Astronomy & Astrophysics最新文献

{"title":"A TESS view of post-eruption variability in novae V1405 Cas, V1716 Sco, and V1674 Her","authors":"G. J. M. Luna, A. Dobrotka, M. Orio","doi":"10.1051/0004-6361/202557972","DOIUrl":"https://doi.org/10.1051/0004-6361/202557972","url":null,"abstract":"We analyzed <i>TESS<i/> archival data of three novae after recent outbursts, searching for the orbital and white dwarf (WD) rotation period and possible variations in these periods. In V1405 Cas, we detected a period of ∼116.88 seconds, which we identified as due to the WD spin, and measured a rate of increase of 0.00165 ± 0.000006 s d<sup>−1<sup/>, which is one of the fastest spin-down rates ever recorded. The rapid spin-down coupled with an X-ray luminosity several orders of magnitude lower than the available spin-down power, strongly indicates that the system is in a magnetic “propeller” state, which means the rotational energy powers the system’s X-ray luminosity. We measured a previously unknown orbital period of 1.357 ± 0.005 days for V1716 Sco. If the X-ray flux modulation with a period of 77.9 s detected in outburst for this nova is due to the rotation of a strongly magnetized white dwarf, which is the case in other novae with similar modulations of the supersoft X-ray source in outburst, the system is in a parameter space that challenges standard models of cataclysmic variable evolution. For V1674 Her, which has already been classified as an intermediate polar (IP), we confirm the known spin period of 501.328 ± 0.024 s and the orbital period of 0.15293 ± 0.00004 days. These suggest that the spin modulation was also the root cause of the periodicity in X-rays in outburst, and that the WD atmosphere in the supersoft X-ray phase was not thermally homogeneous. Our results highlight the power of high-cadence, continuous observations in revealing extreme and unexpected characteristics of accreting white dwarfs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751725","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":"Ultra-fast simulations of the solar dipole and open flux","authors":"Ismo Tähtinen, Timo Asikainen, Kalevi Mursula","doi":"10.1051/0004-6361/202659586","DOIUrl":"https://doi.org/10.1051/0004-6361/202659586","url":null,"abstract":"<i>Context.<i/> The solar dipole captures important information characterizing the large-scale solar magnetic field. The evolution of the solar magnetic field including the solar dipole can be simulated with a surface flux transport (SFT) model, but these simulations are more extensive than is otherwise necessary to produce the evolution of the dipole alone.<i>Aims.<i/> We present a dipole flux transport (DFT) matrix method that combines the classic SFT model with dipole vector representation of the solar magnetic field, which enables significantly faster simulations of the solar dipole.<i>Methods.<i/> By simulating the evolution of basis vectors of a synoptic map, we were able to construct propagator matrices that produce the time evolution of the solar magnetic field by means of matrix multiplication. The computational speedup was achieved by compressing the propagator matrices to very small fraction (< 10<sup>−4<sup/>) of their original size with a recent vector sum method.<i>Results.<i/> Depending on the time resolution, the DFT performs 100−1000 times faster than a 4-year SFT simulation of a single active region, while producing equivalent results. For multiple source regions, daily propagation matrices are sufficient to produce results that agree within 1% with the SFT simulation of solar cycle 24, while performing 80 times faster. If the evolution of individual active regions is needed, the DFT is equipped to perform 50000 times faster than the SFT model.<i>Conclusions.<i/> Overall, DFT makes solar dipole simulations extremely fast, making it possible to run thousands of simulations in a few minutes with a basic laptop setup. As the magnitude of the dipole vector closely matches the open solar flux (OSF) from the potential field source surface model, the DFT can be used to study the development of OSF in various scenarios in an extremely efficient way.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751734","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":"Hunting for methanol in the water-rich, planet-forming disk around HL Tau","authors":"A. Soave, M. Leemker, S. Facchini, L. Maud, K. L. J. Rygl, L. Testi","doi":"10.1051/0004-6361/202558485","DOIUrl":"https://doi.org/10.1051/0004-6361/202558485","url":null,"abstract":"<i>Context<i/>. Methanol, the simplest complex organic molecule found in space, is considered a key compound for the formation of chemical species of prebiotic interest. Methanol detections in protoplanetary disks remain scarce, even though it is frequently detected in the material surrounding other young stellar objects (YSOs).<i>Aims<i/>. We investigated the presence of methanol in the protoplanetary disk around the HL Tau protostar, motivated by the detection of spatially resolved warm water emission.<i>Methods<i/>. Given the similar volatilities of methanol and water, thermally desorbed gas-phase methanol is expected to emit from the same region of the HL Tau disk where water vapor has been observed. Accordingly, we selected and imaged the most promising ALMA archival observations to search for rotational methanol lines.<i>Results<i/>. We find no methanol emission in the analyzed archival datasets. Assuming optically thin emission and local thermodynamic equilibrium (LTE), we derive stringent upper limits on the methanol column density for different excitation temperatures: <7.2 × 10<sup>14<sup/> cm<sup>−2<sup/> at 100 K and <1.8 × 10<sup>15<sup/> cm<sup>−2<sup/> at 200 K, assuming a circular emitting region with a radius of 17 au (~0.12\"). Furthermore, we obtain a stringent upper limit on the methanol-to-water column density ratio (<0.55 × 10<sup>−3<sup/> at 100 K and <1.4 × 10<sup>−3<sup/> at 200 K), which is, on average, an order of magnitude lower than the values measured for other YSOs and Solar System comets.<i>Conclusions<i/>. We argue that the most likely explanation for the methanol nondetection in HL Tau is the presence of optically thick dust in the central region of the disk, which obscures part of the methanol emission. The upper limit on the methanol-to-water ratio in the HL Tau disk is at least an order of magnitude smaller than most clouds, YSOs, and comets, possibly due to radiative transfer and/or excitation effects, or to a different chemical evolution compared to the other sources.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"69 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751759","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":"Turbulence destroys thermal lobes around Mars-sized planetary embryos","authors":"R. O. Chametla, A. Moranchel-Basurto, F. J. Sánchez-Salcedo","doi":"10.1051/0004-6361/202658842","DOIUrl":"https://doi.org/10.1051/0004-6361/202658842","url":null,"abstract":"<i>Context<i/>. The release of heat by a planetary embryo modifies the local density perturbations, forming thermal lobes in its vicinity, and thereby altering the torque exerted by the disk on the embryo. In laminar disks, these thermal torques can dominate the disk-embryo interaction, rendering the classical Lindblad and corotation torques largely subdominant.<i>Aims<i/>. The aim of this work is to investigate how turbulence driven by the magnetorotational instability affects the thermal lobes that formed around a planetary embryo, and to analyze the resulting torque acting on the embryo.<i>Methods<i/>. We evaluate the thermal torques exerted on a planetary embryo of mass <i>M<i/><sub><i>p<i/><sub/> = 0.33 <i>M<i/><sub>♂<sub/> (where is the mass of Mars) and on a planetary core with mass <i>M<i/><sub><i>p<i/><sub/> = 1 <i>M<i/><sub>⊕<sub/>, with each embedded in a turbulent gaseous protoplanetary disk, by means of highresolution three-dimensional magnetohydrodynamics simulations that include thermal diffusion and an initially toroidal magnetic field. The magnetic field strength is characterized by the plasma <i>ß<i/> plasma parameter with <i>ß<i/> ∈ {50, 1000}. We consider two values for the luminosity of the planetary embryo: <i>L<i/> = 0 (cold thermal lobes) and <i>L<i/> = <i>L<i/><sub><i>c<i/><sub/> (hot thermal lobes), where <i>L<i/><sub><i>c<i/><sub/> represents the critical luminosity. For the 0.33 <i>L<i/><sub>♂<sub/> embryo, <i>L<i/><sub><i>c<i/><sub/> = 7.8 × 10<sup>25<sup/>ergs s<sup>−1<sup/> when it orbits a Sun-like star at a distance <i>r<i/><sub><i>p<i/><sub/> = 5.2 au.<i>Results<i/>. We find that, even in the presence of a weak magnetic field and irrespective of the luminosity, for both planetary masses, the development of turbulence in the disk (which takes between 1.5 to 3 orbital periods) completely disrupts the thermal lobes. As a result, the torque acting on both the planetary embryo and the Earth-mass core displays a strongly oscillatory behavior. This suggests that planets with masses in the range 0.03 <i>M<i/><sub>⊕<sub/> ≲ <i>M<i/><sub><i>p<i/><sub/> ≲ 1 <i>M<i/><sub>⊕<sub/> experience stochastic migration, as expected in turbulent disks.<i>Conclusions<i/>. Thermal torques become inefficient in turbulent regions of protoplanetary disks, such as outside the dead zone, in both the inner and outer disk regions where the magnetorotational instability operates.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"98 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751724","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":"No country for old stars","authors":"V. D’Orazi, C. Mateu, G. Iorio, A. Bobrick, Z. Prudil, R. Salinas, A. Bragaglia, L. Mashonkina, R. G. Gratton, I. Ilyn, N. Alvarez Baena, V. F. Braga, A. Nunnari, V. M. Kalari, F. Cusano, S. Tosi","doi":"10.1051/0004-6361/202660253","DOIUrl":"https://doi.org/10.1051/0004-6361/202660253","url":null,"abstract":"<i>Context.<i/> RR Lyrae (RRL) stars are widely considered tracers of ancient (> 10 Gyr) metal-poor stellar populations. However, recent kinematic and photometric studies suggest the existence of a metal-rich RRL subpopulation associated with the thin disk and intermediate ages (∼2–5 Gyr), therefore challenging canonical evolutionary models.<i>Aims.<i/> We aim to provide the first spectroscopic confirmation of a member of this elusive population. Specifically, we target a metal-rich RRL candidate recently identified photometrically as a member of the intermediate-age open cluster Trumpler 5 (∼2.5 Gyr).<i>Methods.<i/> We obtained high-resolution spectroscopy using PEPSI at the LBT and GHOST at Gemini South telescope. We measured radial velocities (RVs) from multiple epochs to constrain cluster membership and derived detailed chemical abundances (Mg, Ca, Sc, Ti, Mn, Fe, Cu, Zn, Y, and Ba) to compare the RRL’s composition with that of red clump stars in the cluster.<i>Results.<i/> The RRL’s systemic velocity ( km s<sup>−1<sup/>) is in excellent agreement with the cluster mean (<i>V<i/> = 50.76 ± 0.49 km s<sup>−1<sup/>). Combining RVs, proper motions, and parallax, the probability of the star being a background interloper is negligible (∼0.002%, better than 4<i>σ<i/>). We derived a metallicity of [Fe/H] = −0.40 ± 0.05, which matches the cluster value. While most abundance ratios (Mg, Ti, Mn, Cu, and Zn) align with cluster members, the RRL exhibits significant depletion in Ca, Sc, Y, and Ba. Notably, [Sc/Fe] is underabundant by ∼0.6 dex relative to the cluster stars, following trends seen in field metal-rich RRLs.<i>Conclusions.<i/> We provide strong constraints on the membership status between an RRL variable and an intermediate-age open cluster. Cluster membership enables accurate measurement of RRL age and chemical anomalies relative to its host, particularly in Sc and neutron-capture elements. These anomalies further reinforce a nonstandard formation channel for this RRL, possibly indicating binary interactions and mass transfer.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751719","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":"Two-stage formation of the Moon from accreting fragmentation and resonance captures","authors":"Jérémy Couturier, Alice C. Quillen, Miki Nakajima","doi":"10.1051/0004-6361/202558833","DOIUrl":"https://doi.org/10.1051/0004-6361/202558833","url":null,"abstract":"<i>Context<i/>. In the canonical Moon-forming model, a Mars-sized object collided with Earth to produce a disk of debris from which the Moon is believed to have accreted.<i>Aims<i/>. In order to build on past works, we simulated disks containing up to 10<sup>5<sup/> debris (called moonlets) and we took fragmentation of the debris into account in the case of violent collisions.<i>Methods<i/>. We used the new software Ncorpi<i>O<i/>N, and in particular its module FalcON, for fast gravity computation using multipole expansions. The built-in fragmentation model of Ncorpi<i>O<i/>N was used to resolve collisions. The initial conditions of our <i>N<i/>-body simulations were output of smoothed particle hydrodynamic (SPH) simulations.<i>Results<i/>. Unlike previous works, we find that the Moon probably did not form in one step but rather in two stages. The first stage lasts a few months to a few tens of years and is dominated by collisions and gravitational scattering. It often leads to several large submoons. In the second stage, of length 10<sup>3<sup/> to 10<sup>5<sup/> years, tidal forces and subsequent migration allow these submoons to be captured in mean motion resonances (MMR), cleaning the system and completing the formation of the Moon through ejections and collisions.<i>Conclusions<i/>. A significant mass is lost during the accretion process, and we favor protolunar disks with initially at least 2<i>M<sub>☾<sub/><i/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"27 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751726","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":"Similar ratios of the rise timescale to the decline timescale of optical light curves in common tidal disruption events","authors":"XueGuang Zhang","doi":"10.1051/0004-6361/202558455","DOIUrl":"https://doi.org/10.1051/0004-6361/202558455","url":null,"abstract":"The entirely similar physical process in tidal disruption events (TDEs) basically indicates that just one parameter might distinguish the variability properties of TDEs from that of other transient events that have different physical processes. We report such a parameter, the timescale ratio <i>R<i/><sub>2/1, <i>rd<i/><sub/> of the rise timescale <i>t<i/><sub>1/2, <i>r<i/><sub/> (from half maximum to maximum) to the decline timescale <i>t<i/><sub>1/2, <i>d<i/><sub/> (from maximum to half maximum). We define this based on 34 optical TDEs with reported <i>t<i/><sub>1/2, <i>r<i/><sub/> and <i>t<i/><sub>1/2, <i>d<i/><sub/>. Among the 34 optical TDEs, AT2020wey is an outlier with <i>R<i/><sub>2/1, <i>rd<i/><sub/> ∼ 2.7, which is 4.5 times higher than the mean value 0.6 of the other optical TDEs. However, when the similar but more flexible model functions are considered, the redetermined <i>R<i/><sub>2/1, <i>rd<i/><sub/> is ∼0.9 in AT2020wey. This is very similar to the values of the other optical TDEs. Therefore, the parameter <i>R<i/><sub>1/2, <i>rd<i/><sub/> ∼ 0.6 might be a potential classification parameter for optical TDEs. Furthermore, <i>R<i/><sub>1/2, <i>rd<i/><sub/> were determined in the unique optical transients AT2019avd, PS1-10adi, SDSS J0946+3512, and J2334+1457. The second flare with <i>R<i/><sub>1/2, <i>rd<i/><sub/> ∼ 11 in AT2019avd is expected to be very different from that of other optical TDEs, but PS1-10adi, SDSS J0946+3512, J2334+1457, and the first flare in AT2019avd are expected to be similar to the other optical TDEs. In the near future, the properties of <i>R<i/><sub>1/2, <i>rd<i/><sub/> determined on a large sample of optical transients might provide further clues to support whether <i>R<i/><sub>1/2, <i>rd<i/><sub/> might be a better classification parameter to distinguish TDEs from other transient events.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751736","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":"Asteroid modelling by starlight diffraction: The shape of Dimorphos, the satellite of (65803) Didymos","authors":"P. Tanga, K. Tsiganis, D. Souami, R. Anderson, E. Barbotin, A. Cazaux, F. Colas, J. Hanuš, F. Marchis, J-L. Dauvergne, G. Langin, A. Leroy, B. Lott, A. Manna, L. Rousselot, A. Siakas, S. Sposetti, Ch. Vigna, F. Weber, A. Wünche","doi":"10.1051/0004-6361/202659734","DOIUrl":"https://doi.org/10.1051/0004-6361/202659734","url":null,"abstract":"<i>Context.<i/> The DART spacecraft impacted Dimorphos, the satellite of (65803) Didymos, in September 2022. Evidence of crater formation and possible global reshaping has been obtained indirectly from spacecraft and ground-based data.<i>Aims.<i/> Since the impact, several stellar occultations by Didymos have been observed, but only one in particular, on January 21, 2023, can provide useful constraints on the size and shape of Dimorphos.<i>Methods.<i/> We modelled the diffraction signatures recorded on multiple occultation chords to constrain the projected shape and size of Dimorphos, assuming an ellipsoidal model. This is the first time diffraction observed simultaneously on several chords of a single event has been used for such a purpose.<i>Results.<i/> The projected shape at the epoch of the event is well constrained and consistent with recent post-DART determinations. When extended to a full three-dimensional ellipsoidal solution, the result remains compatible with previous studies, suggesting an equatorially elongated post-impact shape.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751721","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":"Discovery of planetary-mass binaries in the Lower Centaurus-Crux association","authors":"Claudio Cáceres, Dante Minniti, Andrea Mejías, Matías Gómez, Javier Alonso-García, Valentin D. Ivanov, Joyce B. Pullen, Roberto K. Saito, Leigh C. Smith, Enrique Solano, Juan Carlos Beamín, Daniela Rojas-Bozza, Paolo Soto, Rodrigo Zelada","doi":"10.1051/0004-6361/202347673","DOIUrl":"https://doi.org/10.1051/0004-6361/202347673","url":null,"abstract":"<i>Context<i/>. The recent discovery of free-floating planets (FFPs) in nearby young stellar associations suggests that these objects might be common in the Galaxy. Our search for FFPs in the young Lower Centaurus-Crux (LCC) association using the VISTA Variables in the Vía Láctea VVV and VVVX surveys revealed several candidates with distances <i>d<i/> < 200 pc.<i>Aims<i/>. The main goal of the paper is to identify binary FFPs among this sample. The presence of such binaries is useful to contrast two different main formation scenarios: the formation in the circumstellar disk of the parent star with subsequent ejection by dynamical interactions and the in situ formation by gravitational collapse of a protostellar cloud.<i>Methods<i/>. We used the <i>Gaia<i/>, VVV, VVVX, and DECaPS databases to identify pairs of low-mass objects in the LCC association sharing common proper motions. We examined the optical and near-IR color-magnitude and color-color diagrams, and visually confirmed the detections in the available optical and near-IR images.<i>Results<i/>. We find 17 young low-mass binaries in the LCC association, with distances starting from 68 pc and projected separations ranging from 88 to 6742 au. A couple of candidates have additional faint companions that need confirmation to secure them as triple systems. Adopting an age of 17 Myr for the LCC association, we find that 14 of the components are faint enough to have planetary masses.<i>Conclusions<i/>. Our results indicate that binaries represent ≳2% of the population of FFPs in the LCC association, and this suggests that their preferred formation mechanism is the gravitational collapse independent of a star. Also, many of the recently discovered FFPs in LCC may be unresolved giant binary planets. The wide range of colors and flux reversals observed suggests that the existence of clouds in their atmospheres is important and points to continuity with the BD populations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"27 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751735","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":"AI application to artificial satellite identification in CHEOPS data","authors":"Pablo García-Martín, Luís Gonçalves, Stephan Hellmich, Nicolas Billot, Bruno Merín","doi":"10.1051/0004-6361/202558532","DOIUrl":"https://doi.org/10.1051/0004-6361/202558532","url":null,"abstract":"<i>Context<i/>. The rapid proliferation of artificial satellites poses a growing challenge to astronomical observations, calling for robust methods to flag and mitigate their impact on scientific data quality. Modern astronomical surveys, including space-based missions such as CHEOPS, generate vast data volumes, where the manual identification of these contaminants is unfeasible. Artificial intelligence (AI) has emerged as an essential tool for efficiently processing these large datasets, enabling the automated flagging of transient features to preserve the scientific value of the data.<i>Aims<i/>. We developed and validated a computationally efficient AI algorithm, based on the MobileNetV2 architecture, to detect satellite trails in CHEOPS images. We benchmarked this novel method against traditional linear feature detection algorithms to assess trade-offs in terms of sensitivity and speed.<i>Methods<i/>. We trained a binary classifier using an iteratively enhanced dataset, incorporating “hard-negative” examples (e.g., cosmic rays, stray light, Earth limb proximity) to minimize the false-positive rate. The final model was applied to the entire CHEOPS archive of 1.8 million images (up to June 2025). The detections were cross-matched with the Space-Track database to identify objects, enabling a detailed analysis of their physical parameters and magnitude evolution over time.<i>Results<i/>. The AI model achieved 99.2% accuracy on the test set and identified 12 223 satellite trails in the archive (0.68% of all images), more than double the yield of non-AI methods, demonstrating superior sensitivity to faint trails. The post-processing identification matched these trails to 5565 distinct objects. While our photometric analysis from 2020 to 2025 shows a constant average standard magnitude (13.4 ± 1.7) for the aggregate detection set, an analysis against launch dates reveals a trend of newer objects appearing brighter.<i>Conclusions<i/>. AI-based methods provide a powerful and sensitive tool for detecting satellite trails in space-based observatories. However, they do require careful training to generalize against complex image artifacts.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"41 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735895","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}