Astronomy & Astrophysics最新文献

{"title":"The 𝒯ℛ𝒪𝒴 project","authors":"O. Balsalobre-Ruza, J. Lillo-Box, D. Barrado, A. C. M. Correia, J. P. Faria, P. Figueira, A. Leleu, P. Robutel, N. Santos, E. Herrero-Cisneros","doi":"10.1051/0004-6361/202450717","DOIUrl":"https://doi.org/10.1051/0004-6361/202450717","url":null,"abstract":"<i>Context.<i/> Co-orbital objects, also known as trojans, are frequently found in simulations of planetary system formation. In these configurations, a planet shares its orbit with other massive bodies. It is still unclear why there have not been any co-orbitals discovered thus far in exoplanetary systems (exotrojans) or even pairs of planets found in such a 1:1 mean motion resonance. Reconciling observations and theory is an open subject in the field.<i>Aims.<i/> The main objective of the 𝒯ℛ𝒪𝒴 project is to conduct an exhaustive search for exotrojans using diverse observational techniques. In this work, we analyze the radial velocity time series informed by transits, focusing the search around low-mass stars.<i>Methods.<i/> We employed the <i>α<i/>-test method on confirmed planets searching for shifts between spectral and photometric mid-transit times. This technique is sensitive to mass imbalances within the planetary orbit, allowing us to identify non-negligible co-orbital masses.<i>Results.<i/> Among the 95 transiting planets examined, we find one robust exotrojan candidate with a significant 3-σ detection. Additionally, 25 exoplanets show compatibility with the presence of exotrojan companions at a 1-<i>σ<i/> level, requiring further observations to better constrain their presence. For two of those weak candidates, we find dimmings in their light curves within the predicted Lagrangian region. We established upper limits on the co-orbital masses for either the candidates and null detections.<i>Conclusions.<i/> Our analysis reveals that current high-resolution spectrographs effectively rule out co-orbitals more massive than Saturn around low-mass stars. This work points out to dozens of targets that have the potential to better constraint their exotrojan upper mass limit with dedicated radial velocity observations. We also explored the potential of observing the secondary eclipses of the confirmed exoplanets in our sample to enhance the exotrojan search, ultimately leading to a more accurate estimation of the occurrence rate of exotrojans.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142131016","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":"Weighing Milky Way and Andromeda in an expanding ΛCDM Universe","authors":"David Benisty","doi":"10.1051/0004-6361/202449884","DOIUrl":"https://doi.org/10.1051/0004-6361/202449884","url":null,"abstract":"The dynamics of the Local Group (LG), especially the contribution of the Milky Way (MW) and Andromeda (M 31) galaxies, is sensitive to the presence of dark energy. This work analyzes the evolution of the LG by considering it as a two-body problem in a homogeneous and isotropic expanding spacetime in a full Λcold dark matter (ΛCDM) background. Using the timing argument (TA), which links LG dynamics to LG mass, we find that the full ΛCDM background predicts a ∼10% lower mass for the LG; whereas Λ alone predicts a ∼10% higher mass. The TA mass is modified by (i) simulations and (ii) the effect of the Large Magellanic Cloud (LMC) to alleviate the poorly constrained internal mass distributions of M 31 and the MW, their time evolution, and the unknown distribution of dark matter between them. First, using IllustrisTNG simulations, we accounted for the effects of two extended halos and their environment (rather than point particles) and predicted their mass (3.89 ± 0.62)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Second, the LMC effectively changes the separation and velocities of M 31 towards the MW and reduces the predicted mass to (2.33 ± 0.72)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Despite the uncertainties around dark matter between these galaxies, the overall estimated mass is compatible with the mere sum of the MW and M 31 masses. The total mass of the TA is compatible with other estimates, such as the Hubble flow and the Virial Theorem with other dwarf galaxies. The combined result shows, for the first time, that a lower mass estimate can be obtained from the TA, with a consistent embedding and other systematic effects, and without an additional dark matter halo around the galaxies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118129","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":"Gas-rich “ultra-diffuse” galaxies are consistent with the baryonic Tully–Fisher relation and with Milgromian dynamics","authors":"F. Lelli","doi":"10.1051/0004-6361/202451289","DOIUrl":"https://doi.org/10.1051/0004-6361/202451289","url":null,"abstract":"Some gas-rich “ultra-diffuse” galaxies (UDGs), which are extreme examples of low surface brightness (LSB) dwarf galaxies, have been reported to lack dark matter and to be offset from the baryonic Tully–Fisher relation (BTFR). If confirmed, these UDGs would represent a serious challenge for both ΛCDM galaxy-formation models and Milgromian dynamics. Here I demonstrate that these conclusions are very dubious due to underestimated uncertainties on inclinations and/or distances. First, I show that UDGs are offset from the BTFR in the same way as usual face-on LSB dwarfs due to systematic biases at low inclinations. Next, I analyze the two UDGs with the best available rotation-curve data. The first (AGC 242019) is ideally inclined for kinematic studies; MOND can fit the observed rotation curve with a distance of 12.5 ± 0.6 Mpc, which is consistent with Virgocentric flow models. The second UDG (AGC 114905) is close to face-on, so not ideal for kinematic studies; MOND can fit the observed rotation curve with a distance of 68 ± 13 Mpc and inclination of 15° ±2°, which are consistent with existing data. In particular, I show that the disk inclination is more uncertain than previously estimated due to significant asymmetries (lopsidedness) in the stellar distribution. In conclusion, there is no strong evidence that gas-rich UDGs and gas-rich LSB dwarfs are distinct galaxy populations with different dynamical properties; instead, UDGs seem to be a subset of LSB dwarf galaxies biased toward face-on systems.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118094","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":"FAUST","authors":"M. J. Maureira, J. E. Pineda, H. B. Liu, L. Testi, D. Segura-Cox, C. Chandler, D. Johnstone, P. Caselli, G. Sabatini, Y. Aikawa, E. Bianchi, C. Codella, N. Cuello, D. Fedele, R. Friesen, L. Loinard, L. Podio, C. Ceccarelli, N. Sakai, S. Yamamoto","doi":"10.1051/0004-6361/202451166","DOIUrl":"https://doi.org/10.1051/0004-6361/202451166","url":null,"abstract":"<i>Context.<i/> Planets form in the disks surrounding young stars. The time at which the planet formation process begins is still an open question. Annular substructures such as rings and gaps in disks are intertwined with planet formation, and thus their presence or absence is commonly used to investigate the onset of this process.<i>Aims.<i/> Current observations show that a limited number of disks surrounding protostars exhibit annular substructures, all of them in the Class I stage. The lack of observed features in most of these sources may indicate a late emergence of substructures, but it could also be an artifact of these disks being optically thick. To mitigate the problem of optical depth, we investigated substructures within a very young Class 0 disk characterized by low inclination using observations at longer wavelengths.<i>Methods.<i/> We used 3 mm ALMA observations tracing dust emission at a resolution of 7 au to search for evidence of annular substructures in the disk around the deeply embedded Class 0 protostar Oph A SM1.<i>Results.<i/> The observations reveal a nearly face-on disk (inclination ∼ 16°) extending up to 40 au. The radial intensity profile shows a clear deviation from a smooth profile near 30 au, which we interpret as the presence of either a gap at 28 au or a ring at 34 au with Gaussian widths of au and au, respectively. Crucially, the 3 mm emission at the location of the possible gap or ring is determined to be optically thin, precluding the possibility that this feature in the intensity profile is due to the emission being optically thick.<i>Conclusions.<i/> Annular substructures resembling those in the more evolved Class I and II disks could indeed be present in the Class 0 stage, which is earlier than suggested by previous observations. Similar observations of embedded disks in which the high-optical-depth problem can be mitigated are clearly needed to better constrain the onset of substructures in the embedded stages.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118095","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":"X-Shooting ULLYSES: Massive stars at low metallicity","authors":"A. A. C. Sander, J.-C. Bouret, M. Bernini-Peron, J. Puls, F. Backs, S. R. Berlanas, J. M. Bestenlehner, S. A. Brands, A. Herrero, F. Martins, O. Maryeva, D. Pauli, V. Ramachandran, P. A. Crowther, V. M. A. Gómez-González, A. C. Gormaz-Matamala, W.-R. Hamann, D. J. Hillier, R. Kuiper, C. J. K. Larkin, R. R. Lefever, A. Mehner, F. Najarro, L. M. Oskinova, E. C. Schösser, T. Shenar, H. Todt, A. ud-Doula, J. S. Vink","doi":"10.1051/0004-6361/202449829","DOIUrl":"https://doi.org/10.1051/0004-6361/202449829","url":null,"abstract":"<i>Context.<i/> The spectral analysis of hot, massive stars is a fundamental astrophysical method of determining their intrinsic properties and feedback. With their inherent, radiation-driven winds, the quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment in order to obtain the best solution within a given framework.<i>Aims.<i/> We present an overview of different techniques for the quantitative spectroscopy of hot stars employed within the X-Shooting ULLYSES collaboration, ranging from grid-based approaches to tailored spectral fits. By performing a blind test for selected targets, we gain an overview of the similarities and differences between the resulting stellar and wind parameters. Our study is not a systematic benchmark between different codes or methods; our aim is to provide an overview of the parameter spread caused by different approaches.<i>Methods.<i/> For three different stars from the XShooting ULLYSES sample (SMC O5 star AzV 377, LMC O7 star Sk -69° 50, and LMC O9 star Sk-66° 171), we employ different stellar atmosphere codes (CMFGEN, Fastwind, PoWR) and different strategies to determine their best-fitting model solutions. For our analyses, UV and optical spectroscopy are used to derive the stellar and wind properties with some methods relying purely on optical data for comparison. To determine the overall spectral energy distribution, we further employ additional photometry from the literature.<i>Results.<i/> The effective temperatures found for each of the three different sample stars agree within 3 kK, while the differences in log <i>g<i/> can be up to 0.2 dex. Luminosity differences of up to 0.1 dex result from different reddening assumptions, which seem to be systematically larger for the methods employing a genetic algorithm. All sample stars are found to be enriched in nitrogen. The terminal wind velocities are surprisingly similar and do not strictly follow the <i>u<i/><sub>∞<sub/>−<i>T<i/><sub>eff<sub/> relation.<i>Conclusions.<i/> We find reasonable agreement in terms of the derived stellar and wind parameters between the different methods. Tailored fitting methods tend to be able to minimize or avoid discrepancies obtained with coarser or increasingly automatized treatments. The inclusion of UV spectral data is essential for the determination of realistic wind parameters. For one target (Sk -69° 50), we find clear indications of an evolved status.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118096","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":"Impediments to the cosmic growth of galaxies: The outflow budget from Star Formation and Active Galactic Nuclei","authors":"Johannes Buchner","doi":"10.1051/0004-6361/202451170","DOIUrl":"https://doi.org/10.1051/0004-6361/202451170","url":null,"abstract":"The gas reservoir of galaxies can be altered by outflows that are driven by star formation and luminous active galactic nuclei. Jets heating the surroundings of host galaxies can also prevent the gas from cooling and prevent inflows. Spectacular examples for these three mass-displacement channels have been observed, but their importance in transforming the galaxy population depends on the occurrence rates of the outflow triggers. We investigate the absolute and relative importance of these three channels. In an observation-driven approach, we combined distribution functions and scaling relations to empirically compare average outflow rates across the total stellar mass spectrum of the galaxy and across cosmic time. This hinges on local outflow studies, which should be extended to systematic, large, and diverse samples, and we did not consider a halo-heating effect by radiation-driven outflows so far. Independent of simulations, our results show the dominance of star formation-driven outflows in low-mass galaxies. Massive galaxies today are predominately prevented from growing further by jet heating, while at <i>z<i/> = 1 − 3, all three processes are approximately similarly important. Over the full mass spectrum and cosmic history, outflows driven by the radiation from active galactic nuclei are never the dominant process.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118090","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":"PDRs4All","authors":"J. R. Goicoechea, J. Le Bourlot, J. H. Black, F. Alarcón, E. A. Bergin, O. Berné, E. Bron, A. Canin, E. Chapillon, R. Chown, E. Dartois, M. Gerin, E. Habart, T. J. Haworth, C. Joblin, O. Kannavou, F. Le Petit, T. Onaka, E. Peeters, J. Pety, E. Roueff, A. Sidhu, I. Schroetter, B. Tabone, A. G. G. M. Tielens, B. Trahin, D. Van De Putte, S. Vicente, M. Zannese","doi":"10.1051/0004-6361/202450988","DOIUrl":"https://doi.org/10.1051/0004-6361/202450988","url":null,"abstract":"The gas-phase abundance of carbon, <i>x<i/><sub>C<sub/> = [C/H]<sub>gas<sub/> = <i>x<i/><sub>C<sup>+<sup/><sub/> + <i>x<i/><sub>C<sup>0<sup/><sub/> + <i>x<i/><sub>CO<sub/> + … , and its depletion factors are essential parameters for understanding the gas and solid compositions that are ultimately incorporated into (exo)planets. The majority of protoplanetary disks are born in clusters and, as a result, are exposed to external far-ultraviolet (FUV) radiation. These FUV photons potentially affect the disk’s evolution, chemical composition, and line excitation. We present the first detection of the [C I] 609 μm fine-structure (<sup>3<sup/>P<sub>1<sub/>–<sup>3<sup/>P<sub>0<sub/>) line of neutral carbon (C<sup>0<sup/>), achieved with ALMA, toward one of these disks, d203-506, in the Orion Nebula Cluster. We also report the detection of [C I] forbidden and C I permitted lines (from electronically excited states up to ∼10 eV) observed with JWST in the near-infrared (NIR). These lines trace the irradiated outer disk and photo-evaporative wind. Contrary to the common belief that these NIR lines are C<sup>+<sup/> recombination lines, we find that they are dominated by FUV-pumping of C<sup>0<sup/> followed by fluorescence cascades. They trace the transition from atomic to molecular gas, and their intensities scale with <i>G<i/><sub>0<sub/>. The lack of outstanding NIR O I fluorescent emission, however, implies a sharper attenuation of external FUV radiation with <i>E<i/> ≳ 12 eV (<i>λ<i/> ≲ Lyman-<i>β<i/>). This is related to a lower effective FUV dust absorption cross section compared to that of interstellar grains, implying a more prominent role for FUV shielding by the C<sup>0<sup/> photoionization continuum. The [C I] 609 μm line intensity is proportional to <i>N<i/>(C<sup>0<sup/>) and can be used to infer <i>x<i/><sub>C<sub/>. We derive <i>x<i/><sub>C<sub/> ≃ 1.4 × 10<sup>−4<sup/>. This implies that there is no major depletion of volatile carbon compared to <i>x<i/><sub>C<sub/> measured in the natal cloud, hinting at a young disk. We also show that external FUV radiation impacts the outer disk and wind by vertically shifting the water freeze-out depth, which likely results in less efficient grain growth and settling. This shift leads to nearly solar gas-phase C/O abundance ratios in these irradiated layers.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118093","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":"Search for rotating radio transients in three years of monitoring data","authors":"S. A. Tyul’bashev, M. A. Kitaeva, D. V. Pervoukhin, G. E. Tyul’basheva, E. A. Brylyakova, A. V. Chernosov, I. L. Ovchinnikov","doi":"10.1051/0004-6361/202449762","DOIUrl":"https://doi.org/10.1051/0004-6361/202449762","url":null,"abstract":"The search for rotating radio transients (RRATs) was carried out at a frequency of 111 MHz, as daily observations carried out on the Large Phased Array (LPA) radio telescope at declinations of −9° < <i>δ <<i/> +42°. Overall, 19 new RRATs were discovered for dispersion measures (DMs) from 2.5 to 72.6 pc cm<sup>−3<sup/>. Estimates of the periods were obtained for three RRATs, with two of them (J0408+28; J0440+35) located at distances of 134 and 136 pc from Sun, placing them among the closest of all known RRATs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142085009","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":"Intrinsic line profiles for X-ray fluorescent lines in SKIRT","authors":"Bert Vander Meulen, Peter Camps, Masahiro Tsujimoto, Keiichi Wada","doi":"10.1051/0004-6361/202451370","DOIUrl":"https://doi.org/10.1051/0004-6361/202451370","url":null,"abstract":"<i>Context.<i/> X-ray microcalorimeter instruments are expected to spectrally resolve the intrinsic line shapes of the strongest fluorescent lines. X-ray models should therefore incorporate these intrinsic line profiles to obtain meaningful constraints from observational data.<i>Aims.<i/> We included the intrinsic line profiles of the strongest fluorescent lines in the X-ray radiative transfer code SKIRT to model the cold-gas structure and kinematics based on high-resolution line observations from XRISM/Resolve and <i>Athena<i/>/X-IFU.<i>Methods.<i/> The intrinsic line profiles of the K<i>α<i/> and K<i>β<i/> lines of Cr, Mn, Fe, Co, Ni, and Cu were implemented based on a multi-Lorentzian parameterisation. Line energies are sampled from these Lorentzian components during the radiative transfer routine.<i>Results.<i/> In the optically thin regime, the SKIRT results match the intrinsic line profiles as measured in the laboratory. With a more complex 3D model that also includes kinematics, we find that the intrinsic line profiles are broadened and shifted to an extent that will be detectable with XRISM/Resolve; this model also demonstrates the importance of the intrinsic line shapes for constraining kinematics. We find that observed line profiles directly trace the cold-gas kinematics, without any additional radiative transfer effects.<i>Conclusions.<i/> With the advent of the first XRISM/Resolve data, this update to the X-ray radiative transfer framework of SKIRT is timely and provides a unique tool for constraining the velocity structure of cold gas from X-ray microcalorimeter spectra.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142200045","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":"Climate change in hell: Long-term variation in transits of the evaporating planet K2-22b","authors":"E. Gaidos, H. Parviainen, E. Esparza-Borges, A. Fukui, K. Isogai, K. Kawauchi, J. de Leon, M. Mori, F. Murgas, N. Narita, E. Palle, N. Watanabe","doi":"10.1051/0004-6361/202451332","DOIUrl":"https://doi.org/10.1051/0004-6361/202451332","url":null,"abstract":"<i>Context.<i/> Rocky planets on ultra-short period orbits can have surface magma oceans and rock-vapour atmospheres in which dust can condense. Observations of that dust can inform us about the composition and surface conditions on these objects.<i>Aims.<i/> We constrained the properties and long-term (decade) behaviour of the transiting dust cloud from the evaporating planet K2-22b.<i>Methods.<i/>We observed K2-22b around 40 predicted transits with MuSCAT ground-based multi-optical channel imagers, and complemented these data with long-term monitoring by the ground-based ATLAS (2018-2024) and space-based TESS (2021–2023) surveys.<i>Results.<i/> We detected signals during 7 transits, none of which showed significant wavelength dependence. The expected number of MuSCAT-detected transits is ≥22, indicating a decline in mean transit depth since the <i>K2<i/> discovery observations in 2014.<i>Conclusions.<i/> The lack of a significant wavelength dependence indicates that dust grains are large or the cloud is optically thick. Long-term trends of depth could be due to a magnetic cycle on the host star or to overturn of the planet’s dayside surface magma ocean. The possibility that K2-22b is disappearing altogether is ruled out by the stability of the transit ephemeris against non-gravitational forces, which constrains the mass to be at least comparable to Ceres.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225753","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}