Pub Date : 2026-01-22DOI: 10.1051/0004-6361/202556146
C. Moutou, P. Petit, P. Charpentier, P. Cristofari, C. Baruteau, P. Thébault, L. Arnold, E. Artigau, A. Carmona, N. J. Cook, F. Debras, X. Delfosse, J.-F. Donati, L. Malo, M. Ould-Elhkim
One of the first exoplanet hosts, discovered about thirty years ago, the star 55 Cnc has been continuously observed ever since. It is now known to host at least five planets with orbital periods ranging from 17 hours to 15 years. It is also one of the most extreme metal-rich stars in the neighbourhood, and it has a low-mass secondary star. In this article, we present data obtained at the Canada-France-Hawai’i Telescope with the SPIRou spectropolarimeter on both components of the 55 Cnc stellar system. We revisit the long-period radial-velocity signals of 55 Cnc A, with a focus on the role of the magnetic cycle, and propose the existence of a sixth planet candidate, whose period falls close to that of the magnetic cycle, or half of it. The other massive outer planet has a revised period of 13.15 years and a minimum mass of 3.8 MJup. Although some uncertainty remains about these outer planets, the characterisation of the four inner planets is very robust through the combination of many different datasets, and all signals are consistent in the near-infrared (nIR) and optical domains. In addition, the magnetic topology of the solar-type primary component of the system was observed by SPIRou at the minimum of its activity cycle, characterised by an amplitude ten times smaller than observed that during its maximum in 2017. For the low-mass component 55 Cnc B, we report the discovery of two exoplanets in the system, with a period of 6.799 ± 0.0014 and 33.75 ± 0.04 days and a minimum mass of 3.5 ± 0.8 and 5.3 ± 1.4 M⊕, respectively. The secondary magnetic field is very weak, and the current dataset does not allow its precise characterisation, setting an upper limit of 10 G. The system 55 Cnc stands out as the sixth binary system with planetary systems around both components and the first one with non-equal-mass stellar components.
{"title":"Characterising planetary systems with SPIRou: Questions about the magnetic cycle of 55 Cnc A and two new planets around B★","authors":"C. Moutou, P. Petit, P. Charpentier, P. Cristofari, C. Baruteau, P. Thébault, L. Arnold, E. Artigau, A. Carmona, N. J. Cook, F. Debras, X. Delfosse, J.-F. Donati, L. Malo, M. Ould-Elhkim","doi":"10.1051/0004-6361/202556146","DOIUrl":"https://doi.org/10.1051/0004-6361/202556146","url":null,"abstract":"One of the first exoplanet hosts, discovered about thirty years ago, the star 55 Cnc has been continuously observed ever since. It is now known to host at least five planets with orbital periods ranging from 17 hours to 15 years. It is also one of the most extreme metal-rich stars in the neighbourhood, and it has a low-mass secondary star. In this article, we present data obtained at the Canada-France-Hawai’i Telescope with the SPIRou spectropolarimeter on both components of the 55 Cnc stellar system. We revisit the long-period radial-velocity signals of 55 Cnc A, with a focus on the role of the magnetic cycle, and propose the existence of a sixth planet candidate, whose period falls close to that of the magnetic cycle, or half of it. The other massive outer planet has a revised period of 13.15 years and a minimum mass of 3.8 M<sub>Jup<sub/>. Although some uncertainty remains about these outer planets, the characterisation of the four inner planets is very robust through the combination of many different datasets, and all signals are consistent in the near-infrared (nIR) and optical domains. In addition, the magnetic topology of the solar-type primary component of the system was observed by SPIRou at the minimum of its activity cycle, characterised by an amplitude ten times smaller than observed that during its maximum in 2017. For the low-mass component 55 Cnc B, we report the discovery of two exoplanets in the system, with a period of 6.799 ± 0.0014 and 33.75 ± 0.04 days and a minimum mass of 3.5 ± 0.8 and 5.3 ± 1.4 M<sub>⊕<sub/>, respectively. The secondary magnetic field is very weak, and the current dataset does not allow its precise characterisation, setting an upper limit of 10 G. The system 55 Cnc stands out as the sixth binary system with planetary systems around both components and the first one with non-equal-mass stellar components.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"32 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146021936","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}
Pub Date : 2026-01-22DOI: 10.1051/0004-6361/202555476
Vincenzo Mariani, Agnès Fienga, Zachary Murray, Mickaël Gastineau, Jacques Laskar
Context. One of the main bottlenecks in assessing the accuracy of the Mars orbit is the unknown value of the asteroids in the main asteroid belt. A modeling with 343 asteroids as point masses is used today, with the relative masses fit to observational data.Aims. We propose an innovative method for reducing the number of asteroids implemented as point masses, which in turn reduces the number of parameters to be fit without a significant degradation of the postfit residuals.Methods. We used boosting decision trees to obtain a ranking by relative importance of the 343 asteroids of the current main belt modeling.Results. We were able to remove more than 100 of these asteroids without significantly degrading the postfit residuals and with a significant improvement of the uncertainties. Furthermore, we verified that the postfit masses found with the new modeling (INPOP25c) are consistent with respect to the mass estimation from an independent approach by means of the albedo properties of the asteroids.
{"title":"Boosting decision trees for the selection of main belt asteroids in planetary ephemerides: An alternative model","authors":"Vincenzo Mariani, Agnès Fienga, Zachary Murray, Mickaël Gastineau, Jacques Laskar","doi":"10.1051/0004-6361/202555476","DOIUrl":"https://doi.org/10.1051/0004-6361/202555476","url":null,"abstract":"<i>Context<i/>. One of the main bottlenecks in assessing the accuracy of the Mars orbit is the unknown value of the asteroids in the main asteroid belt. A modeling with 343 asteroids as point masses is used today, with the relative masses fit to observational data.<i>Aims<i/>. We propose an innovative method for reducing the number of asteroids implemented as point masses, which in turn reduces the number of parameters to be fit without a significant degradation of the postfit residuals.<i>Methods<i/>. We used boosting decision trees to obtain a ranking by relative importance of the 343 asteroids of the current main belt modeling.<i>Results<i/>. We were able to remove more than 100 of these asteroids without significantly degrading the postfit residuals and with a significant improvement of the uncertainties. Furthermore, we verified that the postfit masses found with the new modeling (INPOP25c) are consistent with respect to the mass estimation from an independent approach by means of the albedo properties of the asteroids.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"269 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022062","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}
Pub Date : 2026-01-21DOI: 10.1051/0004-6361/202557253
L. P. Chitta, D. I. Pontin, E. R. Priest, D. Berghmans, E. Kraaikamp, L. Rodriguez, C. Verbeeck, A. N. Zhukov, S. Krucker, R. Aznar Cuadrado, D. Calchetti, J. Hirzberger, H. Peter, U. Schühle, S. K. Solanki, L. Teriaca, A. S. Giunta, F. Auchère, L. Harra, D. Müller
Solar flares are the most powerful, magnetically driven, explosions in the heliosphere. The nature of magnetic energy release in the solar corona that heats the plasma and accelerates particles in a flare, however, remains poorly understood. Here, we report high-resolution coronal observations of a flare by the Solar Orbiter mission that reveal initially weaker but rapid reconnection events, on timescales of a few seconds at most, leading to a more prominent activity of a similar nature that explosively causes a flare. Signatures of this process are further imprinted on the widespread raining plasma blobs with short lifetimes, giving rise to the characteristic ribbon-like emission pattern associated with the flare. Our observations unveil the central engine of a flare and emphasize the crucial role of an avalanche-like magnetic energy release mechanism at work.
{"title":"A magnetic avalanche as the central engine powering a solar flare","authors":"L. P. Chitta, D. I. Pontin, E. R. Priest, D. Berghmans, E. Kraaikamp, L. Rodriguez, C. Verbeeck, A. N. Zhukov, S. Krucker, R. Aznar Cuadrado, D. Calchetti, J. Hirzberger, H. Peter, U. Schühle, S. K. Solanki, L. Teriaca, A. S. Giunta, F. Auchère, L. Harra, D. Müller","doi":"10.1051/0004-6361/202557253","DOIUrl":"https://doi.org/10.1051/0004-6361/202557253","url":null,"abstract":"Solar flares are the most powerful, magnetically driven, explosions in the heliosphere. The nature of magnetic energy release in the solar corona that heats the plasma and accelerates particles in a flare, however, remains poorly understood. Here, we report high-resolution coronal observations of a flare by the Solar Orbiter mission that reveal initially weaker but rapid reconnection events, on timescales of a few seconds at most, leading to a more prominent activity of a similar nature that explosively causes a flare. Signatures of this process are further imprinted on the widespread raining plasma blobs with short lifetimes, giving rise to the characteristic ribbon-like emission pattern associated with the flare. Our observations unveil the central engine of a flare and emphasize the crucial role of an avalanche-like magnetic energy release mechanism at work.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"58 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006175","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556855
P. Weber, S. Pérez, C. Baruteau, S. Marino, F. Castillo, M. R. Jankovic, T. Pearce, M. C. Wyatt, A. A. Sefilian, J. Olofsson, G. Cataldi, J. B. Lovell, C. del Burgo, A. M. Hughes, S. Mac Manamon, A. Brennan, L. Matrà, J. Milli, B. Zawadzki, E. Chiang, M. A. MacGregor, D. J. Wilner, M. Bonduelle, J. M. Carpenter, Y. Han, Á. Kóspál, P. Luppe
Context. Debris discs were long considered to be largely gas-free environments, where dynamical evolution is governed primarily by collisional fragmentation, gravitational stirring, and radiative forces. Recent detections of CO molecular line emission in debris discs demonstrate that gas is present, but its abundance and origin are still uncertain. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) observed both the gas and dust of several debris discs at high resolution and revealed a narrow ring of gas and dust in the disc HD 121617, with an asymmetric arc-like feature that is 40% brighter than the rest of the ring.Aims. An important open question is how representative the estimated CO masses are for the total gas mass in debris discs. We aim to constrain the total gas mass in HD 121617 using numerical models under the assumption that the dust arc is produced by hydrodynamical processes involving the gas.Methods. We used the hydrodynamical code Dusty FARGO-ADSG, in which dust is modelled as Lagrangian particles. We explored the effects of radiation pressure and dust feedback, as well as of varying the total gas mass on the dynamical evolution of the system. We compared these simulations with observations via radiative transfer calculations.Results. We find that an unstable gas ring can create a size-dependent radial and azimuthal dust trap. The total gas mass dictates the efficiency of particle trapping as a function of grain size. We find that two of our models, Mgas=50 M⊕ and Mgas=5 M⊕, can simultaneously reproduce the observed arc in the ALMA band 7 continuum image and the radial outward offset of the VLT/SPHERE scattered light ring, driven by the combined effects of gas drag and radiation pressure. We further find a conservative lower limit of Mgas>2.5 M⊕ and a conservative upper limit of Mgas<250 M⊕.Conclusions. If the ALMA band 7 asymmetry is caused by gas drag, reconciling the required gas mass with the observed 12CO emission suggests the presence of significant amounts of H2, consistent with the gas being primordial, that is, long-lived remnant material from the protoplanetary disc phase. In this scenario, HD 121617 would represent a hybrid disc, bridging the protoplanetary and debris disc stages. As an arc-shaped emission can alternatively be reproduced by a planet’s gravitational forcing, future observations are crucial to distinguish between these two scenarios.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"P. Weber, S. Pérez, C. Baruteau, S. Marino, F. Castillo, M. R. Jankovic, T. Pearce, M. C. Wyatt, A. A. Sefilian, J. Olofsson, G. Cataldi, J. B. Lovell, C. del Burgo, A. M. Hughes, S. Mac Manamon, A. Brennan, L. Matrà, J. Milli, B. Zawadzki, E. Chiang, M. A. MacGregor, D. J. Wilner, M. Bonduelle, J. M. Carpenter, Y. Han, Á. Kóspál, P. Luppe","doi":"10.1051/0004-6361/202556855","DOIUrl":"https://doi.org/10.1051/0004-6361/202556855","url":null,"abstract":"<i>Context<i/>. Debris discs were long considered to be largely gas-free environments, where dynamical evolution is governed primarily by collisional fragmentation, gravitational stirring, and radiative forces. Recent detections of CO molecular line emission in debris discs demonstrate that gas is present, but its abundance and origin are still uncertain. The <i>ALMA survey to Resolve exoKuiper belt Substructures (ARKS)<i/> observed both the gas and dust of several debris discs at high resolution and revealed a narrow ring of gas and dust in the disc HD 121617, with an asymmetric arc-like feature that is 40% brighter than the rest of the ring.<i>Aims<i/>. An important open question is how representative the estimated CO masses are for the total gas mass in debris discs. We aim to constrain the total gas mass in HD 121617 using numerical models under the assumption that the dust arc is produced by hydrodynamical processes involving the gas.<i>Methods<i/>. We used the hydrodynamical code Dusty FARGO-ADSG, in which dust is modelled as Lagrangian particles. We explored the effects of radiation pressure and dust feedback, as well as of varying the total gas mass on the dynamical evolution of the system. We compared these simulations with observations via radiative transfer calculations.<i>Results<i/>. We find that an unstable gas ring can create a size-dependent radial and azimuthal dust trap. The total gas mass dictates the efficiency of particle trapping as a function of grain size. We find that two of our models, <i>M<i/><sub>gas<sub/>=50 <i>M<i/><sub>⊕<sub/> and <i>M<i/><sub>gas<sub/>=5 <i>M<i/><sub>⊕<sub/>, can simultaneously reproduce the observed arc in the ALMA band 7 continuum image and the radial outward offset of the VLT/SPHERE scattered light ring, driven by the combined effects of gas drag and radiation pressure. We further find a conservative lower limit of <i>M<i/><sub>gas<sub/>>2.5 <i>M<i/><sub>⊕<sub/> and a conservative upper limit of <i>M<i/><sub>gas<sub/><250 <i>M<i/><sub>⊕<sub/>.<i>Conclusions<i/>. If the ALMA band 7 asymmetry is caused by gas drag, reconciling the required gas mass with the observed <sup>12<sup/>CO emission suggests the presence of significant amounts of H<sub>2<sub/>, consistent with the gas being primordial, that is, long-lived remnant material from the protoplanetary disc phase. In this scenario, HD 121617 would represent a hybrid disc, bridging the protoplanetary and debris disc stages. As an arc-shaped emission can alternatively be reproduced by a planet’s gravitational forcing, future observations are crucial to distinguish between these two scenarios.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"63 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006171","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556568
J. B. Lovell, A. S. Hales, G. M. Kennedy, S. Marino, J. Olofsson, A. M. Hughes, E. Mansell, B. C. Matthews, T. D. Pearce, A. A. Sefilian, D. J. Wilner, B. Zawadzki, M. Booth, M. Bonduelle, A. Brennan, C. del Burgo, J. M. Carpenter, G. Cataldi, E. Chiang, A. Fehr, Y. Han, Th. Henning, A. V. Krivov, P. Luppe, J. P. Marshall, S. Mac Manamon, J. Milli, A. Moór, M. C. Wyatt, S. Ertel, M. R. Jankovic, Á. Kóspál, M. A. MacGregor, L. Matrà, S. Pérez, P. Weber
<i>Context<i/>. Asymmetries in debris discs provide unique clues to understand the evolution and architecture of planetary systems. Previous studies of debris discs at (sub)millimetre wavelengths have suggested the presence of asymmetries in a wide variety of systems, yet the lack of sufficiently sensitive high-resolution observations means that the typical properties of debris disc asymmetries have not been studied at the population level. The aim of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is to expand our understanding of radial and vertical dust structures, as well as gas distributions and kinematics, in debris discs. The ARKS sample of 24 highly resolved targets in ALMA’s Bands 6 and 7 (1.1–1.4 mm and 0.8–1.1 mm, respectively) provided a unique opportunity to study their asymmetries.<i>Aims<i/>. Here, in ARKS VI, we present a systematic analysis of the asymmetries and stellocentric offsets present in the ALMA continuum data for the ARKS survey. Our aims are to (i) identify asymmetries in debris disc dust distributions, (ii) quantify debris disc asymmetry properties, and (iii) discuss the potential origins of debris disc asymmetries. This work is the first systematic analysis of asymmetries in a large sample of well-resolved discs at (sub)millimetre wavelengths.<i>Methods<i/>. We utilised empirical methods to identify emission asymmetries (relative to disc major and minor axes, and azimuthal disc locations) and the presence of offset emission between disc centres and the locations of the host stars, via an analysis of their calibration procedures and disc properties. We associated observational asymmetry types (offset, major and/or minor axis, azimuthal) and plausible physical classes (arcs, eccentricities, and possible clumps and warps) associated with each source.<i>Results<i/>. We show that there are ten systems, almost half of the ARKS sample, that host either a continuum emission asymmetry or offset emission. Three systems host offsets (HD 15115, HD 32297, and HD 109573 (HR 4796)), four host azimuthal asymmetries (HD 9672 (49 Ceti), HD 92945, HD 107146, and HD 121617), two host an asymmetry in their major axis (HD 10647 (q<sup>1<sup/> Eri), and HD 39060 (<i>β<i/> Pic)), and one hosts an asymmetry in their minor axis (HD 61005). We attribute the offset asymmetries to non-zero eccentricities, and three of the azimuthal asymmetries to arcs. The presence of an asymmetry or offset in the ARKS sample appears to be correlated with the fractional luminosity of cold dust. We tentatively suggest that continuum asymmetries are more prevalent in CO-rich debris discs, suggesting that gas interactions may drive debris dust asymmetries. We identify seven other tentative asymmetries, including four in distinct ARKS systems and three in systems with otherwise significant asymmetries.<i>Conclusions<i/>. This study demonstrates that debris disc asymmetries in the ARKS sample are common, and plausibly so in the wider population of debr
上下文。碎片盘的不对称性为理解行星系统的演化和结构提供了独特的线索。先前对（亚）毫米波长的碎片盘的研究表明，在各种各样的系统中都存在不对称，但缺乏足够敏感的高分辨率观测意味着碎片盘不对称的典型特性尚未在种群水平上进行研究。ALMA调查外柯伊伯带亚结构（ARKS）的目的是扩大我们对径向和垂直尘埃结构的理解，以及碎片盘中的气体分布和运动学。ARKS采样了ALMA波段6和7（分别为1.1-1.4 mm和0.8-1.1 mm）的24个高分辨率目标，为研究它们的不对称性提供了独特的机会。这里，在ARKS VI中，我们对ARKS调查中ALMA连续体数据中的不对称性和星心偏移进行了系统分析。我们的目标是(i)确定碎片盘尘埃分布中的不对称性，（ii）量化碎片盘的不对称性特性，以及（iii）讨论碎片盘不对称性的潜在起源。这项工作是第一次系统地分析（亚）毫米波长下高分辨率圆盘的不对称性。我们利用经验方法来识别发射不对称性（相对于盘主轴和小轴，以及盘的方位角位置），以及盘中心和主星位置之间存在的偏移发射，通过分析它们的校准程序和盘的特性。我们将观测到的不对称类型（偏移、主轴和/或小轴、方位角）和与每个源相关的合理物理类别（弧线、偏心、可能的团块和翘曲）联系起来。我们表明，有10个系统，几乎一半的ARKS样本，宿主连续发射不对称或抵消发射。三个系统主机偏移（HD 15115， HD 32297和HD 109573 (HR 4796)），四个主机方位角不对称（HD 9672 (49 Ceti), HD 92945， HD 107146和HD 121617），两个主机在其长轴上具有不对称（HD 10647 （q1 Eri）和HD 39060 (β Pic)），一个主机在其小轴上具有不对称（HD 61005）。我们将偏移不对称归因于非零偏心，并将三个方位角不对称归因于弧。ARKS样品中不对称或偏移的存在似乎与冷尘埃的分数光度有关。我们初步认为，连续体不对称在富含co的碎片盘中更为普遍，这表明气体相互作用可能导致碎片尘埃不对称。我们确定了其他7个暂定不对称，包括4个不同的ARKS系统和3个具有其他显著不对称的系统。这项研究表明，ARKS样本中的碎片盘不对称是常见的，而且在（亚）毫米波长的更广泛的碎片盘中似乎也是如此。这意味着，当我们以更高的灵敏度和分辨率探测这些碎片盘时，（亚）毫米的不对称可能会等待发现。在整个过程中，我们强调了未来的研究，以进一步调查碎片盘不对称的起源，并建立在这里提出的工作。
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"J. B. Lovell, A. S. Hales, G. M. Kennedy, S. Marino, J. Olofsson, A. M. Hughes, E. Mansell, B. C. Matthews, T. D. Pearce, A. A. Sefilian, D. J. Wilner, B. Zawadzki, M. Booth, M. Bonduelle, A. Brennan, C. del Burgo, J. M. Carpenter, G. Cataldi, E. Chiang, A. Fehr, Y. Han, Th. Henning, A. V. Krivov, P. Luppe, J. P. Marshall, S. Mac Manamon, J. Milli, A. Moór, M. C. Wyatt, S. Ertel, M. R. Jankovic, Á. Kóspál, M. A. MacGregor, L. Matrà, S. Pérez, P. Weber","doi":"10.1051/0004-6361/202556568","DOIUrl":"https://doi.org/10.1051/0004-6361/202556568","url":null,"abstract":"<i>Context<i/>. Asymmetries in debris discs provide unique clues to understand the evolution and architecture of planetary systems. Previous studies of debris discs at (sub)millimetre wavelengths have suggested the presence of asymmetries in a wide variety of systems, yet the lack of sufficiently sensitive high-resolution observations means that the typical properties of debris disc asymmetries have not been studied at the population level. The aim of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is to expand our understanding of radial and vertical dust structures, as well as gas distributions and kinematics, in debris discs. The ARKS sample of 24 highly resolved targets in ALMA’s Bands 6 and 7 (1.1–1.4 mm and 0.8–1.1 mm, respectively) provided a unique opportunity to study their asymmetries.<i>Aims<i/>. Here, in ARKS VI, we present a systematic analysis of the asymmetries and stellocentric offsets present in the ALMA continuum data for the ARKS survey. Our aims are to (i) identify asymmetries in debris disc dust distributions, (ii) quantify debris disc asymmetry properties, and (iii) discuss the potential origins of debris disc asymmetries. This work is the first systematic analysis of asymmetries in a large sample of well-resolved discs at (sub)millimetre wavelengths.<i>Methods<i/>. We utilised empirical methods to identify emission asymmetries (relative to disc major and minor axes, and azimuthal disc locations) and the presence of offset emission between disc centres and the locations of the host stars, via an analysis of their calibration procedures and disc properties. We associated observational asymmetry types (offset, major and/or minor axis, azimuthal) and plausible physical classes (arcs, eccentricities, and possible clumps and warps) associated with each source.<i>Results<i/>. We show that there are ten systems, almost half of the ARKS sample, that host either a continuum emission asymmetry or offset emission. Three systems host offsets (HD 15115, HD 32297, and HD 109573 (HR 4796)), four host azimuthal asymmetries (HD 9672 (49 Ceti), HD 92945, HD 107146, and HD 121617), two host an asymmetry in their major axis (HD 10647 (q<sup>1<sup/> Eri), and HD 39060 (<i>β<i/> Pic)), and one hosts an asymmetry in their minor axis (HD 61005). We attribute the offset asymmetries to non-zero eccentricities, and three of the azimuthal asymmetries to arcs. The presence of an asymmetry or offset in the ARKS sample appears to be correlated with the fractional luminosity of cold dust. We tentatively suggest that continuum asymmetries are more prevalent in CO-rich debris discs, suggesting that gas interactions may drive debris dust asymmetries. We identify seven other tentative asymmetries, including four in distinct ARKS systems and three in systems with otherwise significant asymmetries.<i>Conclusions<i/>. This study demonstrates that debris disc asymmetries in the ARKS sample are common, and plausibly so in the wider population of debr","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"45 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006174","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556523
J. Milli, J. Olofsson, M. Bonduelle, R. Bendahan-West, J. P. Marshall, E. Choquet, A. A. Sefilian, Y. Han, B. Zawadzki, S. Mac Manamon, E. Mansell, C. del Burgo, J. M. Carpenter, A. M. Hughes, M. Booth, E. Chiang, S. Ertel, Th. M. Esposito, Th. Henning, J. Hom, M. R. Jankovic, A. V. Krivov, J. B. Lovell, P. Luppe, M. A. MacGregor, S. Marino, B. C. Matthews, L. Matrà, A. Moór, N. Pawellek, T. D. Pearce, S. Pérez, V. Squicciarini, P. Weber, D. J. Wilner, M. C. Wyatt
Context. Debris discs are analogues to our own Kuiper belt around main-sequence stars and are therefore referred to as exoKuiper belts. They have been resolved at high angular resolution at wavelengths spanning the optical/near-infrared to the submillimetre-millimetre regime. Short wavelengths can probe the light scattered by such discs, which is dominated by micron-sized dust particles, while millimetre wavelengths can probe the thermal emission of millimetre-sized particles. Determining differences in the dust distribution between millimetre- and micron-sized dust is fundamental to revealing the dynamical processes affecting the dust in debris discs.Aims. We aim to compare the scattered light from the discs of the ‘ALMA survey to Resolve exoKuiper belt Substructures’ (ARKS) with the thermal emission probed by ALMA. We focus on the radial distribution of the dust, and we also put constraints on the presence of giant planets in those systems.Methods. We used high-contrast scattered light observations obtained with VLT/SPHERE, GPI, and the HST to uniformly study the dust distribution in those systems and compare it to the dust distribution extracted from the ALMA observations carried out in the course of the ARKS project. We also set constraints on the presence of planets by using these high-contrast images combined with exoplanet evolutionary models.Results. Fifteen of the 24 discs comprising the ARKS sample are detected in scattered light, with TYC 9340-437-1 being imaged for the first time at near-infrared wavelengths. For six of those 15 discs, the dust surface density seen in scattered light peaks farther out compared to that observed with ALMA. These six discs except one are known to also host cold CO gas. Conversely, the systems without significant offsets are not known to host gas, except one. Moreover, with our scattered light near-infrared images, we achieve typical sensitivities to planets from 1 to 10 MJup beyond 10 to 20 au, depending on the system age and distance.Conclusions. This observational study suggests that the presence of gas in debris discs may affect the small and large grains differently, pushing the small dust to greater distances where the gas is less abundant.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"J. Milli, J. Olofsson, M. Bonduelle, R. Bendahan-West, J. P. Marshall, E. Choquet, A. A. Sefilian, Y. Han, B. Zawadzki, S. Mac Manamon, E. Mansell, C. del Burgo, J. M. Carpenter, A. M. Hughes, M. Booth, E. Chiang, S. Ertel, Th. M. Esposito, Th. Henning, J. Hom, M. R. Jankovic, A. V. Krivov, J. B. Lovell, P. Luppe, M. A. MacGregor, S. Marino, B. C. Matthews, L. Matrà, A. Moór, N. Pawellek, T. D. Pearce, S. Pérez, V. Squicciarini, P. Weber, D. J. Wilner, M. C. Wyatt","doi":"10.1051/0004-6361/202556523","DOIUrl":"https://doi.org/10.1051/0004-6361/202556523","url":null,"abstract":"<i>Context<i/>. Debris discs are analogues to our own Kuiper belt around main-sequence stars and are therefore referred to as exoKuiper belts. They have been resolved at high angular resolution at wavelengths spanning the optical/near-infrared to the submillimetre-millimetre regime. Short wavelengths can probe the light scattered by such discs, which is dominated by micron-sized dust particles, while millimetre wavelengths can probe the thermal emission of millimetre-sized particles. Determining differences in the dust distribution between millimetre- and micron-sized dust is fundamental to revealing the dynamical processes affecting the dust in debris discs.<i>Aims<i/>. We aim to compare the scattered light from the discs of the ‘ALMA survey to Resolve exoKuiper belt Substructures’ (ARKS) with the thermal emission probed by ALMA. We focus on the radial distribution of the dust, and we also put constraints on the presence of giant planets in those systems.<i>Methods<i/>. We used high-contrast scattered light observations obtained with VLT/SPHERE, GPI, and the HST to uniformly study the dust distribution in those systems and compare it to the dust distribution extracted from the ALMA observations carried out in the course of the ARKS project. We also set constraints on the presence of planets by using these high-contrast images combined with exoplanet evolutionary models.<i>Results<i/>. Fifteen of the 24 discs comprising the ARKS sample are detected in scattered light, with TYC 9340-437-1 being imaged for the first time at near-infrared wavelengths. For six of those 15 discs, the dust surface density seen in scattered light peaks farther out compared to that observed with ALMA. These six discs except one are known to also host cold CO gas. Conversely, the systems without significant offsets are not known to host gas, except one. Moreover, with our scattered light near-infrared images, we achieve typical sensitivities to planets from 1 to 10 <i>M<i/><sub>Jup<sub/> beyond 10 to 20 au, depending on the system age and distance.<i>Conclusions<i/>. This observational study suggests that the presence of gas in debris discs may affect the small and large grains differently, pushing the small dust to greater distances where the gas is less abundant.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"32 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006198","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556493
S. Marino, V. Gupta, P. Weber, T. D. Pearce, A. Brennan, S. Pérez, S. Mac Manamon, L. Matrà, J. Milli, M. Booth, C. del Burgo, G. Cataldi, E. Chiang, Y. Han, Th. Henning, A. M. Hughes, M. R. Jankovic, Á. Kóspál, J. B. Lovell, P. Luppe, E. Mansell, M. A. MacGregor, A. Moór, J. Olofsson, A. A. Sefilian, D. J. Wilner, M. C. Wyatt, B. Zawadzki
Context. ExoKuiper belts around young A-type stars often host CO gas, whose origin is still unclear. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) includes six of these gas-bearing belts, to characterise their dust and gas distributions and investigate the gas origin.Aims. As part of ARKS, we observed the gas-rich system HD 121617 with a 0⋅′′ 12 (14 au) resolution and discovered an arc of enhanced dust density. In this paper, we analyse in detail the dust and gas distributions and the gas kinematics of this system.Methods. We extracted radial and azimuthal profiles of the dust (in the millimetre and near-infrared) and gas emission (12CO and 13CO) from reconstructed images. To constrain the morphology of the arc, we fitted an asymmetric model to the dust emission. To characterise the gas kinematics, we fitted a Keplerian model to the velocity map and extracted the gas azimuthal velocity profile by deprojecting the data.Results. We find that the dust arc is narrow (1–5 au wide at a radius of 75 au), azimuthally extended with a full width at half maximum of ~90°, and asymmetric; the emission is more azimuthally compact in the direction of the system’s rotation, and represents 13% of the total dust mass (0.2 M⊕). From analysis of the scattered light and CO images, we conclude that the arc is much less pronounced or absent for small grains and gas. Finally, we find strong non-Keplerian azimuthal velocities at the inner and outer wings of the ring, as was expected due to strong pressure gradients.Conclusions. The dust arc resembles the asymmetries found in protoplanetary discs, often interpreted as the result of dust trapping in vortices. If the gas disc mass is high enough (≳20 M⊕, requiring a primordial gas origin), both the radial confinement of the ring and the azimuthal arc may result from dust grains responding to gas drag. Alternatively, it could result from planet-disc interactions via mean motion resonances. Further studies should test these hypotheses and may provide a dynamical gas mass estimate in this CO-rich exoKuiper belt.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"S. Marino, V. Gupta, P. Weber, T. D. Pearce, A. Brennan, S. Pérez, S. Mac Manamon, L. Matrà, J. Milli, M. Booth, C. del Burgo, G. Cataldi, E. Chiang, Y. Han, Th. Henning, A. M. Hughes, M. R. Jankovic, Á. Kóspál, J. B. Lovell, P. Luppe, E. Mansell, M. A. MacGregor, A. Moór, J. Olofsson, A. A. Sefilian, D. J. Wilner, M. C. Wyatt, B. Zawadzki","doi":"10.1051/0004-6361/202556493","DOIUrl":"https://doi.org/10.1051/0004-6361/202556493","url":null,"abstract":"<i>Context<i/>. ExoKuiper belts around young A-type stars often host CO gas, whose origin is still unclear. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) includes six of these gas-bearing belts, to characterise their dust and gas distributions and investigate the gas origin.<i>Aims<i/>. As part of ARKS, we observed the gas-rich system HD 121617 with a 0<sub>⋅<sub/><sup>′′<sup/> 12 (14 au) resolution and discovered an arc of enhanced dust density. In this paper, we analyse in detail the dust and gas distributions and the gas kinematics of this system.<i>Methods<i/>. We extracted radial and azimuthal profiles of the dust (in the millimetre and near-infrared) and gas emission (<sup>12<sup/>CO and <sup>13<sup/>CO) from reconstructed images. To constrain the morphology of the arc, we fitted an asymmetric model to the dust emission. To characterise the gas kinematics, we fitted a Keplerian model to the velocity map and extracted the gas azimuthal velocity profile by deprojecting the data.<i>Results<i/>. We find that the dust arc is narrow (1–5 au wide at a radius of 75 au), azimuthally extended with a full width at half maximum of ~90°, and asymmetric; the emission is more azimuthally compact in the direction of the system’s rotation, and represents 13% of the total dust mass (0.2 <i>M<i/><sub>⊕<sub/>). From analysis of the scattered light and CO images, we conclude that the arc is much less pronounced or absent for small grains and gas. Finally, we find strong non-Keplerian azimuthal velocities at the inner and outer wings of the ring, as was expected due to strong pressure gradients.<i>Conclusions<i/>. The dust arc resembles the asymmetries found in protoplanetary discs, often interpreted as the result of dust trapping in vortices. If the gas disc mass is high enough (≳20 <i>M<i/><sub>⊕<sub/>, requiring a primordial gas origin), both the radial confinement of the ring and the azimuthal arc may result from dust grains responding to gas drag. Alternatively, it could result from planet-disc interactions via mean motion resonances. Further studies should test these hypotheses and may provide a dynamical gas mass estimate in this CO-rich exoKuiper belt.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"276 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006201","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202554956
F. Ahlborn, J. Higl, R. Andrassy, G. Leidi, A. Weiss, F. Röpke
Context. The efficient transport of energy and chemical elements by convective motions has a profound effect on the structure and evolution of stars. These motions occur on the relatively short dynamical timescale of convection and are intrinsically multi-dimensional. Stellar models usually rely on the one-dimensional mixing-length approximation of these processes, which is known to break down at convective boundaries. The Kuhfuß, R. (1987, Dissertation, Technische Universität München, München) convection model has been shown to handle convective boundaries in a more consistent way.Aims. We test the assumptions that enter the Kuhfuß model using multi-dimensional hydrodynamics simulations, and we compare the results with existing one-dimensional models. Where possible, we also aim to calibrate the parameters of the Kuhfuß model using the simulations.Methods. We computed one-dimensional stellar models employing the Kuhfuß model of a 3 M⊙ main-sequence star. These models were compared to three-dimensional hydrodynamic simulations obtained with the code called SEVEN-LEAGUE HYDRO and using the Reynolds-averaged Navier Stokes analysis. We analysed the global convective variables and individual contributions to the equations of the convection model.Results. The turbulent kinetic energy as predicted by the Kuhfuß model agrees well with the simulation results. Towards the boundary of the convective core, the simulations show a layer of a positive entropy gradient that coincides with a positive convective flux, as predicted by the convection model. The terms involving pressure fluctuations are found to have a non-negligible magnitude.Conclusions. The agreement of the turbulent kinetic energy equation for the convection model and the simulation is an important sign that the convection model is physically accurate. The gradient of the mean entropy that we found in the multi-dimensional simulations and in the Kuhfuß model confirms the existence of a Deardorff layer, that is, of a layer with a subadiabtic temperature stratification and positive convective flux. This is not predicted by the mixing-length theory. The assumption that turbulence is isotropic and that pressure fluctuations are negligible needs to be revisited in the convection model.
上下文。能量和化学元素通过对流运动的有效传输对恒星的结构和演化有着深远的影响。这些运动发生在相对较短的对流动力学时间尺度上，本质上是多维的。恒星模型通常依赖于这些过程的一维混合长度近似值，众所周知，这种近似值在对流边界处会崩溃。Kuhfuß， R. （1987, Dissertation, Technische Universität m nchen, m nchen）对流模型已被证明以更一致的方式处理对流边界。我们使用多维流体力学模拟来检验进入Kuhfuß模型的假设，并将结果与现有的一维模型进行比较。在可能的情况下，我们还打算使用模拟方法校准Kuhfuß模型的参数。我们用Kuhfuß模型计算了一个3 M⊙主序星的一维恒星模型。这些模型与三维流体动力学模拟进行了比较，这些模拟是用名为SEVEN-LEAGUE HYDRO的代码获得的，并使用了reynolds -average Navier Stokes分析。我们分析了整体对流变量和个体对对流模式方程的贡献。Kuhfuß模型预测的湍流动能与模拟结果吻合较好。在对流核边界处，模拟结果显示出一层正熵梯度，与对流模型预测的正对流通量相吻合。发现涉及压力波动的项具有不可忽略的量级。对流模型湍流动能方程与模拟结果的一致性是对流模型物理精度的重要标志。我们在多维模拟和Kuhfuß模型中发现的平均熵梯度证实了Deardorff层的存在，即具有亚绝热温度分层和正对流通量的层。这是混合长度理论无法预测的。紊流是各向同性和压力波动可以忽略不计的假设需要在对流模型中重新考虑。
{"title":"Validating a non-local stellar convection model with 3D hydrodynamics simulations","authors":"F. Ahlborn, J. Higl, R. Andrassy, G. Leidi, A. Weiss, F. Röpke","doi":"10.1051/0004-6361/202554956","DOIUrl":"https://doi.org/10.1051/0004-6361/202554956","url":null,"abstract":"<i>Context.<i/> The efficient transport of energy and chemical elements by convective motions has a profound effect on the structure and evolution of stars. These motions occur on the relatively short dynamical timescale of convection and are intrinsically multi-dimensional. Stellar models usually rely on the one-dimensional mixing-length approximation of these processes, which is known to break down at convective boundaries. The Kuhfuß, R. (1987, Dissertation, Technische Universität München, München) convection model has been shown to handle convective boundaries in a more consistent way.<i>Aims.<i/> We test the assumptions that enter the Kuhfuß model using multi-dimensional hydrodynamics simulations, and we compare the results with existing one-dimensional models. Where possible, we also aim to calibrate the parameters of the Kuhfuß model using the simulations.<i>Methods.<i/> We computed one-dimensional stellar models employing the Kuhfuß model of a 3 M<sub>⊙<sub/> main-sequence star. These models were compared to three-dimensional hydrodynamic simulations obtained with the code called SEVEN-LEAGUE HYDRO and using the Reynolds-averaged Navier Stokes analysis. We analysed the global convective variables and individual contributions to the equations of the convection model.<i>Results.<i/> The turbulent kinetic energy as predicted by the Kuhfuß model agrees well with the simulation results. Towards the boundary of the convective core, the simulations show a layer of a positive entropy gradient that coincides with a positive convective flux, as predicted by the convection model. The terms involving pressure fluctuations are found to have a non-negligible magnitude.<i>Conclusions.<i/> The agreement of the turbulent kinetic energy equation for the convection model and the simulation is an important sign that the convection model is physically accurate. The gradient of the mean entropy that we found in the multi-dimensional simulations and in the Kuhfuß model confirms the existence of a Deardorff layer, that is, of a layer with a subadiabtic temperature stratification and positive convective flux. This is not predicted by the mixing-length theory. The assumption that turbulence is isotropic and that pressure fluctuations are negligible needs to be revisited in the convection model.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006233","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556505
B. Zawadzki, A. Fehr, A. M. Hughes, E. Mansell, J. Kittling, Y. Han, C. Hou, M. Pan, J. Milli, J. Olofsson, T. Pearce, A. A. Sefilian, A. Nurmohamed, J. Lee, Y. Mpofu, M. Bonduelle, M. Booth, A. Brennan, C. del Burgo, J. M. Carpenter, G. Cataldi, E. Chiang, S. Ertel, Th. Henning, M. R. Jankovic, G. M. Kennedy, Á. Kóspál, A. V. Krivov, J. B. Lovell, P. Luppe, M. A. MacGregor, S. Mac Manamon, S. Marino, J. P. Marshall, L. Matrà, A. Moór, S. Pérez, P. Weber, D. J. Wilner, M. C. Wyatt
Context. Debris disks – collisionally sustained belts of dust and sometimes gas around main sequence stars – are remnants of planet formation processes and are found in systems ≳10 Myr old. Millimeter-wavelength observations are particularly important, as the grains probed by these observations are not strongly affected by radiation pressure and stellar winds, allowing them to probe the dynamics of large bodies producing dust. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is analyzing high-resolution observations of 24 debris disks to enable the characterization of debris disk substructures across a large sample for the first time.Aims. For the most highly inclined disks, it is possible to recover the vertical structure of the disk. We aim to model and analyze the most highly inclined systems in the ARKS sample in order to uniformly extract the vertical dust distributions for a sample of well-resolved debris disks.Methods. We employed both parametric and nonparametric methods to constrain the vertical dust distributions for the most highly inclined ARKS targets.Results. We find a broad range of aspect ratios, revealing a wide diversity in vertical structure, with a range of best-fit parametric values of 0.0026 ≤ hHWHM ≤ 0.193 and a median best-fit value of hHWHM = 0.021. The results obtained by nonparametric modeling are generally consistent with the parametric modeling results. We find that five of the 13 disks are consistent with having total disk masses less than that of Neptune (17 M⊕), assuming stirring by internal processes (self-stirring and collisional and frictional damping). Furthermore, most systems show a significant preference for a Lorentzian vertical profile rather than a Gaussian.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"B. Zawadzki, A. Fehr, A. M. Hughes, E. Mansell, J. Kittling, Y. Han, C. Hou, M. Pan, J. Milli, J. Olofsson, T. Pearce, A. A. Sefilian, A. Nurmohamed, J. Lee, Y. Mpofu, M. Bonduelle, M. Booth, A. Brennan, C. del Burgo, J. M. Carpenter, G. Cataldi, E. Chiang, S. Ertel, Th. Henning, M. R. Jankovic, G. M. Kennedy, Á. Kóspál, A. V. Krivov, J. B. Lovell, P. Luppe, M. A. MacGregor, S. Mac Manamon, S. Marino, J. P. Marshall, L. Matrà, A. Moór, S. Pérez, P. Weber, D. J. Wilner, M. C. Wyatt","doi":"10.1051/0004-6361/202556505","DOIUrl":"https://doi.org/10.1051/0004-6361/202556505","url":null,"abstract":"<i>Context<i/>. Debris disks – collisionally sustained belts of dust and sometimes gas around main sequence stars – are remnants of planet formation processes and are found in systems ≳10 Myr old. Millimeter-wavelength observations are particularly important, as the grains probed by these observations are not strongly affected by radiation pressure and stellar winds, allowing them to probe the dynamics of large bodies producing dust. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is analyzing high-resolution observations of 24 debris disks to enable the characterization of debris disk substructures across a large sample for the first time.<i>Aims<i/>. For the most highly inclined disks, it is possible to recover the vertical structure of the disk. We aim to model and analyze the most highly inclined systems in the ARKS sample in order to uniformly extract the vertical dust distributions for a sample of well-resolved debris disks.<i>Methods<i/>. We employed both parametric and nonparametric methods to constrain the vertical dust distributions for the most highly inclined ARKS targets.<i>Results<i/>. We find a broad range of aspect ratios, revealing a wide diversity in vertical structure, with a range of best-fit parametric values of 0.0026 ≤ <i>h<i/><sub>HWHM<sub/> ≤ 0.193 and a median best-fit value of <i>h<i/><sub>HWHM<sub/> = 0.021. The results obtained by nonparametric modeling are generally consistent with the parametric modeling results. We find that five of the 13 disks are consistent with having total disk masses less than that of Neptune (17 <i>M<i/><sub>⊕<sub/>), assuming stirring by internal processes (self-stirring and collisional and frictional damping). Furthermore, most systems show a significant preference for a Lorentzian vertical profile rather than a Gaussian.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"101 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006200","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}
Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556566
A. Brennan, L. Matrà, S. Mac Manamon, S. Marino, G. Cataldi, A. M. Hughes, P. Weber, Y. Han, J. P. Marshall, B. Zawadzki, P. Luppe, A. A. Sefilian, A. Moór, M. A. MacGregor, J. B. Lovell, A. Kóspál, M. Bonduelle, E. Mansell, M. C. Wyatt, T. D. Pearce, J. M. Carpenter, D. J. Wilner, C. del Burgo, S. Pérez, T. Henning, J. Milli, E. Chiang
Context. CO gas has been detected in ~20 debris discs, typically classified as CO-poor or CO-rich. We present observations of the CO-rich HD 121617 debris disc as part of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS).Aims. We model local CO line profiles in the HD 121617 debris disc to investigate optical depth, CO mass, and temperature. HD 121617 is a well-suited ARKS target due to its previously detected CO emission and moderate inclination, reducing the effect of Keplerian shear.Methods. Using high-resolution ALMA Band 7 observations of 12CO J=3–2 (26 m s−1, 0⋅′′ 1), we create local line profiles by aligning and stacking spectra in concentric annuli of 0⋅′′ 02 width. These profiles are modelled with both a toy model and a RADMC-3D model that includes projection effects and Keplerian shear.Results. The resulting local profiles are Gaussian-shaped and broad due to the effect of Keplerian shear. Fitting a RADMC-3D model to the 13CO data, we find that an optically thick model (temperature of 38 K and mass of 2 × 10−3 M⊕) reproduces the data, particularly the enhanced intensity at orbital azimuths of ~±45° and ±135°, which forms an X-shape in the velocity integrated intensity map, as well as the broader 12CO linewidth compared to 13CO. Scaling this model by the ISM abundance ratio (~77) also reproduces the 12CO data, but high optical depths and model assumptions limit mass constraints.Conclusions. Keplerian shear causes azimuthally averaged line profiles to appear Gaussian regardless of optical depth; therefore, we caution against using the local line profiles to distinguish between optically thin and thick emission. We constrain the mean molecular weight to 12.6−1.1+1.3, dependent on model assumptions. Although model dependent, our 13CO results indicate that C18O might also be optically thick in CO-rich debris discs, contrary to previous assumptions, and that the mean molecular weight is significantly higher than if H2 were the dominant gas species, suggesting a non-primordial composition.
上下文。在约20个碎片盘中检测到CO气体，通常分为贫CO和富CO两类。我们提出了对富含co的HD 121617碎片盘的观测，作为ALMA调查的一部分，以解决外柯伊伯带亚结构（ARKS）。我们模拟了HD 121617碎片盘中的局部CO线剖面，以研究光学深度、CO质量和温度。HD 121617是一个非常适合的ARKS目标，因为它以前检测到CO发射和适度的倾角，减少了开普勒剪切的影响。利用高分辨率ALMA Band 7观测12CO J= 3-2 (26 m s−1,0⋅”1)，我们通过对齐和叠加光谱在0⋅”02宽度的同心环空中创建局部线剖面。这些剖面用玩具模型和RADMC-3D模型建模，其中包括投影效果和开普勒剪切。由于开普勒剪切的影响，得到的局部剖面是高斯形的，而且很宽。将RADMC-3D模型拟合13CO数据，我们发现一个光学厚模型（温度为38 K，质量为2 × 10−3 M⊕）再现了数据，特别是在轨道方位角为~±45°和±135°处的强度增强，在速度综合强度图中形成x形，并且与13CO相比，12CO线宽更宽。用ISM丰度比（~77）对该模型进行缩放也能再现12CO的数据，但较高的光学深度和模型假设限制了质量约束。无论光学深度如何，开普勒剪切都会导致方位平均线轮廓呈现高斯分布；因此，我们警告不要使用局部线轮廓来区分光学薄和厚发射。根据模型假设，我们将平均分子量限制为12.6−1.1+1.3。虽然依赖于模型，但我们的13CO结果表明，在富含co的碎片盘中，C18O也可能具有光学厚度，这与之前的假设相反，并且平均分子量明显高于H2为主要气体的情况，表明其非原始成分。
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