms driving the outburst, we examined two scenarios: one in which the increased accretion rate is confined to a compact sub-au inner region and the other where it affects the entire disk. Methods. To model the disk temperature response to the outburst we performed time-dependent radiation transfer using the HURAKAN code. The disk structure and the luminosity profile roughly correspond to those of the FU Ori system itself, which went into outburst about 90 years ago and reached a luminosity of 450 L_Sun. Results. We find that optically thick disk regions require several years to become fully heated during the outburst and a decade to cool after it. The upper layers and outer parts of the disk, which are optically thin to thermal radiation, are heated and cooled almost instantaneously. This creates an unusual radial temperature profile during the early heating phase with minima at several au both for the fully active and compact active disk scenarios. At the cooling phase, upper layers being colder than the midplane for both scenarios. Near- and mid-infrared SEDs demonstrate a significant and almost instantaneous rise by 1 - 2 orders of magnitude during the outburst, while the millimeter flux shows a change of only a factor of a few, and is slightly delayed with respect to the central region luminosity profile.

astro-ph.EP↗

arXiv2025

Dancing on the Grain: Variety of CO and its isotopologue fluxes as a result of surface chemistry and T Tauri disk properties

At the moment, one of the main ways to infer the disk mass is to use a combination of CO isotopologue line observations. A number of theoretical studies have concluded that CO must be a reliable gas tracer as its relative abundance depends on disk parameters only weakly. However, the observed line fluxes cannot always be easily used to infer the column density, much less the abundance of CO. The aim of this work is to study the dependence of the CO isotopologue millimeter line fluxes on the astrochemical model parameters of a standard protoplanetary disk around a T Tauri star and to conclude whether they or their combinations can be reliably used to determine disk parameters. Our case is set apart from earlier studies in the literature by the usage of a comprehensive chemical network with grain surface chemistry together with line radiative transfer. We use the astrochemical model ANDES together with the radiative transfer code RADMC-3D to simulate CO isotopologue line fluxes from a set of disks with varying key parameters (disk mass, disk radius, stellar mass, and inclination). We study how these values change with one parameter varying and others fixed and approximate the dependences log-linearly. We describe the dependences of CO isotopologue fluxes on all chosen disk parameters. Physical and chemical processes responsible for these dependences are analyzed and explained for each parameter. We show that using a combination of the $^{13}$CO and C$^{18}$O line fluxes, the mass can be estimated only within two orders of magnitude uncertainty and characteristic radius within one order of magnitude uncertainty. We find that inclusion of grain surface chemistry reduces $^{13}$CO and C$^{18}$O fluxes which can explain the underestimation of disk mass in the previous studies.

astro-ph.EP↗

arXiv2025

Mid-infrared evidence for iron-rich dust in the multi-ringed inner disk of HD 144432

Context. Rocky planets form by the concentration of solid particles in the inner few au regions of planet-forming disks. Their chemical composition reflects the materials in the disk available in the solid phase at the time the planets were forming. Aims. We aim to constrain the structure and dust composition of the inner disk of the young star HD 144432, using an extensive set of infrared interferometric data taken by the Very Large Telescope Interferometer (VLTI), combining PIONIER, GRAVITY, and MATISSE observations. Methods. We introduced a new physical disk model, TGMdust, to image the interferometric data, and to fit the disk structure and dust composition. We also performed equilibrium condensation calculations with GGchem. Results. Our best-fit model has three disk zones with ring-like structures at 0.15, 1.3, and 4.1 au. Assuming that the dark regions in the disk at ~0.9 au and at ~3 au are gaps opened by planets, we estimate the masses of the putative gap-opening planets to be around a Jupiter mass. We find evidence for an optically thin emission ($τ<0.4$) from the inner two disk zones ($r<4$ au) at $λ>3\ μ$m. Our silicate compositional fits confirm radial mineralogy gradients. To identify the dust component responsible for the infrared continuum emission, we explore two cases for the dust composition, one with a silicate+iron mixture and the other with a silicate+carbon one. We find that the iron-rich model provides a better fit to the spectral energy distribution. Conclusions. We propose that in the warm inner regions ($r<5$ au) of typical planet-forming disks, most if not all carbon is in the gas phase, while iron and iron sulfide grains are major constituents of the solid mixture along with forsterite and enstatite. Our analysis demonstrates the need for detailed studies of the dust in inner disks with new mid-infrared instruments such as MATISSE and JWST/MIRI.

astro-ph.SR↗

arXiv2025

T CrA has a companion: First direct detection of T CrA B with VLTI/MATISSE

T CrA is a Herbig Ae-type young star in a complex circumstellar environment; it includes a circumstellar disk, accretion streamers, jets, and outflows. It has long been suspected to be a binary. However, until now, there has been no direct detection of a companion. Here we present new VLTI/MATISSE L- and N-band observations of T CrA taken between 2023 May and 2024 August with the aim of testing the binary nature of the system. We modeled the data with a geometric model using the Python tool oimodeler. We detected a companion (T CrA B) with a projected separation of $Δr = 153.2 \pm 1.2$ mas ($\approx 23$ au) toward the west direction at a position angle of $275.4 \pm 0.1^\circ$, in 2024 May-August. Our results support that the companion has a nearly edge-on orbit that is highly misaligned with respect to the circumprimary disk. Such a configuration could cause warping and tearing of the disk around the primary, which has been proposed by recent studies. In the L band the companion is extended, with a full width at half maximum (FWHM) size of $\sim 1$ au, suggesting that the emission comes from a disk around the secondary star. The companion flux is 0.2-0.3 Jy in the L band, and 0.2-0.7 Jy in the N band, accounting for 4-20% of the total emission at those wavelengths. The SED of the companion is compatible with thermal radiation of warm dust (600-800 K).

astro-ph.SR↗

arXiv2025

Molecular inventory of a young eruptive star's environment -- Case study of the classical FU Orionis star V1057 Cyg

Studying accretion-driven episodic outbursts in YSOs is key to understanding the later stages of star and planet formation. FU Orionis-type objects form a YSO subclass, distinguished by rapid, multi-magnitude increases in brightness at optical and near-infrared wavelengths. These outbursts may significantly impact the chemistry and molecular composition around eruptive stars. However, no comprehensive millimeter-wavelength line survey exists for more evolved (Class II) sources, unlike optical and near-infrared coverage. We conducted the first wideband millimeter spectral line survey of V1057 Cyg, a low-mass eruptive FUor with the highest observed peak accretion rate in its class. Using the IRAM 30-m telescope, we surveyed the 72-263 GHz range and complemented this with targeted spectra at 219, 227, 291, and 344 GHz with the APEX 12-m telescope. We conducted radiative transfer and population diagram analyses to get first estimates of the excitation temperatures and column densities. Several molecular species trace large-scale structures, and the position-velocity diagram of $^{12}$CO suggest episodic outburst activity, with outflow dynamical timescales on the order of tens of thousands of years. We identified simple molecules (C-, N-, O-, and S-bearing), deuterated species, molecular ions, and complex organic molecules. With over 30 molecular species (including isotopologues) detected, V1057 Cyg demonstrates rich chemistry for its evolutionary state, compared to other younger (Class 0/I) FUors. V1057 Cyg is a good candidate for future interferometric studies to resolve emission structures, to possibly constrain molecular freeze-out, and detect water and complex organic molecules. Our results highlight the importance of millimeter line surveys in complementing optical/near-infrared studies, improving statistics on molecular inventories in eruptive stars and their environments.

astro-ph.SR↗

arXiv2024

Gaia20bdk -- a new FUor in Sh 2-301 Star Forming Region

Context. We analyse multi-colour photometric and spectroscopic observations of a Young Stellar Object Gaia20bdk. Aims. We aim to investigate the exact nature of the eruptive phenomenon that the star has been experiencing since 2018. Methods. We use public-domain archival photometry to characterise the quiescent phase in order to establish major physical parameters of the progenitor. Then, we use our and public-domain optical and infrared photometry and spectroscopy to study the outburst. Results. Gaia20bdk is a member of the Sharpless 2-301 star-forming region, at a distance of 3.3 kpc. The progenitor is a rather massive 2.7 solar mass, G7-type Class I young star having an effective temperature of 5300 K and bolometric luminosity of 11 solar luminosities. The optical and infrared photometric and spectroscopic data obtained during the outburst show a variety of signatures commonly found in classical FUors. Our disc modelling results in a bolometric luminosity of 100-200 solar luminosities and mass accretion rate of 1-2e-5 solar masses per year, also confirming the object's FUor classification. Further monitoring is necessary to track the light changes, accretion rate and spectral variations, as well as to understood the mechanisms behind the disc flickering.

astro-ph.SR↗

arXiv2024

North-PHASE: Studying Periodicity, Hot Spots, Accretion Stability and Early Evolution in young stars in the northern hemisphere

We present the overview and first results from the North-PHASE Legacy Survey, which follows six young clusters for five years, using the 2 deg$^2$ FoV of the JAST80 telescope from the Javalambre Observatory (Spain). North-PHASE investigates stellar variability on timescales from days to years for thousands of young stars distributed over entire clusters. This allows us to find new YSO, characterise accretion and study inner disk evolution within the cluster context. Each region (Tr37, CepOB3, IC5070, IC348, NGC2264, and NGC1333) is observed in six filters (SDSS griz, u band, and J0660, which covers H$α$), detecting cluster members as well as field variable stars. Tr37 is used to prove feasibility and optimise the variability analysis techniques. In Tr37, variability reveals 50 new YSO, most of them proper motion outliers. North-PHASE independently confirms the youth of astrometric members, efficiently distinguishes accreting and non-accreting stars, reveals the extent of the cluster populations along Tr37/IC1396 bright rims, and detects variability resulting from rotation, dips, and irregular bursts. The proper motion outliers unveil a more complex star formation history than inferred from Gaia alone, and variability highlights previously hidden proper motion deviations in the surrounding clouds. We also find that non-YSO variables identified by North-PHASE cover a different variability parameter space and include long-period variables, eclipsing binaries, RR Lyr, and $δ$ Scuti stars. These early results also emphasize the power of variability to complete the picture of star formation where it is missed by astrometry.

astro-ph.SR↗

arXiv2024

Chemical inventory of the envelope of the Class I protostar L1551 IRS 5

Episodic accretion in protostars leads to luminosity outbursts that end up heating their surroundings. This rise in temperature pushes the snow lines back, enabling the desorption of chemical species from dust grain surfaces, which may significantly alter the chemical history of the accreting envelope. However, a limited number of extensive chemical surveys of eruptive young stars have been performed thus far. In the present study, we carry out a large spectral survey of the binary Class I protostar L1551 IRS 5, known to be a FUor-like object, in the 3mm and 2mm bands with the IRAM-30m telescope. As a result, we detected more than 400 molecular lines. The source displays a great chemical richness with the detection of 75 species, including isotopologues. Among these species, there are 13 hydrocarbons, 25 N-bearing species, 30 O-bearing species, 15 S-bearing species, 12 deuterated molecules, and a total of 10 complex organic molecules (l-C4H2, CH3CCH, CH2DCCH, CH3CHO, CH3CN, CH3OCH3, CH3OCHO, CH3OH, CH2DOH, and HC5N). With the help of local thermodynamic equilibrium (LTE) and non-LTE models, we determined the column densities of most molecules as well as excitation and kinetic temperatures. While most of those molecules trace the cold envelope (< 20 K), the OCS and CH3OH emission arise from the warm (> 100 K) innermost (< 2'' ) regions. We compared the chemical inventory of L1551 IRS 5 and its column density ratios, including isotopic ratios, with other protostellar sources. A broad chemical diversity is seen among Class I objects. More observations with both single-dish telescopes and interferometers are needed to characterize the diversity in a larger sample of protostars, while more astrochemical models would help explain this diversity, in addition to the impact of luminosity outbursts on the chemistry of protostellar envelopes.

astro-ph.GA↗

arXiv2024

Abundant sub-micron grains revealed in newly discovered extreme debris discs

Extreme debris discs (EDDs) are bright and warm circumstellar dusty structures around main sequence stars. They may represent the outcome of giant collisions occuring in the terrestrial region between large planetesimals or planetary bodies, and thus provide a rare opportunity to peer into the aftermaths of these events. Here, we report on results of a mini-survey we conducted with the aim to increase the number of known EDDs, investigate the presence of solid-state features around 10μm in eight EDDs, and classify them into the silica or silicate dominated groups. We identify four new EDDs and derive their fundamental properties. For these, and for four other previously known discs, we study the spectral energy distribution around 10μm by means of VLT/VISIR photometry in three narrow-band filters and conclude that all eight objects likely exhibit solid-state emission features from sub-micron grains. We find that four discs probably belong to the silicate dominated subgroup. Considering the age distribution of the entire EDD sample, we find that their incidence begins to decrease only after 300 Myr, suggesting that the earlier common picture that these objects are related to the formation of rocky planets may not be exclusive, and that other processes may be involved for older objects (>100 Myr). Because most of the older EDD systems have wide, eccentric companions, we suggest that binarity may play a role in triggering late giant collisions.

astro-ph.EP↗