Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202450745
T. Callingham, Amina Helmi
In the solar neighbourhood, only $ of stars in the survey have a line-of-sight velocity ( contained within the RVS catalogue. These limitations restrict conventional dynamical analysis, such as finding and studying substructures in the stellar halo. We aim to present and test a method to infer a probability density function (PDF) for the missing of a star with 5D information within $2.5 kpc $. This technique also allows us to infer the probability that a 5D star is associated with the Milky Way's stellar Disc or the stellar Halo, which can be further decomposed into known stellar substructures. We use stars from the DR3 RVS catalogue to describe the local orbital structure in action space. The method is tested on a 6D DR3 RVS sample and a 6D sample crossmatched to ground-based spectroscopic surveys, stripped of their true The stars predicted membership probabilities, and inferred structure properties are then compared to the true 6D equivalents, allowing the method's accuracy and limitations to be studied in detail. Our predicted PDFs are statistically consistent with the true with accurate uncertainties. We find that the of Disc stars can be well-constrained, with a median uncertainty of $26 Halo stars are typically less well-constrained with a median uncertainty of $72 but those found likely to belong to Halo substructures can be better constrained. The dynamical properties of the total sample and subgroups, such as distributions of integrals of motion and velocities, are also accurately recovered. The group membership probabilities are statistically consistent with our initial labelling, allowing high-quality sets to be selected from 5D samples by choosing a trade-off between higher expected purity and decreasing expected completeness. We have developed a method to estimate 5D stars' and substructure membership. We have demonstrated that it is possible to find likely substructure members and statistically infer the group's dynamical properties.
{"title":"Filling in the blanks. A method to infer the substructure membership and dynamics of 5D stars","authors":"T. Callingham, Amina Helmi","doi":"10.1051/0004-6361/202450745","DOIUrl":"https://doi.org/10.1051/0004-6361/202450745","url":null,"abstract":"In the solar neighbourhood, only $ of stars in the survey have a line-of-sight velocity ( contained within the RVS catalogue. These limitations restrict conventional dynamical analysis, such as finding and studying substructures in the stellar halo. We aim to present and test a method to infer a probability density function (PDF) for the missing of a star with 5D information within $2.5 kpc $.\u0000 This technique also allows us to infer the probability that a 5D star is associated with the Milky Way's\u0000 stellar Disc or the stellar Halo, which can be further decomposed into known stellar substructures. We use stars from the DR3 RVS catalogue to describe the local orbital structure in action space.\u0000 The method is tested on a 6D DR3 RVS sample and a 6D sample crossmatched to ground-based spectroscopic surveys,\u0000 stripped of their true The stars predicted membership probabilities, and inferred structure properties are then compared to the true 6D equivalents, allowing the method's accuracy and limitations to be studied in detail. Our predicted PDFs are statistically consistent with the true with accurate uncertainties.\u0000 We find that the of Disc stars can be well-constrained, with a median uncertainty of $26 Halo stars are typically less well-constrained with a median uncertainty of $72 but those found likely to belong to Halo substructures can be better constrained. The dynamical properties of the total sample and subgroups, such as distributions of integrals of motion and velocities, are also accurately recovered. The group membership probabilities are statistically consistent with our initial labelling, allowing high-quality sets to be selected from 5D samples by choosing a trade-off between higher expected purity and decreasing expected completeness. We have developed a method to estimate 5D stars' and substructure membership.\u0000 We have demonstrated that it is possible to find likely substructure members\u0000 and statistically infer the group's dynamical properties.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"40 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449701
I. Chataigner, F. Pauzat, O. Tasseau, Y. Ellinger, J. Guillemin
Most of the molecules identified in the interstellar medium (ISM) are organic compounds and more than 50 have one isomer or more. Statistically, the most stable isomer of a given chemical formula is the most abundant. This occurrence is verified up to sim 90 of the detected species leading to the so-called minimum energy principle (MEP). Our main objective is to increase the list of the 14 bis-nitrogen species already detected. We focus on ten C$_ x $H$_ y $N$_ z $ isomer families with x=(1,2,3), y=(0,2,4,6,8), z=2. To this end, we look for a reliable and economic way to provide energy scales. We employed standard quantum chemistry methods to determine the relative position of each isomer on the energy scales of each family. We systematically applied density functional theory (DFT) treatments using basis sets of increasing size and quality (6-311++G** and cc-pVQZ). When reasonably feasible, we then performed high-level coupled cluster calculations (CCSD) using the same basis sets to refine relative energies. All 14 bis-nitrogen species already identified in the ISM indeed satisfy the MEP. We determine the relative thermodynamic stability of the isomers with a C$_ x $H$_ y $N$_ $ formula of each of the ten sets (94 compounds altogether), and hightlight those that are potentially detectable. By increasing the number of carbon atoms, we find 15 compounds that are by far the most stable candidates. We confirm that, within the limits of thermodynamics, MEP is an efficient and easily applicable tool for identifying the isomers in a given series that have a greater probability of being detected. Computationally, the combination “B3LYP/cc-pVQZ” provides a suitable compromise for determining energy differences and dipole moments. Clearly, the isomers containing the NCN sequence should be prioritized over those with CNN in future observation campaigns.
在星际介质（ISM）中发现的大多数分子都是有机化合物，其中 50 多种分子有一种或多种同分异构体。据统计，特定化学式中最稳定的异构体含量最高。根据所谓的 "最小能量原则"（MEP），这种情况在模拟 90 种被探测到的物质中得到了验证。我们的主要目标是增加已探测到的 14 种双氮物质。我们的重点是十个 C$_ x $H$_ y $N$_ z $ 异构体家族，x=(1,2,3)，y=(0,2,4,6,8)，z=2。为此，我们寻找一种可靠而经济的方法来提供能量标度。我们采用标准的量子化学方法来确定每个异构体在每个族的能级上的相对位置。我们系统地应用了密度泛函理论（DFT）处理方法，并使用了规模和质量不断增加的基集（6-311++G** 和 cc-pVQZ）。在合理可行的情况下，我们使用相同的基集进行了高水平耦合簇计算（CCSD），以完善相对能量。在 ISM 中已经确定的所有 14 种双氮物质都确实满足 MEP 的要求。我们确定了十组化合物（共 94 个化合物）中每一组的 C$_ x $H$_ y $N$_ $ 式的异构体的相对热力学稳定性，并突出了那些有可能被探测到的化合物。通过增加碳原子数，我们发现 15 种化合物是迄今为止最稳定的候选化合物。我们证实，在热力学的限制范围内，MEP 是一种高效且易于应用的工具，可用于识别特定系列中被检测到概率较大的异构体。在计算上，"B3LYP/cc-pVQZ "组合为确定能量差和偶极矩提供了一个合适的折衷方案。显然，在未来的观测活动中，含有 NCN 序列的同分异构体应优先于含有 CNN 序列的同分异构体。
{"title":"Thermodynamical stability of [CNN and NCN] sequences as indication of most abundant structures in the ISM","authors":"I. Chataigner, F. Pauzat, O. Tasseau, Y. Ellinger, J. Guillemin","doi":"10.1051/0004-6361/202449701","DOIUrl":"https://doi.org/10.1051/0004-6361/202449701","url":null,"abstract":"Most of the molecules identified in the interstellar medium (ISM) are organic compounds and more than 50 have one isomer or more. Statistically, the most stable isomer of a given chemical formula is the most abundant. This occurrence is verified up to sim 90 of the detected species leading to the so-called minimum energy principle (MEP). Our main objective is to increase the list of the 14 bis-nitrogen species already detected. We focus on ten C$_ x $H$_ y $N$_ z $ isomer families with x=(1,2,3), y=(0,2,4,6,8), z=2. To this end, we look for a reliable and economic way to provide energy scales. We employed standard quantum chemistry methods to determine the relative position of each isomer on the energy scales of each family. We systematically applied density functional theory (DFT) treatments using basis sets of increasing size and quality (6-311++G** and cc-pVQZ). When reasonably feasible, we then performed high-level coupled cluster calculations (CCSD) using the same basis sets to refine relative energies. All 14 bis-nitrogen species already identified in the ISM indeed satisfy the MEP. We determine the relative thermodynamic stability of the isomers with a C$_ x $H$_ y $N$_ $ formula of each of the ten sets (94 compounds altogether), and hightlight those that are potentially detectable. By increasing the number of carbon atoms, we find 15 compounds that are by far the most stable candidates. We confirm that, within the limits of thermodynamics, MEP is an efficient and easily applicable tool for identifying the isomers in a given series that have a greater probability of being detected. Computationally, the combination “B3LYP/cc-pVQZ” provides a suitable compromise for determining energy differences and dipole moments. Clearly, the isomers containing the NCN sequence should be prioritized over those with CNN in future observation campaigns.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"13 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141808982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202450229
K. Belczynski, Christine Done, S. Hagen, J. Lasota, K. Sen
Black-hole (BH) high-mass X-ray binary (HMXB) systems are likely to be the progenitors of BH-BH mergers detected in gravitational waves by LIGO/Virgo/KAGRA (LVK). Yet merging BHs reach higher masses ($ than BHs in HMXBs ($ and typically exhibit lower spins BH 0.25$ with a larger values tail) than what is often claimed for BHs in HMXBs BH 0.9$). This could suggest that these two classes of systems belong to different populations, but here we show that this may not necessarily be the case. The difference in masses is easily explained as the known HMXB-BHs are in galaxies with relatively high metallicity, so their progenitor stars are subject to strong mass loss from winds, leading to relatively low-mass BH at core collapse. Conversely, LVK is also able to detect BHs from low-metallicity galaxies that are known to naturally produce more massive stellar-origin BHs. However, the difference in spin is more difficult to explain. Models with efficient angular momentum transport in stellar interiors produce slowly spinning progenitors for both LVK and HMXB BHs. Known HMXBs have orbital periods that are too long for efficient tidal spin-up and are also unlikely to have undergone significant accretion spin-up. Instead, we show that the derived value of the BH spin depends strongly on how the HMXB accretion disc emission is modelled. We argue that since Cyg X-1 is never observed to be in a soft spectral state, the appropriate spectral models must take into account the Comptonisation of the disc photosphere. We show that such models are consistent with low spin values, namely: $a_ BH This was recently confirmed by other teams for both Cyg X-1 and LMC X-1 and here we show this is also the case for M33 X-7. We conclude that all known HMXB BHs can exhibit a low spin in accordance with the results of stellar evolution models. Hence, the observations presented in this work are consistent with the scenario where LVK BHs and HMXB BHs belong to the same population.
{"title":"Common origin for black holes in both high mass X-ray binaries and gravitational-wave sources","authors":"K. Belczynski, Christine Done, S. Hagen, J. Lasota, K. Sen","doi":"10.1051/0004-6361/202450229","DOIUrl":"https://doi.org/10.1051/0004-6361/202450229","url":null,"abstract":"Black-hole (BH) high-mass X-ray binary (HMXB) systems are likely to be the progenitors of BH-BH mergers detected in gravitational waves by LIGO/Virgo/KAGRA (LVK). Yet merging BHs reach higher masses ($ than BHs in HMXBs ($ and typically exhibit lower spins BH 0.25$ with a larger values tail) than what is often claimed for BHs in HMXBs BH 0.9$). This could suggest that these two classes of systems belong to different populations, but here we show that this may not necessarily be the case. The difference in masses is easily explained as the known HMXB-BHs are in galaxies with relatively high metallicity, so their progenitor stars are subject to strong mass loss from winds, leading to relatively low-mass BH at core collapse. Conversely, LVK is also able to detect BHs from low-metallicity galaxies that are known to naturally produce more massive stellar-origin BHs. However, the difference in spin is more difficult to explain. Models with efficient angular momentum transport in stellar interiors produce slowly spinning progenitors for both LVK and HMXB BHs. Known HMXBs have orbital periods that are too long for efficient tidal spin-up and are also unlikely to have undergone significant accretion spin-up. Instead, we show that the derived value of the BH spin depends strongly on how the HMXB accretion disc emission is modelled. We argue that since Cyg X-1 is never observed to be in a soft spectral state, the appropriate spectral models must take into account the Comptonisation of the disc photosphere. We show that such models are consistent with low spin values, namely: $a_ BH This was recently confirmed by other teams for both Cyg X-1 and LMC X-1 and here we show this is also the case for M33 X-7. We conclude that all known HMXB BHs can exhibit a low spin in accordance with the results of stellar evolution models. Hence, the observations presented in this work are consistent with the scenario where LVK BHs and HMXB BHs belong to the same population.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"5 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202450738
Bikramaditya Mandal, M. Żółtowski, Martin Cordiner, Francois Lique, D. Babikov
The goal is to develop a database of rate coefficients for rotational state-to-state transitions in H$_ $O + H$_ $O collisions that is suitable for the modeling of energy transfer in nonequilibrium conditions, in which the distribution of rotational states of H$_ $O deviates from local thermodynamic equilibrium. A two-temperature model was employed that assumed that although there is no equilibrium between all possible degrees of freedom in the system, the translational and rotational degrees of freedom can be expected to achieve their own equilibria independently, and that they can be approximately characterized by Boltzmann distributions at two different temperatures, $T_ kin $ and $T_ rot Upon introducing our new parameterization of the collisional rates, taking into account their dependence on both $T_ kin $ and $T_ rot $, we find a change of up to 20 in the H$_ $O rotational level populations for both ortho and para-H$_ $O for the part of the cometary coma where the nonequilibrium regime occurs.
{"title":"Rotational state-to-state transition rate coefficients for H2O + H2O collisions at nonequilibrium conditions","authors":"Bikramaditya Mandal, M. Żółtowski, Martin Cordiner, Francois Lique, D. Babikov","doi":"10.1051/0004-6361/202450738","DOIUrl":"https://doi.org/10.1051/0004-6361/202450738","url":null,"abstract":"The goal is to develop a database of rate coefficients for rotational state-to-state transitions in H$_ $O + H$_ $O collisions that is suitable for the modeling of energy transfer in nonequilibrium conditions, in which the distribution of rotational states of H$_ $O deviates from local thermodynamic equilibrium. A two-temperature model was employed that assumed that although there is no equilibrium between all possible degrees of freedom in the system, the translational and rotational degrees of freedom can be expected to achieve their own equilibria independently, and that they can be approximately characterized by Boltzmann distributions at two different temperatures, $T_ kin $ and $T_ rot Upon introducing our new parameterization of the collisional rates, taking into account their dependence on both $T_ kin $ and $T_ rot $, we find a change of up to 20 in the H$_ $O rotational level populations for both ortho and para-H$_ $O for the part of the cometary coma where the nonequilibrium regime occurs.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"49 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449708
D. Porquet, J. Reeves, S. Hagen, A. Lobban, V. Braito, N. Grosso, F. Marin
ESO 141-G55 is a nearby X-ray bright broad-line Seyfert,1 (BLS1) that has been classified as a bare active galactic nucleus (AGN) due to a lack of warm absorption along its line of sight, providing an unhampered view into its disc-corona system. We aim to probe its disc-corona system thanks to the first simultaneous XMM-Newton and NuSTAR observation obtained October 1--2, 2022. We carried out an X-ray broadband spectral analysis to determine the dominant process(es) at work as well as a spectral energy distribution (SED) analysis to determine the disc-corona properties. The simultaneous broadband X-ray spectrum of ESO,141-G55 is characterised by the presence of a prominent smooth soft X-ray excess, a broad Fe,Kalpha emission line, and a significant Compton hump. The high-resolution reflection grating spectrometer spectra confirmed the lack of intrinsic warm-absorbing gas along our line of sight in the AGN rest frame, verifying that it is still in a bare state. However, soft X-ray emission lines were observed, indicating substantial warm gas out of our line of sight. The intermediate inclination of the disc-corona system (sim circ $) may offer us a favourable configuration to observe ultra-fast outflows from the disc, but none were found in this 2022 observation, contrary to a previous 2007 XMM-Newton one. We ruled out relativistic reflection alone on a standard disc based on the X-ray broadband analysis, while a combination of soft and hard Comptonisation by a warm and hot corona ( relagn ) plus relativistic reflection ( reflkerrd ) reproduces the ESO,141-G55 SED quite well. The hot corona temperature is very hot, sim 140,keV, and much higher than about 80 of AGNs, whereas the warm corona temperature, sim 0.3,keV, is similar to the values found in other sub-Eddington AGNs. ESO,141-G55 is accreting at a moderate Eddington accretion rate (sim 10--20). Our analysis points to a significant contribution of an optically thick warm corona to both the soft X-ray and UV emission in ESO,141-G55, adding to the growing evidence that the accretion of AGNs (even at a moderate accretion rate) appears to deviate from standard disc theory.
{"title":"Revealing the burning and soft heart of the bright bare active galactic nucleus ESO 141-G55: X-ray broadband and SED analysis","authors":"D. Porquet, J. Reeves, S. Hagen, A. Lobban, V. Braito, N. Grosso, F. Marin","doi":"10.1051/0004-6361/202449708","DOIUrl":"https://doi.org/10.1051/0004-6361/202449708","url":null,"abstract":"ESO 141-G55 is a nearby X-ray bright broad-line Seyfert,1 (BLS1) that has been classified as a bare active galactic nucleus (AGN) due to a lack of warm absorption along its line of sight, providing an unhampered view into its disc-corona system. We aim to probe its disc-corona system thanks to the first simultaneous XMM-Newton and NuSTAR observation obtained October 1--2, 2022. We carried out an X-ray broadband spectral analysis to determine the dominant process(es) at work as well as a spectral energy distribution (SED) analysis to determine the disc-corona properties. The simultaneous broadband X-ray spectrum of ESO,141-G55 is characterised by the presence of a prominent smooth soft X-ray excess, a broad Fe,Kalpha emission line, and a significant Compton hump. The high-resolution reflection grating spectrometer spectra confirmed the lack of intrinsic warm-absorbing gas along our line of sight in the AGN rest frame, verifying that it is still in a bare state. However, soft X-ray emission lines were observed, indicating substantial warm gas out of our line of sight. The intermediate inclination of the disc-corona system (sim circ $) may offer us a favourable configuration to observe ultra-fast outflows from the disc, but none were found in this 2022 observation, contrary to a previous 2007 XMM-Newton one. We ruled out relativistic reflection alone on a standard disc based on the X-ray broadband analysis, while a combination of soft and hard Comptonisation by a warm and hot corona ( relagn ) plus relativistic reflection ( reflkerrd ) reproduces the ESO,141-G55 SED quite well. The hot corona temperature is very hot, sim 140,keV, and much higher than about 80 of AGNs, whereas the warm corona temperature, sim 0.3,keV, is similar to the values found in other sub-Eddington AGNs. ESO,141-G55 is accreting at a moderate Eddington accretion rate (sim 10--20). Our analysis points to a significant contribution of an optically thick warm corona to both the soft X-ray and UV emission in ESO,141-G55, adding to the growing evidence that the accretion of AGNs (even at a moderate accretion rate) appears to deviate from standard disc theory.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"35 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141810085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449167
C. Stadler, C. Laffon, Ph. Parent
Measuring the sticking coefficient of molecules pertinent to astrochemistry - such as CO - on substrates that mimic interstellar dust grains is crucial for the comprehensive understanding of gas-grain chemical processes. Although astrochemical models assume a sticking coefficient of 1, recent laboratory experiments on H2O and CO2 have revealed significantly lower values when measured on small grain analogs. As the effect of grain size on molecular adsorption has been largely ignored to date, further experiments are needed to determine the accretion rates of species known to freeze out on dust grains. Our aim is to determine the sticking coefficients of CO and N2 on sub-micrometric silicate and carbon grains. By quantifying realistic sticking coefficients on these dust grain analogs, we can improve the accuracy of astrochemists' predictions of molecular abundances as affected by gas-grain interactions. The molecules of interest were added to various substrates at 10 K in an ultra-high vacuum. The amount of adsorbate that stuck to the substrate was quantified using X-ray photoelectron spectroscopy. These quantities were compared to a reference with a sticking coefficient of 1, allowing the deduction of the sticking coefficient for each substrate. The average sticking coefficients of CO and N2 on grain analogs are 0.17 for CO and 0.14 for N2 on olivine powder, and 0.05 for CO and 0.07 on N2 on soot, instead of the presumed 1. This is in line with the low values previously reported for H2O and CO2 These laboratory results indicate that CO and N2 in addition to H2O and CO2 also exhibit a low sticking coefficient on dust grain analogs. It is thus necessary to reconsider the interactions between gaseous species and dust particles as a low-efficiency process. This reduction in accretion and reaction rates has important implications for how we understand astrochemistry.
测量与天体化学有关的分子（如一氧化碳）在模拟星际尘粒的基质上的粘滞系数，对于全面了解气粒化学过程至关重要。尽管天体化学模型假定粘滞系数为 1，但最近对 H2O 和 CO2 进行的实验室实验表明，在小颗粒模拟物上测量的粘滞系数要低得多。由于迄今为止人们在很大程度上忽视了颗粒大小对分子吸附的影响，因此需要进一步的实验来确定已知会冻结在尘埃颗粒上的物种的吸附率。我们的目标是确定 CO 和 N2 在亚微米硅酸盐和碳颗粒上的粘附系数。通过量化这些尘粒类似物上的实际粘滞系数，我们可以提高天体化学专家预测受气体-尘粒相互作用影响的分子丰度的准确性。在 10 K 的超高真空条件下，将相关分子添加到各种基底上。使用 X 射线光电子能谱对粘附在基底上的吸附物数量进行量化。将这些数量与吸附系数为 1 的参照物进行比较，从而推导出每种基底的吸附系数。这些实验室结果表明，除了 H2O 和 CO2 外，CO 和 N2 在尘粒类似物上的粘附系数也很低。因此，有必要将气体物种与尘粒之间的相互作用重新视为一种低效率过程。这种吸积和反应速率的降低对我们如何理解天体化学具有重要影响。
{"title":"Experimental sticking coefficients of CO and N_2 on sub-micrometric cosmic grain analogs","authors":"C. Stadler, C. Laffon, Ph. Parent","doi":"10.1051/0004-6361/202449167","DOIUrl":"https://doi.org/10.1051/0004-6361/202449167","url":null,"abstract":"Measuring the sticking coefficient of molecules pertinent to astrochemistry - such as CO - on substrates that mimic interstellar dust grains is crucial for the comprehensive understanding of gas-grain chemical processes. Although astrochemical models assume a sticking coefficient of 1, recent laboratory experiments on H2O and CO2 have revealed significantly lower values when measured on small grain analogs. As the effect of grain size on molecular adsorption has been largely ignored to date, further experiments are needed to determine the accretion rates of species known to freeze out on dust grains. Our aim is to determine the sticking coefficients of CO and N2 on sub-micrometric silicate and carbon grains. By quantifying realistic sticking coefficients on these dust grain analogs, we can improve the accuracy of astrochemists' predictions of molecular abundances as affected by gas-grain interactions. The molecules of interest were added to various substrates at 10 K in an ultra-high vacuum. The amount of adsorbate that stuck to the substrate was quantified using X-ray photoelectron spectroscopy. These quantities were compared to a reference with a sticking coefficient of 1, allowing the deduction of the sticking coefficient for each substrate. The average sticking coefficients of CO and N2 on grain analogs are 0.17 for CO and 0.14 for N2 on olivine powder, and 0.05 for CO and 0.07 on N2 on soot, instead of the presumed 1. This is in line with the low values previously reported for H2O and CO2 These laboratory results indicate that CO and N2 in addition to H2O and CO2 also exhibit a low sticking coefficient on dust grain analogs. It is thus necessary to reconsider the interactions between gaseous species and dust particles as a low-efficiency process. This reduction in accretion and reaction rates has important implications for how we understand astrochemistry.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"68 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141806730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202450552
Longkang Dai, Wencheng Shao, Zheng Sheng
Atmospheric chemistry plays a crucial role in the evolution of climate habitability on Venus. It has been widely explored by chemistry-transport models, but some characteristics are still poorly interpreted. This study is devoted to developing an open-access chemistry-transport model spanning both the middle and lower atmospheres of Venus. It provides a scheme for the structure of the chemistry, especially for the sulfur and oxygen, and investigates the influence of the cloud diffusivity and the SO$_ $ dissolution that are adopted in the clouds. The developed model is based on the VULCAN framework and was updated with the state-of-the-art Venusian atmospheric chemistry. It includes vertical eddy diffusion retrieved recently with the Venus Express observations, and it resolves radiative transfer containing gas absorption and scattering, Mie scattering of the cloud droplets, and absorption of the unknown UV absorber. The obtained abundance profiles of SO, SO$_ $, CO, COS, O, O$_ $, O$_ $, HCl, and NO are in overall agreement with the observations. The results show that the increase in cloud diffusivity has slight effects on the chemical structure. The SO$_ $ mainly dissolves in 50-90 km and evaporates below the clouds. The rapid dissolution-release cycle is responsible for the large upward flux of SO$_ $ at 58 km. At around 70 km, SO has a significant peak that is larger than that of previous studies by an order of magnitude, and S and SO$_ $ also show slight increases. They are attributed to the buffering effects of liquid SO$_ $ in the clouds. O$_ $ is significantly eliminated by SO in this layer. We emphasize the superior regulation of the sulfur cycle on O$_ $ at 70 km and its potential contributions to the long-standing problem of the overestimated O$_ $ abundance.
{"title":"An investigation into Venusian atmospheric chemistry based on an open-access photochemistry-transport model at 0-112 km","authors":"Longkang Dai, Wencheng Shao, Zheng Sheng","doi":"10.1051/0004-6361/202450552","DOIUrl":"https://doi.org/10.1051/0004-6361/202450552","url":null,"abstract":"Atmospheric chemistry plays a crucial role in the evolution of climate habitability on Venus. It has been widely explored by chemistry-transport models, but some characteristics are still poorly interpreted. This study is devoted to developing an open-access chemistry-transport model spanning both the middle and lower atmospheres of Venus. It provides a scheme for the structure of the chemistry, especially for the sulfur and oxygen, and investigates the influence of the cloud diffusivity and the SO$_ $ dissolution that are adopted in the clouds. The developed model is based on the VULCAN framework and was updated with the state-of-the-art Venusian atmospheric chemistry. It includes vertical eddy diffusion retrieved recently with the Venus Express observations, and it resolves radiative transfer containing gas absorption and scattering, Mie scattering of the cloud droplets, and absorption of the unknown UV absorber. The obtained abundance profiles of SO, SO$_ $, CO, COS, O, O$_ $, O$_ $, HCl, and NO are in overall agreement with the observations. The results show that the increase in cloud diffusivity has slight effects on the chemical structure. The SO$_ $ mainly dissolves in 50-90 km and evaporates below the clouds. The rapid dissolution-release cycle is responsible for the large upward flux of SO$_ $ at 58 km. At around 70 km, SO has a significant peak that is larger than that of previous studies by an order of magnitude, and S and SO$_ $ also show slight increases. They are attributed to the buffering effects of liquid SO$_ $ in the clouds. O$_ $ is significantly eliminated by SO in this layer. We emphasize the superior regulation of the sulfur cycle on O$_ $ at 70 km and its potential contributions to the long-standing problem of the overestimated O$_ $ abundance.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"22 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141808783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449755
G. Valle, M. Dell'Omodarme, P. P. Prada Moroni, S. Degl'innocenti
We conducted an investigation on the chemical abundances of 4,316 stars in the red giant branch (RGB) phase from the recently released APO-K2 catalogue. Our aim was to characterize the abundance trends of the single elements with afe , mainly focusing on C, N, and O, which are the most relevant for the estimation of stellar ages. The chemical analysis of the RGB sample involved cross-matching data from the APO-K2 catalogue with individual element abundances from APOGEE DR17. The analysis detected a statistically significant difference in the (C+N+O)/Fe -- afe trend with respect to the simple alpha -enhancement scenario. This difference remained robust across different choices for the reference solar mixture and potential zero-point calibrations of C and N abundances. The primary discrepancy was a steeper increase in O/Fe with afe , reaching a 0.1 dex difference at $ = 0.3$. Notably, the impact on the evolutionary timescale of such oxygen over-abundance with respect to the commonly adopted uniform alpha -enhancement is rather limited. We verified that stellar models computed using an ad hoc O-rich mixture sped up the evolution by only 1 at $ = 0.3$, due to the counterbalancing effects of O enrichment on both the evolutionary timescale and the Fe/H relationship.
{"title":"Element abundances of galactic RGB stars in the APO-K2 catalogue. Dissimilarity in the scaling with [alpha/Fe]","authors":"G. Valle, M. Dell'Omodarme, P. P. Prada Moroni, S. Degl'innocenti","doi":"10.1051/0004-6361/202449755","DOIUrl":"https://doi.org/10.1051/0004-6361/202449755","url":null,"abstract":"We conducted an investigation on the chemical abundances of 4,316 stars in the red giant branch (RGB) phase from the recently released APO-K2 catalogue. Our aim was to characterize the abundance trends of the single elements with afe , mainly focusing on C, N, and O, which are the most relevant for the estimation of stellar ages. The chemical analysis of the RGB sample involved cross-matching data from the APO-K2 catalogue with individual element abundances from APOGEE DR17. The analysis detected a statistically significant difference in the (C+N+O)/Fe -- afe trend with respect to the simple alpha -enhancement scenario. This difference remained robust across different choices for the reference solar mixture and potential zero-point calibrations of C and N abundances. The primary discrepancy was a steeper increase in O/Fe with afe , reaching a 0.1 dex difference at $ = 0.3$. Notably, the impact on the evolutionary timescale of such oxygen over-abundance with respect to the commonly adopted uniform alpha -enhancement is rather limited. We verified that stellar models computed using an ad hoc O-rich mixture sped up the evolution by only 1 at $ = 0.3$, due to the counterbalancing effects of O enrichment on both the evolutionary timescale and the Fe/H relationship.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"9 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449258
Bin Liu, Junzhi Wang, Bo Zhang, Shanghuo Li, Shu Liu, Juan Li, Bo Peng, Min Fang, Xiaofeng Mai
Observing low-frequency decimeter hydrogen radio recombination lines (RRLs) with large single-dish telescopes, such as the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the L band, is a unique method for probing massive star formation on scales of hundreds of parsecs. This approach is particularly effective for detecting relatively weak and extended emissions from low-density gas ionized by massive stars. Deep, unbiased decimeter or centimeter RRL surveys with large single-dish telescopes can significantly enhance our understanding of the diffuse ionized gas along the Galactic plane. This, in turn, will improve our knowledge of the life cycle of matter in the interstellar medium and the dynamics of the Galaxy. In this context, we present a pilot project for such a blind L-band RRL survey targeting the Galactic plane and conducted using FAST. The results include the detection of RRL clumps and the identification of an off-arm active massive star-forming region near the Sagittarius-Carina arm. The ongoing and upcoming massive star formation in this region may be associated with the kink in the Sagittarius-Carina arm near 23$^ circ $ azimuth.
利用大型单碟望远镜（如 L 波段的五百米孔径球面射电望远镜（FAST））观测低频十亿分氢射电重组线（RRLs），是探测数百帕尺度大质量恒星形成的一种独特方法。这种方法对于探测大质量恒星电离出的低密度气体发出的相对微弱和延伸的辐射特别有效。利用大型单碟望远镜进行的深度、无偏差的分米波或厘米波RRL巡天可以大大提高我们对银河面上弥漫电离气体的了解。这反过来又会增进我们对星际介质中物质生命周期和银河系动力学的了解。在此背景下，我们介绍了一个利用 FAST 进行的以银河系平面为目标的 L 波段 RRL 盲巡天试验项目。结果包括探测到了RRL团块，并在人马座-卡里纳臂附近发现了一个臂外活跃的大质量恒星形成区。该区域正在形成和即将形成的大质量恒星可能与人马座-卡里纳臂在方位角 23$^ circ $ 附近的扭结有关。
{"title":"A pilot study of Galactic radio recombination lines using FAST: Identification of diffuse ionized gas clumps and off-arm star-forming regions","authors":"Bin Liu, Junzhi Wang, Bo Zhang, Shanghuo Li, Shu Liu, Juan Li, Bo Peng, Min Fang, Xiaofeng Mai","doi":"10.1051/0004-6361/202449258","DOIUrl":"https://doi.org/10.1051/0004-6361/202449258","url":null,"abstract":"Observing low-frequency decimeter hydrogen radio recombination lines (RRLs) with large single-dish telescopes, such as the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the L band, is a unique method for probing massive star formation on scales of hundreds of parsecs. This approach is particularly effective for detecting relatively weak and extended emissions from low-density gas ionized by massive stars.\u0000Deep, unbiased decimeter or centimeter RRL surveys with large single-dish telescopes can significantly enhance our understanding of the diffuse ionized gas along the Galactic plane. This, in turn, will improve our knowledge of the life cycle of matter in the interstellar medium and the dynamics of the Galaxy. In this context, we present a pilot project for such a blind L-band RRL survey targeting the Galactic plane and conducted using FAST. The results include the detection of RRL clumps and the identification of an off-arm active massive star-forming region near the Sagittarius-Carina arm. The ongoing and upcoming massive star formation in this region may be associated with the kink in the Sagittarius-Carina arm near 23$^ circ $ azimuth.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"26 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141806158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202449296
P. Charalampopoulos, R. Kotak, T. Wevers, G. Leloudas, T. Kravtsov, M. Pursiainen, P. Ramsden, T. Reynolds, A. Aamer, J. P. Anderson, I. Arcavi, Y.-Z. Cai, T.-W. Chen, M. Dennefeld, L. Galbany, M. Gromadzki, C. P. Gutierrez, N. Ihanec, T. Kangas, E. Kankare, E. Kool, A. Lawrence, P. Lundqvist, L. Makrygianni, S. Mattila, T. Muller-bravo, M. Nicholl, F. Onori, A. Sahu, S. Smartt, J. Sollerman, Y. Wang, D. Young
We present an extensive analysis of the optical and ultraviolet (UV) properties of AT 2023clx, the closest optical/UV tidal disruption event (TDE) to date ($z=0.01107$), which occurred in the nucleus of the interacting low-ionization nuclear emission-line region (LINER) galaxy, NGC 3799. After correcting for the host reddening ($ h $ = 0.179 mag), we find its peak absolute $g$-band magnitude to be $-18.03 0.07$ mag, and its peak bolometric luminosity to be L_ pk $. AT 2023clx displays several distinctive features: first, it rose to peak within $10.4 days, making it the fastest rising TDE to date. Our SMBH mass estimate of $ M BH ---estimated using several standard methods--- rules out the possibility of an intermediate-mass BH as the reason for the fast rise. Dense spectral follow-up reveals a blue continuum that cools slowly and broad Balmer and He II lines as well as weak He I emission features that are typically seen in TDEs. The early, broad (width $ $) profile of Halpha matches theoretical expectations from an optically thick outflow. A flat Balmer decrement ($L_ H alpha $/$L_ H beta 1.58$) suggests that the lines are collisionally excited rather than being produced via photoionisation, in contrast to typical active galactic nuclei. A second distinctive feature, seen for the first time in TDE spectra, is a sharp, narrow emission peak at a rest wavelength of sim 6353 This feature is clearly visible up to 10,d post-peak; we attribute it to clumpy material preceding the bulk outflow, which manifests as a high-velocity component of Halpha ($-9,584 $). Its third distinctive feature is the rapid cooling during the first sim 20 days after peak, reflected as a break in the temperature evolution. Combining these findings, we propose a scenario for AT 2023clx involving the disruption of a very low-mass star ($ with an outflow launched in our line of sight and with disruption properties that led to efficient circularisation and prompt accretion disc formation, observed through a low-density photosphere.
我们对AT 2023clx的光学和紫外线（UV）特性进行了广泛的分析，它是迄今为止最接近的光学/紫外线潮汐扰动事件（TDE）（$z=0.01107$），发生在相互作用的低电离核发射线区（LINER）星系NGC 3799的星系核中。在校正了宿主红化（$ h $ = 0.179 mag）之后，我们发现它的峰值绝对g$波段星等为$-18.03 0.07$，峰值测光光度为L_ pk$。 AT 2023clx有几个显著特点：首先，它在10.4天内就达到了峰值，是迄今为止上升最快的TDE。我们用几种标准方法估算出的SMBH质量为$ M BH--排除了中等质量BH作为快速上升原因的可能性。密集的光谱跟踪显示了缓慢冷却的蓝色连续波、宽广的巴尔默线和He II线，以及通常在TDEs中看到的微弱的He I发射特征。Halpha的早期宽（宽度$$）剖面符合光学厚外流的理论预期。平坦的巴尔默递减（$L_ H alpha $/$L_ H beta 1.58$）表明，这些谱线是碰撞激发的，而不是通过光离子化产生的，这与典型的活动星系核不同。第二个显著特点是在TDE光谱中首次看到的一个尖锐、狭窄的发射峰，其静止波长为sim 6353，这个特征在峰后10,d以内都清晰可见；我们将其归因于大量流出之前的团块物质，它表现为Halpha的高速成分（$-9,584 $）。它的第三个显著特点是在峰值后的最初20天内迅速冷却，反映为温度演化的中断。结合这些发现，我们为AT 2023clx提出了一种设想，即一颗质量很低的恒星（$）在我们的视线范围内发生了扰动，其流出物是通过低密度光球层观测到的，其扰动特性导致了高效的环化和吸积盘的迅速形成。
{"title":"The fast transient AT 2023clx in the nearby LINER galaxy NGC 3799 as a tidal disruption of a very low-mass star","authors":"P. Charalampopoulos, R. Kotak, T. Wevers, G. Leloudas, T. Kravtsov, M. Pursiainen, P. Ramsden, T. Reynolds, A. Aamer, J. P. Anderson, I. Arcavi, Y.-Z. Cai, T.-W. Chen, M. Dennefeld, L. Galbany, M. Gromadzki, C. P. Gutierrez, N. Ihanec, T. Kangas, E. Kankare, E. Kool, A. Lawrence, P. Lundqvist, L. Makrygianni, S. Mattila, T. Muller-bravo, M. Nicholl, F. Onori, A. Sahu, S. Smartt, J. Sollerman, Y. Wang, D. Young","doi":"10.1051/0004-6361/202449296","DOIUrl":"https://doi.org/10.1051/0004-6361/202449296","url":null,"abstract":"We present an extensive analysis of the optical and ultraviolet (UV) properties of AT 2023clx, the closest optical/UV tidal disruption event (TDE) to date ($z=0.01107$), which occurred in the nucleus of the interacting low-ionization nuclear emission-line region (LINER) galaxy, NGC 3799. After correcting for the host reddening ($ h $ = 0.179 mag), we find its peak absolute $g$-band magnitude to be $-18.03 0.07$ mag, and its peak bolometric luminosity to be L_ pk $. AT 2023clx displays several distinctive features: first, it rose to peak within $10.4 days, making it the fastest rising TDE to date. Our SMBH mass estimate of $ M BH ---estimated using several standard methods--- rules out the possibility of an intermediate-mass BH as the reason for the fast rise. Dense spectral follow-up reveals a blue continuum that cools slowly and broad Balmer and He II lines as well as weak He I emission features that are typically seen in TDEs. The early, broad (width $ $) profile of Halpha matches theoretical expectations from an optically thick outflow. A flat Balmer decrement ($L_ H alpha $/$L_ H beta 1.58$) suggests that the lines are collisionally excited rather than being produced via photoionisation, in contrast to typical active galactic nuclei. A second distinctive feature, seen for the first time in TDE spectra, is a sharp, narrow emission peak at a rest wavelength of sim 6353 This feature is clearly visible up to 10,d post-peak; we attribute it to clumpy material preceding the bulk outflow, which manifests as a high-velocity component of Halpha ($-9,584 $). Its third distinctive feature is the rapid cooling during the first sim 20 days after peak, reflected as a break in the temperature evolution. Combining these findings, we propose a scenario for AT 2023clx involving the disruption of a very low-mass star ($ with an outflow launched in our line of sight and with disruption properties that led to efficient circularisation and prompt accretion disc formation, observed through a low-density photosphere.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"41 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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