Astronomy & Astrophysics最新文献

{"title":"Near-infrared periodicity in the SPICY catalog. True young stellar objects versus contaminants","authors":"C. Ordenes-Huanca,A. Bayo,M. Zoccali,V. Guzmán,A. Rojas-Arriagada","doi":"10.1051/0004-6361/202660194","DOIUrl":"https://doi.org/10.1051/0004-6361/202660194","url":null,"abstract":"Infrared (IR) large-sky surveys allow us to study how localized star formation is, enabling searches for young stellar objects (YSOs) not only at the centers of known stellar nurseries but also across the Galactic plane. However, these spatially unbiased searches suffer from contamination, most notably from dusty asymptotic giant branch stars characterized by long-period variability. Using time-series analysis, and taking advantage of the different variability timescales of YSOs against long-period variables (LPVs), we assess the level of contamination of one of the most spatially unbiased YSO catalogs ( /IRAC Candidate YSO, SPICY). Distinguishing between these two groups lets us draw more robust conclusions about the frequency of isolated YSOs in our Galaxy and their implications. Spitzer We cross-matched the SPICY and VIRAC2 catalogs (VVV/VVVX Survey), built near-IR light curves for common sources, and computed their periods and amplitudes. Contaminants were identified as sources with periodic flux variations with periods of P≥ 80,d and amplitudes of Δ ̊m s mag . From 58,737 common sources, we identify 742 SPICY objects as LPV contaminants based on their long-period variability, and identify 307 high-confidence periodic YSO candidates exhibiting short-period flux changes consistent with cool spots. Near- and mid-IR amplitudes are correlated only among LPVs, suggesting a common pulsation origin. In addition, the spatial distribution of the identified populations further supports our classification, with LPVs preferentially associated with the bulge and YSOs at the lowest galactic latitudes.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the ultrahot Neptune LTT 9779 b with CRIRES+. Non-detection of helium transmission spectra and detection of H2O on the dayside","authors":"S. Liu,F. Yan,L. Nortmann,B. Guo,D. Cont,F. Lesjak,D. Shulyak,A. Reiners,N. Piskunov,A. P. Hatzes,U. Seemann,A. Lavail,A. D. Rains,H. L. Ruh,L. Boldt-Christmas,M. Rengel,O. Kochukhov,T. Marquart","doi":"10.1051/0004-6361/202662567","DOIUrl":"https://doi.org/10.1051/0004-6361/202662567","url":null,"abstract":"Ultrahot Neptunes reside in the most extreme irradiation regime of the hot Neptune desert and remain challenging targets for atmospheric characterization because of their intrinsically low planet-to-star flux ratios. We present high-resolution transit and dayside thermal emission spectroscopy of the ultrahot Neptune LTT 9779 b obtained with CRIRES+$, aimed at probing both atmospheric escape and dayside molecular emission. No significant absorption is detected in the metastable łambda 1083,nm triplet during transit, yielding a 3σ upper limit of 0.45% on the excess helium absorption depth and supporting previous non-detections that suggest weak ongoing atmospheric escape. For the dayside emission spectra in the K band, our cross-correlation analysis reveals an He i absorption signal and a tentative feature, with the combined signal reaching a detection significance of 4.8σ. Both the CRIRES^+ and previous JWST data favor a non-inverted temperature structure, providing no evidence of a thermal inversion on the planetary dayside. We further perform a joint atmospheric retrieval combining the CRIRES^+ high-resolution spectra with JWST/NIRISS SOSS secondary-eclipse observations. The joint retrieval yields a low abundance, while the abundance remains weakly constrained. The inferred planetary equatorial rotational velocity, v_ ̊m eq =4.9^ +4.4 _ -3.0 -1 , is consistent within 1σ with the synchronous rotation velocity expected for a tidally locked planet (sim2.8 ). However, the large uncertainties prevent us from placing strong constraints on the planet's rotation state. Future phase-resolved CRIRES$^+ observations with broader orbital-phase coverage and higher signal-to-noise ratios would improve the abundance constraints and probe the atmospheric dynamics of this rare ultrahot Neptune. -1","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"78 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early emergence of super-soft-source emission in RS,Oph","authors":"J.-U. Ness,J.P. Osborne,M. Orio,S. Starrfield,S. Mitrani,E. Behar","doi":"10.1051/0004-6361/202661136","DOIUrl":"https://doi.org/10.1051/0004-6361/202661136","url":null,"abstract":"Early in the 2006 outburst of the recurrent nova RS,Oph, detected the onset of the super-soft-source (SSS) phase. An observation obtained on day 26.1 revealed a highly unusual soft X-ray spectrum containing transient narrow emission features that could not be identified with known transitions and are atypical of SSS spectra. Here, we analyse a new observation obtained at a comparable stage of the 2021 outburst. By presenting a complete census of temporal and spectral properties, we aim to demonstrate a high degree of complexity, deriving requirements for future model approaches. To minimise model-dependent bias, we used models only for demonstration purposes and based our interpretation primarily on observational evidence. We used the 2006d26.1 EPIC/pn spectrum to derive a minimal model for the onset of SSS emission and compare it with the simultaneous RGS spectrum. We investigated the detailed properties of the 2021d37.1 RGS spectrum through comparisons with spectra from other epochs of the 2006 and 2021 RS,Oph outbursts, spectra extracted from four variability intervals within the observation, and spectra of other novae with similar characteristics. These comparisons were used to identify plausible emission mechanisms and guide spectral interpretation. We also searched for 35 s periodic signals in the 2021d37.1 RGS and simultaneous NICER data, motivated by their detection during the 2006d26.1 observation. A blackbody model reproduces the low-resolution 2006d26.1 EPIC/pn spectrum but fails to describe the simultaneous RGS data. The 2021d37.1 RGS spectrum closely resembles that from 2006d26.1 and consists of a slowly fading shock component and a highly variable soft component with several unidentified features. While the shock emission evolves on timescales of days, the soft component varies on hourly timescales and dominates the observed variability, with individual features showing distinct behaviour. The soft emission resembles that of the novae V1716,Sco and V1494,Aql -- the latter of which has recently been interpreted with a charge--exchange model -- but not that of the persistent SSS Cal,87. No significant 35 s periodicity is detected. Our results demonstrate that low spectral-resolution observations can fail to reveal the complex line-dominated emission seen by higher resolution instruments. The rapidly variable soft component in RS,Oph, together with radiative recombination continua features, x emission, and the previously detected 35 s period, suggests that a hidden photoionising source is present. At the same time, the observed spectral complexity and variability indicate that quantitatively reproducing these spectra is likely to require modelling that accounts for geometry, density structure, dynamics, absorption, clumpiness, and other effects. We therefore focus on empirical comparisons and conclude that the enigmatic spectra observed shortly before the emergence of a clear SSS spectrum form an intermediate class between SSS emission","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SPHERE/ZIMPOL observations of the symbiotic system R Aquarii. II. Dynamics of the dust in the Mira wind and the Hα gas in the jet","authors":"H.M. Schmid,E. Lagadec,J. Milli,C. Tschudi,J. Ma,N. Engler,J.L. Beuzit,A. Boccaletti,G. Chauvin,R. Claudi,S. Desidera,K. Dohlen,M. Feldt,R. Gratton,Th. Henning,M. Kasper,M. Langlois,F. Ménard,D. Mouillet,A. Vigan","doi":"10.1051/0004-6361/202661903","DOIUrl":"https://doi.org/10.1051/0004-6361/202661903","url":null,"abstract":"R Aqr is a resolved symbiotic Mira binary and a prototype target for the study of complex hydrodynamic processes including dust-driven mass loss, mass transfer, accretion, and jet outflows and the formation of strongly asymmetric circumstellar structures. With the aim of gaining a better understanding of the complex hydrodynamics of R Aqr, we conducted an investigation based on new high-resolution imaging of the Hα emission from the ionized gas and of the polarization from scattering dust. We analyzed SPHERE/ZIMPOL Hα and polarization maps with a resolution of ≈ 25 mas (5 AU) for the innermost region -- rłapprox 2'' (łapprox 400 AU) -- of the R Aqr system. Data for four epochs were taken covering 6.7 years, including the dust eclipse phase around 2021, providing the angular motion and structural changes for the Hα and dust clouds, which are measured and described in detail. The results are compared with literature data and put into context with respect to models for AGB star binaries. The central Hα emission traces the orbital motion of the hot component. The circumstellar polarization from scattering dust shows interaction effects near the binary (łapprox 60 AU), including a flattened distribution aligned with the orbital plane, corotating dust, and a reduction of the scattering signal during the dust eclipse phase. The polarization shows for gapprox 60 AU a steady outflow with about a dozen dust clouds, a few of which have a comet-like core and tail features. The dust velocity is about 20 km,s ^ -1 , and this is faster than for the CO gas measured with ALMA. Several prominent Hα clouds near the binary (łapprox 200 AU) also show scattering polarization because they are just partly ionized dust clouds from the Mira wind. We also found small faster-moving transient Hα clouds, pointing to outflow instabilities such as those in clumpy winds of hot stars. The observed temporal changes of the Hα emission, in particular the overall angular shift during the dust eclipse event, can be explained by strong illumination changes from the hot component. At a larger separation (gapprox 500 AU), the Hα clouds move faster ($>100 km,s ^ -1 $), in agreement with previous studies. This acceleration in the outflow is probably a result of gas heating by photoionization and shocks in the clumpy outflow, and the produced overpressure gives rise to the two well-known jet-like features expanding in polar directions. Monitoring of the inner regions of R Aqr shows the motion and evolution of different structures in the dusty Mira wind and the ionized outflow of the hot component, and these features provide unambiguous information about the hydrodynamics of the circumstellar material. Such observations are very useful to clarify the complex phenomena taking place in interacting binaries with asymptotic giant branch stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"16 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing the recovery of the NGC 6505 Einstein ring in deep OSN 1.5 m imaging","authors":"Homer Dávila Gutiérrez,Julio Carlos Bertua Marasca,Alejandro Heredia Teva,Irene Naranjo Arroyo,Fernando Núñez Martínez,Miguel Ruiz Travesí,Eugenio Grande Sáez","doi":"10.1051/0004-6361/202661980","DOIUrl":"https://doi.org/10.1051/0004-6361/202661980","url":null,"abstract":"The discovery of a complete Einstein ring around the nearby elliptical galaxy NGC 6505 (z = 0.042) by the mission provides a rare, precisely characterised low-redshift strong lens. Its Einstein radius, theta_ Euclid ̊m E = 2.500 ≈ regime of these observations and not as a general detectability law. is comparable to the angular resolution attainable from typical mid-aperture ground-based facilities, which makes the recoverability of the ring from the ground an open practical question. We tested whether the ring can be recovered in deep Cousins-R imaging of NGC 6505 obtained with the 1.5 m T150 telescope at the Sierra Nevada Observatory (OSN), totalling 8.03 h of integration at a final effective seeing with a full width at half maximum (FWHM) of 2.47 / = 1.01). After subtracting a non-parametric isophotal model of the galaxy, we searched the residual for coherent arc- or ring-like structure and found none at the -measured Einstein radius, with a maximum value of 1.5σ for the adopted radial recovery metric. An injection--recovery experiment using a simplified -informed synthetic ring, processed through the same isophotal-modelling and residual-analysis pipeline, yielded a maximum recovered significance between 0.42σ and 1.86σ across three point spread function descriptions, which is below our operational 3σ recovery threshold in every case. We interpret this as a dataset-specific non-recovery driven by the theta_ (theta_ ̊m E FWHM Euclid Euclid ̊m E FWHM","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Collisional excitation of E- and Z-ethanimine to model cold molecular clouds","authors":"Francesca Tonolo,Vivek Vijay,Ernesto Quintas-Sánchez,Adrian Batista Planas,Carolin Joy,Richard Dawes,François Lique,Dmitri Babikov","doi":"10.1051/0004-6361/202662226","DOIUrl":"https://doi.org/10.1051/0004-6361/202662226","url":null,"abstract":"Ethanimine is a prebiotically relevant complex organic molecule that has been proposed as a key precursor of amino acids in the interstellar medium. To date, both its E and Z isomers have only been detected toward the Sgr B2(N) molecular cloud. The pronounced non-local thermodynamic equilibrium (non-LTE) effects predicted for this molecule require accurate collisional rate coefficients for reliable astrophysical modeling and future astronomical searches. We aim to provide the first collisional datasets for both ethanimine isomers with the main cold molecular clouds collision partners, He and -H_2, in order to support non-LTE radiative-transfer modeling. para State-to-state rate coefficients for collisions with He were computed by integration over mixed close-coupling (CC) and coupled-states (CS) scattering cross sections at different energy ranges. In addition, comparisons with mixed quantum-classical theory (MQCT) calculations performed for both He and -H_2 collisions enabled the derivation of transition-specific scaling factors, which were applied to predict collisional rate coefficients for -H_2. para para We present the first state-to-state collisional datasets for both E- and Z-ethanimine in collision with He and para -1 and over the 5--100,K temperature range. The datasets reported here provide the first collisional information suitable for non-LTE modeling of ethanimine in cold interstellar environments. They represent a key step toward more reliable abundance determinations and may facilitate future astronomical detections of both ethanimine isomers beyond Sgr B2(N).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The universal thickness of mid-infrared bubbles","authors":"Michael M. Schulreich,A. Beate C. Patzer","doi":"10.1051/0004-6361/202662873","DOIUrl":"https://doi.org/10.1051/0004-6361/202662873","url":null,"abstract":"Several hundred ring-like structures seen at 8̆m in the GLIMPSE surveys share a strikingly uniform morphology: the thickness dR of the emitting shell is a nearly constant fraction of its outer radius R, dR/R Spitzer across a factor of 40 in size and across all exciting stellar spectral types. No explanation for this invariance has been given so far. We investigated which physical quantity sets the observed shell thickness and whether the near-constancy of dR/R is a genuine physical fingerprint or a measurement artifact. We derived purely analytic constraints on the location, temperature, and heating of the emitting grains and compared the resulting predictions for the scaling of dR/R with bubble radius against the combined GLIMPSE I and II bubble catalogs (591 objects, 91 with kinematic distances). Grains in radiative equilibrium at the observed radii only reach 20--35,K and fall short of the required 8̆m emissivity by more than 20 orders of magnitude; the emission must be carried by stochastically heated polycyclic aromatic hydrocarbons and very small grains, and it therefore originates in the photon-dominated region, where the ring width is the far-ultraviolet penetration depth. This gives dR/R= / , independent of radius. A swept-up shell instead predicts PDR cloud with Rs the initial Strömgren radius. We found a pronounced angular-resolution systematic that inflates dR/R for the smallest bubbles; once this is accounted for, dR/R=0.217. Its residual dependence on physical radius is 0.03 consistent with zero; a fixed ambient density is excluded at 20σ and the swept-up shell at 9--28σ. The implied ambient columns are Ncl ̧mq, with a scatter of only 0.112,dex. 21 The near-universal appearance of mid-infrared bubbles follows from the ratio of two nearly invariant column densities: the dust-opacity-fixed far-ultraviolet shielding column, and the Larson-like column of the parent molecular cloud. It requires no reference to stellar wind properties.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Before fragmentation: From uniform clouds to stellar clusters","authors":"A. Giannetti,T.G.S. Pillai,J. Kauffmann,A. Palau,E. Vázquez-Semadeni,K. Morii,P. Sanhueza","doi":"10.1051/0004-6361/202660386","DOIUrl":"https://doi.org/10.1051/0004-6361/202660386","url":null,"abstract":"Our systematic study of the early stages of fragmentation in massive clumps has revealed a striking anomaly: sim15% of the Cold Cores with ALMA (CoCoA) survey sample exhibit no fragmentation at all. These sources could represent the initial conditions before core formation. We set out to investigate whether these unfragmented clumps are indeed at the onset of core and cluster formation and whether gravity or turbulence dominates their early fragmentation. To understand the nature of these extreme sources, we studied the transition from uniform gas to active cluster formation and compared contrasting predictions of turbulence- and gravity-dominated models of clump fragmentation. We used ALMA observations of three massive clumps spanning this phase (from two minimally fragmented clumps to one significantly fragmented source). Our analysis includes direct gas-phase volume density estimates from CH_3OH$(2_K - 1_K)$ line ratios (independent of dust properties, temperature, and geometry) and unfiltered kinematics of the dense gas (CH_3OH and mathrm N_2H^+ J=1-0) and a comparison between the mass build-up and chemical timescales derived from methanol abundances. The fragmented source exhibits higher average volume densities and a core-to-envelope density contrast five to six times larger than the minimally fragmented sources. All sources display parsec-scale velocity differences comparable to their linewidths, and both the velocity differences and the linewidths are similar to the gravitational velocity. This suggests that the linewidth is dominated by the large-scale systematic motions and that the latter are driven by gravity. We also estimated high CH_3OH abundances (∼10 -9 ) across the clumps. These abundances and the inferred mass build-up timescales align with astrochemical models where complex molecules form at intermediate densities before the appearance of cores. All independent physical and chemical diagnostics in our analysis are consistent with a scenario where the minimally fragmented clumps represent an early evolutionary phase that potentially marks the onset of core fragmentation driven by gravitational collapse. If turbulence were the primary driver of fragmentation, sources with comparable Mach numbers (mathcal M ≈ 6-8 in our sample) should exhibit similar structural properties. Instead, we observed significant variations in density contrast and fragmentation. These findings challenge purely turbulence-supported models and lend support to hierarchical gravity-driven models of clump fragmentation, where large-scale ordered motions account for a significant fraction of the observed linewidths and drive the evolution of the clump towards increasingly dense and fragmented states.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"37 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cosmic web Lyα emission in a sample of overdense regions","authors":"Davide Tornotti,Michele Fumagalli,Matteo Fossati,Roland Bacon,Fabrizio Arrigoni Battaia,Rajeshwari Dutta,Michele Fulghieri,Céline Péroux,Marc Rafelski,Mitchell Revalski","doi":"10.1051/0004-6361/202661083","DOIUrl":"https://doi.org/10.1051/0004-6361/202661083","url":null,"abstract":"We present a complete and homogeneous analysis of the łya emission properties of the cosmic web at 3 łesssim z łesssim 5 as a function of the overdensity of Lyα emitters (LAEs) in the MUSE Ultra Deep Field (MUDF) and the MUSE Extremely Deep Field (MXDF). We identified 41 overdensities, probing environments that are δ ≈ 2-10 times denser than the field. We searched for extended emission down to surface brightness (SB) levels of 3-5 10^ -20 revealing filamentary structures beyond the scale of the circumgalactic medium, confirming that LAEs act as signposts of the cosmic web. A trend with overdensity emerges: non-detections are mainly at δ < 2, a ≈ 1 dex scatter in SB appears for 2 łesssim δ łesssim 3.5, and detections reach a maximum intrinsic SB of ≈ 2 10^ -19 for δ ≳ 3.5. Emitting regions occupy a fraction of projected area f_ s ≈ 0.20-0.25 inside filaments, yielding a cosmological incidence for łya emission in the cosmic web ell(̊m Lyα) of ≈ 1.22, which is similar to the one of partially neutral Lyman limit systems. This analysis indicates that the emitting gas is partially ionized at moderate densities (n_H ≈ 10^ -3 - 10^ -1 cm ^ -3 ), likely tracing the denser spines of intergalactic filaments and embedded substructures. Finally, we forecast how oriented stacking in larger samples of overdensities from shallower observations could yield an expanded view of the cosmic web before the next-generation wide-field spectroscopic instruments become operational.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detecting transiting exoplanets in simulated PLATO data. A comparison of light curve filter and transit search algorithms","authors":"Geert Jan Talens,Leigh C. Smith,Luca Malavolta,Lionel Garcia,Simon Hodgkin,Suzanne Aigrain","doi":"10.1051/0004-6361/202660423","DOIUrl":"https://doi.org/10.1051/0004-6361/202660423","url":null,"abstract":"Our goal is to test and compare transit search methodologies, and provide recommendations as to the best practices to be implemented by the upcoming ESA PLATO mission, in order to achieve its goal of detecting Earth-like planets in the habitable zones of Sun-like stars. We generated simulated two-year PLATO light curves with injected planets with sizes 0.5--2.0 R_⊕, and compared the performance of the ̧etra , ̆mbra , and νance transit search methods. ̧etra and ̆mbra require pre-filtered light curves and we tested four filters: the biweight, Huber spline, LOcally WEighted Scatterplot Smoothing (LOWESS), and the LOWESS-based young stars detrending (YSD) filters. νance uses a Gaussian process to model the stellar variability at all proposed transit parameters. νance achieves the best performance, recovering 61.2% of signals using a simple harmonic oscillator Gaussian process kernel, and it performs especially well for both hot and fast-rotating stars. However, when multiple Huber spline filter windows are considered, both ̧etra and ̆mbra can match νance 's performance. Using four windows ̧etra recovers 61.3% of signals, and using just two windows ̆mbra recovers 61.7% of signals. Recovery rates exceeding νance are possible by using more windows. The computational cost of running νance is so high that running ̧etra or ̆mbra on multiple windows is preferred. The PLATO pipeline should use the Huber spline with a range of window sizes as its primary light curve filter. ̧etra should be updated to use the warped least-squares templates implemented in ̆mbra . The use of νance should be considered for hot, rapidly rotating stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"7 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149089768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}