@article{14103,
abstract = {Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observing ∼250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES programme. The complementary X-Shooting ULLYSES (XShootU) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO’s Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the XShootU project is expected to be a game changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope spectra of the first stellar generations, the individual spectra of low-Z stars need to be understood, which is exactly where XShootU can deliver.},
author = {Vink, Jorick S. and Mehner, A. and Crowther, P. A. and Fullerton, A. and Garcia, M. and Martins, F. and Morrell, N. and Oskinova, L. M. and St-Louis, N. and ud-Doula, A. and Sander, A. A. C. and Sana, H. and Bouret, J.-C. and Kubátová, B. and Marchant, P. and Martins, L. P. and Wofford, A. and van Loon, J. Th. and Grace Telford, O. and Götberg, Ylva Louise Linsdotter and Bowman, D. M. and Erba, C. and Kalari, V. M. and Abdul-Masih, M. and Alkousa, T. and Backs, F. and Barbosa, C. L. and Berlanas, S. R. and Bernini-Peron, M. and Bestenlehner, J. M. and Blomme, R. and Bodensteiner, J. and Brands, S. A. and Evans, C. J. and David-Uraz, A. and Driessen, F. A. and Dsilva, K. and Geen, S. and Gómez-González, V. M. A. and Grassitelli, L. and Hamann, W.-R. and Hawcroft, C. and Herrero, A. and Higgins, E. R. and John Hillier, D. and Ignace, R. and Istrate, A. G. and Kaper, L. and Kee, N. D. and Kehrig, C. and Keszthelyi, Z. and Klencki, J. and de Koter, A. and Kuiper, R. and Laplace, E. and Larkin, C. J. K. and Lefever, R. R. and Leitherer, C. and Lennon, D. J. and Mahy, L. and Maíz Apellániz, J. and Maravelias, G. and Marcolino, W. and McLeod, A. F. and de Mink, S. E. and Najarro, F. and Oey, M. S. and Parsons, T. N. and Pauli, D. and Pedersen, M. G. and Prinja, R. K. and Ramachandran, V. and Ramírez-Tannus, M. C. and Sabhahit, G. N. and Schootemeijer, A. and Reyero Serantes, S. and Shenar, T. and Stringfellow, G. S. and Sudnik, N. and Tramper, F. and Wang, L.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{X-shooting ULLYSES: Massive stars at low metallicity. I. Project description}},
doi = {10.1051/0004-6361/202245650},
volume = {675},
year = {2023},
}
@article{14256,
abstract = {Context. Space asteroseismology is revolutionizing our knowledge of the internal structure and dynamics of stars. A breakthrough is ongoing with the recent discoveries of signatures of strong magnetic fields in the core of red giant stars. The key signature for such a detection is the asymmetry these fields induce in the frequency splittings of observed dipolar mixed gravito-acoustic modes.
Aims. We investigate the ability of the observed asymmetries of the frequency splittings of dipolar mixed modes to constrain the geometrical properties of deep magnetic fields.
Methods. We used the powerful analytical Racah-Wigner algebra used in quantum mechanics to characterize the geometrical couplings of dipolar mixed oscillation modes with various realistically plausible topologies of fossil magnetic fields. We also computed the induced perturbation of their frequencies.
Results. First, in the case of an oblique magnetic dipole, we provide the exact analytical expression of the asymmetry as a function of the angle between the rotation and magnetic axes. Its value provides a direct measure of this angle. Second, considering a combination of axisymmetric dipolar and quadrupolar fields, we show how the asymmetry is blind to the unraveling of the relative strength and sign of each component. Finally, in the case of a given multipole, we show that a negative asymmetry is a signature of non-axisymmetric topologies.
Conclusions. Asymmetries of dipolar mixed modes provide a key bit of information on the geometrical topology of deep fossil magnetic fields, but this is insufficient on its own. Asteroseismic constraints should therefore be combined with spectropolarimetric observations and numerical simulations, which aim to predict the more probable stable large-scale geometries.},
author = {Mathis, S. and Bugnet, Lisa Annabelle},
issn = {1432-0746},
journal = {Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{Asymmetries of frequency splittings of dipolar mixed modes: A window on the topology of deep magnetic fields}},
doi = {10.1051/0004-6361/202346832},
volume = {676},
year = {2023},
}
@article{11488,
abstract = {Hydrogen Lyα haloes (LAHs) are commonly used as a tracer of the circumgalactic medium (CGM) at high redshifts. In this work, we aim to explore the existence of Lyα haloes around individual UV-selected galaxies, rather than around Lyα emitters (LAEs), at high redshifts. Our sample was continuum-selected with F775W ≤ 27.5, and spectroscopic redshifts were assigned or constrained for all the sources thanks to the deepest (100- to 140-h) existing Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) data with adaptive optics. The final sample includes 21 galaxies that are purely F775W-magnitude selected within the redshift range z ≈ 2.9 − 4.4 and within a UV magnitude range −20 ≤ M1500 ≤ −18, thus avoiding any bias toward LAEs. We tested whether galaxy’s Lyα emission is significantly more extended than the MUSE PSF-convolved continuum component. We find 17 LAHs and four non-LAHs. We report the first individual detections of extended Lyα emission around non-LAEs. The Lyα halo fraction is thus as high as 81.0−11.2+10.3%, which is close to that for LAEs at z = 3 − 6 in the literature. This implies that UV-selected galaxies generally have a large amount of hydrogen in their CGM. We derived the mean surface brightness (SB) profile for our LAHs with cosmic dimming corrections and find that Lyα emission extends to 5.4 arcsec (≃40 physical kpc at the midpoint redshift z = 3.6) above the typical 1σ SB limit. The incidence rate of surrounding gas detected in Lyα per one-dimensional line of sight per unit redshift, dn/dz, is estimated to be 0.76−0.09+0.09 for galaxies with M1500 ≤ −18 mag at z ≃ 3.7. Assuming that Lyα emission and absorption arise in the same gas, this suggests, based on abundance matching, that LAHs trace the same gas as damped Lyα systems (DLAs) and sub-DLAs.},
author = {Kusakabe, Haruka and Verhamme, Anne and Blaizot, Jérémy and Garel, Thibault and Wisotzki, Lutz and Leclercq, Floriane and Bacon, Roland and Schaye, Joop and Gallego, Sofia G. and Kerutt, Josephine and Matthee, Jorryt J and Maseda, Michael and Nanayakkara, Themiya and Pelló, Roser and Richard, Johan and Tresse, Laurence and Urrutia, Tanya and Vitte, Eloïse},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: formation / galaxies: evolution / cosmology: observations},
publisher = {EDP Sciences},
title = {{The MUSE eXtremely Deep Field: Individual detections of Lyα haloes around rest-frame UV-selected galaxies at z ≃ 2.9–4.4}},
doi = {10.1051/0004-6361/202142302},
volume = {660},
year = {2022},
}
@article{11490,
abstract = {Directly characterising the first generations of stars in distant galaxies is a key quest of observational cosmology. We present a case study of ID53 at z = 4.77, the UV-brightest (but L⋆) star-forming galaxy at z > 3 in the MUSE eXtremely Deep Field with a mass of ≈109 M⊙. In addition to very strong Lyman-α (Lyα) emission, we clearly detect the (stellar) continuum and an N V P Cygni feature, interstellar absorption, fine-structure emission and nebular C IV emission lines in the 140 h spectrum. Continuum emission from two spatially resolved components in Hubble Space Telescope data are blended in the MUSE data, but we show that the nebular C IV emission originates from a subcomponent of the galaxy. The UV spectrum can be fit with recent BPASS stellar population models combined with single-burst or continuous star formation histories (SFHs), a standard initial mass function, and an attenuation law. Models with a young age and low metallicity (log10(age/yr) = 6.5–7.6 and [Z/H] = −2.15 to −1.15) are preferred, but the details depend on the assumed SFH. The intrinsic Hα luminosity of the best-fit models is an order of magnitude higher than the Hα luminosity inferred from Spitzer/IRAC data, which either suggests a high escape fraction of ionising photons, a high relative attenuation of nebular to stellar dust, or a complex SFH. The metallicity appears lower than the metallicity in more massive galaxies at z = 3 − 5, consistent with the scenario according to which younger galaxies have lower metallicities. This chemical immaturity likely facilitates Lyα escape, explaining why the Lyα equivalent width is anti-correlated with stellar metallicity. Finally, we stress that uncertainties in SFHs impose a challenge for future inferences of the stellar metallicity of young galaxies. This highlights the need for joint (spatially resolved) analyses of stellar spectra and photo-ionisation models.},
author = {Matthee, Jorryt J and Feltre, Anna and Maseda, Michael and Nanayakkara, Themiya and Boogaard, Leindert and Bacon, Roland and Verhamme, Anne and Leclercq, Floriane and Kusakabe, Haruka and Urrutia, Tanya and Wisotzki, Lutz},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / techniques: spectroscopic / galaxies: stellar content / galaxies: formation},
publisher = {EDP Sciences},
title = {{Deciphering stellar metallicities in the early universe: Case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field}},
doi = {10.1051/0004-6361/202142187},
volume = {660},
year = {2022},
}
@article{11497,
abstract = {Context. The hydrogen Lyman α line is often the only measurable feature in optical spectra of high-redshift galaxies. Its shape and strength are influenced by radiative transfer processes and the properties of the underlying stellar population. High equivalent widths of several hundred Å are especially hard to explain by models and could point towards unusual stellar populations, for example with low metallicities, young stellar ages, and a top-heavy initial mass function. Other aspects influencing equivalent widths are the morphology of the galaxy and its gas properties.
Aims. The aim of this study is to better understand the connection between the Lyman α rest-frame equivalent width (EW0) and spectral properties as well as ultraviolet (UV) continuum morphology by obtaining reliable EW0 histograms for a statistical sample of galaxies and by assessing the fraction of objects with large equivalent widths.
Methods. We used integral field spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with broad-band data from the Hubble Space Telescope (HST) to measure EW0. We analysed the emission lines of 1920 Lyman α emitters (LAEs) detected in the full MUSE-Wide (one hour exposure time) and MUSE-Deep (ten hour exposure time) surveys and found UV continuum counterparts in archival HST data. We fitted the UV continuum photometric images using the Galfit software to gain morphological information on the rest-UV emission and fitted the spectra obtained from MUSE to determine the double peak fraction, asymmetry, full-width at half maximum, and flux of the Lyman α line.
Results. The two surveys show different histograms of Lyman α EW0. In MUSE-Wide, 20% of objects have EW0 > 240 Å, while this fraction is only 11% in MUSE-Deep and ≈16% for the full sample. This includes objects without HST continuum counterparts (one-third of our sample), for which we give lower limits for EW0. The object with the highest securely measured EW0 has EW0 = 589 ± 193 Å (the highest lower limit being EW0 = 4464 Å). We investigate the connection between EW0 and Lyman α spectral or UV continuum morphological properties.
Conclusions. The survey depth has to be taken into account when studying EW0 distributions. We find that in general, high EW0 objects can have a wide range of spectral and UV morphological properties, which might reflect that the underlying causes for high EW0 values are equally varied.},
author = {Kerutt, J. and Wisotzki, L. and Verhamme, A. and Schmidt, K. B. and Leclercq, F. and Herenz, E. C. and Urrutia, T. and Garel, T. and Hashimoto, T. and Maseda, M. and Matthee, Jorryt J and Kusakabe, H. and Schaye, J. and Richard, J. and Guiderdoni, B. and Mauerhofer, V. and Nanayakkara, T. and Vitte, E.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: formation / galaxies: evolution / cosmology: observations},
publisher = {EDP Sciences},
title = {{Equivalent widths of Lyman α emitters in MUSE-Wide and MUSE-Deep}},
doi = {10.1051/0004-6361/202141900},
volume = {659},
year = {2022},
}
@article{11602,
abstract = {During the survey phase of the Kepler mission, several thousand stars were observed in short cadence, allowing for the detection of solar-like oscillations in more than 500 main-sequence and subgiant stars. These detections showed the power of asteroseismology in determining fundamental stellar parameters. However, the Kepler Science Office discovered an issue in the calibration that affected half of the store of short-cadence data, leading to a new data release (DR25) with corrections on the light curves. In this work, we re-analyzed the one-month time series of the Kepler survey phase to search for solar-like oscillations that might have been missed when using the previous data release. We studied the seismic parameters of 99 stars, among which there are 46 targets with new reported solar-like oscillations, increasing, by around 8%, the known sample of solar-like stars with an asteroseismic analysis of the short-cadence data from this mission. The majority of these stars have mid- to high-resolution spectroscopy publicly available with the LAMOST and APOGEE surveys, respectively, as well as precise Gaia parallaxes. We computed the masses and radii using seismic scaling relations and we find that this new sample features massive stars (above 1.2 M⊙ and up to 2 M⊙) and subgiants. We determined the granulation parameters and amplitude of the modes, which agree with the scaling relations derived for dwarfs and subgiants. The stars studied here are slightly fainter than the previously known sample of main-sequence and subgiants with asteroseismic detections. We also studied the surface rotation and magnetic activity levels of those stars. Our sample of 99 stars has similar levels of activity compared to the previously known sample and is in the same range as the Sun between the minimum and maximum of its activity cycle. We find that for seven stars, a possible blend could be the reason for the non-detection with the early data release. Finally, we compared the radii obtained from the scaling relations with the Gaia ones and we find that the Gaia radii are overestimated by 4.4%, on average, compared to the seismic radii, with a scatter of 12.3% and a decreasing trend according to the evolutionary stage. In addition, for homogeneity purposes, we re-analyzed the DR25 of the main-sequence and subgiant stars with solar-like oscillations that were previously detected and, as a result, we provide the global seismic parameters for a total of 525 stars.},
author = {Mathur, S. and García, R. A. and Breton, S. and Santos, A. R. G. and Mosser, B. and Huber, D. and Sayeed, M. and Bugnet, Lisa Annabelle and Chontos, A.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{Detections of solar-like oscillations in dwarfs and subgiants with Kepler DR25 short-cadence data}},
doi = {10.1051/0004-6361/202141168},
volume = {657},
year = {2022},
}
@article{11621,
abstract = {Context. Asteroseismology has revealed small core-to-surface rotation contrasts in stars in the whole Hertzsprung–Russell diagram. This is the signature of strong transport of angular momentum (AM) in stellar interiors. One of the plausible candidates to efficiently carry AM is magnetic fields with various topologies that could be present in stellar radiative zones. Among them, strong axisymmetric azimuthal (toroidal) magnetic fields have received a lot of interest. Indeed, if they are subject to the so-called Tayler instability, the accompanying triggered Maxwell stresses can transport AM efficiently. In addition, the electromotive force induced by the fluctuations of magnetic and velocity fields could potentially sustain a dynamo action that leads to the regeneration of the initial strong axisymmetric azimuthal magnetic field.
Aims. The key question we aim to answer is whether we can detect signatures of these deep strong azimuthal magnetic fields. The only way to answer this question is asteroseismology, and the best laboratories of study are intermediate-mass and massive stars with external radiative envelopes. Most of these are rapid rotators during their main sequence. Therefore, we have to study stellar pulsations propagating in stably stratified, rotating, and potentially strongly magnetised radiative zones, namely magneto-gravito-inertial (MGI) waves.
Methods. We generalise the traditional approximation of rotation (TAR) by simultaneously taking general axisymmetric differential rotation and azimuthal magnetic fields into account. Both the Coriolis acceleration and the Lorentz force are therefore treated in a non-perturbative way. Using this new formalism, we derive the asymptotic properties of MGI waves and their period spacings.
Results. We find that toroidal magnetic fields induce a shift in the period spacings of gravity (g) and Rossby (r) modes. An equatorial azimuthal magnetic field with an amplitude of the order of 105 G leads to signatures that are detectable in period spacings for high-radial-order g and r modes in γ Doradus (γ Dor) and slowly pulsating B (SPB) stars. More complex hemispheric configurations are more difficult to observe, particularly when they are localised out of the propagation region of MGI modes, which can be localised in an equatorial belt.
Conclusions. The magnetic TAR, which takes into account toroidal magnetic fields in a non-perturbative way, is derived. This new formalism allows us to assess the effects of the magnetic field in γ Dor and SPB stars on g and r modes. We find that these effects should be detectable for equatorial fields thanks to modern space photometry using observations from Kepler, TESS CVZ, and PLATO.},
author = {Dhouib, H. and Mathis, S. and Bugnet, Lisa Annabelle and Van Reeth, T. and Aerts, C.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, magnetohydrodynamics (MHD) / waves / stars, rotation / stars: magnetic field / stars, oscillations / methods},
publisher = {EDP Sciences},
title = {{Detecting deep axisymmetric toroidal magnetic fields in stars: The traditional approximation of rotation for differentially rotating deep spherical shells with a general azimuthal magnetic field}},
doi = {10.1051/0004-6361/202142956},
volume = {661},
year = {2022},
}
@article{11498,
abstract = {Rest-frame ultraviolet (UV) emission lines probe electron densities, gas-phase abundances, metallicities, and ionization parameters of the emitting star-forming galaxies and their environments. The strongest main UV emission line, Lyα, has been instrumental in advancing the general knowledge of galaxy formation in the early universe. However, observing Lyα emission becomes increasingly challenging at z ≳ 6 when the neutral hydrogen fraction of the circumgalactic and intergalactic media increases. Secondary weaker UV emission lines provide important alternative methods for studying galaxy properties at high redshift. We present a large sample of rest-frame UV emission line sources at intermediate redshift for calibrating and exploring the connection between secondary UV lines and the emitting galaxies’ physical properties and their Lyα emission. The sample of 2052 emission line sources with 1.5 < z < 6.4 was collected from integral field data from the MUSE-Wide and MUSE-Deep surveys taken as part of Guaranteed Time Observations. The objects were selected through untargeted source detection (i.e., no preselection of sources as in dedicated spectroscopic campaigns) in the three-dimensional MUSE data cubes. We searched optimally extracted one-dimensional spectra of the full sample for UV emission features via emission line template matching, resulting in a sample of more than 100 rest-frame UV emission line detections. We show that the detection efficiency of (non-Lyα) UV emission lines increases with survey depth, and that the emission line strength of He IIλ1640 Å, [O III] λ1661 + O III] λ1666, and [Si III] λ1883 + Si III] λ1892 correlate with the strength of [C III] λ1907 + C III] λ1909. The rest-frame equivalent width (EW0) of [C III] λ1907 + C III] λ1909 is found to be roughly 0.22 ± 0.18 of EW0(Lyα). We measured the velocity offsets of resonant emission lines with respect to systemic tracers. For C IVλ1548 + C IVλ1551 we find that ΔvC IV ≲ 250 km s−1, whereas ΔvLyα falls in the range of 250−500 km s−1 which is in agreement with previous results from the literature. The electron density ne measured from [Si III] λ1883 + Si III] λ1892 and [C III] λ1907 + C III] λ1909 line flux ratios is generally < 105 cm−3 and the gas-phase abundance is below solar at 12 + log10(O/H)≈8. Lastly, we used “PhotoIonization Model Probability Density Functions” to infer physical parameters of the full sample and individual systems based on photoionization model parameter grids and observational constraints from our UV emission line searches. This reveals that the UV line emitters generally have ionization parameter log10(U) ≈ −2.5 and metal mass fractions that scatter around Z ≈ 10−2, that is Z ≈ 0.66 Z⊙. Value-added catalogs of the full sample of MUSE objects studied in this work and a collection of UV line emitters from the literature are provided with this paper.},
author = {Schmidt, K. B. and Kerutt, J. and Wisotzki, L. and Urrutia, T. and Feltre, A. and Maseda, M. V. and Nanayakkara, T. and Bacon, R. and Boogaard, L. A. and Conseil, S. and Contini, T. and Herenz, E. C. and Kollatschny, W. and Krumpe, M. and Leclercq, F. and Mahler, G. and Matthee, Jorryt J and Mauerhofer, V. and Richard, J. and Schaye, J.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, ultraviolet: galaxies / galaxies: high-redshift / galaxies: ISM / ISM: lines and bands / methods: observational / techniques: imaging spectroscopy},
publisher = {EDP Sciences},
title = {{Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at 1.5 < z < 6.4}},
doi = {10.1051/0004-6361/202140876},
volume = {654},
year = {2021},
}
@article{11500,
abstract = {We report the discovery of diffuse extended Lyα emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5−4 cMpc. These structures have been observed in overdensities of Lyα emitters in the MUSE Extremely Deep Field, a 140 h deep MUSE observation located in the Hubble Ultra-Deep Field. Among the 22 overdense regions identified, five are likely to harbor very extended Lyα emission at high significance with an average surface brightness of 5 × 10−20 erg s−1 cm−2 arcsec−2. Remarkably, 70% of the total Lyα luminosity from these filaments comes from beyond the circumgalactic medium of any identified Lyα emitter. Fluorescent Lyα emission powered by the cosmic UV background can only account for less than 34% of this emission at z ≈ 3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Lyα emission of a large population of ultra low-luminosity Lyα emitters (< 1040 erg s−1), provided that the faint end of the Lyα luminosity function is steep (α ⪅ −1.8), it extends down to luminosities lower than 1038 − 1037 erg s−1, and the clustering of these Lyα emitters is significant (filling factor < 1/6). If these Lyα emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates < 10−4 M⊙ yr−1. These observations provide the first detection of the cosmic web in Lyα emission in typical filamentary environments and the first observational clue indicating the existence of a large population of ultra low-luminosity Lyα emitters at high redshift.},
author = {Bacon, R. and Mary, D. and Garel, T. and Blaizot, J. and Maseda, M. and Schaye, J. and Wisotzki, L. and Conseil, S. and Brinchmann, J. and Leclercq, F. and Abril-Melgarejo, V. and Boogaard, L. and Bouché, N. F. and Contini, T. and Feltre, A. and Guiderdoni, B. and Herenz, C. and Kollatschny, W. and Kusakabe, H. and Matthee, Jorryt J and Michel-Dansac, L. and Nanayakkara, T. and Richard, J. and Roth, M. and Schmidt, K. B. and Steinmetz, M. and Tresse, L. and Urrutia, T. and Verhamme, A. and Weilbacher, P. M. and Zabl, J. and Zoutendijk, S. L.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: groups: general / cosmology: observations},
publisher = {EDP Sciences},
title = {{The MUSE Extremely Deep Field: The cosmic web in emission at high redshift}},
doi = {10.1051/0004-6361/202039887},
volume = {647},
year = {2021},
}
@article{11605,
abstract = {Context. The discovery of moderate differential rotation between the core and the envelope of evolved solar-like stars could be the signature of a strong magnetic field trapped inside the radiative interior. The population of intermediate-mass red giants presenting surprisingly low-amplitude mixed modes (i.e. oscillation modes that behave as acoustic modes in their external envelope and as gravity modes in their core) could also arise from the effect of an internal magnetic field. Indeed, stars more massive than about 1.1 solar masses are known to develop a convective core during their main sequence. The field generated by the dynamo triggered by this convection could be the progenitor of a strong fossil magnetic field trapped inside the core of the star for the remainder of its evolution.
Aims. Observations of mixed modes can constitute an excellent probe of the deepest layers of evolved solar-like stars, and magnetic fields in those regions can impact their propagation. The magnetic perturbation on mixed modes may therefore be visible in asteroseismic data. To unravel which constraints can be obtained from observations, we theoretically investigate the effects of a plausible mixed axisymmetric magnetic field with various amplitudes on the mixed-mode frequencies of evolved solar-like stars.
Methods. First-order frequency perturbations due to an axisymmetric magnetic field were computed for dipolar and quadrupolar mixed modes. These computations were carried out for a range of stellar ages, masses, and metallicities.
Conclusions. We show that typical fossil-field strengths of 0.1 − 1 MG, consistent with the presence of a dynamo in the convective core during the main sequence, provoke significant asymmetries on mixed-mode frequency multiplets during the red giant branch. We provide constraints and methods for the detectability of such magnetic signatures. We show that these signatures may be detectable in asteroseismic data for field amplitudes small enough for the amplitude of the modes not to be affected by the conversion of gravity into Alfvén waves inside the magnetised interior. Finally, we infer an upper limit for the strength of the field and the associated lower limit for the timescale of its action in order to redistribute angular momentum in stellar interiors.},
author = {Bugnet, Lisa Annabelle and Prat, V. and Mathis, S. and Astoul, A. and Augustson, K. and García, R. A. and Mathur, S. and Amard, L. and Neiner, C.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, stars, oscillations / stars, magnetic field / stars, interiors / stars, evolution / stars, rotation},
publisher = {EDP Sciences},
title = {{Magnetic signatures on mixed-mode frequencies: I. An axisymmetric fossil field inside the core of red giants}},
doi = {10.1051/0004-6361/202039159},
volume = {650},
year = {2021},
}
@article{11606,
abstract = {Context. Our knowledge of the dynamics of stars has undergone a revolution through the simultaneous large amount of high-quality photometric observations collected by space-based asteroseismology and ground-based high-precision spectropolarimetry. They allowed us to probe the internal rotation of stars and their surface magnetism in the whole Hertzsprung-Russell diagram. However, new methods should still be developed to probe the deep magnetic fields in these stars.
Aims. Our goal is to provide seismic diagnoses that allow us to probe the internal magnetism of stars.
Methods. We focused on asymptotic low-frequency gravity modes and high-frequency acoustic modes. Using a first-order perturbative theory, we derived magnetic splittings of their frequencies as explicit functions of stellar parameters.
Results. As in the case of rotation, we show that asymptotic gravity and acoustic modes can allow us to probe the different components of the magnetic field in the cavities in which they propagate. This again demonstrates the high potential of using mixed-modes when this is possible.},
author = {Mathis, S. and Bugnet, Lisa Annabelle and Prat, V. and Augustson, K. and Mathur, S. and Garcia, R. A.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, asteroseismology / waves / stars, magnetic field / stars, oscillations / methods, analytical},
publisher = {EDP Sciences},
title = {{Probing the internal magnetism of stars using asymptotic magneto-asteroseismology}},
doi = {10.1051/0004-6361/202039180},
volume = {647},
year = {2021},
}
@article{11608,
abstract = {In order to understand stellar evolution, it is crucial to efficiently determine stellar surface rotation periods. Indeed, while they are of great importance in stellar models, angular momentum transport processes inside stars are still poorly understood today. Surface rotation, which is linked to the age of the star, is one of the constraints needed to improve the way those processes are modelled. Statistics of the surface rotation periods for a large sample of stars of different spectral types are thus necessary. An efficient tool to automatically determine reliable rotation periods is needed when dealing with large samples of stellar photometric datasets. The objective of this work is to develop such a tool. For this purpose, machine learning classifiers constitute relevant bases to build our new methodology. Random forest learning abilities are exploited to automate the extraction of rotation periods in Kepler light curves. Rotation periods and complementary parameters are obtained via three different methods: a wavelet analysis, the autocorrelation function of the light curve, and the composite spectrum. We trained three different classifiers: one to detect if rotational modulations are present in the light curve, one to flag close binary or classical pulsators candidates that can bias our rotation period determination, and finally one classifier to provide the final rotation period. We tested our machine learning pipeline on 23 431 stars of the Kepler K and M dwarf reference rotation catalogue for which 60% of the stars have been visually inspected. For the sample of 21 707 stars where all the input parameters are provided to the algorithm, 94.2% of them are correctly classified (as rotating or not). Among the stars that have a rotation period in the reference catalogue, the machine learning provides a period that agrees within 10% of the reference value for 95.3% of the stars. Moreover, the yield of correct rotation periods is raised to 99.5% after visually inspecting 25.2% of the stars. Over the two main analysis steps, rotation classification and period selection, the pipeline yields a global agreement with the reference values of 92.1% and 96.9% before and after visual inspection. Random forest classifiers are efficient tools to determine reliable rotation periods in large samples of stars. The methodology presented here could be easily adapted to extract surface rotation periods for stars with different spectral types or observed by other instruments such as K2, TESS or by PLATO in the near future.},
author = {Breton, S. N. and Santos, A. R. G. and Bugnet, Lisa Annabelle and Mathur, S. and García, R. A. and Pallé, P. L.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, methods: data analysis / stars: solar-type / stars: activity / stars: rotation / starspots},
publisher = {EDP Sciences},
title = {{ROOSTER: A machine-learning analysis tool for Kepler stellar rotation periods}},
doi = {10.1051/0004-6361/202039947},
volume = {647},
year = {2021},
}
@article{11609,
abstract = {Context. Stellar interiors are the seat of efficient transport of angular momentum all along their evolution. In this context, understanding the dependence of the turbulent transport triggered by the instabilities of the vertical and horizontal shears of the differential rotation in stellar radiation zones as a function of their rotation, stratification, and thermal diffusivity is mandatory. Indeed, it constitutes one of the cornerstones of the rotational transport and mixing theory, which is implemented in stellar evolution codes to predict the rotational and chemical evolutions of stars.
Aims. We investigate horizontal shear instabilities in rotating stellar radiation zones by considering the full Coriolis acceleration with both the dimensionless horizontal Coriolis component f̃ and the vertical component f.
Methods. We performed a linear stability analysis using linearized equations derived from the Navier-Stokes and heat transport equations in the rotating nontraditional f-plane. We considered a horizontal shear flow with a hyperbolic tangent profile as the base flow. The linear stability was analyzed numerically in wide ranges of parameters, and we performed an asymptotic analysis for large vertical wavenumbers using the Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) approximation for nondiffusive and highly-diffusive fluids.
Results. As in the traditional f-plane approximation, we identify two types of instabilities: the inflectional and inertial instabilities. The inflectional instability is destabilized as f̃ increases and its maximum growth rate increases significantly, while the thermal diffusivity stabilizes the inflectional instability similarly to the traditional case. The inertial instability is also strongly affected; for instance, the inertially unstable regime is also extended in the nondiffusive limit as 0 < f < 1 + f̃ 2/N2, where N is the dimensionless Brunt-Väisälä frequency. More strikingly, in the high thermal diffusivity limit, it is always inertially unstable at any colatitude θ except at the poles (i.e., 0° < θ < 180°). We also derived the critical Reynolds numbers for the inertial instability using the asymptotic dispersion relations obtained from the WKBJ analysis. Using the asymptotic and numerical results, we propose a prescription for the effective turbulent viscosities induced by the inertial and inflectional instabilities that can be possibly used in stellar evolution models. The characteristic time of this turbulence is short enough so that it is efficient to redistribute angular momentum and to mix chemicals in stellar radiation zones.},
author = {Park, J. and Prat, V. and Mathis, S. and Bugnet, Lisa Annabelle},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, hydrodynamics / turbulence / stars, rotation / stars, evolution},
publisher = {EDP Sciences},
title = {{Horizontal shear instabilities in rotating stellar radiation zones: II. Effects of the full Coriolis acceleration}},
doi = {10.1051/0004-6361/202038654},
volume = {646},
year = {2021},
}
@article{13455,
abstract = {The majority of massive stars live in binary or multiple systems and will interact with a companion during their lifetimes, which helps to explain the observed diversity of core-collapse supernovae. Donor stars in binary systems can lose most of their hydrogen-rich envelopes through mass transfer. As a result, not only are the surface properties affected, but so is the core structure. However, most calculations of the core-collapse properties of massive stars rely on single-star models. We present a systematic study of the difference between the pre-supernova structures of single stars and stars of the same initial mass (11–21 M⊙) that have been stripped due to stable post-main-sequence mass transfer at solar metallicity. We present the pre-supernova core composition with novel diagrams that give an intuitive representation of the isotope distribution. As shown in previous studies, at the edge of the carbon-oxygen core, the binary-stripped star models contain an extended gradient of carbon, oxygen, and neon. This layer remains until core collapse and is more extended in mass for higher initial stellar masses. It originates from the receding of the convective helium core during core helium burning in binary-stripped stars, which does not occur in single-star models. We find that this same evolutionary phase leads to systematic differences in the final density and nuclear energy generation profiles. Binary-stripped star models have systematically higher total masses of carbon at the moment of core collapse compared to single-star models, which likely results in systematically different supernova yields. In about half of our models, the silicon-burning and oxygen-rich layers merge after core silicon burning. We discuss the implications of our findings for the “explodability”, supernova observations, and nucleosynthesis of these stars. Our models are publicly available and can be readily used as input for detailed supernova simulations.},
author = {Laplace, E. and Justham, S. and Renzo, M. and Götberg, Ylva Louise Linsdotter and Farmer, R. and Vartanyan, D. and de Mink, S. E.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{Different to the core: The pre-supernova structures of massive single and binary-stripped stars}},
doi = {10.1051/0004-6361/202140506},
volume = {656},
year = {2021},
}
@article{13457,
abstract = {Context. Observations of massive stars in open clusters younger than ∼8 Myr have shown that a majority of them are in binary systems, most of which will interact during their life. While these can be used as a proxy of the initial multiplicity properties, studying populations of massive stars older than ∼20 Myr allows us to probe the outcome of these interactions after a significant number of systems have experienced mass and angular momentum transfer and may even have merged.
Aims. Using multi-epoch integral-field spectroscopy, we aim to investigate the multiplicity properties of the massive-star population in the dense core of the ∼40 Myr old cluster NGC 330 in the Small Magellanic Cloud in order to search for possible imprints of stellar evolution on the multiplicity properties.
Methods. We obtained six epochs of VLT/MUSE observations operated in wide-field mode with the extended wavelength setup and supported by adaptive optics. We extracted spectra and measured radial velocities for stars brighter than mF814W = 19. We identified single-lined spectroscopic binaries through significant RV variability with a peak-to-peak amplitude larger than 20 km s−1. We also identified double-lined spectroscopic binaries, and quantified the observational biases for binary detection. In particular, we took into account that binary systems with similar line strengths are difficult to detect in our data set.
Results. The observed spectroscopic binary fraction among stars brighter than mF814W = 19 (approximately 5.5 M⊙ on the main sequence) is fSBobs = 13.2 ± 2.0%. Considering period and mass ratio ranges from log(P) = 0.15−3.5 (about 1.4 to 3160 d), q = 0.1−1.0, and a representative set of orbital parameter distributions, we find a bias-corrected close binary fraction of fcl = 34−7+8%. This fraction seems to decline for the fainter stars, which indicates either that the close binary fraction drops in the B-type domain, or that the period distribution becomes more heavily weighted toward longer orbital periods. We further find that both fractions vary strongly in different regions of the color-magnitude diagram, which corresponds to different evolutionary stages. This probably reveals the imprint of the binary history of different groups of stars. In particular, we find that the observed spectroscopic binary fraction of Be stars (fSBobs = 2 ± 2%) is significantly lower than that of B-type stars (fSBobs = 9 ± 2%).
Conclusions. We provide the first homogeneous radial velocity study of a large sample of B-type stars at a low metallicity ([Fe/H] ≲ −1.0). The overall bias-corrected close binary fraction (log(P) < 3.5 d) of the B-star population in NGC 330 is lower than the fraction reported for younger Galactic and Large Magellanic Cloud clusters in previous works. More data are needed, however, to establish whether the observed differences are caused by an age or a metallicity effect.},
author = {Bodensteiner, J. and Sana, H. and Wang, C. and Langer, N. and Mahy, L. and Banyard, G. and de Koter, A. and de Mink, S. E. and Evans, C. J. and Götberg, Ylva Louise Linsdotter and Patrick, L. R. and Schneider, F. R. N. and Tramper, F.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{The young massive SMC cluster NGC 330 seen by MUSE. II. Multiplicity properties of the massive-star population}},
doi = {10.1051/0004-6361/202140507},
volume = {652},
year = {2021},
}
@article{11501,
abstract = {We investigated the ultraviolet (UV) spectral properties of faint Lyman-α emitters (LAEs) in the redshift range 2.9 ≤ z ≤ 4.6, and we provide material to prepare future observations of the faint Universe. We used data from the MUSE Hubble Ultra Deep Survey to construct mean rest-frame spectra of continuum-faint (median MUV of −18 and down to MUV of −16), low stellar mass (median value of 108.4 M⊙ and down to 107 M⊙) LAEs at redshift z ≳ 3. We computed various averaged spectra of LAEs, subsampled on the basis of their observational (e.g., Lyα strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and star-formation rate) properties. We searched for UV spectral features other than Lyα, such as higher ionization nebular emission lines and absorption features. We successfully observed the O III]λ1666 and [C III]λ1907+C III]λ1909 collisionally excited emission lines and the He IIλ1640 recombination feature, as well as the resonant C IVλλ1548,1551 doublet either in emission or P-Cygni. We compared the observed spectral properties of the different mean spectra and find the emission lines to vary with the observational and physical properties of the LAEs. In particular, the mean spectra of LAEs with larger Lyα equivalent widths, fainter UV magnitudes, bluer UV spectral slopes, and lower stellar masses show the strongest nebular emission. The line ratios of these lines are similar to those measured in the spectra of local metal-poor galaxies, while their equivalent widths are weaker compared to the handful of extreme values detected in individual spectra of z > 2 galaxies. This suggests that weak UV features are likely ubiquitous in high z, low-mass, and faint LAEs. We publicly released the stacked spectra, as they can serve as empirical templates for the design of future observations, such as those with the James Webb Space Telescope and the Extremely Large Telescope.},
author = {Feltre, Anna and Maseda, Michael V. and Bacon, Roland and Pradeep, Jayadev and Leclercq, Floriane and Kusakabe, Haruka and Wisotzki, Lutz and Hashimoto, Takuya and Schmidt, Kasper B. and Blaizot, Jeremy and Brinchmann, Jarle and Boogaard, Leindert and Cantalupo, Sebastiano and Carton, David and Inami, Hanae and Kollatschny, Wolfram and Marino, Raffaella A. and Matthee, Jorryt J and Nanayakkara, Themiya and Richard, Johan and Schaye, Joop and Tresse, Laurence and Urrutia, Tanya and Verhamme, Anne and Weilbacher, Peter M.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution / galaxies: high-redshift / ISM: lines and bands / ultraviolet: ISM / ultraviolet: galaxies},
publisher = {EDP Sciences},
title = {{The MUSE Hubble Ultra Deep Field Survey: XV. The mean rest-UV spectra of Lyα emitters at z > 3}},
doi = {10.1051/0004-6361/202038133},
volume = {641},
year = {2020},
}
@article{11503,
abstract = {Context. The Lyα emitter (LAE) fraction, XLAE, is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of XLAE are still under debate.
Aims. Thanks to deep data obtained with the integral field spectrograph Multi Unit Spectroscopic Explorer (MUSE), we can measure the evolution of the LAE fraction homogeneously over a wide redshift range of z ≈ 3–6 for UV-faint galaxies (down to UV magnitudes of M1500 ≈ −17.75). This is a significantly fainter range than in former studies (M1500 ≤ −18.75) and it allows us to probe the bulk of the population of high-redshift star-forming galaxies.
Methods. We constructed a UV-complete photometric-redshift sample following UV luminosity functions and measured the Lyα emission with MUSE using the latest (second) data release from the MUSE Hubble Ultra Deep Field Survey.
Results. We derived the redshift evolution of XLAE for M1500 ∈ [ − 21.75; −17.75] for the first time with a equivalent width range EW(Lyα) ≥ 65 Å and found low values of XLAE ≲ 30% at z ≲ 6. The best-fit linear relation is XLAE = 0.07+0.06−0.03z − 0.22+0.12−0.24. For M1500 ∈ [ − 20.25; −18.75] and EW(Lyα) ≥ 25 Å, our XLAE values are consistent with those in the literature within 1σ at z ≲ 5, but our median values are systematically lower than reported values over the whole redshift range. In addition, we do not find a significant dependence of XLAE on M1500 for EW(Lyα) ≥ 50 Å at z ≈ 3–4, in contrast with previous work. The differences in XLAE mainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lyα emission, hence XLAE is biased towards higher values when those samples are used.
Conclusions. Our results suggest either a lower increase of XLAE towards z ≈ 6 than previously suggested, or even a turnover of XLAE at z ≈ 5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed LAE fractions much better than models where SF is a smooth function of time.},
author = {Kusakabe, Haruka and Blaizot, Jérémy and Garel, Thibault and Verhamme, Anne and Bacon, Roland and Richard, Johan and Hashimoto, Takuya and Inami, Hanae and Conseil, Simon and Guiderdoni, Bruno and Drake, Alyssa B. and Christian Herenz, Edmund and Schaye, Joop and Oesch, Pascal and Matthee, Jorryt J and Anna Marino, Raffaella and Borello Schmidt, Kasper and Pelló, Roser and Maseda, Michael and Leclercq, Floriane and Kerutt, Josephine and Mahler, Guillaume},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics, dark ages / reionization / first stars / early Universe / cosmology: observations / galaxies: evolution / galaxies: high-redshift / intergalactic medium},
publisher = {EDP Sciences},
title = {{The MUSE Hubble Ultra Deep Field Survey: XIV. Evolution of the Lyα emitter fraction from z = 3 to z = 6}},
doi = {10.1051/0004-6361/201937340},
volume = {638},
year = {2020},
}
@article{11504,
abstract = {We present spatially resolved maps of six individually-detected Lyman α haloes (LAHs) as well as a first statistical analysis of the Lyman α (Lyα) spectral signature in the circum-galactic medium of high-redshift star-forming galaxies (−17.5 > MUV > −21.5) using the Multi-Unit Spectroscopic Explorer. Our resolved spectroscopic analysis of the LAHs reveals significant intrahalo variations of the Lyα line profile. Using a three-dimensional two-component model for the Lyα emission, we measured the full width at half maximum (FWHM), the peak velocity shift, and the asymmetry of the Lyα line in the core and in the halo of 19 galaxies. We find that the Lyα line shape is statistically different in the halo compared to the core (in terms of width, peak wavelength, and asymmetry) for ≈40% of our galaxies. Similarly to object-by-object based studies and a recent resolved study using lensing, we find a correlation between the peak velocity shift and the width of the Lyα line both at the interstellar and circum-galactic scales. This trend has been predicted by radiative transfer simulations of galactic winds as a result of resonant scattering in outflows. While there is a lack of correlation between the spectral properties and the spatial scale lengths of our LAHs, we find a correlation between the width of the line in the LAH and the halo flux fraction. Interestingly, UV bright galaxies (MUV < −20) show broader, more redshifted, and less asymmetric Lyα lines in their haloes. The most significant correlation found is for the FWHM of the line and the UV continuum slope of the galaxy, suggesting that the redder galaxies have broader Lyα lines. The generally broad and red line shapes found in the halo component suggest that the Lyα haloes are powered either by scattering processes through an outflowing medium, fluorescent emission from outflowing cold clumps of gas, or a mix of both. Considering the large diversity of the Lyα line profiles observed in our sample and the lack of strong correlation, the interpretation of our results is still broadly open and underlines the need for realistic spatially resolved models of the LAHs.},
author = {Leclercq, Floriane and Bacon, Roland and Verhamme, Anne and Garel, Thibault and Blaizot, Jérémy and Brinchmann, Jarle and Cantalupo, Sebastiano and Claeyssens, Adélaïde and Conseil, Simon and Contini, Thierry and Hashimoto, Takuya and Herenz, Edmund Christian and Kusakabe, Haruka and Marino, Raffaella Anna and Maseda, Michael and Matthee, Jorryt J and Mitchell, Peter and Pezzulli, Gabriele and Richard, Johan and Schmidt, Kasper Borello and Wisotzki, Lutz},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics galaxies: high-redshift / galaxies: formation / galaxies: evolution / cosmology: observations},
publisher = {EDP Sciences},
title = {{The MUSE Hubble Ultra Deep field survey: XIII. Spatially resolved spectral properties of Lyman α haloes around star-forming galaxies at z > 3}},
doi = {10.1051/0004-6361/201937339},
volume = {635},
year = {2020},
}
@article{13463,
abstract = {Present and upcoming time-domain astronomy efforts, in part driven by gravitational-wave follow-up campaigns, will unveil a variety of rare explosive transients in the sky. Here, we focus on pulsational pair-instability evolution, which can result in signatures that are observable with electromagnetic and gravitational waves. We simulated grids of bare helium stars to characterize the resulting black hole (BH) masses together with the ejecta composition, velocity, and thermal state. We find that the stars do not react “elastically” to the thermonuclear ignition in the core: there is not a one-to-one correspondence between pair-instability driven ignition and mass ejections, which causes ambiguity as to what is an observable pulse. In agreement with previous studies, we find that for initial helium core masses of 37.5 M⊙ ≲ MHe, init ≲ 41 M⊙, corresponding to carbon-oxygen core masses 27.5 M⊙ ≲ MCO ≲ 30.1 M⊙, the explosions are not strong enough to affect the surface. With increasing initial helium core mass, they become progressively stronger causing first large radial expansion (41 M⊙ ≲ MHe, init ≲ 42 M⊙, corresponding to 30.1 M⊙ ≲ MCO ≲ 30.8 M⊙) and, finally, also mass ejection episodes (for MHe, init ≳ 42 M⊙, or MCO ≳ 30.8 M⊙). The lowest mass helium core to be fully disrupted in a pair-instability supernova is MHe, init ≃ 80 M⊙, corresponding to MCO ≃ 55 M⊙. Models with MHe, init ≳ 200 M⊙ (MCO ≳ 114 M⊙) reach the photodisintegration regime, resulting in BHs with masses of MBH ≳ 125 M⊙. Although this is currently considered unlikely, if BHs from these models form via (weak) explosions, the previously-ejected material might be hit by the blast wave and convert kinetic energy into observable electromagnetic radiation. We characterize the hydrogen-free circumstellar material from the pulsational pair-instability of helium cores by simply assuming that the ejecta maintain a constant velocity after ejection. We find that our models produce helium-rich ejecta with mass of 10−3 M⊙ ≲ MCSM ≲ 40 M⊙, the larger values corresponding to the more massive progenitor stars. These ejecta are typically launched at a few thousand km s−1 and reach distances of ∼1012 − 1015 cm before the core-collapse of the star. The delays between mass ejection events and the final collapse span a wide and mass-dependent range (from subhour to 104 years), and the shells ejected can also collide with each other, powering supernova impostor events before the final core-collapse. The range of properties we find suggests a possible connection with (some) type Ibn supernovae.},
author = {Renzo, M. and Farmer, R. and Justham, S. and Götberg, Ylva Louise Linsdotter and de Mink, S. E. and Zapartas, E. and Marchant, P. and Smith, N.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{Predictions for the hydrogen-free ejecta of pulsational pair-instability supernovae}},
doi = {10.1051/0004-6361/202037710},
volume = {640},
year = {2020},
}
@article{13464,
abstract = {Massive binaries that merge as compact objects are the progenitors of gravitational-wave sources. Most of these binaries experience one or more phases of mass transfer, during which one of the stars loses all or part of its outer envelope and becomes a stripped-envelope star. The evolution of the size of these stripped stars is crucial in determining whether they experience further interactions and understanding their ultimate fate. We present new calculations of stripped-envelope stars based on binary evolution models computed with MESA. We use these to investigate their radius evolution as a function of mass and metallicity. We further discuss their pre-supernova observable characteristics and potential consequences of their evolution on the properties of supernovae from stripped stars. At high metallicity, we find that practically all of the hydrogen-rich envelope is removed, which is in agreement with earlier findings. Only progenitors with initial masses below 10 M⊙ expand to large radii (up to 100 R⊙), while more massive progenitors remain compact. At low metallicity, a substantial amount of hydrogen remains and the progenitors can, in principle, expand to giant sizes (> 400 R⊙) for all masses we consider. This implies that they can fill their Roche lobe anew. We show that the prescriptions commonly used in population synthesis models underestimate the stellar radii by up to two orders of magnitude. We expect that this has consequences for the predictions for gravitational-wave sources from double neutron star mergers, particularly with regard to their metallicity dependence.},
author = {Laplace, E. and Götberg, Ylva Louise Linsdotter and de Mink, S. E. and Justham, S. and Farmer, R.},
issn = {1432-0746},
journal = {Astronomy & Astrophysics},
keywords = {Space and Planetary Science, Astronomy and Astrophysics},
publisher = {EDP Sciences},
title = {{The expansion of stripped-envelope stars: Consequences for supernovae and gravitational-wave progenitors}},
doi = {10.1051/0004-6361/201937300},
volume = {637},
year = {2020},
}