Pub Date : 2025-03-14DOI: 10.1051/0004-6361/202451999
Héctor J. Martínez, Martín de los Rios, Valeria Coenda, Hernán Muriel, Andrés N. Ruiz, Sofía A. Cora, Cristian A. Vega-Martínez
Context. Studies of galaxy populations classified according to their kinematic behaviours and dynamical state using the projected phase space diagram (PPSD) are affected by misclassification and contamination, leading to systematic errors in determining the characteristics of the different galaxy classes.Aims. We propose a method for statistically correcting the determination of galaxy properties’ distributions that accounts for the contamination caused by misclassified galaxies from other classes.Methods. Using a sample of massive clusters and the galaxies in their surroundings taken from the MULTIDARK PLANCK 2 simulation combined with the semi-analytic model of galaxy formation SAG, we computed the confusion matrix associated with a classification scheme in the PPSD. Based on positions in the PPSD, galaxies are classified as cluster members, backsplash galaxies, recent infallers, infalling galaxies, or interlopers. This classification is determined using probabilities calculated by the code ROGER along with a threshold criterion. By inverting the confusion matrix, we are able to get better determinations of distributions of galaxy properties, such as colour.Results. Compared to a direct estimation based solely on the predicted galaxy classes, our method provides better estimates of the mass-dependent colour distribution for the galaxy classes most affected by misclassification: cluster members, backsplash galaxies, and recent infallers. We applied the method to a sample of observed X-ray clusters and galaxies.Conclusions. Our method can be applied to any classification of galaxies in the PPSD, and to any other galaxy property besides colour, provided an estimation of the confusion matrix is available. Blue, low-mass galaxies in clusters are almost exclusively recent infaller galaxies that have not yet been quenched by the environmental action of the cluster. Backsplash galaxies are on average redder than expected.
背景利用投影相空间图（PPSD）根据星系的运动行为和动力学状态对星系群进行分类的研究受到分类错误和污染的影响，从而导致在确定不同星系类别的特征时出现系统误差。我们提出了一种对星系特性分布的测定进行统计校正的方法，这种方法考虑到了其他类别星系的误分类所造成的污染。利用MULTIDARK PLANCK 2模拟中的大质量星系团及其周围的星系样本，结合星系形成的半解析模型SAG，我们计算了与PPSD中的分类方案相关的混淆矩阵。根据星系在 PPSD 中的位置，星系被划分为星系团成员、背斜星系、近期内陷星系、内陷星系或外来者。这种分类是利用 ROGER 代码计算出的概率和阈值标准确定的。通过倒转混淆矩阵，我们可以更好地确定星系属性的分布，比如颜色。与仅仅根据预测的星系类别进行直接估算相比，我们的方法能更好地估算出受误判影响最大的星系类别的质量依赖性颜色分布：星系团成员、背斜星系和新近注入者。我们将该方法应用于观测到的X射线星系团和星系样本。只要有混淆矩阵的估计值，我们的方法可以应用于PPSD中的任何星系分类，也可以应用于除颜色以外的任何其他星系属性。星团中的蓝色低质量星系几乎都是新近塌陷的星系，它们还没有被星团的环境作用所熄灭。背斜星系平均比预期的要红。
{"title":"Improving the accuracy of observable distributions for galaxies classified in the projected phase space diagram","authors":"Héctor J. Martínez, Martín de los Rios, Valeria Coenda, Hernán Muriel, Andrés N. Ruiz, Sofía A. Cora, Cristian A. Vega-Martínez","doi":"10.1051/0004-6361/202451999","DOIUrl":"https://doi.org/10.1051/0004-6361/202451999","url":null,"abstract":"<i>Context.<i/> Studies of galaxy populations classified according to their kinematic behaviours and dynamical state using the projected phase space diagram (PPSD) are affected by misclassification and contamination, leading to systematic errors in determining the characteristics of the different galaxy classes.<i>Aims.<i/> We propose a method for statistically correcting the determination of galaxy properties’ distributions that accounts for the contamination caused by misclassified galaxies from other classes.<i>Methods.<i/> Using a sample of massive clusters and the galaxies in their surroundings taken from the MULTIDARK PLANCK 2 simulation combined with the semi-analytic model of galaxy formation SAG, we computed the confusion matrix associated with a classification scheme in the PPSD. Based on positions in the PPSD, galaxies are classified as cluster members, backsplash galaxies, recent infallers, infalling galaxies, or interlopers. This classification is determined using probabilities calculated by the code ROGER along with a threshold criterion. By inverting the confusion matrix, we are able to get better determinations of distributions of galaxy properties, such as colour.<i>Results.<i/> Compared to a direct estimation based solely on the predicted galaxy classes, our method provides better estimates of the mass-dependent colour distribution for the galaxy classes most affected by misclassification: cluster members, backsplash galaxies, and recent infallers. We applied the method to a sample of observed X-ray clusters and galaxies.<i>Conclusions.<i/> Our method can be applied to any classification of galaxies in the PPSD, and to any other galaxy property besides colour, provided an estimation of the confusion matrix is available. Blue, low-mass galaxies in clusters are almost exclusively recent infaller galaxies that have not yet been quenched by the environmental action of the cluster. Backsplash galaxies are on average redder than expected.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"89 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635801","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 : 2025-03-14DOI: 10.1051/0004-6361/202453167
L. A. Gutiérrez-Soto, R. Lopes de Oliveira, S. Akras, D. R. Gonçalves, L. F. Lomelí-Núñez, C. Mendes de Oliveira, E. Telles, A. Alvarez-Candal, M. Borges Fernandes, S. Daflon, C. E. Ferreira Lopes, M. Grossi, D. Hazarika, P. K. Humire, C. Lima-Dias, A. R. Lopes, J. L. Nilo Castellón, S. Panda, A. Kanaan, T. Ribeiro, W. Schoenell
Context. We use the Southern Photometric Local Universe Survey (S-PLUS) Fourth Data Release (DR4) to identify and classify Hα excess point source candidates in the southern sky. This approach combines photometric data from 12 S-PLUS filters with machine learning techniques to improve source classification and advance our understanding of Hα-related phenomena.Aims. Our goal is to enhance the classification of Hα excess point sources by distinguishing between Galactic and extragalactic objects, particularly those with redshifted emission lines, and to identify sources where the Hα excess is associated with variability phenomena, such as short-period RR Lyrae stars.Methods. We selected Hα excess candidates using the (r − J0660) versus (r − i) colour–colour diagram from the S-PLUS main survey (MS) and Galactic Disk Survey (GDS). For the MS sample, dimensionality reduction was achieved using UMAP, followed by HDBSCAN clustering. We refined this by incorporating infrared data, which improved the separation of source types. A random forest model was then trained on the clustering results to identify key colour features for the classification of Hα excess sources. New effective colour–colour diagrams were constructed by combining data from S-PLUS MS and infrared data. These diagrams, alongside tentative colour criteria, offer a preliminary classification of Hα excess sources without the need for complex algorithms.Results. Combining multi-wavelength photometric data with machine learning techniques significantly improved the classification of Hα excess sources. We identified 6956 sources with an excess in the J0660 filter, and cross-matching with SIMBAD allowed us to explore the types of objects present in our catalogue, including emission-line stars, young stellar objects, nebulae, stellar binaries, cataclysmic variables, variable stars, and extragalactic sources such as Quasi-Stellar Objects (QSOs), Active Galactic Nuclei (AGN), and galaxies. The cross-match also revealed X-ray sources, transients, and other peculiar objects. Using S-PLUS colours and machine learning, we successfully separated RR Lyrae stars from other Galactic stars and from extragalactic objects. Additionally, we achieved a clear separation between Galactic and extragalactic sources. However, distinguishing cataclysmic variables from QSOs at specific redshifts remained challenging. Incorporating infrared data refined the classification, enabling us to separate Galactic from extragalactic sources and to distinguish cataclysmic variables from QSOs. The Random Forest model, trained on HDBSCAN results, highlighted key colour features that distinguish the different classes of Hα excess sources, providing a robust framework for future studies, such as follow-up spectroscopy.
{"title":"Mapping Hα excess candidate point sources in the southern hemisphere using S-PLUS data","authors":"L. A. Gutiérrez-Soto, R. Lopes de Oliveira, S. Akras, D. R. Gonçalves, L. F. Lomelí-Núñez, C. Mendes de Oliveira, E. Telles, A. Alvarez-Candal, M. Borges Fernandes, S. Daflon, C. E. Ferreira Lopes, M. Grossi, D. Hazarika, P. K. Humire, C. Lima-Dias, A. R. Lopes, J. L. Nilo Castellón, S. Panda, A. Kanaan, T. Ribeiro, W. Schoenell","doi":"10.1051/0004-6361/202453167","DOIUrl":"https://doi.org/10.1051/0004-6361/202453167","url":null,"abstract":"<i>Context.<i/> We use the Southern Photometric Local Universe Survey (S-PLUS) Fourth Data Release (DR4) to identify and classify Hα excess point source candidates in the southern sky. This approach combines photometric data from 12 S-PLUS filters with machine learning techniques to improve source classification and advance our understanding of Hα-related phenomena.<i>Aims.<i/> Our goal is to enhance the classification of Hα excess point sources by distinguishing between Galactic and extragalactic objects, particularly those with redshifted emission lines, and to identify sources where the Hα excess is associated with variability phenomena, such as short-period RR Lyrae stars.<i>Methods.<i/> We selected Hα excess candidates using the (<i>r<i/> − <i>J<i/>0660) versus (<i>r<i/> − <i>i<i/>) colour–colour diagram from the S-PLUS main survey (MS) and Galactic Disk Survey (GDS). For the MS sample, dimensionality reduction was achieved using UMAP, followed by HDBSCAN clustering. We refined this by incorporating infrared data, which improved the separation of source types. A random forest model was then trained on the clustering results to identify key colour features for the classification of Hα excess sources. New effective colour–colour diagrams were constructed by combining data from S-PLUS MS and infrared data. These diagrams, alongside tentative colour criteria, offer a preliminary classification of Hα excess sources without the need for complex algorithms.<i>Results.<i/> Combining multi-wavelength photometric data with machine learning techniques significantly improved the classification of Hα excess sources. We identified 6956 sources with an excess in the <i>J<i/>0660 filter, and cross-matching with SIMBAD allowed us to explore the types of objects present in our catalogue, including emission-line stars, young stellar objects, nebulae, stellar binaries, cataclysmic variables, variable stars, and extragalactic sources such as Quasi-Stellar Objects (QSOs), Active Galactic Nuclei (AGN), and galaxies. The cross-match also revealed X-ray sources, transients, and other peculiar objects. Using S-PLUS colours and machine learning, we successfully separated RR Lyrae stars from other Galactic stars and from extragalactic objects. Additionally, we achieved a clear separation between Galactic and extragalactic sources. However, distinguishing cataclysmic variables from QSOs at specific redshifts remained challenging. Incorporating infrared data refined the classification, enabling us to separate Galactic from extragalactic sources and to distinguish cataclysmic variables from QSOs. The Random Forest model, trained on HDBSCAN results, highlighted key colour features that distinguish the different classes of Hα excess sources, providing a robust framework for future studies, such as follow-up spectroscopy.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"33 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635789","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}
Context. Fast radio bursts (FRBs) are a class of transients characterised by their millisecond-scale duration and relatively high dispersion measures. Some FRBs have been observed to repeat. For such repeating FRBs, measuring the period is key to identifying their physical mechanisms. However, periods have only been measured for two FRBs – FRB 20112002A and FRB 20180916B – because most repeating FRBs have a low event count, making it challenging to measure their periods.Aims. We aim to introduce a composite periodogram strategy designed to measure periods of repeating FRBs out of low event counts.Methods. We combined the χ2 periodogram with the inactivity fraction periodogram (F0) to maximise the detection likelihood and minimise noise. Our approach was validated using FRB 20180916B, whereby we successfully recovered the known period with as few as five events. We then applied this method to 17 FRBs whose event counts range from three to 12.Results. A candidate period is identified in FRB 20190804E, FRB 20190915D, FRB 20200223B, FRB 20201130A, and FRB 20201221B, with a probability of chance coincidence ≤0.050. Additionally, we did further checks to eliminate false positives and concluded that the candidate periods for FRB 20190804E (168.39−0.07+3.86 days) and FRB 20201130A (11.38−0.10+0.10 days) are likely close to its true period. These values provide a basis for informed follow-up observations.
{"title":"Composite periodogram analysis for low-event-count fast radio burst repeaters","authors":"Murthadza Aznam, Zamri Zainal Abidin, Norsiah Hashim, Tomotsugu Goto, Tetsuya Hashimoto, Muhammad Hassan Zakie, Matdhesh Kummar Jayaganthan","doi":"10.1051/0004-6361/202452508","DOIUrl":"https://doi.org/10.1051/0004-6361/202452508","url":null,"abstract":"<i>Context.<i/> Fast radio bursts (FRBs) are a class of transients characterised by their millisecond-scale duration and relatively high dispersion measures. Some FRBs have been observed to repeat. For such repeating FRBs, measuring the period is key to identifying their physical mechanisms. However, periods have only been measured for two FRBs – FRB 20112002A and FRB 20180916B – because most repeating FRBs have a low event count, making it challenging to measure their periods.<i>Aims.<i/> We aim to introduce a composite periodogram strategy designed to measure periods of repeating FRBs out of low event counts.<i>Methods.<i/> We combined the χ<sup>2<sup/> periodogram with the inactivity fraction periodogram (<i>F<i/><sub>0<sub/>) to maximise the detection likelihood and minimise noise. Our approach was validated using FRB 20180916B, whereby we successfully recovered the known period with as few as five events. We then applied this method to 17 FRBs whose event counts range from three to 12.<i>Results.<i/> A candidate period is identified in FRB 20190804E, FRB 20190915D, FRB 20200223B, FRB 20201130A, and FRB 20201221B, with a probability of chance coincidence ≤0.050. Additionally, we did further checks to eliminate false positives and concluded that the candidate periods for FRB 20190804E (168.39<sub>−0.07<sub/><sup>+3.86<sup/> days) and FRB 20201130A (11.38<sub>−0.10<sub/><sup>+0.10<sup/> days) are likely close to its true period. These values provide a basis for informed follow-up observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"104 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635794","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 : 2025-03-14DOI: 10.1051/0004-6361/202452984
C. Katsavrias, G. Nicolaou, G. Livadiotis, A. Vourlidas, L. B. Wilson III, I. Sandberg
Context. A polytropic process describes the transition of a fluid from one state to another through a specific relationship between the fluid density and temperature, and the value of the polytropic index that governs this relationship determines the heat transfer and the effective degrees of freedom of this specific process.Aims. In this paper, we investigate in depth the proton polytropic behaviour in interplanetary coronal mass ejections (ICMEs). Moreover, for the first time (to our knowledge and at such an extent) we further investigate the behaviour of both the total and partial polytropic indices within ICMEs with various magnetic field configurations inside the magnetic obstacles.Methods. To that end we used a list of 401 ICMEs identified from Wind measurements during more than two solar cycles (1995–2001), during which we derived the distributions of the polytropic index in the near-Earth space (L1).Results. Our results show that sheaths are sub-adiabatic, indicating turbulent plasma, while the value of γ further depends on the existence of a shock. Furthermore, the polytropic behaviour of the protons inside the ICME magnetic obstacles is dependent on the magnetic field configuration, with flux ropes with rotation above 90 deg exhibiting sub-adiabatic γ, while ejecta with no clear rotation exhibiting super-adiabatic γ, supporting the scenario that changes during the interplanetary evolution might affect the magnetic field configuration inside the magnetic obstacle.
{"title":"The Polytropic Index of Interplanetary Coronal Mass Ejections near L1","authors":"C. Katsavrias, G. Nicolaou, G. Livadiotis, A. Vourlidas, L. B. Wilson III, I. Sandberg","doi":"10.1051/0004-6361/202452984","DOIUrl":"https://doi.org/10.1051/0004-6361/202452984","url":null,"abstract":"<i>Context.<i/> A polytropic process describes the transition of a fluid from one state to another through a specific relationship between the fluid density and temperature, and the value of the polytropic index that governs this relationship determines the heat transfer and the effective degrees of freedom of this specific process.<i>Aims.<i/> In this paper, we investigate in depth the proton polytropic behaviour in interplanetary coronal mass ejections (ICMEs). Moreover, for the first time (to our knowledge and at such an extent) we further investigate the behaviour of both the total and partial polytropic indices within ICMEs with various magnetic field configurations inside the magnetic obstacles.<i>Methods.<i/> To that end we used a list of 401 ICMEs identified from Wind measurements during more than two solar cycles (1995–2001), during which we derived the distributions of the polytropic index in the near-Earth space (L1).<i>Results.<i/> Our results show that sheaths are sub-adiabatic, indicating turbulent plasma, while the value of <i>γ<i/> further depends on the existence of a shock. Furthermore, the polytropic behaviour of the protons inside the ICME magnetic obstacles is dependent on the magnetic field configuration, with flux ropes with rotation above 90 deg exhibiting sub-adiabatic <i>γ<i/>, while ejecta with no clear rotation exhibiting super-adiabatic <i>γ<i/>, supporting the scenario that changes during the interplanetary evolution might affect the magnetic field configuration inside the magnetic obstacle.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635783","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 : 2025-03-14DOI: 10.1051/0004-6361/202453501
Raghav Arora, Christoph Federrath, Mark Krumholz, Robi Banerjee
Context. Dense filaments, also known as feathers, are kiloparsec-scale dusty features present in nearby main sequence galaxies. Distinct from the spiral arms, filaments constitute a major portion of dense gas concentration. They are expected to play an important role in star formation and are known to harbour embedded star-forming regions and H II regions.Aims. We explore the origin of filaments and feathers in disc galaxies via global gravitational instability.Methods. We conduct a parameter study using three-dimensional hydrodynamical simulations of isolated disc galaxies that are isothermal, self-gravitating and are initialised in equilibrium. Our galaxies are uniquely characterised by two dimensionless parameters, the Toomre Q and the rotational Mach number, ℳc = vc/cs (ratio of circular velocity to sound speed). We carry out simulations covering a wide range in both parameters.Results. We find that galaxies with Q = 1 form filaments within a single rotation, while galaxies with Q ≥ 2 do not, even within a couple of rotations. These filaments are kiloparsec long and are semi-regularly spaced along the azimuth of the galaxy. Their morphology, density contrast and formation timescale vary with ℳc, with filament spacing and instability onset time both inversely proportional to ℳc and the density contrast increasing with ℳc. However, filament growth rates in all Q = 1 galaxies are ∼0.5 Ω, where Ω is the angular frequency. We compare the filament spacing in our simulations with the ones in JWST/Mid-Infrared Instrument and HST observations of nearby galaxies and find them to be in agreement.Conclusions. Our study suggests that self-gravity and rotation alone are sufficient to form filaments and feathers, even in the absence of spiral arms or magnetic fields. The morphologies of the resulting filaments are determined primarily by ℳc, which parametrises the importance of thermal versus rotational support.
{"title":"Formation of filaments and feathers in disc galaxies: Is self-gravity enough?","authors":"Raghav Arora, Christoph Federrath, Mark Krumholz, Robi Banerjee","doi":"10.1051/0004-6361/202453501","DOIUrl":"https://doi.org/10.1051/0004-6361/202453501","url":null,"abstract":"<i>Context.<i/> Dense filaments, also known as feathers, are kiloparsec-scale dusty features present in nearby main sequence galaxies. Distinct from the spiral arms, filaments constitute a major portion of dense gas concentration. They are expected to play an important role in star formation and are known to harbour embedded star-forming regions and H II regions.<i>Aims.<i/> We explore the origin of filaments and feathers in disc galaxies via global gravitational instability.<i>Methods.<i/> We conduct a parameter study using three-dimensional hydrodynamical simulations of isolated disc galaxies that are isothermal, self-gravitating and are initialised in equilibrium. Our galaxies are uniquely characterised by two dimensionless parameters, the Toomre <i>Q<i/> and the rotational Mach number, ℳ<sub>c<sub/> = <i>v<i/><sub>c<sub/>/<i>c<i/><sub>s<sub/> (ratio of circular velocity to sound speed). We carry out simulations covering a wide range in both parameters.<i>Results.<i/> We find that galaxies with <i>Q<i/> = 1 form filaments within a single rotation, while galaxies with <i>Q<i/> ≥ 2 do not, even within a couple of rotations. These filaments are kiloparsec long and are semi-regularly spaced along the azimuth of the galaxy. Their morphology, density contrast and formation timescale vary with ℳ<sub>c<sub/>, with filament spacing and instability onset time both inversely proportional to ℳ<sub>c<sub/> and the density contrast increasing with ℳ<sub>c<sub/>. However, filament growth rates in all <i>Q<i/> = 1 galaxies are ∼0.5 Ω, where Ω is the angular frequency. We compare the filament spacing in our simulations with the ones in JWST/Mid-Infrared Instrument and HST observations of nearby galaxies and find them to be in agreement.<i>Conclusions.<i/> Our study suggests that self-gravity and rotation alone are sufficient to form filaments and feathers, even in the absence of spiral arms or magnetic fields. The morphologies of the resulting filaments are determined primarily by ℳ<sub>c<sub/>, which parametrises the importance of thermal versus rotational support.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"65 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635788","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 : 2025-03-14DOI: 10.1051/0004-6361/202553698
Cheikh T. Bop, François Lique
Cyanopolyynes are abundant and widespread in cold molecular clouds. Their abundances are typically determined under the assumption of local thermodynamic equilibrium (LTE) or through non-LTE analysis based on approximate collisional rate coefficients. Here, we present the first quantum mechanical scattering data for HC5N and HC7N in collisions with helium. We used both close-coupling (CC) and coupled-states (CS) methods to compute excitation cross-sections. We then derived rate coefficients for the first energy levels of HC5N and HC7N. A comparative analysis between the CC and CS results reveals an agreement better than a factor of two for high-magnitude rate coefficients. However, we found that the derivation of approximate HC5N and HC7N rate coefficients from those of HCN and HC3N using a size proportionality relationship, as has been previously done in the literature, leads to an overestimation of the collisional data by up to two orders of magnitude. To assess the sensitivity of cyanopolyyne line intensities to collisional rate coefficients, we compared LTE predictions with various non-LTE models using different rate coefficients. Under the typical physical conditions of cold molecular clouds, the LTE assumption and radiative transfer calculations based on approximate collisional rate coefficients strongly overestimate high-frequency line intensities, while the non-LTE models based on the HC3N collisional rate coefficients as a proxy for HC5N and HC7N remain accurate within 10%. We therefore recommend revisiting the abundance estimates for HC5N and HC7N using the new rate coefficients. For HC9N and HC11N, adopting HC7N collisional data in line modelling is expected to be highly accurate.
{"title":"Guidelines for non-LTE modelling of cyanopolyynes","authors":"Cheikh T. Bop, François Lique","doi":"10.1051/0004-6361/202553698","DOIUrl":"https://doi.org/10.1051/0004-6361/202553698","url":null,"abstract":"Cyanopolyynes are abundant and widespread in cold molecular clouds. Their abundances are typically determined under the assumption of local thermodynamic equilibrium (LTE) or through non-LTE analysis based on approximate collisional rate coefficients. Here, we present the first quantum mechanical scattering data for HC<sub>5<sub/>N and HC<sub>7<sub/>N in collisions with helium. We used both close-coupling (CC) and coupled-states (CS) methods to compute excitation cross-sections. We then derived rate coefficients for the first energy levels of HC<sub>5<sub/>N and HC<sub>7<sub/>N. A comparative analysis between the CC and CS results reveals an agreement better than a factor of two for high-magnitude rate coefficients. However, we found that the derivation of approximate HC5N and HC7N rate coefficients from those of HCN and HC<sub>3<sub/>N using a size proportionality relationship, as has been previously done in the literature, leads to an overestimation of the collisional data by up to two orders of magnitude. To assess the sensitivity of cyanopolyyne line intensities to collisional rate coefficients, we compared LTE predictions with various non-LTE models using different rate coefficients. Under the typical physical conditions of cold molecular clouds, the LTE assumption and radiative transfer calculations based on approximate collisional rate coefficients strongly overestimate high-frequency line intensities, while the non-LTE models based on the HC<sub>3<sub/>N collisional rate coefficients as a proxy for HC<sub>5<sub/>N and HC7N remain accurate within 10%. We therefore recommend revisiting the abundance estimates for HC<sub>5<sub/>N and HC<sub>7<sub/>N using the new rate coefficients. For HC<sub>9<sub/>N and HC<sub>11<sub/>N, adopting HC<sub>7<sub/>N collisional data in line modelling is expected to be highly accurate.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"61 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635803","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 : 2025-03-14DOI: 10.1051/0004-6361/202553790
Hedieh Abdollahi, László Molnár, Vázsony Varga
The existence of dynamically young and metal-rich RR Lyrae stars challenges conventional notions of these variable stars. One possible scenario for their formation and evolution is via binary channels involving mass transfer. This study presents the detection of nine fundamental-mode RR Lyrae stars residing in the thin disk of the Milky Way with metallicities higher than [Fe/H] > −1.0 dex and showing proper motion anomalies. Our thin disk classification is based on kinematics and supported by α-element abundances, where possible. We searched for indications of the light-travel time effect (LTTE) in the available literature sources and the TESS photometric data of the stars but found no signs of periodic variations induced by companions within the expected period range. This could be because of a lack of observations as well as sparse measurements and large gaps in the data. We propose a continued search for signs of binarity and a subsequent long-term follow-up of nine targets that satisfy all of our search criteria. Beyond these targets, we also report the detection of slow phase changes in the Blazhko star ST Pic, which could be compatible with the LTTE.
年轻且富含金属的动态天琴座RR星的存在挑战了关于这些变星的传统观念。它们形成和演化的一种可能情况是通过涉及质量转移的双星通道。本研究发现了九颗位于银河系薄盘中的天琴座RR基本模式恒星，它们的金属性高于[Fe/H] > -1.0 dex，并显示出正常运动异常。我们的薄盘分类是以运动学为基础的，并尽可能得到α元素丰度的支持。我们在现有的文献来源和恒星的 TESS 测光数据中寻找光旅行时间效应（LTTE）的迹象，但没有发现伴星在预期周期范围内引起周期性变化的迹象。这可能是由于缺乏观测以及测量数据稀少和数据缺口较大造成的。我们建议继续寻找伴星的迹象，并对符合我们所有搜索标准的九个目标进行后续长期跟踪。除了这些目标之外，我们还报告了在布拉兹科星 ST Pic 中探测到的缓慢相变，这可能与 LTTE 相符。
{"title":"Search for binary-channel metal-rich RR Lyrae candidates","authors":"Hedieh Abdollahi, László Molnár, Vázsony Varga","doi":"10.1051/0004-6361/202553790","DOIUrl":"https://doi.org/10.1051/0004-6361/202553790","url":null,"abstract":"The existence of dynamically young and metal-rich RR Lyrae stars challenges conventional notions of these variable stars. One possible scenario for their formation and evolution is via binary channels involving mass transfer. This study presents the detection of nine fundamental-mode RR Lyrae stars residing in the thin disk of the Milky Way with metallicities higher than [Fe/H] > −1.0 dex and showing proper motion anomalies. Our thin disk classification is based on kinematics and supported by <i>α<i/>-element abundances, where possible. We searched for indications of the light-travel time effect (LTTE) in the available literature sources and the TESS photometric data of the stars but found no signs of periodic variations induced by companions within the expected period range. This could be because of a lack of observations as well as sparse measurements and large gaps in the data. We propose a continued search for signs of binarity and a subsequent long-term follow-up of nine targets that satisfy all of our search criteria. Beyond these targets, we also report the detection of slow phase changes in the Blazhko star ST Pic, which could be compatible with the LTTE.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635781","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 : 2025-03-14DOI: 10.1051/0004-6361/202038068
Matthäus Schulik, Bertram Bitsch, Anders Johansen, Michiel Lambrechts
Dust growth is often indirectly inferred observationally in star-forming environments, is theoretically predicted to produce millimetresized particles in circumstellar discs, and has also acted on the predecessors of the terrestrial meteoritic record. For those reasons, it is believed that young gas giants under formation in protoplanetary discs that have putative circumplanetary discs (CPDs) surrounding them, such as PDS 70c, should contain millimetre-sized particles. We modelled the spectra of a set of CPDs, which we obtained from radiation hydrodynamic simulations at varying Rosseland opacities, κR . The κR from the hydrodynamic simulations are matched with consistent opacity sets of an interstellar-medium-like composition, but grown to larger sizes. Our high κR hydro data nominally corresponds to 10 µm-sized particles, and our low κR cases correspond to millimetre-sized particles. We investigated the resulting broad spectral features at first, while keeping the overall optical depth in the planetary envelope constant. Dust growth to size distributions dominated by millimetre particles generally results in broad, featureless spectra with black-body like slopes in the far-infrared, while size distributions dominated by small dust develop steeper slopes in the far-infrared and maintain some features stemming from individual minerals. We find that significant dust growth from microns to millimetres can explain the broad features of the PDS 70c data, when upscaling the dust masses from our simulations by one hundred times. Furthermore, our results indicate that the spectral range of 30–500 µm is an ideal hunting ground for broadband features arising from the CPD, but that longer wavelengths observed with ALMA can also be used for massive CPDs.
{"title":"The influence of dust growth on the observational properties of circumplanetary discs","authors":"Matthäus Schulik, Bertram Bitsch, Anders Johansen, Michiel Lambrechts","doi":"10.1051/0004-6361/202038068","DOIUrl":"https://doi.org/10.1051/0004-6361/202038068","url":null,"abstract":"Dust growth is often indirectly inferred observationally in star-forming environments, is theoretically predicted to produce millimetresized particles in circumstellar discs, and has also acted on the predecessors of the terrestrial meteoritic record. For those reasons, it is believed that young gas giants under formation in protoplanetary discs that have putative circumplanetary discs (CPDs) surrounding them, such as PDS 70c, should contain millimetre-sized particles. We modelled the spectra of a set of CPDs, which we obtained from radiation hydrodynamic simulations at varying Rosseland opacities, <i>κ<i/><sub>R<sub/> . The <i>κ<i/><sub>R<sub/> from the hydrodynamic simulations are matched with consistent opacity sets of an interstellar-medium-like composition, but grown to larger sizes. Our high <i>κ<i/><sub>R<sub/> hydro data nominally corresponds to 10 µm-sized particles, and our low <i>κ<i/><sub>R<sub/> cases correspond to millimetre-sized particles. We investigated the resulting broad spectral features at first, while keeping the overall optical depth in the planetary envelope constant. Dust growth to size distributions dominated by millimetre particles generally results in broad, featureless spectra with black-body like slopes in the far-infrared, while size distributions dominated by small dust develop steeper slopes in the far-infrared and maintain some features stemming from individual minerals. We find that significant dust growth from microns to millimetres can explain the broad features of the PDS 70c data, when upscaling the dust masses from our simulations by one hundred times. Furthermore, our results indicate that the spectral range of 30–500 µm is an ideal hunting ground for broadband features arising from the CPD, but that longer wavelengths observed with ALMA can also be used for massive CPDs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"24 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635802","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 : 2025-03-14DOI: 10.1051/0004-6361/202452447
K. Abe, S. Abe, A. Abhishek, F. Acero, A. Aguasca-Cabot, I. Agudo, C. Alispach, N. Alvarez Crespo, D. Ambrosino, L. A. Antonelli, C. Aramo, A. Arbet-Engels, C. Arcaro, K. Asano, P. Aubert, A. Baktash, M. Balbo, A. Bamba, A. Baquero Larriva, U. Barres de Almeida, J. A. Barrio, L. Barrios Jiménez, I. Batkovic, J. Baxter, J. Becerra González, E. Bernardini, J. Bernete, A. Berti, I. Bezshyiko, P. Bhattacharjee, C. Bigongiari, E. Bissaldi, O. Blanch, G. Bonnoli, P. Bordas, G. Borkowski, G. Brunelli, A. Bulgarelli, M. Bunse, I. Burelli, L. Burmistrov, M. Buscemi, M. Cardillo, S. Caroff, A. Carosi, M. S. Carrasco, F. Cassol, N. Castrejón, D. Cerasole, G. Ceribella, Y. Chai, K. Cheng, A. Chiavassa, M. Chikawa, G. Chon, L. Chytka, G. M. Cicciari, A. Cifuentes, J. L. Contreras, J. Cortina, H. Costantini, P. Da Vela, M. Dalchenko, F. Dazzi, A. De Angelis, M. de Bony de Lavergne, B. De Lotto, R. de Menezes, R. Del Burgo, L. Del Peral, C. Delgado, J. Delgado Mengual, D. della Volpe, M. Dellaiera, A. Di Piano, F. Di Pierro, R. Di Tria, L. Di Venere, C. Díaz, R. M. Dominik, D. Dominis Prester, A. Donini, D. Dore, D. Dorner, M. Doro, L. Eisenberger, D. Elsässer, G. Emery, J. Escudero, V. Fallah Ramazani, F. Ferrarotto, A. Fiasson, L. Foffano, L. Freixas Coromina, S. Fröse, Y. Fukazawa, R. Garcia López, C. Gasbarra, D. Gasparrini, D. Geyer, J. Giesbrecht Paiva, N. Giglietto, F. Giordano, P. Gliwny, N. Godinovic, R. Grau, D. Green, J. Green, S. Gunji, P. Günther, J. Hackfeld, D. Hadasch, A. Hahn, T. Hassan, K. Hayashi, L. Heckmann, M. Heller, J. Herrera Llorente, K. Hirotani, D. Hoffmann, D. Horns, J. Houles, M. Hrabovsky, D. Hrupec, D. Hui, M. Iarlori, R. Imazawa, T. Inada, Y. Inome, S. Inoue, K. Ioka, M. Iori, A. Iuliano, J. Jahanvi, I. Jimenez Martinez, J. Jimenez Quiles, J. Jurysek, M. Kagaya, O. Kalashev, V. Karas, H. Katagiri, J. Kataoka, D. Kerszberg, Y. Kobayashi, K. Kohri, A. Kong, H. Kubo, J. Kushida, B. Lacave, M. Lainez, G. Lamanna, A. Lamastra, L. Lemoigne, M. Linhoff, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, A. Lorini, J. Lozano Bahilo, H. Luciani, P. L. Luque-Escamilla, P. Majumdar, M. Makariev, M. Mallamaci, D. Mandat, M. Manganaro, G. Manicò, K. Mannheim, S. Marchesi, M. Mariotti, P. Marquez, G. Marsella, J. Martí, O. Martinez, G. Martínez, M. Martínez, A. Mas-Aguilar, G. Maurin, D. Mazin, J. Méndez-Gallego, S. Menon, E. Mestre Guillen, S. Micanovic, D. Miceli, T. Miener, J. M. Miranda, R. Mirzoyan, T. Mizuno, M. Molero Gonzalez, E. Molina, T. Montaruli, A. Moralejo, D. Morcuende, A. Morselli, V. Moya, H. Muraishi, S. Nagataki, T. Nakamori, A. Neronov, L. Nickel, D. Nieto Castaño, M. Nievas Rosillo, L. Nikolic, K. Nishijima, K. Noda, D. Nosek, V. Novotny, S. Nozaki, M. Ohishi, Y. Ohtani, T. Oka, A. Okumura, R. Orito, J. Otero-Santos, P. Ottanelli, E. Owen, M. Palatiello, D. Paneque, F. R. Pantaleo, R. Paoletti, J. M. Paredes, M. Pech, M. Pecimotika, M. Peresano, F. Pfeifle, E. Pietropaolo, M. Pihet, G. Pirola, C. Plard, F. Podobnik, E. Pons, E. Prandini, M. Prouza, S. Rainò, R. Rando, W. Rhode, M. Ribó, C. Righi, V. Rizi, G. Rodriguez Fernandez, M. D. Rodríguez Frías, P. Romano, A. Ruina, E. Ruiz-Velasco, T. Saito, S. Sakurai, D. A. Sanchez, H. Sano, T. Šarić, Y. Sato, F. G. Saturni, V. Savchenko, F. Schiavone, B. Schleicher, F. Schmuckermaier, J. L. Schubert, F. Schussler, T. Schweizer, M. Seglar Arroyo, T. Siegert, A. Simongini, J. Sitarek, V. Sliusar, A. Stamerra, J. Strišković, M. Strzys, Y. Suda, A. Sunny, H. Tajima, H. Takahashi, M. Takahashi, J. Takata, R. Takeishi, P. H. T. Tam, S. J. Tanaka, D. Tateishi, T. Tavernier, P. Temnikov, Y. Terada, K. Terauchi, T. Terzic, M. Teshima, M. Tluczykont, C. Toennis, F. Tokanai, D. F. Torres, P. Travnicek, A. Tutone, M. Vacula, J. van Scherpenberg, M. Vázquez Acosta, S. Ventura, S. Vercellone, G. Verna, I. Viale, A. Vigliano, C. F. Vigorito, E. Visentin, V. Vitale, V. Voitsekhovskyi, G. Voutsinas, I. Vovk, T. Vuillaume, R. Walter, L. Wan, M. Will, J. Wójtowicz, T. Yamamoto, R. Yamazaki, Y. Yao, P. K. H. Yeung, T. Yoshida, T. Yoshikoshi, W. Zhang, N. Zywucka
Context. The recurrent nova RS Ophiuchi (RS Oph) underwent a thermonuclear eruption in August 2021. In this event, RS Oph was detected by the High Energy Stereoscopic System (H.E.S.S.), the Major Atmospheric Gamma Imaging Cherenkov (MAGIC), and the first Large-Sized Telescope (LST-1) of the future Cherenkov Telescope Array Observatory (CTAO) at very-high gamma-ray energies above 100 GeV. This means that novae are a new class of very-high-energy (VHE) gamma-ray emitters.Aims. We report the analysis of the RS Oph observations with LST-1. We constrain the particle population that causes the observed emission in hadronic and leptonic scenarios. Additionally, we study the prospects of detecting further novae using LST-1 and the upcoming LST array of CTAO-North.Methods. We conducted target-of-opportunity observations with LST-1 from the first day of this nova event. The data were analysed in the framework of cta-lstchain and Gammapy, the official CTAO-LST reconstruction and analysis packages. One-zone hadronic and leptonic models were considered to model the gamma-ray emission of RS Oph using the spectral information from Fermi-LAT and LST-1, together with public data from the MAGIC and H.E.S.S. telescopes.Results. RS Oph was detected at 6.6σ with LST-1 in the first 6.35 hours of observations following the eruption. The hadronic scenario is preferred over the leptonic scenario considering a proton energy spectrum with a power-law model with an exponential cutoff whose position increases from (0.26 ± 0.08) TeV on day 1 up to (1.6 ± 0.6) TeV on day 4 after the eruption. The deep sensitivity and low energy threshold of the LST-1/LST array will allow us to detect faint novae and increase their discovery rate.
{"title":"Detection of RS Oph with LST-1 and modelling of its HE/VHE gamma-ray emission","authors":"K. Abe, S. Abe, A. Abhishek, F. Acero, A. Aguasca-Cabot, I. Agudo, C. Alispach, N. Alvarez Crespo, D. Ambrosino, L. A. Antonelli, C. Aramo, A. Arbet-Engels, C. Arcaro, K. Asano, P. Aubert, A. Baktash, M. Balbo, A. Bamba, A. Baquero Larriva, U. Barres de Almeida, J. A. Barrio, L. Barrios Jiménez, I. Batkovic, J. Baxter, J. Becerra González, E. Bernardini, J. Bernete, A. Berti, I. Bezshyiko, P. Bhattacharjee, C. Bigongiari, E. Bissaldi, O. Blanch, G. Bonnoli, P. Bordas, G. Borkowski, G. Brunelli, A. Bulgarelli, M. Bunse, I. Burelli, L. Burmistrov, M. Buscemi, M. Cardillo, S. Caroff, A. Carosi, M. S. Carrasco, F. Cassol, N. Castrejón, D. Cerasole, G. Ceribella, Y. Chai, K. Cheng, A. Chiavassa, M. Chikawa, G. Chon, L. Chytka, G. M. Cicciari, A. Cifuentes, J. L. Contreras, J. Cortina, H. Costantini, P. Da Vela, M. Dalchenko, F. Dazzi, A. De Angelis, M. de Bony de Lavergne, B. De Lotto, R. de Menezes, R. Del Burgo, L. Del Peral, C. Delgado, J. Delgado Mengual, D. della Volpe, M. Dellaiera, A. Di Piano, F. Di Pierro, R. Di Tria, L. Di Venere, C. Díaz, R. M. Dominik, D. Dominis Prester, A. Donini, D. Dore, D. Dorner, M. Doro, L. Eisenberger, D. Elsässer, G. Emery, J. Escudero, V. Fallah Ramazani, F. Ferrarotto, A. Fiasson, L. Foffano, L. Freixas Coromina, S. Fröse, Y. Fukazawa, R. Garcia López, C. Gasbarra, D. Gasparrini, D. Geyer, J. Giesbrecht Paiva, N. Giglietto, F. Giordano, P. Gliwny, N. Godinovic, R. Grau, D. Green, J. Green, S. Gunji, P. Günther, J. Hackfeld, D. Hadasch, A. Hahn, T. Hassan, K. Hayashi, L. Heckmann, M. Heller, J. Herrera Llorente, K. Hirotani, D. Hoffmann, D. Horns, J. Houles, M. Hrabovsky, D. Hrupec, D. Hui, M. Iarlori, R. Imazawa, T. Inada, Y. Inome, S. Inoue, K. Ioka, M. Iori, A. Iuliano, J. Jahanvi, I. Jimenez Martinez, J. Jimenez Quiles, J. Jurysek, M. Kagaya, O. Kalashev, V. Karas, H. Katagiri, J. Kataoka, D. Kerszberg, Y. Kobayashi, K. Kohri, A. Kong, H. Kubo, J. Kushida, B. Lacave, M. Lainez, G. Lamanna, A. Lamastra, L. Lemoigne, M. Linhoff, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, A. Lorini, J. Lozano Bahilo, H. Luciani, P. L. Luque-Escamilla, P. Majumdar, M. Makariev, M. Mallamaci, D. Mandat, M. Manganaro, G. Manicò, K. Mannheim, S. Marchesi, M. Mariotti, P. Marquez, G. Marsella, J. Martí, O. Martinez, G. Martínez, M. Martínez, A. Mas-Aguilar, G. Maurin, D. Mazin, J. Méndez-Gallego, S. Menon, E. Mestre Guillen, S. Micanovic, D. Miceli, T. Miener, J. M. Miranda, R. Mirzoyan, T. Mizuno, M. Molero Gonzalez, E. Molina, T. Montaruli, A. Moralejo, D. Morcuende, A. Morselli, V. Moya, H. Muraishi, S. Nagataki, T. Nakamori, A. Neronov, L. Nickel, D. Nieto Castaño, M. Nievas Rosillo, L. Nikolic, K. Nishijima, K. Noda, D. Nosek, V. Novotny, S. Nozaki, M. Ohishi, Y. Ohtani, T. Oka, A. Okumura, R. Orito, J. Otero-Santos, P. Ottanelli, E. Owen, M. Palatiello, D. Paneque, F. R. Pantaleo, R. Paoletti, J. M. Paredes, M. Pech, M. Pecimotika, M. Peresano, F. Pfeifle, E. Pietropaolo, M. Pihet, G. Pirola, C. Plard, F. Podobnik, E. Pons, E. Prandini, M. Prouza, S. Rainò, R. Rando, W. Rhode, M. Ribó, C. Righi, V. Rizi, G. Rodriguez Fernandez, M. D. Rodríguez Frías, P. Romano, A. Ruina, E. Ruiz-Velasco, T. Saito, S. Sakurai, D. A. Sanchez, H. Sano, T. Šarić, Y. Sato, F. G. Saturni, V. Savchenko, F. Schiavone, B. Schleicher, F. Schmuckermaier, J. L. Schubert, F. Schussler, T. Schweizer, M. Seglar Arroyo, T. Siegert, A. Simongini, J. Sitarek, V. Sliusar, A. Stamerra, J. Strišković, M. Strzys, Y. Suda, A. Sunny, H. Tajima, H. Takahashi, M. Takahashi, J. Takata, R. Takeishi, P. H. T. Tam, S. J. Tanaka, D. Tateishi, T. Tavernier, P. Temnikov, Y. Terada, K. Terauchi, T. Terzic, M. Teshima, M. Tluczykont, C. Toennis, F. Tokanai, D. F. Torres, P. Travnicek, A. Tutone, M. Vacula, J. van Scherpenberg, M. Vázquez Acosta, S. Ventura, S. Vercellone, G. Verna, I. Viale, A. Vigliano, C. F. Vigorito, E. Visentin, V. Vitale, V. Voitsekhovskyi, G. Voutsinas, I. Vovk, T. Vuillaume, R. Walter, L. Wan, M. Will, J. Wójtowicz, T. Yamamoto, R. Yamazaki, Y. Yao, P. K. H. Yeung, T. Yoshida, T. Yoshikoshi, W. Zhang, N. Zywucka","doi":"10.1051/0004-6361/202452447","DOIUrl":"https://doi.org/10.1051/0004-6361/202452447","url":null,"abstract":"<i>Context.<i/> The recurrent nova RS Ophiuchi (RS Oph) underwent a thermonuclear eruption in August 2021. In this event, RS Oph was detected by the High Energy Stereoscopic System (H.E.S.S.), the Major Atmospheric Gamma Imaging Cherenkov (MAGIC), and the first Large-Sized Telescope (LST-1) of the future Cherenkov Telescope Array Observatory (CTAO) at very-high gamma-ray energies above 100 GeV. This means that novae are a new class of very-high-energy (VHE) gamma-ray emitters.<i>Aims.<i/> We report the analysis of the RS Oph observations with LST-1. We constrain the particle population that causes the observed emission in hadronic and leptonic scenarios. Additionally, we study the prospects of detecting further novae using LST-1 and the upcoming LST array of CTAO-North.<i>Methods.<i/> We conducted target-of-opportunity observations with LST-1 from the first day of this nova event. The data were analysed in the framework of cta-lstchain and Gammapy, the official CTAO-LST reconstruction and analysis packages. One-zone hadronic and leptonic models were considered to model the gamma-ray emission of RS Oph using the spectral information from <i>Fermi<i/>-LAT and LST-1, together with public data from the MAGIC and H.E.S.S. telescopes.<i>Results.<i/> RS Oph was detected at 6.6<i>σ<i/> with LST-1 in the first 6.35 hours of observations following the eruption. The hadronic scenario is preferred over the leptonic scenario considering a proton energy spectrum with a power-law model with an exponential cutoff whose position increases from (0.26 ± 0.08) TeV on day 1 up to (1.6 ± 0.6) TeV on day 4 after the eruption. The deep sensitivity and low energy threshold of the LST-1/LST array will allow us to detect faint novae and increase their discovery rate.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"69 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635795","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 : 2025-03-14DOI: 10.1051/0004-6361/202453349
Dominik Ostertag, Mario Flock
<i>Context.<i/> The process of planet formation in protoplanetary disks and the drivers behind the formation of their seeds are still major unknowns. It is a broadly accepted theory that multiple processes can trap dusty material in radially narrow rings or vortex-like structures, preventing the dust from drifting inwards. However, it is still necessary to identify the relevant process behind the clumping of this dusty material, which can result in its collapse under gravity. One promising candidate is the streaming instability arising from the aerodynamic interaction between dust and gas once their densities are similar.<i>Aims.<i/> We used a global disk model based on recent observational constraints to investigate the capacity of the streaming instability to form dust clumps, which would then undergo gravitational collapse. Furthermore, our goal is to verify the observability of the produced structures using Atacama Large Millimeter/submillimeter Array (ALMA) or Next Generation Very Large Array (ngVLA).<i>Methods.<i/> For the first time, we present global 2D (<i>R<i/>, <i>z<i/>) hydrodynamic simulations using the FARGO3D code, where the dust is treated as a pressureless fluid. The disk model assumes stratification, realistic boundary conditions, and meaningful resolution to resolve the fast-growing modes. We chose two values for the total dust-to-gas mass ratio <i>Z<i/> = 0.01 and <i>Z<i/> = 0.02. We then compared the maximum clump density to the local Hill density and computed the optical depth of the dust disk.<i>Results.<i/> With a dust-to-gas mass ratio of <i>Z<i/> = 0.01, we confirm previous streaming instability simulations, which did not indicate any ability to form strong concentrations of dust clumps. With <i>Z<i/> = 0.02, dense clumps form within 20 orbits; however, they reached only 30% of the Hill density, even when applying disk parameters from the massive protoplanetary disks GM Aur, HD 163296, IM Lup, MWC 480, and TW Hya, which all share astonishingly similar surface density profiles.<i>Conclusions.<i/> Our results show that clumping by the streaming instability to trigger self-gravity is less efficient than previously thought, especially when more realistic density profiles are applied. By extrapolating our results, we estimated the gravitational collapse of concentrated pebbles earliest at 480 orbits; whereas for more frequent, less massive, or more compact disks, this time frame can reach up to 1000 orbits. Our results predict that substructures caused by streaming instability can vary between optical thin and optical thick at ALMA Band 1 wavelength for less massive disks. However, the average clump separation is 0.03 au at 10 au distance to the star, which is far too small to be observable with ALMA and even ngVLA. For the currently observed disks and best-fit surface density profiles, we predict efficient planetesimal formation outside 10 au, where the ratio of Hill- and gas midplane density is sufficiently small. Our resul
背景原行星盘中行星的形成过程及其种子形成背后的驱动因素仍是一大未知数。一个被广泛接受的理论是，多种过程可以将尘埃物质困在径向狭窄的环状或漩涡状结构中，阻止尘埃向内漂移。然而，仍有必要确定这些尘埃物质团聚背后的相关过程，这可能会导致它们在重力作用下坍塌。尘埃和气体密度相近时，尘埃和气体之间的空气动力相互作用会产生流不稳定性，这是一个很有希望的候选过程。我们使用了一个基于最新观测约束的全球圆盘模型，来研究流不稳定性形成尘埃团块的能力，这些尘埃团块随后会发生引力坍缩。此外，我们的目标是利用阿塔卡马大型毫米波/亚毫米波阵列（ALMA）或下一代甚大阵列（ngVLA）验证所产生结构的可观测性。我们首次使用 FARGO3D 代码进行了全球二维（R，z）流体力学模拟，其中尘埃被视为无压流体。该圆盘模型假定存在分层现象、现实的边界条件以及能够解析快速增长模式的有效分辨率。我们选择了尘气总质量比 Z = 0.01 和 Z = 0.02 这两个值。然后，我们将最大团块密度与当地希尔密度进行了比较，并计算了尘埃盘的光学深度。当尘埃与气体的质量比为 Z = 0.01 时，我们证实了之前的流不稳定性模拟，这些模拟并没有表明尘埃团块能够形成强大的聚集。当 Z = 0.02 时，在 20 个轨道内形成了致密的尘块；然而，即使采用大质量原行星盘 GM Aur、HD 163296、IM Lup、MWC 480 和 TW Hya 的盘参数，它们也只达到了希尔密度的 30%，而这些原行星盘都有着惊人相似的表面密度曲线。我们的研究结果表明，通过流不稳定性来引发自引力的团聚效应没有以前想象的那么有效，尤其是在应用了更现实的密度剖面时。通过推断我们的结果，我们估计集中卵石的引力坍缩最早发生在 480 个轨道上；而对于更频繁、质量更小或更紧凑的磁盘，这个时间范围可以达到 1000 个轨道。我们的结果预测，对于质量较小的磁盘，在 ALMA 波段 1 波长处，由流变不稳定性引起的子结构可以在光学薄和光学厚之间变化。然而，在距离恒星 10 au 的距离上，星团的平均分离度为 0.03 au，这个距离太小，ALMA 甚至 ngVLA 都无法观测到。对于目前观测到的星盘和最佳拟合表面密度剖面，我们预测在10au以外的地方会有效地形成行星，因为那里的希尔密度和气体中面密度之比足够小。我们的结果表明，即使对于大质量的II类星盘，尘埃浓度也可以在480-1000个轨道内达到临界希尔密度，根据径向位置的不同，相当于几万年或几十万年。
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