Astronomy & Astrophysics最新文献

{"title":"The Cosmic Timeline Implied by the JWST Reionization Crisis","authors":"F. Melia","doi":"10.1051/0004-6361/202450835","DOIUrl":"https://doi.org/10.1051/0004-6361/202450835","url":null,"abstract":"JWST's discovery of well-formed galaxies and supermassive black holes only a \u0000 few hundred Myr after the big bang, and the identification of polycyclic aromatic\u0000 hydrocarbons (PAHs) at $z=6.71$, seriously challenge the timeline predicted by Lambda CDM. \u0000 Moreover, the implied bright UV-irradiation of the early Universe suggests a reionization \u0000 history much too short to comply with the observed evolution of the hydrogen ionization \u0000 fraction, $x_ HII (z)$. A recent analysis of reionization after JWST by Munoz:2024 has concluded\u0000 that the Lambda CDM timeline simply cannot accommodate the combined JWST- Planck observations even if exotic fixes are introduced to modify the standard reionization model.\u0000 In this paper, we argue that this so-called `photon budget crisis' is more likely\u0000 due to flaws in the cosmological model itself. We aim to re-analyze the data in the context\u0000 of established astrophysics with $R_ h =ct$ as the background cosmology, an approach\u0000 that has already been shown to mitigate the tension created by the too-early appearance \u0000 of galaxies, quasars and PAHs. We employ the standard reionization model using the JWST-measured UV luminosity\u0000 function in the early Universe and the timeline and physical conditions in both \u0000 Lambda CDM and $R_ h =ct$. The former has already been fully probed and discussed \u0000 by Munoz:2024 and we here merely redo the calculation to ensure consistency with \u0000 their pioneering work. We then contrast the predicted reionization histories in these two \u0000 scenarios and compare them with the data. We confirm that the reionization history predicted by Lambda CDM is in significant tension\u0000 with the observations, and demonstrate that the latter are instead in excellent agreement with \u0000 the $R_ h =ct$ timeline. Together, the four anomalies uncovered by JWST, including the newly discovered reionization\u0000 `crisis' discussed in this paper, provide strong evidence against the timeline \u0000 predicted by Lambda CDM and in favor of the evolutionary history in $R_ h =ct$.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"72 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141338115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetohydrodynamic simulations of the space weather in Proxima b: Habitability conditions and radio emission","authors":"L. Peña-Moñino, Miguel Pérez-Torres, Jacobo Varela, P. Zarka","doi":"10.1051/0004-6361/202349042","DOIUrl":"https://doi.org/10.1051/0004-6361/202349042","url":null,"abstract":"The habitability of exoplanets hosted by M dwarf stars dramatically depends\u0000on the space weather, where the magnetic and ram pressure of the stellar wind, and the exoplanet magnetic field are the three main players. These three parameters also likely drive the radio emission arising close to the planet. Our aim is to characterize the magneto-plasma environment and thus the habitability of the Earth-like planet Proxima b, which is inside the habitable zone of its host M dwarf star Proxima, when it is subject to average calm space weather conditions, and to more extreme space weather conditions, for example a coronal mass ejection (CME) event. We study the role of the stellar wind and planetary magnetic field, and their mutual orientation. We also\u0000determine the radio emission arising from the interaction between the\u0000stellar wind of Proxima and the magnetosphere of its planet Proxima b, which\u0000is relevant to guiding radio observations aimed at unveiling planets. We used the PLUTO code to run a set of 3D magneto-hydrodynamic simulations\u0000focused on the space weather around planet Proxima b. \u0000We considered both calm and space weather conditions for Proxima b, under three different scenarios:\u0000(a) Proxima b subject to calm space weather in a sub-Alfvénic regime, where the stellar wind\u0000magnetic pressure dominates over the wind's ram pressure; (b) Proxima b subject to calm space weather in a super-Alfvénic regime, where the ram pressure of the wind dominates, and a bow\u0000shock is formed; and (c) Proxima b subject to a coronal mass ejection event, when the dynamical and magnetic pressure of the stellar wind from its host star are increased enormously for a short period of time. We find that if Proxima b has a magnetic field similar to that of the Earth ($B_ p = B_ 0.32$ G) or larger, the magnetopause standoff distance is large enough to shield the surface from the stellar wind for essentially any planetary tilt but the most extreme values (close to degree $) under a calm space weather. \u0000 Even if Proxima b is subject to more extreme space weather conditions, for example a CME event from its host star, the planet is well shielded by an Earth-like magnetosphere ( B_ $i or if it has a tilt smaller than that of the Earth. Otherwise, the planetary magnetic field must be larger to shield the planet from particle precipitation on the surface. For calm space weather conditions, the radio emission caused by the day-side reconnection regions can be as high as 7$ in the super-Alfvénic regime, and is on average almost an order of magnitude larger than the radio emission in the sub-Alfvénic cases, due to the much larger contribution of the bow shock, which is not formed in the sub-Alfvénic regime. We also find that the energy dissipation at the bow shock is essentially independent of the angle between the planet's magnetic dipole and the incident stellar wind flow. If Proxima b is subject to extreme space weather conditions, the radio emission is more than two orders of mag","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"31 34","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141340492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correcting Fabry-Perot etalon effects in solar observations","authors":"P. Santamarina Guerrero, D. Orozco Suárez, F. J. Bailén, J. Blanco Rodríguez","doi":"10.1051/0004-6361/202449825","DOIUrl":"https://doi.org/10.1051/0004-6361/202449825","url":null,"abstract":"Data processing pipelines of Fabry-P'erot interferometers (FPI) must take into account the side effects these devices introduce in the observations. Interpretation of these observations without proper correction can lead to inaccurate or false results, with consequent impact on their physical interpretation. Corrections typically require prior knowledge of the properties of the etalon and the way they affect the incoming light in order to calibrate the data successfully. We have developed an algorithm to derive etalon properties from flat-field observations and tested its applicability and accuracy using simulated observations and real measurements. We employed analytical expressions of the transmission profiles for FPIs in collimated and telecentric configurations to derive their expected impact on the observations. These analytical expressions allowed us to develop a customized optimization algorithm capable of inferring the properties of the etalon from the observations. The algorithm's performance has been tested on simulated observations with an etalon in collimated and telecentric setups employing various noise levels and spectral samplings. Additionally, we explored how tilting the etalon in a telecentric configuration influences the algorithm's effectiveness. Lastly, we also applied the algorithm to a set of real flat-field observations taken with the high-resolution telescope of the Polarimetric and Helioseismic Imager on board the Solar Orbiter mission (HRT-SO/PHI). The algorithm is able to retrieve the gain and etalon induced transmission velocity shifts (cavity map), with an average accuracy ranging between $0.4 $ and $0.1 $ for the former and between 120 $ and 30 ms$^ $ for the latter. Both reducing the noise level and increasing the spectral sampling of the observations proved to greatly increase the algorithm's performance, as expected. Results also suggest that determination of the observed object from the data is possible but an additional error between 40 ms$^ $ and 10 ms$^ $ is to be expected in the inferred cavity map. Furthermore, we show that neglecting the asymmetries arising from either tilts of the etalon or imperfections in the telecentrism can lead to large errors when determining the gain. Tests with HRT-SO/PHI data have verified the applicability of the algorithm in real cases. Our presented method enabled us to derive the transmission profile of FPIs from observations of collimated and telecentric configurations. It has proven to be robust against the presence of noise and limited spectral line sampling. The results reported here also show the importance of accounting for the asymmetries arising in real telecentric mounts when interpreting the results of real instruments.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"24 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141341616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Euclid preparation. XLV. Optical emission-line predictions of intermediate-z galaxy populations in GAEA for the Euclid Deep and Wide Surveys","authors":"L. Scharré, M. Hirschmann, G. De Lucia, S. Charlot, F. Fontanot, M. Spinelli, L. Xie, A. Feltre, V. Allevato, A. Plat, M. Bremer, S. Fotopoulou, L. Gabarra, B. Granett, Michele Moresco, C. Scarlata, L. Pozzetti, L. Spinoglio, M. Talia, G. Zamorani, B. Altieri, A. Amara, S. Andreon, N. Auricchio, M. Baldi, S. Bardelli, D. Bonino, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, F. Castander, M. Castellano, S. Cavuoti, A. Cimatti, G. Congedo, C. Conselice, L. Conversi, Y. Copin, L. Corcione, F. Courbin, H. Courtois, A. Da Silva, H. Degaudenzi, J. Dinis, M. Douspis, F. Dubath, X. Dupac, S. Dusini, M. Farina, S. Farrens, S. Ferriol, M. Frailis, E. Franceschi, S. Galeotta, B. Garilli, B. Gillis, C. Giocoli, A. Grazian, F. Grupp, L. Guzzo, S. Haugan, W. Holmes, I. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, E. Keihänen, S. Kermiche, A. Kiessling, T. Kitching, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, S. Ligori, P. Lilje, V. Lindholm, I. Lloro, D. Maino, ","doi":"10.1051/0004-6361/202449500","DOIUrl":"https://doi.org/10.1051/0004-6361/202449500","url":null,"abstract":"In anticipation of the upcoming Euclid Wide and Deep Surveys, we present optical emission-line predictions at intermediate redshifts from 0.4 to 2.5. Our approach combines a mock light cone from the Gaea semi-analytic model with advanced photoionisation models to construct emission-line catalogues. This allows us to self-consistently model nebular emission from H ii regions around young stars, and, for the first time with a semi-analytic model, narrow-line regions of active galactic nuclei (AGN) and evolved stellar populations. Gaea Mpc $, marks the largest volume this set of models has been applied to. We validate our methodology against observational and theoretical data at low redshift. \u0000 Our analysis focuses on seven optical emission lines: Halpha , Hbeta S ii N ii O i O iii 5007$, and O ii 3727, 3729$. In assessing selection bias, we find that it will predominantly observe line-emitting galaxies, which are massive (stellar mass $ solarmass $), star-forming (specific star-formation rate $> 10^ yr^ $), and metal-rich (oxygen-to-hydrogen abundance $ logten(O/H)+12 > 8$). We provide percentages of emission-line populations in our underlying Gaea sample with a mass resolution limit of $10^ solarmass $ and an $H$-band magnitude cut of 25. \u0000 We compare results with and without an estimate of interstellar dust attenuation, which we model using a Calzetti law with a mass-dependent scaling. According to this estimate, the presence of dust may decrease observable percentages by a further 20-30 with respect to the overall population, which presents challenges for detecting intrinsically fainter lines. We predict to observe around 30--70 of Halpha - N ii S ii -, and O iii -emitting galaxies at redshift below 1. At higher redshift, these percentages decrease below 10. Hbeta O ii and O i emission are expected to appear relatively faint, thus limiting observability to at most 5 at the lower end of their detectable redshift range, and below 1 at the higher end. This is the case both for these lines individually and in combination with other lines. \u0000 For galaxies with line emission above the flux threshold in the Euclid Deep Survey, we find that BPT diagrams can effectively distinguish between different galaxy types up to around redshift 1.8, attributed to the bias toward metal-rich systems. Moreover, we show that the relationships of Halpha and O iii +Hbeta to the star-formation rate, as well as the O iii -AGN luminosity relation, exhibit minimal, if any, changes with increasing redshift when compared to local calibrations. Based on the line ratios $ N ii /H N ii O ii $, and $ N ii S ii $, we further propose novel redshift-invariant tracers for the black hole accretion rate-to-star formation rate ratio. Lastly, we find that commonly used metallicity estimators display gradual shifts in normalisations with increasing redshift, while maintaining the overall shape of local calibrations. This is in tentative agreement with recent JWST data.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"36 28","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141340327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ingot-like class of wavefront sensors for laser guide stars","authors":"R. Ragazzoni, E. Portaluri, D. Greggio, M. Dima, C. Arcidiacono, M. Bergomi, S. Di Filippo, T.S. Gomes Machado, K.R. Santhakumari, V. Viotto, F. Battaini, E. Carolo, S. Chinellato, J. Farinato, D. Magrin, L. Marafatto, G. Umbriaco, D. Vassallo","doi":"10.1051/0004-6361/202449697","DOIUrl":"https://doi.org/10.1051/0004-6361/202449697","url":null,"abstract":"Full sky coverage adaptive optics (AO) on extremely large telescopes requires the adoption of several laser guide stars as references. With such large apertures, the apparent elongation of the beacons is absolutely significant. With a few exceptions, wavefront sensors (WFSs) designed for natural guide stars can be adapted and used in suboptimal mode in this context. We analyse and describe the geometrical properties of a class of WFSs that are specifically designed to deal with laser guide stars propagated from a location in the immediate vicinity of the telescope aperture. We describe, in three dimensions, the loci where the light of the laser guide stars would focus in the focal volume located behind the focal plane where astronomical objects are reimaged. We also describe the properties of several types of optomechanical devices that act as perturbers for this new class of pupil plane sensors, through refraction and reflections. We refer to these as ingot WFSs. We provide the recipes both for the most reasonably complex version of these WFSs, with six pupils and, for the simplest one, only three pupils. Both of them are referred to on the basis of the European Extremely Large Telescope (ELT) case.\u0000 We outlined elements that are meant to give a qualitative idea of how the sensitivity of this new class of sensors compares to conventional ones. We present a new class of WFSs, based on an extension to the case of elongated sources at a finite distance of the pyramid WFS. We point out which advantages of the pyramid can be retained and how it may be adopted to optimize the sensing procedure.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"5 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141343281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scattering properties of protoplanetary dust analogs with microwave analogy: Rough compact grains","authors":"Vanesa Tobon Valencia, J. Geffrin, François Ménard, J. Milli, Jean-Baptiste Renard, H. Tortel, A. Litman","doi":"10.1051/0004-6361/202347529","DOIUrl":"https://doi.org/10.1051/0004-6361/202347529","url":null,"abstract":"Scattering simulations of perfect spheres are not sufficient to explain the observations of scattered light coming from protoplanetary and debris disks, specially when dust sizes are of the same order of magnitude as the wavelength used to perform the observations. Moreover, examples of grains collected from the Solar System have proved that the morphology of interstellar dust is irregular. These evidences lead to consider that the dust that participates in these circumstellar disks has morphologies more complex than spheres. We aim to measure and simulate the scattering properties of six rough compact grains to identify how their morphology affect their scattering properties . These grains are intended to be dust analogs of protoplanetary and debris disks with convexity ranging from $75$ to $99$. Grains were 3D printed using stereolithography, controlling their shape and refractive index. These analogs were measured with our microwave scattering experiment (microwave analogy) at wavelengths ranging from $ meter $ to $ meter $, leading to size parameters from $X=1.07$ to $X=7.73$. In parallel, their scattering properties were simulated with our finite element method bf(FEM) which contained the same geometric file as the 3D printed grains. We retrieved five scattering properties of such grains, that is, the phase function, the degree of linear polarization (DLP), and three other Mueller matrix elements $ ij Two types of studies were performed. First, a study on the scattering properties averaged over several orientations of grains at different wavelengths. Second, a study on the same scattering properties where a power law size distribution effect was applied. The very good correspondence between the measured and simulated Mueller matrix elements demonstrated the accuracy of our measurement setup as well as the efficiency of our FEM simulations. For the first study, DLP proved to be a good indicator of the grain morphology, in terms of convexity and shape anisotropy . For the second study, backscattering enhancements of the phase function were related to the grains convexity. The maximum DLP and its negative polarization branches as well as the $ levels were related to the shape anisotropy of our grains.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"56 28","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141344635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Timing and scintillation studies of PSR J1439-5501","authors":"J. Jang, R. Main, V. Venkatraman Krishnan, M. Bailes, A. Cameron, D. Champion, P. Freire, A. Parthasarathy, S. Buchner, M. Kramer","doi":"10.1051/0004-6361/202347505","DOIUrl":"https://doi.org/10.1051/0004-6361/202347505","url":null,"abstract":"PSR J1439$-$5501 is a mildly recycled pulsar in a 2.12-day circular orbit around a heavy white dwarf. A white dwarf cooling model has estimated the companion mass to be between 1--1.3 M$_ odot $ and the inclination angle to be greater than 55degree . Such high mass and inclination are expected to induce a Shapiro delay, namely, a relativistic time delay in the signal propagation caused by the curved space-time induced by the companion. Until now, however, no Shapiro delay has been measured in this system. Our aim is to detect the Shapiro delay and, thus, to independently measure the mass and inclination of PSR J1439$-$5501 by using data from the Parkes and MeerKAT radio telescopes. The Shapiro delay parameters were measured through pulsar timing, which coherently accounts for every rotation of the pulsar. These measurements were then used to estimate the masses of the component stars and the inclination angle of the binary. A scintillation analysis was additionally performed by investigating the secondary spectra, which are the Fourier-transformed observed scintillation patterns. The obtained secondary spectral variations were analyzed in terms of the orbital motion and annual variation to estimate the ascending nodes, distance, and the location of the screen. We obtained a highly significant measurement of the Shapiro delay, which allows estimates of the pulsar mass ($1.57^ $ M$_ odot $), the white dwarf (WD) companion mass ($1.27^ $ M$_ odot $), and inclination angle, ($75(1) or $105(1) These estimates assume that the companion mass cannot exceed the Chandrasekhar mass limit (1.48 $ odot $), along with a lower limit of $1.17 odot $ for NS masses. These results are consistent with previous studies, but the precision of the component masses has been improved significantly. The orbital and spin parameters and the large WD mass make this system very similar to that of PSR J2222$-$0137 and PSR J1528$-$3146, thereby suggesting a common evolutionary mechanism. The scintillation analysis suggests that the longitude of the ascending node is $16(7) or $-20(6) depending on the sense of the inclination angle. The screen distance is 260 pm 100 pc, potentially associated with the edge of the Local Bubble.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"18 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141342748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The low-frequency power spectrum of slow solar wind turbulence","authors":"Mason Dorseth, Jean C. Perez, S. Bourouaine, J. C. Palacios, N. Raouafi","doi":"10.1051/0004-6361/202449869","DOIUrl":"https://doi.org/10.1051/0004-6361/202449869","url":null,"abstract":"An important challenge in the accurate estimation of power spectra of plasma fluctuations in the solar wind at very low frequencies is that it requires extremely long signals, which will necessarily contain a mixture of qualitatively different solar wind streams, such as fast and slow winds, different magnetic polarities, or a mixture of compressible and incompressible fluctuations, along with other transient structures. This mixture of streams with qualitatively different properties unavoidably affects the structure of the power spectra by conflating all these different properties into a single power spectrum. In this work, we present a conditional statistical analysis that allows us to accurately estimate the power spectrum, at arbitrarily low frequencies, for ``pure'' slow solar wind streams, defined as those for which the solar wind speed is below $500 The conditional analysis is based on the estimation of autocorrelation functions (ACF) of arbitrarily long but discontiguous signals, which result from excluding portions of the signal that do not satisfy the required properties. We use numerical simulations of magnetohydrodynamic (MHD) turbulence and magnetic field signals from the spacecraft to test the estimator's convergence to its true ensemble-averaged counterpart. Finally, we use this methodology on a fourteen-year-long data interval to obtain the magnetic power spectrum of slow wind at extremely low frequencies. We show, for the first time, a full $1/f$ range in the slow wind, with a low-frequency spectral break below which the spectrum flattens and exhibits a well-defined peak at the solar rotation frequency.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141341857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing atmospheric escape through metastable He I triplet lines in 15 exoplanets observed with SPIRou","authors":"A. Masson, S. Vinatier, B. B'ezard, M. L'opez-Puertas, M. Lamp'on, F. Debras, A. Carmona, B. Klein, E. Artigau, W. Dethier, S. Pelletier, T. Hood, R. Allart, V. Bourrier, C. Cadieux, B. Charnay, N. B. Cowan, N. Cook, X. Delfosse, J. Donati, P.-G. Gu, G. H'ebrard, E. Martioli, C. Moutou, O. Venot, A. Wyttenbach","doi":"10.1051/0004-6361/202449608","DOIUrl":"https://doi.org/10.1051/0004-6361/202449608","url":null,"abstract":"For several years, the metastable helium triplet line has been successfully used as a tracer to probe atmospheric escape in transiting exoplanets. This absorption in the near-infrared (1083.3,nm) can be observed from the ground using high-resolution spectroscopy, providing new constraints on the mass-loss rate and the temperature characterizing the upper atmosphere of close-in exoplanets. The aim of this work is to search for the He triplet signature in 15 transiting exoplanets ---ranging from super-Earths to ultrahot Jupiters--- observed with SPIRou a high-resolution ($R near-infrared spectropolarimeter at the CFHT, in order to bring new constraints or to improve existing ones regarding atmospheric escape through a homogeneous study. We developed a full data processing and analysis pipeline to correct for the residual telluric and stellar contributions. We then used two different 1D models based on the Parker-wind equations and nonlocal thermodynamic equilibrium (NLTE) radiative transfer to interpret the observational results. We confirm published He triplet detections for HAT-P-11,b, HD,189733,b, and WASP-69,b. We tentatively detect the signature of escaping He in HD,209458,b, GJ,3470,b, and WASP-76,b. We report new constraints on the mass-loss rate and temperature for our three detections and set upper limits for the tentative and nondetections. We notably report improved constraints on the mass-loss rate and temperature of the escaping gas for TOI-1807,b, and report a nondetection for the debated atmospheric escape in GJ,1214,b. We also conducted the first search for the He signature in GJ,486,b since its discovery and report a nondetection of the He triplet. Finally, we studied the impact of important model assumptions on our retrieved parameters, notably the limitations of 1D models and the influence of the H/He ratio on the derived constraints.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"54 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141349656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Synchrotron polarization with a partially random magnetic field: General approach and application to X-ray polarization from supernova remnants","authors":"R. Bandiera, O.O. Petruk","doi":"10.1051/0004-6361/202450103","DOIUrl":"https://doi.org/10.1051/0004-6361/202450103","url":null,"abstract":"Diagnostics based on the polarization properties of the synchrotron emission can provide precious information on both the ordered structure and the random level of the magnetic field. While this issue has already been analyzed in the radio band, the polarization data recently obtained by the mission IXPE have shown the need to extend this analysis to the X-ray band. While our immediate targets are young supernova remnants, the scope of this analysis is wider. Our aim is to extend the analysis to particle energy distributions more complex than a power law, and to investigate a wider range of cases involving a composition of ordered and random magnetic fields. Since an analytical approach is only possible in a limited number of cases, we devised for this purpose an optimized numerical scheme, and we directly used it to investigate particle energy distributions in the form of a power law with an exponential or super-exponential cutoff. We also considered a general combination of an ordered field plus an anisotropic random component. We show that the previously derived analytic formulae, valid for power-law distributions, may also be good approximations of the polarization degree in the more general case with a cutoff, as typically seen in X-rays. We explicitly analyzed the young supernova remnants SN 1006, Tycho, and Cas A. In particular, for SN 1006 we proved the consistency between the radio and X-ray polarization degrees, favoring the case of a predominantly random field with an anisotropic distribution. In addition, for the power-law case we investigated the effect of a compression on ordered and on random magnetic field components, aimed at describing the mid-age radio supernova remnants. This work allows a more efficient exploitation of radio and X-ray measurements of the synchrotron polarization, and is addressed to present observations with IXPE and to future projects.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":"101 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141352531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}