bluuebunny/crossref_metadata_2025 huggingface dataset:
Milky Way globular clusters on cosmological timescales
Authors: Ishchenko Maryna , Berczik Peter , Sobolenko Margarita
Published: March 2024

Context. The present epoch of the Gaia success gives us a possibility to predict the dynamical evolution of our Solar System in the global Galactic framework with high precision.

Aims. We statistically investigated the total interaction of globular clusters with the Solar System during six billion years of look-back time. We estimated the gravitational influence of globular clusters’ flyby onto the Oort cloud system.

Methods. To perform the realistic orbital dynamical evolution for each individual cluster, we used our own high-order parallel dynamical N-body φ-GPU code that we developed. To reconstruct the orbital trajectories of clusters, we used five external dynamical time variable galactic potentials selected from the IllustrisTNG-100 cosmological database and one static potential. To detect a cluster’s close passages near the Solar System, we adopted a simple distance criteria of below 200 pc. To take into account a cluster’s measurement errors (based on Gaia DR3), we generated 1000 initial positions and velocity randomisations for each cluster in each potential.

Results. We found 35 globular clusters that have had close passages near the Sun in all the six potentials during the whole lifetime of the Solar System. We can conclude that at a relative distance of 50 pc between a GC and the SolS, we obtain on average ∼15% of the close passage probability over all six billion years, and at dR = 100 pc, we get on average ∼35% of the close passage probability over all six billion years. The globular clusters BH 140, UKS 1, and Djorg 1 have a mean minimum relative distance to the Sun of 9, 19, and 17 pc, respectively. We analysed the gravitational energetic influence on the whole Oort cloud system from the closest selected globular cluster flyby. We generally found that a globular cluster with a typical mass above a few times 105 M⊙ and with deep close passages in a 1–2 pc immediately results in the ejection more than ∼30% of particles from the Oort cloud system.

Conclusions. We can assume that a globular cluster with close passages near the Sun is not a frequent occurrence but also not an exceptional event in the Solar System’s lifetime.
Photodissociation and induced chemical asymmetries on ultra-hot gas giants
Authors: Baeyens Robin , Désert Jean-Michel , Petrignani Annemieke , Carone Ludmila , Schneider Aaron David
Published: March 2024

Context. Recent observations have resulted in the detection of chemical gradients on ultra-hot gas giants. Notwithstanding their high temperature, chemical reactions in ultra-hot atmospheres may occur in disequilibrium, due to vigorous day-night circulation and intense UV radiation from their stellar hosts.

Aims. The goal of this work is to explore whether photochemistry is affecting the composition of ultra-hot giant planets, and if it can introduce horizontal chemical gradients. In particular, we focus on hydrogen cyanide (HCN) on WASP-76 b, as it is a photochemically active molecule with a reported detection on only one side of this planet.

Methods. We used a pseudo-2D chemical kinetics code to model the chemical composition of WASP-76 b along its equator. Our approach improved on chemical equilibrium models by computing vertical mixing, horizontal advection, and photochemistry.

Results. We find that the production of HCN is initiated through the thermal and photochemical dissociation of CO and N2 on the day side of WASP-76 b. The resulting radicals are subsequently transported to the night side via the equatorial jet stream, where they recombine into different molecules. This process results in an HCN gradient with a maximal abundance on the planet’s morning limb. We verified that photochemical dissociation is a necessary condition for this mechanism, as thermal dissociation alone proves insufficient. Other species produced via night-side disequilibrium chemistry are SO2 and S2.

Conclusions. Our model acts as a proof of concept for chemical gradients on ultra-hot exoplanets. We demonstrate that even ultra-hot planets can exhibit disequilibrium chemistry and recommend that future studies do not neglect photochemistry in their analyses of ultra-hot planets.
Long-term monitoring of large-scale magnetic fields across optical and near-infrared domains with ESPaDOnS, Narval, and SPIRou
Authors: Bellotti S. , Morin J. , Lehmann L. T. , Petit P. , Hussain G. A. J. , Donati J.-F. , Folsom C. P. , Carmona A. , Martioli E. , Klein B. , Fouqué P. , Moutou C. , Alencar S. , Artigau E. , Boisse I. , Bouchy F. , Bouvier J. , Cook N. J. , Delfosse X. , Doyon R. , Hébrard G.
Published: March 2024

Context. Dynamo models describing the generation of stellar magnetic fields for partly and fully convective stars are guided by observational constraints. Zeeman-Doppler imaging has revealed a variety of magnetic field geometries and, for fully convective stars in particular, a dichotomy: either strong, mostly axisymmetric, and dipole-dominated or weak, non-axisymmetric, and multipole-dominated. This dichotomy is explained either by dynamo bistability (i.e., two coexisting and stable dynamo branches) or by long-term magnetic cycles with polarity reversals, but there is no definite conclusion on the matter.

Aims. Our aim is to monitor the evolution of the large-scale field for a sample of nearby M dwarfs with masses between 0.1 and 0.6 M⊙, which is of prime interest to inform distinct dynamo theories and explain the variety of magnetic field geometries studied in previous works. This also has the potential to put long-term cyclic variations of the Sun’s magnetic field into a broader context.

Methods. We analysed optical spectropolarimetric data sets collected with ESPaDOnS and Narval between 2005 and 2016, and near-infrared SPIRou data obtained between 2019 and 2022 for three well-studied, active M dwarfs: EV Lac, DS Leo, and CN Leo. We looked for secular changes in time series of longitudinal magnetic field, width of unpolarised mean-line profiles, and large-scale field topology as retrieved with principal component analysis and Zeeman-Doppler imaging.

Results. We retrieved pulsating (EV Lac), stable (DS Leo), and sine-like (CN Leo) long-term trends in longitudinal field. The width of near-infrared mean-line profiles exhibits rotational modulation only for DS Leo, whereas in the optical it is evident for both EV Lac and DS Leo. The line width variations are not necessarily correlated to those of the longitudinal field, suggesting complex relations between small- and large-scale field. We also recorded topological changes in the form of a reduced axisymmetry for EV Lac and transition from a toroidal-dominated to poloidal-dominated regime for DS Leo. For CN Leo, the topology remained predominantly poloidal, dipolar, and axisymmetric, with only an oscillation in field strength.

Conclusions. Our results show a peculiar evolution of the magnetic field for each M dwarf individually, with DS Leo and EV Lac manifesting more evident variations than CN Leo. These findings confirm that M dwarfs with distinct masses and rotation periods can undergo magnetic long-term variations and suggest an underlying variety of cyclic behaviours of their magnetic fields.
Modeling the effects of starspots on stellar magnetic cycles
Authors: Zhang Zebin , Jiang Jie , Kitchatinov Leonid
Published: March 2024

Context. Observations show that faster rotating stars tend to have stronger magnetic activity and shorter magnetic cycles. The cyclical magnetic activity of the Sun and stars is believed to be driven by the dynamo process. The success of the Babcock-Leighton (BL) dynamo in explaining the solar cycle suggests that starspots could play an important role in stellar magnetic cycles.

Aims. We aim to extend the BL mechanism to solar-mass stars with various rotation rates and explore the effects of emergence properties of starspots in latitudes and tilt angles on stellar magnetic cycles.

Methods. We adopt a kinematic BL-type dynamo model operating in the bulk of the convection zone. The profiles of the large-scale flow fields are from the mean-field hydrodynamical model for various rotators. The BL source term in the model is constructed based on the rotation dependence of starspot emergence; that is, faster rotators have starspots at higher latitudes with larger tilt angles.

Results. Faster rotators have poloidal flux appearing closer to about ±55° latitudes, where the toroidal field generation efficiency is the strongest because of the peak in the strength of the latitudinal differential rotation there. It takes a shorter time for faster rotators to transport the surface poloidal field from their emergence latitude to the ±55° latitudes of efficient Ω-effect, which shortens their magnetic cycles. The faster rotators operate in a more supercritical regime because of a stronger BL α-effect relating to the tilt angles, which leads to stronger saturated magnetic fields and makes the coupling of the poloidal field between two hemispheres more difficult. The magnetic field parity therefore shifts from the hemispherically asymmetric mixed mode to quadrupole, and further to dipole when a star spins down.

Conclusions. The emergence of starspots plays an essential role in the large-scale stellar dynamo.
A possible relation between global CO excitation and massive molecular outflows in local ULIRGs
Authors: Montoya Arroyave I. , Cicone C. , Andreani P. , Weiss A. , De Breuck C. , Lundgren A. , Severgnini P. , Hagedorn B. , Rubinur K. , Baumschlager B. , Makroleivaditi E.
Published: March 2024

Local ultra-luminous infrared galaxies (ULIRGs) have been observed to host ubiquitous molecular outflows, including the most massive and powerful ever detected. These sources have also exceptionally excited global, galaxy-integrated CO ladders. A connection between outflows and molecular gas excitation has however never been established, since previous multi-J CO surveys were limited in spectral resolution and sensitivity and so they could only probe the global molecular gas conditions. In this work, we address this question using new, ground-based, sensitive heterodyne spectroscopy of multiple CO rotational lines (up to CO(7−6)) in a sample of 17 local ULIRGs. We used the Atacama Pathfinder Experiment (APEX) telescope to survey the CO(Jup ≥ 4) lines at a high signal-to-noise ratio, and complemented these data with CO(Jup ≤ 3) APEX and Atacama Large Millimeter Array (ALMA and ACA) observations presented in Montoya Arroyave et al. (2023, A&A, 673, A13). We detected a total of 74 (out of 75) CO lines, with up to six transitions per source. The resulting CO spectral line energy distributions (SLEDs) show a wide range in gas excitation, in agreement with previous studies on ULIRGs. Some CO SLEDs peak at Jup ∼ 3, 4, which we classify as “lower excitation”, while others plateau or keep increasing up to the highest-J CO transition probed, and we classify these as “higher excitation”. Our analysis includes for completeness the results of CO SLED fits performed with a single large velocity gradient component, but our main focus is the investigation of possible links between global CO excitation and the presence of broad and/or high-velocity CO spectral components that can contain outflowing gas. We discovered an increasing trend of line width as a function of Jup of the CO transition, which is significant at the 4σ level and appears to be driven by the eight sources that we classified as higher excitation. We further analyzed such higher-excitation ULIRGs, by performing a decomposition of their CO spectral profiles into multiple components, and we derived CO ladders that are clearly more excited for the spectral components characterized by higher velocities and/or velocity dispersion. Because these sources are known to host widespread molecular outflows, we favor an interpretation whereby the highly excited CO-emitting gas in ULIRGs resides in galactic-scale massive molecular outflows whose emission fills a large fraction of the beam of our APEX high-J CO observations. On the other hand, our results challenge alternative scenarios for which the high CO excitation in ULIRGs can be explained by classical component of the interstellar medium, such as photon- or X-ray dominated regions around the nuclear sources.
A 500 pc volume-limited sample of hot subluminous stars
Authors: Dawson H. , Geier S. , Heber U. , Pelisoli I. , Dorsch M. , Schaffenroth V. , Reindl N. , Culpan R. , Pritzkuleit M. , Vos J. , Soemitro A. A. , Roth M. M. , Schneider D. , Uzundag M. , Vučković M. , Antunes Amaral L. , Istrate A. G. , Justham S. , Østensen R. H. , Telting J. H. , Djupvik A. A. , Raddi R. , Green E. M. , Jeffery C. S. , Kepler S. O. , Munday J. , Steinmetz T. , Kupfer T.
Published: March 2024

We present the first volume-limited sample of spectroscopically confirmed hot subluminous stars out to 500 pc, defined using the accurate parallax measurements from the Gaia space mission data release 3 (DR3). The sample comprises a total of 397 members, with 305 (~77%) identified as hot subdwarf stars, including 83 newly discovered systems. Of these, we observe that 178 (~58%) are hydrogen-rich sdBs, 65 are sdOBs (~21%), 32 are sdOs (~11%), and 30 are He-sdO/Bs (~10%). Among them, 48 (~16%) exhibit an infrared excess in their spectral energy distribution fits, suggesting a composite binary system. The hot subdwarf population is estimated to be 90% complete, assuming that most missing systems are these composite binaries located within the main sequence (MS) in the Gaia colour-magnitude diagram. The remaining sources in the sample include cataclysmic variables, blue horizontal branch stars, hot white dwarfs, and MS stars. We derived the mid-plane density ρ0 and scale height hz for the non-composite hot subdwarf star population using a hyperbolic sechant profile (sech2). The best-fit values are ρ0 = 5.17 ± 0.33 × 10−7 stars pc−3 and hz = 281 ± 62 pc. When accounting for the composite-colour hot subdwarfs and their estimated completeness, the mid-plane density increases to ρ0 = 6.15−0.53+1.16 × 10−7 stars pc−3. This corrected space density is an order of magnitude lower than predicted by population synthesis studies, supporting previous observational estimates.
CON-quest
Authors: Nishimura Y. , Aalto S. , Gorski M. D. , König S. , Onishi K. , Wethers C. , Yang C. , Barcos-Muñoz L. , Combes F. , Díaz-Santos T. , Gallagher J. S. , García-Burillo S. , González-Alfonso E. , Greve T. R. , Harada N. , Henkel C. , Imanishi M. , Kohno K. , Linden S. T. , Mangum J. G. , Martín S. , Muller S. , Privon G. C. , Ricci C. , Stanley F. , van der Werf P. P. , Viti S.
Published: March 2024

Context. Nuclear regions of ultraluminous and luminous infrared galaxies (U/LIRGs) are powered by starbursts and/or active galactic nuclei (AGNs). These regions are often obscured by extremely high columns of gas and dust. Molecular lines in the submillimeter windows have the potential to determine the physical conditions of these compact obscured nuclei (CONs).

Aims. We aim to reveal the distributions of HCN and HCO+ emission in local U/LIRGs and investigate whether and how they are related to galaxy properties.

Methods. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have conducted sensitive observations of the HCN J = 3−2 and HCO+J = 3−2 lines toward 23 U/LIRGs in the local Universe (z < 0.07) with a spatial resolution of ∼0.3″ (∼50−400 pc).

Results. We detected both HCN and HCO+ in 21 galaxies, only HCN in one galaxy, and neither in one galaxy. The global HCN/HCO+ line ratios, averaged over scales of ∼0.5−4 kpc, range from 0.4 to 2.3, with an unweighted mean of 1.1. These line ratios appear to have no systematic trend with bolometric AGN luminosity or star formation rate. The line ratio varies with position and velocity within each galaxy, with an average interquartile range of 0.38 on a spaxel-by-spaxel basis. In eight out of ten galaxies known to have outflows and/or inflows, we found spatially and kinematically symmetric structures of high line ratios. These structures appear as a collimated bicone in two galaxies and as a thin spherical shell in six galaxies.

Conclusions. Non-LTE analysis suggests that the high HCN/HCO+ line ratio in outflows is predominantly influenced by the abundance ratio. Chemical model calculations indicate that the enhancement of HCN abundance in outflows is likely due to high-temperature chemistry triggered by shock heating. These results imply that the HCN/HCO+ line ratio can aid in identifying the outflow geometry when the shock velocity of the outflows is sufficiently high to heat the gas.
New constraints on Triton’s atmosphere from the 6 October 2022 stellar occultation
Authors: Yuan Ye , Zhang Chen , Li Fan , Chen Jian , Fu Yanning , Bai Chunhai , Gao Xing , Wang Yong , Zhong Tuhong , Gao Yixing , Wang Liang , Chen Donghua , Zhang Yixing , Zhang Yang , Xie Wenpeng , Zhang Shupi , Liu Ding , Cao Jun , Yin Xiangdong , Mo Xiaojun , Liu Jing , Han Xinru , Liu Tong , Chen Yuqiang , Gao Zhendong , Zeng Xiang , Niu Guihua , Zheng Xiansheng , Lin Yuchen , Ye Peiyu , Liang Weitang , Zhu Chengcheng , Hu Zhiqiang , He Jianguo , Zhang Wei , Chen Yue , Cheng Zhuo , Zhang Yang , Sun Tianrui , Guo Chenyang , Lu Yue , Lin Jiajun , Tan Wei , Zhou Jia , Xu Jun , He Jun , Ye Jiahui , Li Delai , Zhang Shuai , Qu Qingyue
Published: March 2024

The atmosphere of Triton was probed directly by observing a ground-based stellar occultation on 6 October 2022. This rare event yielded 23 positive light curves collected from 13 separate observation stations contributing to our campaign. The significance of this event lies in its potential to directly validate the modest pressure fluctuation on Triton, a phenomenon not definitively verified by previous observations, including only five stellar occultations, and the Voyager 2 radio occultation in 1989. Using an approach consistent with a comparable study, we precisely determined a surface pressure of 14.07−0.13+0.21 μbar in 2022. This new pressure rules out any significant monotonic variation in pressure between 2017 and 2022 through direct observations, as it is in alignment with the 2017 value. Additionally, both the pressures in 2017 and 2022 align with the 1989 value. This provides further support for the conclusion drawn from the previous volatile transport model simulation, which is consistent with the observed alignment between the pressures in 1989 and 2017; that is to say, the pressure fluctuation is modest. Moreover, this conclusion suggests the existence of a northern polar cap extended down to at least 45°N–60°N and the presence of nitrogen between 30°S and 0°.
Impact of aeolian erosion on dust evolution in protoplanetary discs
Authors: Michoulier Stéphane , Gonzalez Jean-François , Grishin Evgeni , Petetin Clement
Published: March 2024

Context. Many barriers prevent dust from forming planetesimals via coagulation in protoplanetary discs, such as bouncing, collisional fragmentation, or aeolian erosion. Modelling dust and the different phenomena that can alter its evolution is therefore necessary. Multiple solutions have been proposed, but they still need to be confirmed.

Aims. In this paper, we explore the role that aeolian erosion plays in the evolution of dust.

Methods. We used a mono-disperse model to account for dust growth and fragmentation, implemented in a 1D code to compute the evolution of single grains and in a 3D smoothed particle hydrodynamics (SPH) code to compute the global evolution of dust and gas. We tested the erosion model in our code and ensured it matched previous results.

Results. With a disc model that reproduces observations, we show with both 1D and 3D studies that erosion is not significant during the evolution of dust when we take fragmentation into consideration. With a low-viscosity disc, fragmentation is less of a problem, but grain growth is also less important, which prevents the formation of large objects. In dust traps, close to the star, erosion is also not impactful, even when fragmentation is turned off.

Conclusions. We show in this paper that aeolian erosion is negligible when radial drift, fragmentation, and dust traps are taken into account and that it does not alter the dust evolution in the disc. However, it can have an impact on later stages, when the streaming instability forms large clumps close to the star, or when planetesimals are captured.
Breaking the baryon-dark matter degeneracy in a model-independent way through the Sunyaev-Zeldovich effect
Authors: Alfano Anna Chiara , Luongo Orlando , Muccino Marco
Published: March 2024

Context.In cosmological fits, it is common to fix the baryon densityωbvia the cosmic microwave background. We here constrainωbby means of a model-independent interpolation of the acoustic parameter from correlated baryonic acoustic oscillations.

Aims.The proposed technique is used to alleviate the degeneracy between baryonic and dark matter abundances.

Methods.We propose a model-independent Bézier parametric interpolation and applied it to intermediate-redshift data. We first interpolated the observational Hubble data to extract cosmic bounds over the (reduced) Hubble constanth0and interpolated the angular diameter distances,D(z), of the galaxy clusters, inferred from the Sunyaev-Zeldovich effect, to constrain the spatial curvature, Ωk. Through the Hubble points andD(z) determined in this way, we interpolated uncorrelated data of baryonic acoustic oscillations bounding the baryonωband total matterωmdensities, reinforcing the constraints onh0and Ωkwith the same technique. Finally, to remove the matter sector degeneracy, we obtainedωbby interpolating the acoustic parameter from correlated baryonic acoustic oscillations.

Results.Monte Carlo Markov chain simulations agree at 1σconfidence level with the flat ΛCDM model and are roughly suitable at 1σwith its nonflat extension, while the Hubble constant appears in tension up to the 2σconfidence levels.

Conclusions.Our method excludes very small extensions of the standard cosmological model, and on the Hubble tension side, seems to match local constraints slightly.
The interplay between forming planets and photoevaporating discs
Authors: Weber M. L. , Picogna G. , Ercolano B.
Published: March 2024

Context. Disc winds and planet–disc interactions are two crucial mechanisms that define the structure, evolution, and dispersal of protoplanetary discs. While winds are capable of removing material from discs, eventually leading to their dispersal, massive planets can shape their disc by creating sub-structures such as gaps and spiral arms.

Aims. We studied the interplay between an X-ray photoevaporative disc wind and the sub-structures generated due to planet–disc interactions to determine how their mutual interactions affect the disc’s and the planet’s evolution.

Methods. We performed 3D hydrodynamic simulations of viscous discs (α = 6.9 × 10−4) that host a Jupiter-like planet and undergo X-ray photoevaporation. We traced the gas flows within the disc and wind and measured the rate of accretion onto the planet, as well as the gravitational torque that is acting on it.

Results. Our results show that the planetary gap removes the wind’s pressure support, allowing wind material to fall back into the gap. This opens new pathways for material from the inner disc (and part of the outer disc) to be redistributed through the wind towards the gap. Consequently, the gap becomes shallower and the flow of mass across the gap in both directions is significantly increased, as is the planet’s mass-accretion rate (by factors of ≈5 and ≈2, respectively). Moreover, the wind-driven redistribution results in a denser inner disc and a less dense outer disc, which, combined with the recycling of a significant portion of the inner wind, leads to longer lifetimes for the inner disc, contrary to the expectation in a planet-induced photoevaporation scenario that has been proposed in the past.
Galaxies in the zone of avoidance: Misclassifications using machine learning tools
Authors: Marchant Cortés P. , Nilo Castellón J. L. , Alonso M. V. , Baravalle L. , Villalon C. , Sgró M. A. , Daza-Perilla I. V. , Soto M. , Milla Castro F. , Minniti D. , Masetti N. , Valotto C. , Lares M.
Published: March 2024

Context. Automated methods for classifying extragalactic objects in large surveys offer significant advantages compared to manual approaches in terms of efficiency and consistency. However, the existence of the Galactic disk raises additional concerns. These regions are known for high levels of interstellar extinction, star crowding, and limited data sets and studies.

Aims. In this study, we explore the identification and classification of galaxies in the zone of avoidance (ZoA). In particular, we compare our results in the near-infrared (NIR) with X-ray data.

Methods. We analyzed the appearance of objects in the Galactic disk classified as galaxies using a published machine-learning (ML) algorithm and make a comparison with the visually confirmed galaxies from the VVV NIRGC catalog.

Results. Our analysis, which includes the visual inspection of all sources cataloged as galaxies throughout the Galactic disk using ML techniques reveals significant differences. Only four galaxies were found in both the NIR and X-ray data sets. Several specific regions of interest within the ZoA exhibit a high probability of being galaxies in X-ray data but closely resemble extended Galactic objects. Our results indicate the difficulty in using ML methods for galaxy classification in the ZoA, which is mainly due to the scarcity of information on galaxies behind the Galactic plane in the training set. They also highlight the importance of considering specific factors that are present to improve the reliability and accuracy of future studies in this challenging region.
Ponderomotive forces in magnetized nonthermal space plasmas due to cyclotron waves
Authors: Espinoza-Troni Joaquín , Asenjo Felipe A. , Moya Pablo S.
Published: March 2024

Context. The ponderomotive force is involved in a variety of space plasma phenomena characterized by the family of Kappa distributions. Therefore, evaluating these nonthermal effects in the ponderomotive force is required.

Aims. The Karpman–Washimi ponderomotive interaction due to cyclotron waves is evaluated for different space conditions considering low-temperature magnetized plasmas described by an isotropic Kappa distribution and with a wave propagation parallel to the background magnetic field.

Methods. We performed a brief analysis of the influence of the Kappa distribution in the dispersion relation for a low-temperature plasma expansion at the lowest order in which the thermal effects can be appreciated without considering the damping characteristics of the wave. The different factors of the ponderomotive force were obtained and analyzed separately as a function of the wavenumber, the spectral index κ, and the plasma beta.

Results. We found a relevant influence of the nonthermal effects in all factors of the ponderomotive force for magnetized plasmas. The effect of the Kappa distribution has been evaluated for a wide variety of space environments, such as the solar wind and the different regions of our magnetosphere, where it has been found that these results can be relevant for the solar wind, the magnetosheath, the plasma sheet, and the polar cusps. We also analyzed the role of the nonthermal effect in the induced Karpman–Washimi ponderomotive magnetization in the context of spatial plasmas and the total radiated power associated with it.

Conclusions. We find that even for nearly cold magnetized plasmas and waves far from the resonances, the effect of the kappa parameter in the ponderomotive force cannot be neglected. This suggests a significant role of the Kappa distribution in ponderomotive phenomena of space physics.
The physical properties of T Pyx as measured by MUSE
Authors: Izzo L. , Pasquini L. , Aydi E. , Della Valle M. , Gilmozzi R. , Harvey E. A. , Molaro P. , Otulakowska-Hypka M. , Selvelli P. , Thöne C. C. , Williams R.
Published: March 2024

Context. T Pyx is one of the most enigmatic recurrent novae, and it has been proposed as a potential Galactic type-Ia supernova progenitor.

Aims. Using spatially resolved data obtained with MUSE, we characterized the geometrical distribution of the material expelled in previous outbursts surrounding the white dwarf progenitor.

Methods. We used a 3D model for the ejecta to determine the geometric distribution of the extended remnant. We also calculated the nebular parallax distance (d = 3.55 ± 0.77 kpc) based on the measured velocity and spatial shift of the 2011 bipolar ejecta. Our findings confirm previous results, including the data from the Gaia mission.

Results. The remnant of T Pyx can be described by a two-component model consisting of a tilted ring at i = 63.7 relative to its normal vector and fast bipolar ejecta perpendicular to the plane of the equatorial ring.

Conclusions. We found an upper limit for the bipolar outflow ejected mass in 2011 of the bipolar outflow of Mej, b < (3.0 ± 1.0)×10−6 M⊙, which is lower than previous estimates given in the literature. However, only a detailed physical study of the equatorial component can provide an accurate estimate of the total ejecta of the last outburst, a fundamental step to understanding if T Pyx will end its life as a type-Ia supernova.
Giant radio galaxies in the LOFAR deep fields
Authors: Simonte M. , Andernach H. , Brüggen M. , Miley G. K. , Barthel P.
Published: March 2024

Context. The reason why some radio galaxies (RGs) grow to form so-called giant radio galaxies (GRGs) with sizes > 700 kpc, is still unknown.

Aims. In this study, we compare the radio, optical and environmental properties of GRGs with those of a control sample of smaller RGs we found in the three LOw-Frequency ARray (LOFAR) deep fields, namely the Boötes, ELAIS-N1, Lockman Hole, for a total area of ≈95 deg2.

Methods. We inspected the LOFAR deep fields and created a catalogue of 1609 extended radio galaxies (ERGs). By visual inspection, we identified their host galaxies and spectroscopically or photometrically classified 280 of these as GRGs. We studied their properties, such as their accretion state, stellar mass and star formation rate (SFR) using deep optical and infrared survey data. Moreover, we explored the environment in terms of the surface number density of neighbouring galaxies within these surveys. Integrated flux densities and radio luminosities were also determined for a subset of ERGs through available survey images at 50, 150, 610, and 1400 MHz to compute integrated spectral indices.

Results. Considering the fraction of GRGs displaying an FRII morphology alongside the host galaxy properties, we suggest that GRGs consistently possess sufficient power to overcome jet frustration caused by the interstellar medium. Moreover, clear differences emerge in the environmental densities between GRGs and smaller RGs, using the number of neighbouring galaxies within 10 Mpc from the host galaxy as a proxy. GRGs preferentially reside in sparser environments compared to their smaller counterparts. In particular, only 3.6% of the GRGs reside within a 3D comoving distance of 5 Mpc from a previously reported galaxy cluster. We found that larger sources exhibit steeper integrated spectral indices, suggesting that GRGs are late-stage versions of RGs. These results suggest that GRGs are amongst the oldest radio sources with the most stable nuclear activity that reside in sparse environments.
Probing the emission mechanism and nature of the pulsating compact object in the X-ray binary SAX J1324.4−6200
Authors: Ducci L. , Bozzo E. , Burgay M. , Malacaria C. , Ridolfi A. , Romano P. , Serim M. M. , Vercellone S. , Santangelo A.
Published: March 2024

Recently, there has been renewed interest in the Be X-ray binary (Be/XRB) SAX J1324.4−6200 because of its spatial coincidence with a variable γ-ray source detected by Fermi/LAT. To explore more thoroughly its properties, new X-ray observations were carried out in 2023 by NuSTAR, XMM-Newton, and Swift satellites, jointly covering the energy range from 0.2 − 79 keV. SAX J1324.4−6200 was caught at an X-ray flux of ∼10−11 erg cm−2 s−1. The X-ray spectrum fits well with an absorbed power law with a high energy cutoff. Other acceptable fits require an additional blackbody component (kTbb ≈ 1.1 keV) or a Gaussian in absorption (Egabs ≈ 6.9 keV). We measured a NuSTAR spin period of 175.8127 ± 0.0036 s and an XMM-Newton spin period of 175.862 ± 0.025 s. We show that all the available spin period measurements of SAX J1324.4−6200, spanning 29 yr, are highly correlated with time, resulting in a remarkably stable spin-down of Ṗ = 6.09 ± 0.06 × 10−9 s s−1. We find that if SAX J1324.4−6200 hosts an accretion-powered pulsar, accretion torque models indicate a surface magnetic field of ∼1012 − 13 G. The X-ray properties emerging from our analysis strenghten the hypothesis that SAX J1324.4−6200 belongs to the small group of persistent Be/XRBs. We also performed radio observations with the Parkes Murriyang telescope, to search for radio pulsations. However, no radio pulsations compatible with the rotational ephemeris of SAX J1324.4−6200 were detected. We rule out the hypothesis that SAX J1324.4−6200 is a γ-ray binary where the emission is produced by interactions between the pulsar and the companion winds. Other models commonly used to account for the production of γ-rays in accreting pulsars cannot reproduce the bright emission from SAX J1324.4−6200. We examined other possible mechanisms behind the γ-ray emission and note that there is a ∼0.5% chance probability that an unknown extragalactic active galactic nucleus (AGN) observed through the Galactic plane may coincidentally fall within the Fermi/LAT error circle of the source and be responsible for the γ-ray emission.
A sequence of Type Ib, IIb, II-L, and II-P supernovae from binary-star progenitors with varying initial separations
Authors: Dessart Luc , Gutiérrez Claudia P. , Ercolino Andrea , Jin Harim , Langer Norbert
Published: March 2024

Over the last decade, evidence has accumulated that massive stars do not typically evolve in isolation but instead follow a tumultuous journey with a companion star on their way to core collapse. While Roche-lobe overflow appears instrumental for the production of a large fraction of Type Ib and Ic supernovae (SNe), variations in the initial orbital period, Pinit, of massive interacting binaries may also produce a wide diversity of case B, BC, or C systems, with pre-SN stars endowed from minute to massive H-rich envelopes. Focusing here on the explosion of the primary donor star, originally 12.6 M⊙, we used radiation hydrodynamics and nonlocal thermodynamic equilibrium time-dependent radiative transfer to document the gas and radiation properties of such SNe, covering Types Ib, IIb, II-L, and II-P. Variations in Pinit are the root cause of the wide diversity of our SN light curves, which present single-peak, double-peak, fast-declining, or plateau-like morphologies in the V band. The different ejecta structures, expansion rates, and relative abundances (e.g., H, He, and 56Ni) can lead to a great deal of diversity in terms of spectral line shapes (absorption versus emission strength and width) and evolution. We emphasize that Hα is a key tracer of these modulations, and that He I 7065 Å is an enduring optical diagnostic for the presence of He. Our grid of simulations fares well against representative Type Ib, IIb, and II-P SNe, but interaction with circumstellar material, which is ignored in this work, is likely at the origin of the tension between our Type II-L SN models and observations (e.g., of SN 2006Y). Remaining discrepancies in the rise time to bolometric maximum of our models call for a proper account of both small-scale and large-scale structures in core-collapse SN ejecta. Discrepant Type II-P SN models, with a high plateau brightness but small spectral line widths, can be fixed by adopting more compact red-supergiant star progenitors.
The LOFAR – eFEDS survey: The incidence of radio and X-ray AGN and the disk–jet connection
Authors: Igo Z. , Merloni A. , Hoang D. , Buchner J. , Liu T. , Salvato M. , Arcodia R. , Bellstedt S. , Brüggen M. , Croston J. H. , de Gasperin F. , Georgakakis A. , Hardcastle M. J. , Nandra K. , Ni Q. , Pasini T. , Shimwell T. , Wolf J.
Published: March 2024

Context. Radio jets are present in a diverse sample of AGN. However, the mechanisms of jet powering are not fully understood, and it remains unclear to what extent they obey mass-invariant scaling relations similar to those found for the triggering and fuelling of X-ray-selected AGN.

Aims. We use the multi-wavelength data in the eFEDS field observed by eROSITA/Spectrum-Roentgen-Gamma (SRG) and LOFAR to study the incidence of X-ray and radio AGN as a function of several stellar mass (M*)-normalised AGN power indicators.

Methods. From the LOFAR – eFEDS survey, we defined a new sample of radio AGN, with optical counterparts from Legacy Survey DR9, according to a radio-excess relative to their host star formation rate. We further divided the sample into compact and complex radio morphologies. In this work, we used the subset matching to the well-characterised, highly complete spectroscopic GAMA09 galaxies (0 < z < 0.4). We release this value-added LOFAR – eFEDS catalogue*. We calculated the fraction of GAMA09 galaxies hosting radio, X-ray, and both radio and X-ray AGN as functions of the specific black hole kinetic (λJet) and radiative (λEdd) power.

Results. Despite the soft-X-ray eROSITA-selected sample, the incidence of X-ray AGN as a function of λEdd shows the same mass-invariance and power law slope (−0.65) as that found in previous studies once corrected for completeness. Across the M* range probed, the incidence of compact radio AGN as a function of λJet is described by a power law with constant slope, showing that it is not only high mass galaxies hosting high power jets and vice versa. This slope is steeper than that of the X-ray incidence, which has a value of around −1.5. Furthermore, higher-mass galaxies are more likely to host radio AGN across the λJet range, indicating some residual mass dependence of jet powering. Upon adding complex radio morphologies, including 34 FRIIs, three of which are giant radio galaxies, the incidence not only shows a larger mass dependence but also a jet power dependence, being clearly boosted at high λJet values. Importantly, the latter effect cannot be explained by such radio AGN residing in more dense environments (or more massive dark matter haloes). The similarity in the incidence of quiescent and star-forming radio AGN reveals that radio AGN are not only found in “red and dead” galaxies. Overall, our incidence analysis reveals some fundamental statistical properties of radio AGN samples, but highlights open questions regarding the use of a single radio luminosity–jet power conversion. We explore how different mass and accretion rate dependencies of the incidence can explain the observed results for varying disk–jet coupling models.
Increasing the raw contrast of VLT/SPHERE with the dark hole technique
Authors: Galicher R. , Potier A. , Mazoyer J. , Wahhaj Z. , Baudoz P. , Chauvin G.
Published: March 2024

Context. Imaging exoplanetary systems is essential to characterizing exoplanet atmospheres and orbits as well as circumstellar disks and to studying planet-disk interactions to understand the planet formation processes. Imaging exoplanets or circumstellar disks in the visible and near-infrared is challenging, however, because these objects are very faint relative to their star, even though only fractions of an arcsecond away. Coronagraphic instruments have already allowed the imaging of a few exoplanets, but their performance is limited by wavefront aberrations. Adaptive optics systems partly compensate for the Earth’s atmosphere turbulence, but they cannot fully control the wavefront. Some of the starlight leaks through the coronagraph and forms speckles in the astrophysical image. Focal plane wavefront control, used as a second stage after the adaptive optics system, has been proposed to minimize the speckle intensity within an area called the dark hole.

Aims. We previously demonstrated the on-sky performance of dark hole techniques, pairwise probing coupled with electric field conjugation, using the apodized pupil Lyot coronagraph of the VLT/SPHERE instrument. In this paper, we probe their performance using the SPHERE four-quadrant phase mask coronagraph, and we demonstrate the interest of combining dark hole techniques and reference differential imaging.

Methods. We used these dark hole techniques on-sky to create a dark hole in the narrow band around 1.7 |j.m observing HR 4796. We then recorded broadband images of HR 4796 and a reference star at theHband.

Results. The dark hole techniques improved theH-band detection limit by a factor of three. The dark hole was stable from one star to a nearby star enabling reference differential imaging.

Conclusions. This stability offers two new strategies of observation. First, one can quickly create a dark hole observing a bright star before pointing to a faint target star. Furthermore, one can couple dark hole techniques and reference differential imaging. A very interesting point is that the performance of these methods does not depend on the astrophysical signal.
Seven new triply eclipsing triple star systems
Authors: Rappaport S. A. , Borkovits T. , Mitnyan T. , Gagliano R. , Eisner N. , Jacobs T. , Tokovinin A. , Powell B. , Kostov V. , Omohundro M. , Kristiansen M. H. , Jayaraman R. , Terentev I. , Schwengeler H. M. , LaCourse D. , Garai Z. , Pribulla T. , Maxted P. F. L. , Bíró I. B. , Csányi I. , Pál A. , Vanderburg A.
Published: March 2024

Aims. We have identified nearly a hundred close triply eclipsing hierarchical triple star systems from data taken with the space telescope TESS. These systems are noteworthy in that we can potentially determine their dynamical and astrophysical parameters with a high precision. In the present paper, we report the comprehensive study of seven new compact triply eclipsing triple star systems taken from this larger sample: TICs 133771812, 176713425, 185615681, 287756035, 321978218, 323486857, and 650024463.

Methods. Most of the data for this study come from TESS observations, but two of them have Gaia measurements of their outer orbits, and we obtained supplemental radial velocity (RV) measurements for three of the systems. The eclipse timing variation curves extracted from the TESS data, the photometric light curves, the RV points, and the spectral energy distribution (SED) are combined in a complex photodynamical analysis to yield the stellar and orbital parameters of all seven systems.

Results. Four of the systems are quite compact with outer periods in the range of 41–56 days. All of the systems are substantially flat, with mutual inclination angles of ≲2°. Including the systems reported in this work, we have now studied in considerable detail some 30 triply eclipsing triples with TESS, and are accumulating a meaningful census of these systems.
A new analytical model of the cosmic-ray energy flux for Galactic diffuse radio emission
Authors: Bracco Andrea , Padovani Marco , Galli Daniele
Published: March 2024

Low-frequency radio observations of diffuse synchrotron radiation offer a unique vantage point from which to investigate the intricate relationship between gas and magnetic fields in the formation of structures within the Galaxy, spanning from the diffuse interstellar medium (ISM) to star-forming regions. Achieving this pivotal objective hinges on a comprehensive understanding of cosmic-ray properties; these dictate the effective energy distribution of relativistic electrons, which are primarily responsible for the observable synchrotron radiation. Notably, cosmic-ray electrons (CRe) with energies of between 100 MeV and 10 GeV play a crucial role in determining the majority of the sky brightness below the GHz range. However, their energy flux (je) remains elusive because of solar modulation. We propose a way to derive observational constraints on this energy gap of interstellar CRe through the brightness temperature spectral index of low-frequency radio emission, here denoted βobs. We introduce a new parametric analytical model that fits available data for je in accordance with the βobs values measured in the literature between 50 MHz and 1 GHz for diffuse emission in the Milky Way. Our model accounts for multiple observations considering magnetic-field strengths consistent with existing measurements below 10 μG. We present a first all-sky map of the average component of the magnetic field perpendicular to the line of sight and validate our methodology against state-of-the art numerical simulations of the diffuse ISM. This research makes headway in modeling Galactic diffuse emission with a practical, parametric form. It provides essential insights that will help preparations for the imminent arrival of the Square Kilometre Array.
A benchmark case for aeroacoustic simulations involving fluid-structure-acoustic interaction transferred from the process of human phonation
Authors: Schoder Stefan , Falk Sebastian , Wurzinger Andreas , Lodermeyer Alexander , Becker Stefan , Kniesburges Stefan
Published: March 2024

Modeling fluid-structure-acoustic interaction is a highly challenging task and currently there is a lack of available benchmark datasets. For instance, to understand the processes of human phonation, it is essential to fully understand the fluid-structure-acoustic interaction process. In this article, a synthetic human phonation model is presented for benchmarking numerical methods in the field of aerodynamics, aeroacoustics and the highly-complex fluid-structure-acoustic interaction process of the voice production. The objective is to present the wide range of experimental data available, including the model geometry, the material characteristics, quantitiesreferred to the vocal fold dynamics, fluid mechanical quantities and the acoustic field. Firstly, the experimental setup is specified. Secondly, the experimental data is described in detail, accompanied by illustrations. Having the dataset in hand, finally, it is shown how to use this data to validate a computational phonation model called simVoice successfully. In conclusion, this benchmarking dataset offers the opportunity to validate structural dynamics, aerodynamics and aeroacoustics of a highly-complex fluid-structure-acoustic interaction simulation, obtained from different mathematical formulations and numerical procedures.
Comparaison de la dosimétrie et de la qualité d’image des équipements de radiologie conventionnelle utilisés pour les radiographies du Thorax et de l’ASP au niveau d’un GHT (Groupement Hospitalier de Territoire)
Authors: Couzon F. , Liogier A. , Boutet C. , Gineys V.
Published: March 2024

Objectifs : Cette étude a pour but d’établir une cartographie territoriale complète et détaillée des salles de radiologie présentes sur un « Groupement Hospitalier de Territoire (GHT) », aussi bien pour la qualité d’image que pour la dosimétrie des radiographies du thorax et de l’ASP. Matériels et méthodes : Sur les différentes installations du GHT, la mesure du kerma dans l’air incident (Ki) et l’évaluation de la qualité d’image à l’aide de l’objet test TOR 18-FG ont été réalisées sur un fantôme de PMMA simulant l’atténuation d’un patient de gabarit standard. Une étude rétrospective complémentaire a également permis d’évaluer la performance clinique des installations. Résultats : L’engagement territorial a permis de recueillir des données pour 23 salles de radiologie au total. Pour la partie dosimétrique, il existe des facteurs 10,3 ; 8,6 et 8,2 entre les valeurs extrêmes des Ki respectivement pour les radiographies « ASP debout » (Abdomen Sans Préparation), « ASP couché » et « Thorax de face ». Concernant la qualité d’image, les disparités observées sont beaucoup plus faibles et semblent plus liées à la technologie de détection. Conclusion : Le travail effectué a permis de mettre en évidence des variations considérables concernant la dosimétrie des radiographies étudiées. Si le paramétrage des protocoles est souvent à l’origine de ces différences, les utilisateurs ont également un rôle majeur dans la radioprotection des patients.