@article{21045,
abstract = {The abundant population of little red dots (LRDs), compact objects with red UV to optical colors and broad Balmer lines at high redshift, is revealing new insights into the properties of early active galactic nuclei (AGN). Perhaps the most surprising features of this population are the presence of Balmer absorption and ubiquitous strong Balmer breaks. Recent models link these features to an active supermassive black hole (SMBH) cocooned in very dense gas (NH ∼ 1024 cm−2). We present a stringent test of such models using VLT/MUSE observations of A2744-45924, the most luminous LRD known to date (LHα ≈ 1044 erg s−1), located behind the Abell-2744 lensing cluster at z = 4.464 (μ = 1.8). We detect a moderately extended Lyα nebula (h ≈ 5.7 pkpc), spatially offset from the point-like Hα seen by JWST by ≈1.6 pkpc. The Lyα emission is narrow (FWHM = 270 ± 15 km s−1), and faint (Lyα = 0.07Hα) compared to Lyα nebulae typically observed around quasars of similar luminosity. We detect compact N IV]λ1486 emission, spatially aligned with Hα, and a spatial shift in the far-UV continuum matching the Lyα offset. We discuss that Hα and Lyα have distinct physical origins: Hα originates from the AGN, while Lyα is powered by star formation. In the environment of A2744-45924, we identified four extended Lyα halos (Δz < 0.02, Δr < 100 pkpc). Their Lyα luminosities match the expectations based on Hα emission, and show no evidence for radiation from A2744-45924 affecting its surroundings. The lack of strong, compact, and broad Lyα and the absence of a luminous extended halo, suggest that the UV AGN light is obscured by dense gas cloaking the SMBH with a covering factor close to unity.},
author = {Torralba Torregrosa, Alberto and Matthee, Jorryt J and Pezzulli, Gabriele and Urrutia, Tanya and Gronke, Max and Mascia, Sara and D’Eugenio, Francesco and Di Cesare, Claudia and Eilers, Anna Christina and Greene, Jenny E. and Iani, Edoardo and Ishikawa, Yuzo and Mackenzie, Ruari and Naidu, Rohan P. and Navarrete, Benjamín and Kotiwale, Gauri},
issn = {1432-0746},
journal = {Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth}},
doi = {10.1051/0004-6361/202555596},
volume = {705},
year = {2026},
}
@article{21160,
abstract = {Context. AM Canum Venaticorum (AM CVn) stars are ultra-compact binary systems composed of a white dwarf primary accreting from a hydrogen-deficient donor. They play a crucial role in astrophysics as potential progenitors of Type Ia supernovae and as laboratories for gravitational wave studies. However, their formation and evolutionary history remain incomplete. Three formation channels have been discussed in the literature: the white dwarf, He-star, and cataclysmic variable channels.
Aims. The chemical composition of the accretor atmosphere reflects the material transferred from the donor. In this work we took the first accurate measurements of the fundamental parameters of the accreting white dwarf in ZTF J225237.05−051917.4, including the abundances of key elements such as carbon, nitrogen, and silicon, by analysing ultraviolet spectra obtained with the Hubble Space Telescope (HST). These measurements provide new insight into the evolutionary history of the system and, together with existing optical observations, establish it as a benchmark to develop our pipeline, paving the way for its application to a larger sample of AM CVn systems.
Methods. We determined the binary parameters through photometric analysis and constrained the atmospheric parameters of the white dwarf accretor, including its effective temperature, surface gravity, and chemical abundances, by fitting the HST ultraviolet spectrum with synthetic spectral models. We then inferred the system’s formation channel by comparing the results with theoretical evolutionary models.
Results. According to our measurements, the accretor’s effective temperature (Teff) is 23 300 ± 600 K and the surface gravity (log g) is 8.4 ± 0.3, which imply an accretor mass (MWD) of 0.86 ± 0.16 M⊙. We find a high nitrogen-to-carbon abundance ratio by mass of > 153.
Conclusions. The accretor is significantly hotter than previous estimates based on simplified blackbody fits to the spectral energy distribution, underscoring the importance of detailed spectral modelling for accurately determining system parameters. Our results show that ultraviolet spectroscopy is well suited to constraining the formation channels of AM CVn systems. Of the three proposed formation channels, the He-star channel can be excluded given the high nitrogen-to-carbon ratio. Our results are consistent with both the white dwarf and cataclysmic variable channels.},
author = {Yu, W. and Pala, A. F. and Kupfer, T. and Gänsicke, B. T. and Koester, D. and Belloni, D. and Wong, T. L.S. and Schreiber, M. R. and van Roestel, Joannes C and Brown, A. J. and Waagen, E. O. and González-Carballo, J. L. and Bednarz, S. and Bernacki, K. and De Martino, D. and Fernández Mañanes, E. and González Farfán, R. and Green, M. J. and Groot, P. J. and Hambsch, F. J. and Knigge, C. and Martin-Velasco, J. L. and Morales-Aimar, M. and Myers, G. and Naves Nogues, R. and Poggiani, R. and Popowicz, A. and Ramsay, G. and Reina-Lorenz, E. and Rodríguez-Gil, P. and Salto-González, J. L. and Sion, E. M. and Steeghs, D. and Szkody, P. and Toloza, O. and Tovmassian, G.},
issn = {1432-0746},
journal = {Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{The evolutionary history of ultra-compact accreting binaries: I. Chemical abundances and the formation channel of the eclipsing AM CVn system ZTF J225237.05-051917.4 from HST spectroscopy}},
doi = {10.1051/0004-6361/202557568},
volume = {706},
year = {2026},
}
@article{21274,
abstract = {Many white dwarfs are observed in compact double white dwarf binaries, and through the emission of gravitational waves, a large fraction are destined to merge. The merger remnants that do not explode in a Type Ia supernova are expected to initially be rapidly rotating and highly magnetized. In this work, we present our discovery of the variable white dwarf ZTF J200832.79+444939.67, hereafter ZTF J2008+4449, as a likely merger remnant showing signs of circumstellar material without a stellar or substellar companion. The nature of ZTF J2008+4449 as a merger remnant is supported by its physical properties: it is hot (35 500 ± 300 K) and massive (1.12 ± 0.03 M
⊙
), rapidly rotating with a period of ≈6.6 minutes, and likely possesses exceptionally strong magnetic fields (∼400−600 MG) at its surface. Remarkably, we detect a significant period derivative of (1.80 ± 0.09)×10
−12
s/s, indicating that the white dwarf is spinning down, and a soft X-ray emission that is inconsistent with photospheric emission. As the presence of a mass-transferring stellar or brown dwarf companion is excluded by infrared photometry, the detected spin-down and X-ray emission could be tell-tale signs of a magnetically driven wind or of interaction with circumstellar material, possibly originating from the fallback of gravitationally bound merger ejecta or from the tidal disruption of a planetary object. We also detect Balmer emission, which requires the presence of ionized hydrogen in the vicinity of the white dwarf, showing Doppler shifts as high as ≈2000 km s
−1
. The unusual variability of the Balmer emission on the spin period of the white dwarf is consistent with the trapping of a half ring of ionized gas in the magnetosphere of the white dwarf.
},
author = {Cristea, Andrei-Alexandru and Caiazzo, Ilaria and Cunningham, Tim and Raymond, John C. and Vennes, Stephane and Kawka, Adela and Desai, Aayush A and Miller, David R. and Hermes, J. J. and Fuller, Jim and Heyl, Jeremy and van Roestel, Jan and Burdge, Kevin B. and Rodriguez, Antonio C. and Pelisoli, Ingrid and Gänsicke, Boris T. and Szkody, Paula and Kenyon, Scott J. and Vanderbosch, Zach and Drake, Andrew and Ferrario, Lilia and Wickramasinghe, Dayal and Karambelkar, Viraj R. and Justham, Stephen and Pakmor, Ruediger and El-Badry, Kareem and Prince, Thomas and Kulkarni, S. R. and Graham, Matthew J. and Masci, Frank J. and Groom, Steven L. and Purdum, Josiah and Dekany, Richard and Bellm, Eric C.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{A half ring of ionized circumstellar material trapped in the magnetosphere of a white dwarf merger remnant}},
doi = {10.1051/0004-6361/202556432},
volume = {706},
year = {2026},
}
@article{21341,
abstract = {We aim to characterise the mass-metallicity relation (MZR) and the 3D correlation between the stellar mass, metallicity, and star formation rate (SFR) known as the fundamental metallicity relation (FMR) for galaxies at 5 < z < 7. Using ∼800 [O III] selected galaxies from deep NIRCam grism surveys, we present our stacked measurements of direct-Te metallicities, which we used to test recent strong-line metallicity calibrations. Our measured direct-Te metallicities (0.1–0.2 Z⊙ for M★ ≈ 5 × 107 − 9 M⊙, respectively) match recent JWST/NIRSpec-based results. However, there are significant inconsistencies between observations and hydrodynamical simulations. We observe a flatter MZR slope than the SPHINX20 and FLARES simulations, which cannot be attributed to selection effects. With simple models, we show that the effect of an [O III] flux-limited sample on the observed shape of the MZR is strongly dependent on the FMR. If the FMR is similar to the one in the local Universe, the intrinsic high-redshift MZR should be even flatter than is observed. In turn, a 3D relation where SFR correlates positively with metallicity at fixed mass would imply an intrinsically steeper MZR. Our measurements indicate that metallicity variations at fixed mass show little dependence on the SFR, suggesting a flat intrinsic MZR. This could indicate that the low-mass galaxies at these redshifts are out of equilibrium and that metal enrichment occurs rapidly in low-mass galaxies. However, being limited by our stacking analysis, we are yet to probe the scatter in the MZR and its dependence on SFR. Large carefully selected samples of galaxies with robust metallicity measurements can put tight constraints on the high-redshift FMR and help us to understand the interplay between gas flows, star formation, and feedback in early galaxies.},
author = {Kotiwale, Gauri and Matthee, Jorryt J and Kashino, Daichi and Vijayan, Aswin P. and Torralba Torregrosa, Alberto and Di Cesare, Claudia and Iani, Edoardo and Bordoloi, Rongmon and Leja, Joel and Maseda, Michael V. and Tacchella, Sandro and Shivaei, Irene and Heintz, Kasper E. and Danhaive, A. Lola and Mascia, Sara and Kramarenko, Ivan and Navarrete, Benjamín and Mackenzie, Ruari and Naidu, Rohan P. and Sobral, David},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy}},
doi = {10.1051/0004-6361/202556597},
volume = {706},
year = {2026},
}
@article{21380,
abstract = {Context. Extreme emission line galaxies (EELGs) are believed to significantly contribute to the star formation activity and mass assembly in galaxies. EELGs likely also play a leading role in the cosmic re-ionization as their interstellar medium may allow a significant fraction of their ionizing photons to escape (> 5%). Finding low-redshift analogues of these high-z galaxies is therefore essential to characterizing the physical conditions in the interstellar medium of these galaxies and understanding the processes that re-ionized the Universe.
Aims. We aimed to develop a robust and efficient method for the photometric identification of EELGs using the J-PAS survey. J-PAS will cover approximately 8500 deg2 of the sky with 54 narrow-band filters in the optical range plus i-SDSS, enabling detailed studies of the physical properties of these galaxies. In this work we focused on an initial subset of the survey: a 30 square degree area with complete observations in all bands.
Methods. We combine equivalent width (EW) measurements from J-PAS narrow-band photometry with artificial intelligence techniques to identify galaxies with emission lines exceeding 300 Å. We validated our selection using spectroscopic data from DESI DR1 and characterized the selected sample through spectral energy distribution fitting with CIGALE.
Results. We identify 917 EELGs up to z = 0.8 over 30 deg2, achieving a purity of 95% and a completeness of 96% for i-SDSS < 22.5 mag. Importantly, active galactic nucleus contamination was carefully considered and is estimated to be around 5%. Furthermore, a cross-match with DESI yielded 79 counterparts; their redshifts are in excellent agreement with our photometric estimates, thereby confirming the reliability of our redshift determination. In addition, the derived emission line fluxes are in good agreement with spectroscopic measurements. Moreover, the selected sample reveals strong correlations between the ionizing photon production efficiency (ξion) and EW(Hβ), which are consistent with previous observational studies at low and high redshifts and theoretical expectations. Finally, most of the sources surpass the ionizing efficiency threshold required for re-ionization, highlighting their relevance as local analogues of early-Universe galaxies.},
author = {Giménez-Alcázar, A. and Amorín, R. and Vílchez, J. M. and Hernán-Caballero, A. and González-Otero, M. and Arroyo-Polonio, A. and Iglesias-Páramo, J. and Lumbreras-Calle, A. and Fernández-Ontiveros, J. A. and López-Sanjuan, C. and Bonatto, L. and González Delgado, R. M. and Kehrig, C. and Torralba Torregrosa, Alberto and Rahna, P. T. and Jiménez-Teja, Y. and Márquez, I. and Breda, I. and Álvarez-Candal, A. and Abramo, R. and Alcaniz, J. and Benitez, N. and Bonoli, S. and Carneiro, S. and Cenarro, J. and Cristóbal-Hornillos, D. and Dupke, R. and Ederoclite, A. and Hernández-Monteagudo, C. and Marín-Franch, A. and Mendes de Oliveira, C. and Moles, M. and Sodré, L. and Taylor, K. and Varela, J. and Vázquez Ramió, H.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{J-PAS: First identification, physical properties, and ionization efficiency of extreme emission line galaxies}},
doi = {10.1051/0004-6361/202557358},
volume = {706},
year = {2026},
}
@article{21450,
abstract = {Stellar wind mass loss of massive stars is often assumed to depend on their metallicity Z. Therefore, evolutionary models predict that massive stars in lower-Z environments are able to retain more of their hydrogen-rich layers and evolve into brighter cool supergiants (cool SGs; Teff < 7 kK). Surprisingly, in galaxies in the metallicity range 0.2 ≲ Z/Z⊙ ≲ 1.5, previous studies have not found a metallicity dependence on the upper luminosity limit Lmax of cool SGs. Here, we add four galaxies to the sample studied for this purpose with data from the Hubble Space Telescope and the James Webb Space Telescope (JWST). Observations of the extremely metal-poor dwarf galaxy I Zw 18 from JWST allow us to extend the studied metallicity range down to Z/Z⊙ ≈ 1/40. For cool SGs in all studied galaxies, including I Zw 18, we find a constant value of Lmax ≈ 105.6 L⊙, similar to literature results for 0.2 ≲ Z/Z⊙ ≲ 1.5. In I Zw 18 and the other studied galaxies, the presence of Wolf-Rayet stars has been previously inferred. Although we cannot rule out that some of them become intermediate-temperature objects, this paints a picture in which evolved stars with L > 105.6 L⊙ burn helium as hot, helium-rich stars down to extremely low metallicity. We argue that metallicity-independent late-phase mass loss would be the most likely mechanism responsible for this. Regardless of the exact stripping mechanism (winds or, for example, binary interaction), for the Early Universe our results imply a limitation on black hole masses and a contribution of stars born with M ≳ 30 M⊙ to its surprisingly strong nitrogen enrichment. We propose a scenario in which single stars at low metallicity emit sufficiently hard ionizing radiation to produce He II and C IV lines. In this scenario, late-phase metallicity-independent mass loss produces hot, helium-rich stars. Due to the well-understood metallicity dependence on the radiation-driven winds of hot stars, a window of opportunity would open below 0.2 Z⊙, where self-stripped helium-rich stars can exist without dense Wolf-Rayet winds that absorb hard ionizing radiation.},
author = {Schootemeijer, Abel and Götberg, Ylva Louise Linsdotter and Langer, Norbert and Bortolini, Giacomo and Hirschauer, Alec S. and Patrick, Lee},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{A constant upper luminosity limit of cool supergiant stars down to the extremely low metallicity of I Zw 18}},
doi = {10.1051/0004-6361/202557675},
volume = {707},
year = {2026},
}
@article{21451,
abstract = {The population of the little red dots (LRDs) may represent a key phase of supermassive black hole (SMBH) growth. A cocoon of dense excited gas is emerging as a key component to explain the most striking properties of LRDs, such as strong Balmer breaks and Balmer absorption, as well as the weak IR emission. To dissect the structure of LRDs, we analyzed new deep JWST/NIRSpec PRISM and G395H spectra of FRESCO-GN-9771, one of the most luminous known LRDs at z = 5.5. These spectra reveal a strong Balmer break, broad Balmer lines, and very narrow [O III] emission. We revealed a forest of optical [Fe II] lines, which we argue are emerging from a dense (nH = 109 − 10 cm−3) warm layer with electron temperature Te ≈ 7000 K. The broad wings of Hα and Hβ have an exponential profile due to electron scattering in this same layer. The high Hα : Hβ : Hγ flux ratio of ≈10.4 : 1 : 0.14 is an indicator of collisional excitation and resonant scattering dominating the Balmer line emission. A narrow Hγ component, unseen in the other two Balmer lines due to outshining by the broad components, could trace the ISM of a normal host galaxy with a star formation rate of ∼5 M⊙ yr−1. The warm layer is mostly opaque to Balmer transitions, producing a characteristic P Cygni profile in the line centers suggesting outflowing motions. This same layer is responsible for shaping the Balmer break. The broadband spectrum can be reasonably matched by a simple photoionized slab model that dominates the λ > 1500 Å continuum and a low-mass (∼108 M⊙) galaxy that could explain the narrow [O III], with only a subdominant contribution to the UV continuum. Our findings indicate that Balmer lines are not directly tracing the gas kinematics near the SMBH and that the BH mass scale is likely much lower than virial indicators suggest.},
author = {Torralba Torregrosa, Alberto and Matthee, Jorryt J and Pezzulli, Gabriele and Naidu, Rohan P. and Ishikawa, Yuzo and Brammer, Gabriel B. and Chang, Seok Jun and Chisholm, John and De Graaff, Anna and D’Eugenio, Francesco and Di Cesare, Claudia and Eilers, Anna Christina and Greene, Jenny E. and Gronke, Max and Iani, Edoardo and Kokorev, Vasily and Kotiwale, Gauri and Kramarenko, Ivan and Ma, Yilun and Mascia, Sara and Navarrete, Benjamín and Nelson, Erica and Oesch, Pascal and Simcoe, Robert A. and Wuyts, Stijn},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings}},
doi = {10.1051/0004-6361/202557537},
volume = {707},
year = {2026},
}
@article{21452,
abstract = {Galaxies exhibit a tight correlation between their star formation rate (SFR) and stellar mass over a wide redshift range known as the star-forming main sequence (SFMS). With JWST, the SFMS can now be investigated at high redshifts down to masses of ∼106 M⊙, using sensitive star formation rate tracers such as the Hα emission, which allow us to probe the variability in the star formation histories. We present inferences of the SFMS based on 316 Hα-selected galaxies at z ∼ 4 − 5 with log(M★/M⊙) = 6.4 − 10.6. These galaxies were identified behind the Abell 2744 lensing cluster with NIRCam grism spectroscopy from the survey All the Little Things (ALT). At face value, our data suggest a shallow slope in the SFMS (SFR ∝ M★α, with α = 0.45). After we corrected this for the Hα-flux limited nature of our survey using a Bayesian framework, the slope steepened to α = 0.59+0.10−0.09, whereas current data on their own are inconclusive on the mass dependence of the scatter. These slopes differ significantly from the slope of ∼1 that is expected from the observed evolution of the galaxy stellar mass function and from simulations. When we fixed the slope to α = 1, we found evidence for a decreasing intrinsic scatter with stellar mass (from ∼0.5 dex at M★ = 108 M⊙ to 0.4 dex at M★ = 1010 M⊙). This difference might be explained by a (combination of) luminosity-dependent SFR(Hα) calibration, a population of (mini)-quenched low-mass galaxies, or underestimated dust attenuation in high-mass galaxies. Future deep observations with different facilities can quantify these processes, which will enable us to achieve better insights into the variability of the star formation histories.},
author = {Di Cesare, Claudia and Matthee, Jorryt J and Naidu, Rohan P. and Torralba, Alberto and Kotiwale, Gauri and Kramarenko, Ivan and Blaizot, Jeremy and Rosdahl, Joakim and Leja, Joel and Iani, Edoardo and Adamo, Angela and Covelo-Paz, Alba and Furtak, Lukas J. and Heintz, Kasper E. and Mascia, Sara and Navarrete, Benjamín and Oesch, Pascal A. and Romano, Michael and Shivaei, Irene and Tacchella, Sandro},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations}},
doi = {10.1051/0004-6361/202557790},
volume = {707},
year = {2026},
}
@article{21481,
abstract = {The Hα emission line in galaxies is a powerful tracer of their recent star formation activity. With the advent of JWST, we are now able to routinely observe Hα in galaxies at high redshift (z ≳ 3) and thus measure their star formation rates (SFRs). However, using classical SFR(Hα) calibrations to derive the SFRs leads to biased results because high-redshift galaxies are commonly characterized by low metallicities and bursty star formation histories, affecting the conversion factor between the Hα luminosity (LHα) and the SFR. We developed a set of new SFR(Hα) calibrations that allowed us to predict the SFRs of Hα-emitters at z ≳ 3 with very little error. We used the SPHINX cosmological simulations to select a sample of star-forming galaxies representative of the Hα-emitter population observed with JWST. We then derived linear corrections to the classical SFR(Hα) calibrations that took variations in the physical properties (e.g., stellar metallicities) among individual galaxies into account. We obtained two new SFR(Hα) calibrations that compared to the classical calibrations reduce the root mean squared error (RMSE) in the predicted SFRs by ΔRMSE ≈ 0.04 dex and ΔRMSE ≈ 0.06 dex, respectively. Using the recent JWST NIRCam/grism observations of Hα-emitters at z ∼ 6, we show that the new calibrations affect the high-redshift galaxy population statistics: (i) the estimated cosmic SFR density decreases by ΔρSFR ≈ 12%, and (ii) the observed slope of the star formation main sequence increases by Δ∂logSFR/∂logM★ = 0.08 ± 0.02.},
author = {Kramarenko, Ivan and Rosdahl, J. and Blaizot, J. and Matthee, Jorryt J and Katz, H. and Di Cesare, Claudia},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{H α as a tracer of star formation in the SPHINX cosmological simulations}},
doi = {10.1051/0004-6361/202557114},
volume = {707},
year = {2026},
}
@article{21658,
abstract = {Dipolar (ℓ = 1) mixed modes have revealed a surprisingly weak differential rotation between the core and the envelope of evolved solar-like stars. Quadrupolar (ℓ = 2) mixed modes also contain information regarding internal dynamics but are very rarely characterised due to their low amplitude and the challenging identification of adjacent or overlapping rotationally split multiplets affected by near-degeneracy effects. We aim to extend the broadly used asymptotic seismic diagnostics beyond ℓ = 1 mixed modes by developing an analogue asymptotic description of ℓ = 2 mixed modes while explicitly accounting for near-degeneracy effects that distort their rotational multiplets. We have derived a new asymptotic formulation of near-degenerate mixed ℓ = 2 modes that describes off-diagonal terms representing the interaction between modes of adjacent radial orders. This formalism, expressed directly in the mixed-mode basis, provides analytical expressions for the near-degeneracy effects. We implemented the formalism within a global Bayesian mode-fitting framework for a direct fit of all ℓ = 0, 1, 2 modes in the power spectrum density. We were able to asymptotically model the asymmetric rotational splitting present in various radial orders of ℓ = 2 modes observed in young red giant stars without the need for any numerical stellar modelling. We applied our formalism to the Kepler target KIC 7341231, and it yielded core and envelope rotation rates consistent with previous numerical modelling while providing improved constraints from the global and model-independent approach. We also characterised the new target, KIC 8179973, measuring its rotation rate and mixed-mode parameters for the first time. As our framework relies on a direct global fit, it allows for much better precision on the asteroseismic parameters and rotation rate estimates than standard methods, yielding better constraints for rotation inversions. We have placed the first observational constraints on the asymptotic ℓ = 2 mixed-mode parameters (ΔΠ2, q2, and εg, 2), thus paving the way towards the use of asymptotic seismology beyond ℓ = 1 mixed modes.},
author = {Liagre, Bastien Raymond Bernard and Desai, Aayush A and Einramhof, Lukas and Bugnet, Lisa Annabelle},
issn = {1432-0746},
journal = {Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{Near-degeneracy effects in quadrupolar mixed modes: From an asymptotic description to data fitting}},
doi = {10.1051/0004-6361/202558023},
volume = {707},
year = {2026},
}
@article{21659,
abstract = {The recent detection of solar equatorial Rossby waves has renewed interest in the study of gravito-inertial waves propagating in the convective envelope of solar-type stars. In particular, the ability of these envelope gravito-inertial modes to couple with those trapped in the radiative interior could open up new opportunities for probing the deep-layer dynamics of solar-type stars. The possibility for such a coupling to occur is particularly favoured among pre-main-sequence (PMS) solar-type stars. Indeed, due to the contraction of the protostellar object, they are able to reach high rotation frequencies before nuclear reactions are ignited and magnetic braking becomes the driving mechanism for their rotational evolution. In this work, we studied the coupling between the envelope inertial waves and the radiative interior g modes in PMS stars, focussing on the case of prograde dipolar modes. We considered the cases of 0.5 M⊙ and 1 M⊙ PMS models, each with three different scenarios of rotational evolution. We show that for stars that have formed with a sufficient amount of angular momentum, this coupling can occur in frequency ranges that are accessible to space-borne photometry, creating inertial dips in the period spacing pattern. Using an asymptotic analysis, we characterised the shape of these inertial dips to show that they depend on rotation and on the stiffness of the convective-radiative interface.},
author = {Breton, S. N. and Pezzotti, C. and Mathis, S. and Bugnet, Lisa Annabelle and Di Mauro, M. P. and Joergensen, J. and Zwintz, K. and Lanza, A. F.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {Wiley},
title = {{Core-envelope coupling of gravito-inertial waves in pre-main-sequence solar-type stars}},
doi = {10.1051/0004-6361/202659309},
volume = {707},
year = {2026},
}
@article{20930,
abstract = {Context. Beta Pictoris is an A-type star that hosts a complex planetary system with two massive gas giants and a prominent debris disc. Variable absorption lines in its stellar spectrum have been interpreted as signatures of exocomets – comet-like bodies transiting the star. Stellar flybys can gravitationally perturb objects in the outer comet reservoir, altering their orbits and potentially injecting them into the inner system, thereby triggering exocomet showers.
Aims. We assessed the contribution of stellar flybys to the observed exocomet activity by reconstructing the stellar encounter history of β Pictoris in the past and future.
Methods. We used Gaia DR3 data, supplemented with radial velocities from complementary spectroscopic surveys, to compile a catalogue of stars currently within 80 pc of β Pictoris. Their orbits were integrated backwards and forwards in time in an axisymmetric Galactic potential (via the GALA package) to identify encounters within 2 pc of the system.
Results. We identified 99 416 stars currently within 80 pc of β Pictoris with resolved kinematics. Among these, 49 stars (including the eight components of five binaries) encounter β Pictoris within 2 pc between –1.5 Myr and +2 Myr. For four of the binaries, the centre-of-mass trajectories also pass within 2 pc. We estimated the sample to be more than 60% complete within 0.5 Myr of today.
Conclusions. Despite β Pictoris being the eponym of its famous moving group, none of the identified encounters involved its moving group members; all are unrelated field stars. We found no encounter capable of shaping the observed disc structures, although stellar flybys may contribute to the long-term evolution of an Oort Cloud-like structure. Our catalogue constitutes the most complete reconstruction of the β Pictoris encounter history to date and provides a robust foundation for future dynamical simulations.},
author = {Gragera-Más, J. L. and Torres Rodriguez, Santiago and Mustill, A. J. and Villaver, E.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{A kinematic history of stellar encounters with Beta Pictoris}},
doi = {10.1051/0004-6361/202555940},
volume = {704},
year = {2025},
}
@article{20931,
abstract = {Context. Asymmetries in the observed rotational splittings of a multiplet contain information about the star’s rotation profile and internal magnetic field. Moreover, the frequency regularities of multiplets can be used for mode identification. However, to exploit this information, highly accurate theoretical predictions are needed.
Aims. We aim to quantify the difference in the predicted mode asymmetries between a 1D perturbative method and a 2D method that includes a 2D stellar structure model, which takes rotation into account. We then place these differences between 1D and 2D methods in the context of asteroseismic measurements of internal magnetic fields. We only focus on the asymmetries and not on possible additional frequency peaks that can arise when the magnetic and rotation axis are misaligned.
Methods. We coupled the 1D pulsation codes GYRE and StORM to the 2D stellar structure code ESTER and compared the oscillation predictions with the results from the 2D TOP pulsation code. We focused on zero-age main-sequence models representative of rotating β Cephei pulsators spinning at up to 20 per cent of the critical Keplerian rotation rate. Specifically, we investigated low-radial-order gravity and pressure modes.
Results. We find a generally good agreement between the oscillation frequencies resulting from the 1D and 2D pulsation codes. We report differences in predicted mode multiplet asymmetries of mostly below 0.06 d−1. Since the magnetic asymmetries are small compared to the differences in the rotational asymmetries resulting from the 1D and 2D predictions, accurate measurements of the magnetic field are in most cases challenging.
Conclusions. Differences in the predicted mode asymmetries of a rotating star between 1D perturbative methods and 2D non-perturbative methods can greatly hinder accurate measurements of internal magnetic fields in main-sequence pulsators with low-order modes. Nevertheless, reasonably accurate measurements could be possible with npg ≥ 2 modes if the internal rotation is roughly below 10 per cent of the Keplerian critical rotation frequency for (aligned) magnetic fields of the order of a few hundred kilogauss. While the differences between the 1D and 2D frequency predictions are mostly too large for internal magnetic field detections, the rotational asymmetries predicted by StORM are in general accurate enough for asteroseismic modelling of the stellar rotation in main-sequence stars with identified low-order modes.},
author = {Mombarg, J. S.G. and Vanlaer, V. and Das, Srijan B and Rieutord, M. and Aerts, C. and Bugnet, Lisa Annabelle and Mathis, S. and Reese, D. R. and Ballot, J.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{Is a 1D perturbative method sufficient for asteroseismic modelling of β Cephei pulsators? Implications for measurements of rotation and internal magnetic fields}},
doi = {10.1051/0004-6361/202557247},
volume = {704},
year = {2025},
}
@article{20932,
abstract = {Identifying Lyman continuum (LyC) leakers at intermediate redshifts is crucial for understanding the properties of cosmic reionizers because the opacity of the intergalactic medium (IGM) prevents the direct detection of LyC emission from sources during the Epoch of Reionization (EoR). In this study, we confirm two new LyC candidate leakers at z ∼ 3 in the Abell 2744 cluster field, with absolute escape fractions (fesc) of 0.83−0.80+0.15 and 0.74−0.70+0.23, respectively. The LyC emission was detected using HST/WFC3/F275W and F336W imaging. These two candidate leakers appear to be faint (MUV = −17.61 ± 0.06 and −18.22 ± 0.10), exhibit blue UV continuum slopes (β = −2.43 ± 0.05 and −1.92 ± 0.09), have low masses (M★ ∼ 107.51 ± 0.03 and 107.17 ± 0.15 M⊙) and Lyα equivalent widths of 90 ± 3 Å and 28 ± 12 Å, respectively. These two LyC candidate leakers were detected in a catalog of 91 spectroscopically confirmed sources using public spectra from the JWST and/or MUSE. We also analyzed properties that were proposed as indirect indicators of LyC emission, such as Lyα, the O32 ratio, and M★. We created a galaxy subsample that was selected according to these properties, stacked the LyC observations of this subsample, and assessed the limits of the escape fractions in the stacks. We aim to enhance our understanding of LyC escape mechanisms and improve our predictions of the LyC fesc during the EoR by analyzing the individual candidates and the stacks in the context of the currently limited sample of known LyC leakers at z ∼ 3.},
author = {Liu, Y. and Mascia, Sara and Pentericci, L. and Watson, P. and Alavi, A. and Bergamini, P. and Bradač, M. and Calabrò, A. and Glazebrook, K. and Henry, A. and Llerena, M. and Merlin, E. and Metha, B. and Nanayakkara, T. and Napolitano, L. and Roy, N. and Siana, B. and Vanzella, E. and Vulcani, B. and Wang, X.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{A Lyman continuum analysis of ∼100 galaxies at z spec∼ 3 in the Abell 2744 cluster field}},
doi = {10.1051/0004-6361/202556410},
volume = {704},
year = {2025},
}
@article{21060,
abstract = {Compact, star-forming galaxies with high star formation rate surface densities (ΣSFR) are often efficient Lyman continuum (LyC) emitters at z ≤ 4.5, likely because intense stellar feedback creates low-density channels that allow photons to escape. Irregular or disturbed morphologies, such as those resulting from mergers, can also facilitate LyC escape by creating anisotropic gas distributions. We investigated the influence of galaxy morphology on LyC production and escape at redshifts 5 ≤ z ≤ 7 using observations from various James Webb Space Telescope (JWST) surveys. Our sample consists of 436 sources, which are predominantly low-mass (∼10^8.15 M ), star-forming galaxies with ionizing photon efficiency (ξion) values consistent with canonical expectations. Since direct measurements of fesc are not possible during the Epoch of Reionization (EoR), we predicted fesc for high-redshift galaxies by applying survival analysis to a subsample of LyC emitters from the Low-Redshift Lyman Continuum Survey (LzLCS), selected to be direct analogs of reionization-era galaxies. We find that these galaxies exhibit, on average, modest predicted escape fractions (∼0.04). In addition, we evaluated the correlation between morphological features and LyC emission. Our findings indicate that neither ξion nor the predicted fesc values show a significant correlation with the presence of merger signatures. This suggests that in low-mass galaxies at z ≥ 5, strong morphological disturbances are not the primary mechanism driving LyC emission and leakage. Instead, compactness and star formation activity likely play a more pivotal role in regulating LyC escape. },
author = {Mascia, Sara and Pentericci, L. and Llerena, M. and Calabrò, A. and Matthee, Jorryt J and Flury, S. and Pacucci, F. and Jaskot, A. and Amorín, R. O. and Bhatawdekar, R. and Castellano, M. and Cleri, N. and Costantin, L. and Davis, K. and Di Cesare, Claudia and Dickinson, M. and Fontana, A. and Guo, Y. and Giavalisco, M. and Holwerda, B. W. and Hu, W. and Huertas-Company, M. and Jung, Intae and Kartaltepe, J. and Kashino, D. and Koekemoer, A. M. and Lucas, R. A. and Lotz, J. and Napolitano, L. and Jogee, S. and Wilkins, S.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe}},
doi = {10.1051/0004-6361/202553760},
volume = {701},
year = {2025},
}
@article{21252,
abstract = {Context. Recent observational results from asteroseismic studies show that an important fraction of solar-like stars do not present detectable stochastically excited acoustic oscillations. This non-detectability seems to correlate with a high rotation rate in the convective envelope and a high surface magnetic activity. At the same time, the properties of stellar convection are affected by rotation and magnetism.
Aims. We investigate the role of rotation in the excitation of acoustic modes in the convective envelope of solar-like stars, to evaluate its impact on the energy injected in the oscillations.
Methods. We derived theoretical prescriptions for the excitation of acoustic waves in the convective envelope of rotating solar-like stars. We adopted the rotating mixing-length Theory to model the influence of rotation on convection. We used the MESA stellar evolution code and the GYRE stellar oscillation code to estimate the power injected in the oscillations from our theoretical prescriptions.
Results. We demonstrate that the power injected in the acoustic modes is insensitive to rotation if a Gaussian time-correlation function is assumed, while it can decrease by up to 60% for a Lorentzian time-correlation function, for a 20 Ω⊙ rotation rate. We show that the modification of the excitation rate by rotation depends not only on the rotation rate but also on the radial and angular orders of the considered oscillation mode. This result can allow for better constraints on the properties of stellar convection by studying observationally acoustic mode excitation.
Conclusions. These results demonstrate how important it is to take into account the modification of stellar convection by rotation when evaluating the amplitude of the stellar oscillations it stochastically excites. They open the path for understanding the large variety of observed acoustic-mode amplitudes at the surface of solar-like stars as a function of surface rotation rates.},
author = {Bessila, L. and Deckx van Ruys, A. and Buriasco, V. and Mathis, S. and Bugnet, Lisa Annabelle and García, R. A. and Mathur, S.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{The impact of rotation on the stochastic excitation of stellar acoustic modes in solar-like pulsators}},
doi = {10.1051/0004-6361/202452093},
volume = {700},
year = {2025},
}
@article{18852,
abstract = {Recent observations have found a growing number of hypervelocity stars with speeds of ≈1500 − 2500 km s−1 that could have only been produced through thermonuclear supernovae in white dwarf binaries. Most of the observed hypervelocity runaways in this class display a surprising inflated structure: their current radii are roughly an order of magnitude greater than they would have been as white dwarfs filling their Roche lobe. While many simulations exist studying the dynamical phase leading to supernova detonation in these systems, no detailed calculations of the long-term structure of the runaways have yet been performed. We used an existing AREPO hydrodynamical simulation of a supernova in a white dwarf binary as a starting point for the evolution of these stars with the one-dimensional stellar evolution code MESA. We show that the supernova shock is not energetic enough to inflate the white dwarf over timescales longer than a few thousand years, significantly shorter than the 105 − 6 year lifetimes inferred for observed hypervelocity runaways. Although they experience a shock from a supernova less than ≈0.02 R⊙ away, our models do not experience significant interior heating, and all contract back to radii of around 0.01 R⊙ within about 104 years. Explaining the observed inflated states requires either an additional source of significant heating or some other physics that is not yet accounted for in the subsequent evolution.},
author = {Bhat, Aakash and Bauer, Evan B. and Pakmor, Rüdiger and Shen, Ken J. and Caiazzo, Ilaria and Rajamuthukumar, Abinaya Swaruba and El-Badry, Kareem and Kerzendorf, Wolfgang E.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
number = {1},
publisher = {EDP Sciences},
title = {{Supernova shocks cannot explain the inflated state of hypervelocity runaways from white dwarf binaries}},
doi = {10.1051/0004-6361/202451371},
volume = {693},
year = {2025},
}
@article{18854,
abstract = {Context. One of the surprising early findings with JWST has been the discovery of a strong “roll-over” or a softening of the absorption edge of Lyα in a large number of galaxies at z ≳ 6, in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as strong cumulative damped Lyα absorption (DLA) wings from high column densities of neutral atomic hydrogen (H I), signifying major gas accretion events in the formation of these galaxies.
Aims. To explore this new phenomenon systematically, we assembled the JWST/NIRSpec PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 584 galaxies at z = 5.0 − 13.4, designed to study the physical properties and gas in and around galaxies during the reionization epoch.
Methods. We characterized this benchmark sample in full and spectroscopically derived the galaxy redshifts, metallicities, star formation rates, and ultraviolet (UV) slopes. We defined a new diagnostic, the Lyα damping parameter DLyα, to measure and quantify the net effect of Lyα emission strength, the H I fraction in the intergalactic medium, or the local H I column density for each source. The JWST-PRIMAL survey is based on the spectroscopic DAWN JWST Archive (DJA-Spec). We describe DJA-Spec in this paper, detailing the reduction methods, the post-processing steps, and basic analysis tools. All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories.
Results. We find that the fraction of galaxies showing strong integrated DLAs with NHI > 1021 cm−2 only increases slightly from ≈60% at z ≈ 6 up to ≈65 − 90% at z > 8. Similarly, the prevalence and prominence of Lyα emission is found to increase with decreasing redshift, in qualitative agreement with previous observational results. Strong Lyα emitters (LAEs) are predominantly found to be associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties, but predominantly at high redshifts and low metallicities.
Conclusions. Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine H I gas accretion. At z = 8 − 10, this gas gradually cools and forms into stars that ionize their local surroundings, forming large ionized bubbles and producing strong observed Lyα emission at z < 8.},
author = {Heintz, K. E. and Brammer, G. B. and Watson, D. and Oesch, P. A. and Keating, L. C. and Hayes, M. J. and Abdurro'Uf, Unknown and Arellano-Córdova, K. Z. and Carnall, A. C. and Christiansen, C. R. and Cullen, F. and Davé, R. and Dayal, P. and Ferrara, A. and Finlator, K. and Fynbo, J. P.U. and Flury, S. R. and Gelli, V. and Gillman, S. and Gottumukkala, R. and Gould, K. and Greve, T. R. and Hardin, S. E. and Hsiao, T. Y.Y. and Hutter, A. and Jakobsson, P. and Killi, M. and Khosravaninezhad, N. and Laursen, P. and Lee, M. M. and Magdis, G. E. and Matthee, Jorryt J and Naidu, R. P. and Narayanan, D. and Pollock, C. and Prescott, M. K.M. and Rusakov, V. and Shuntov, M. and Sneppen, A. and Smit, R. and Tanvir, N. R. and Terp, C. and Toft, S. and Valentino, F. and Vijayan, A. P. and Weaver, J. R. and Wise, J. H. and Witstok, J.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{The JWST-PRIMAL archival survey: A JWST/NIRSpec reference sample for the physical properties and Lyman-α absorption and emission of ∼600 galaxies at z = 5.0-13.4}},
doi = {10.1051/0004-6361/202450243},
volume = {693},
year = {2025},
}
@article{18866,
abstract = {Using JWST Near Infrared Camera (NIRCam) images of the globular cluster 47,Tucanæ, (or NGC,104), taken at two epochs just 7 months apart, we derived proper-motion membership down to F322W2 ∼ 27. We identified an intriguing feature at the very low-mass end of the main sequence, around ∼ 0.08,M_⋅, at magnitudes F322W2 ∼ 24 and m_ F150W2 ∼ 25. This feature, dubbed 'kink', is characterized by a prominent discontinuity in the slope of the main sequence. A similar discontinuity is seen in theoretical isochrones with oxygen-poor chemistries, related to the rapid onset of absorption. We therefore hypothesize that the cluster hosts disproportionately more oxygen-poor stars near the bottom of the main sequence compared to the upper main sequence and the red giant branch. Our results show no strong or conclusive evidence of a rise in the brown dwarf luminosity function at faint magnitudes, in contrast to previous findings likely affected by faint red background galaxies. In our analysis, we accounted for this contamination by using proper motion membership.},
author = {Scalco, M. and Gerasimov, R. and Bedin, L. R. and Vesperini, E. and Correnti, M. and Nardiello, D. and Burgasser, A. and Richer, H. and Caiazzo, Ilaria and Heyl, J. and Libralato, M. and Anderson, J. and Griggio, M.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{JWST photometry and astrometry of 47 Tucanae. Discontinuity in the stellar sequence at the star--brown dwarf transition}},
doi = {10.1051/0004-6361/202452907},
volume = {694},
year = {2025},
}
@article{19069,
abstract = {Context. The hydrogen Lyman-alpha (Lyα) line, the brightest rest-frame ultraviolet line of high-redshift galaxies, exhibits a large variety of shapes, which is due to factors at different scales, from the interstellar medium to the intergalactic medium (IGM).
Aims. The aim of this work is to provide a systematic inventory and classification of the spectral shapes of Lyα emission lines to better understand the general population of high-redshift Lyα emitting galaxies (LAEs).
Methods. Using the unprecedentedly deep data from the MUSE eXtremely Deep Field (MXDF; up to 140 hour exposure time), we selected 477 galaxies observed in the ∼2.8−6.6 redshift range, 15 of which have a systemic redshift from nebular lines. We developed a method to classify Lyα emission lines in four spectral and three spatial categories by combining a pure spectral analysis with a narrow-band image analysis. We measured spectral properties, such as the peak separation and the blue-to-total flux ratio for the double-peaked galaxies.
Results. To ensure a robust sample for statistical analysis, we define two unbiased subsets, inclusive and restrictive, by applying thresholds for signal-to-noise ratio, peak separation, and Lyα luminosity, yielding a final unbiased sample of 206 galaxies. Our analysis reveals that between 32% and 51% of the galaxies exhibit double-peaked profiles, with peak separations ranging from 150 km s−1 to nearly 1600 km s−1. The fraction of double-peaked galaxies seems to evolve dependently with the Lyα luminosity, while we do not see a severe decrease in this fraction with redshift, which is expected given the IGM attenuation at high redshift. An artificial increase in the number of double-peaked galaxies at the highest redshifts may cause the observation of a plateau instead of a decrease. A notable number of these double-peaked profiles show blue-dominated spectra, suggesting unique gas dynamics and inflow characteristics in some high-redshift galaxies. The consequent fraction of blue-dominated spectra needs to be confirmed by obtaining new systemic redshift measurements. Among the double-peaked galaxies, 4% are spurious detections, that is, the blue and red peaks do not come from the same spatial location. Around 20% out of the 477 sources of the parent sample lie in a complex environment, meaning there are other clumps or galaxies at the same redshift within a distance of 30 kpc.
Conclusions. Our results suggest that the double-peaked LAE fraction may trace the evolution of IGM attenuation, but the faintest galaxies must be observed at high redshift. We also need more data to confirm the trend seen at low redshift. In addition, it is crucial to obtain secure systemic redshifts for LAEs to better constrain the nature of the Lyα double-peaked lines. Statistical samples of double-peaked and triple-peaked galaxies are a promising probe of the evolution of the physical properties of galaxies across cosmic time.},
author = {Vitte, Eloïse and Verhamme, Anne and Hibon, Pascale and Leclercq, Floriane and Alcalde Pampliega, Belén and Kerutt, Josephine and Kusakabe, Haruka and Matthee, Jorryt J and Guo, Yucheng and Bacon, Roland and Maseda, Michael and Richard, Johan and Pharo, John and Schaye, Joop and Boogaard, Leindert and Nanayakkara, Themiya and Contini, Thierry},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
publisher = {EDP Sciences},
title = {{The MUSE eXtremely Deep Field: Classifying the spectral shapes of Ly α -emitting galaxies}},
doi = {10.1051/0004-6361/202450426},
volume = {694},
year = {2025},
}