Solar filaments or prominences are common features in the Sun's atmosphere that contain cool chromospheric material suspended within the hot corona. However, the intricate topology of these structures and the mechanisms driving their instability and upward material transfer are not well understood. Investigating these issues is essential for gaining insight into the fundamental laws that govern solar activity. This study is to analyze a specific twisted prominence observed on February 10, 2021, and to explore its dynamics, including stability, motion, and material transfer. The study also aims to propose a mechanism, based on the K'arm'an Vortex Street instability, to explain the destabilization of the prominence. The study utilizes high-resolution H$_ alpha $ observations from the 1-m New Vacuum Solar Telescope and space-borne observations from the Solar Dynamics Observatory. These observations capture the characteristics and behavior of the twisted prominence. We analyzed the data to investigate the equilibrium state, subsequent destabilization, vortex motion, oscillations, resonations, untwisting, and upward mass loading of the prominence. We also detected and measured the speeds of outflows surrounding the prominence. The study reveals that the observed twisted prominence exhibited a stretched and twisted structure at its apex, distinguishing it from familiar cloudy prominences. Following a period of more than 30 hours in equilibrium, the prominence underwent destabilization, leading to a series of dynamic phenomena, such as vortex motion, oscillations, resonations, untwisting, and the upward transfer of mass. Consequently, material from the top of the prominence was carried upward and deposited into the overlying magnetic arcades. Noteworthy, outflows surrounding the prominence were characterized by speeds exceeding 40 km s$^ Based on these findings, we propose, for the first time, a mechanism rooted in the K'arm'an Vortex Street instability to explain the destabilization of the prominence. The estimated typical Strouhal Number of 0.23pm 0.06, which is related to vortex shedding, falls within the expected range for the K'arm'an Vortex Street effect, as predicted by simulations. These discoveries provide new insights into the dynamics and fundamental topology of solar prominences and reveal a previously unknown mechanism for mass loading into the upper atmosphere.
{"title":"Unraveling the untwisting process and upward mass transfer of a twisted prominence driven by vortex motion","authors":"X.F. Zhang, G.P. Zhou, C.L. Jin, Y.Z. Zhang, G.W. Li, Z.H. Shang, L.P. Li, S.B. Yang, S.H. Yang, J.X. Wang","doi":"10.1051/0004-6361/202348070","DOIUrl":"https://doi.org/10.1051/0004-6361/202348070","url":null,"abstract":"Solar filaments or prominences are common features in the Sun's atmosphere that contain cool chromospheric material suspended within the hot corona. However, the intricate topology of these structures and the mechanisms driving their instability and upward material transfer are not well understood. Investigating these issues is essential for gaining insight into the fundamental laws that govern solar activity. This study is to analyze a specific twisted prominence observed on February 10, 2021, and to explore its dynamics, including stability, motion, and material transfer. The study also aims to propose a mechanism, based on the K'arm'an Vortex Street instability, to explain the destabilization of the prominence. The study utilizes high-resolution H$_ alpha $ observations from the 1-m New Vacuum Solar Telescope and space-borne observations from the Solar Dynamics Observatory. These observations capture the characteristics and behavior of the twisted prominence. We analyzed the data to investigate the equilibrium state, subsequent destabilization, vortex motion, oscillations, resonations, untwisting, and upward mass loading of the prominence. We also detected and measured the speeds of outflows surrounding the prominence. The study reveals that the observed twisted prominence exhibited a stretched and twisted structure at its apex, distinguishing it from familiar cloudy prominences. Following a period of more than 30 hours in equilibrium, the prominence underwent destabilization, leading to a series of dynamic phenomena, such as vortex motion, oscillations, resonations, untwisting, and the upward transfer of mass. Consequently, material from the top of the prominence was carried upward and deposited into the overlying magnetic arcades. Noteworthy, outflows surrounding the prominence were characterized by speeds exceeding 40 km s$^ Based on these findings, we propose, for the first time, a mechanism rooted in the K'arm'an Vortex Street instability to explain the destabilization of the prominence. The estimated typical Strouhal Number of 0.23pm 0.06, which is related to vortex shedding, falls within the expected range for the K'arm'an Vortex Street effect, as predicted by simulations. These discoveries provide new insights into the dynamics and fundamental topology of solar prominences and reveal a previously unknown mechanism for mass loading into the upper atmosphere.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"44 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809516","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: 10.1051/0004-6361/202450069
L.R. Baalmann, S. Hunziker, A. Péronne, J.W. Kirchner, K. Glassmeier, D.M. Malaspina, L. Wilson III, C. Strähl, S. Chadda, V.J. Sterken
Dust particle impacts on the Wind spacecraft were detected with its plasma wave instrument Wind/WAVES. Frequency analysis on the resulting dust impact time series has revealed spectral peaks indicative of a solar rotation signature. We investigated whether this solar rotation signature is embedded in the interplanetary or in the interstellar dust (ISD) and whether it is caused by co-rotating interaction regions (CIRs), by the sector structure of the interplanetary magnetic field (IMF), or by external effects. We performed frequency analysis on different subsets of the data to investigate the origin of these spectral peaks, comparing segments of Wind's orbit when the spacecraft moved against or with the ISD inflow direction and comparing the time periods of the ISD focusing phase and the ISD defocusing phase of the solar magnetic cycle. A superposed epoch analysis of the number of dust impacts during CIRs was used to investigate the systematic effect of CIRs. Case studies of time periods with frequent or infrequent occurrences of CIRs were performed and compared to synthetic data of cosmic dust impacts affected by CIRs. We performed similar case studies for time periods with a stable or chaotic IMF sector structure. The superposed epoch analysis was repeated for a time series of the spacecraft floating potential. Spectral peaks were found at the solar rotation period of $ sim d $ and its harmonics at $13.5 d $ and $9 d $. This solar rotation signature may affect both interplanetary and interstellar dust. The appearance of this signature correlates with the occurrence of CIRs but not with the stability of the IMF sector structure. The CIRs cause, on average, a reduction in the number of dust impact detections. Periodic changes of the spacecraft's floating potential were found to partially counteract this reduction by enhancing the instrument's sensitivity to dust impacts; these changes of the floating potential are thus unlikely to be the cause of the solar rotation signature.
利用等离子波仪器 Wind/WAVES 检测了尘埃粒子对 Wind 航天器的撞击。对由此产生的尘埃撞击时间序列进行频率分析，发现了表明太阳自转特征的光谱峰。我们研究了这种太阳自转特征是包含在行星际还是星际尘埃（ISD）中，以及它是由共转相互作用区（CIR）、行星际磁场（IMF）的扇形结构还是外部效应引起的。我们对数据的不同子集进行了频率分析，以研究这些光谱峰的起源，比较了 Wind 轨道上航天器逆 ISD 流入方向或顺 ISD 流入方向移动的区段，并比较了太阳磁力周期中 ISD 聚焦阶段和 ISD 失焦阶段的时间段。对CIR期间尘埃撞击次数的叠加历时分析用于研究CIR的系统性影响。我们对频繁或不频繁发生 CIR 的时段进行了案例研究，并与受 CIR 影响的宇宙尘埃撞击合成数据进行了比较。我们还对具有稳定或混乱的 IMF 扇形结构的时段进行了类似的案例研究。对航天器浮动电势的时间序列重复了叠加纪元分析。在太阳自转周期 $ sim d $ 及其谐波 $13.5 d $ 和 $9 d $ 处发现了光谱峰。这种特征的出现与CIR的发生有关，但与IMF扇形结构的稳定性无关。CIRs平均会导致尘埃撞击探测次数的减少。发现航天器浮动电势的周期性变化通过提高仪器对尘埃撞击的灵敏度而部分抵消了这种减少；因此浮动电势的这些变化不太可能是太阳旋转特征的原因。
{"title":"A solar rotation signature in cosmic dust: Frequency analysis of dust particle impacts on the Wind spacecraft","authors":"L.R. Baalmann, S. Hunziker, A. Péronne, J.W. Kirchner, K. Glassmeier, D.M. Malaspina, L. Wilson III, C. Strähl, S. Chadda, V.J. Sterken","doi":"10.1051/0004-6361/202450069","DOIUrl":"https://doi.org/10.1051/0004-6361/202450069","url":null,"abstract":"Dust particle impacts on the Wind spacecraft were detected with its plasma wave instrument Wind/WAVES. Frequency analysis on the resulting dust impact time series has revealed spectral peaks indicative of a solar rotation signature. We investigated whether this solar rotation signature is embedded in the interplanetary or in the interstellar dust (ISD) and whether it is caused by co-rotating interaction regions (CIRs), by the sector structure of the interplanetary magnetic field (IMF), or by external effects. We performed frequency analysis on different subsets of the data to investigate the origin of these spectral peaks, comparing segments of Wind's orbit when the spacecraft moved against or with the ISD inflow direction and comparing the time periods of the ISD focusing phase and the ISD defocusing phase of the solar magnetic cycle. A superposed epoch analysis of the number of dust impacts during CIRs was used to investigate the systematic effect of CIRs. Case studies of time periods with frequent or infrequent occurrences of CIRs were performed and compared to synthetic data of cosmic dust impacts affected by CIRs. We performed similar case studies for time periods with a stable or chaotic IMF sector structure. The superposed epoch analysis was repeated for a time series of the spacecraft floating potential. Spectral peaks were found at the solar rotation period of $ sim d $ and its harmonics at $13.5 d $ and $9 d $. This solar rotation signature may affect both interplanetary and interstellar dust. The appearance of this signature correlates with the occurrence of CIRs but not with the stability of the IMF sector structure. The CIRs cause, on average, a reduction in the number of dust impact detections. Periodic changes of the spacecraft's floating potential were found to partially counteract this reduction by enhancing the instrument's sensitivity to dust impacts; these changes of the floating potential are thus unlikely to be the cause of the solar rotation signature.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"51 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1051/0004-6361/202450513
Isaure Gonz'alez Rivera de La Vernhe, Vanessa Hill, G. Kordopatis, Felipe Gran, Emma Fern'andez-Alvar, Anke Ardern-Arentsen, Guillaume F. Thomas, F. Sestito, Camila Navarrete, N. Martin, E. Starkenburg, Akshara Viswanathan, G. Battaglia, K. Venn, S. Vitali
Metal-poor stars hold key information on the early Milky Way. Through the identification and characterisation of substructures, one can understand internal mechanisms (including merger and accretion events), which are indispensable to reconstruct the formation history of the Galaxy. To allow an investigation of a population of very metal-poor stars ( Fe/H < -1.7) with disc-like orbits (planar and prograde), high angular momenta ($L_z$/$J_ tot $ > 0.5) and rotational velocities ($V_ $) proposed in the literature, we used a sample of sim 3M giant stars with Gaia DR3 BP/RP information and Pristine-Gaia metallicities down to -4.0 dex that we aimed to decontaminate. To achieve this, we constructed a sample as free as possible from spurious photometric estimates, an issue commonly encountered for high $V_ metal-poor stars. We created a statistically robust sample of sim 36 000 Pristine-Gaia very metal-poor ( Fe/H < -1.7) giant stars, using APOGEE and LAMOST data (adding GALAH and GSP-spec for verification) to estimate and remove contamination. We investigated the spatial and kinematic properties of the decontaminated sample, making use of $V_ as well as the action space, which are both powerful tools to disentangle stellar populations. The global distribution of very metal-poor stars in our sample shows the typical kinematics, orbital properties, and spatial distributions of a halo; however, as in previous works, we found a pronounced asymmetry in the $L_z$ and $V_ distributions, in favour of prograde stars. We showed that this excess is predominantly due to prograde-planar stars (10 $$ of the very metal-poor population), which can be detected down to Fe/H = -2.9 at a 2sigma confidence level. This prograde-planar population contains stars with $V_ $ and $Z_ max $ < 1.5,kpc. While the overall orbital configurations max $ - $R_ max $ or action space distributions) of our sample match that of a halo, the highly prograde and planar subset (2 $$ of the very metal-poor population) also bears characteristics classically associated with a thick disc: (i) a spatial distribution compatible with a short-scaled thick disc, (ii) a $Z_ max $ - $R_ max $ distribution similar to the one expected from the thick disc prediction of the Gaia Universe Model Snapshot, and (iii) a challenge to erase its signature assuming a stationary or prograde halo with $ V_ phi $ sim 30-40 km.s$^ $. Altogether, these results seem to rule out that these highly prograde and planar stars are part of a thin disc population and, instead, support a contribution from a metal-weak thick disc. Higher resolution spectra are needed to fully disentangle the origin(s) of the population.
贫金属恒星掌握着早期银河系的关键信息。通过识别和描述亚结构，我们可以了解内部机制（包括合并和吸积事件），这对于重建银河系的形成历史是不可或缺的。为了研究文献中提出的具有盘状轨道（平面和顺行）、高角矩（$L_z$/$J_ tot $ > 0.5）和旋转速度（$V_ $）的极度贫金属恒星群（Fe/H <-1.7），我们使用了具有盖亚DR3 BP/RP信息和Pristine-Gaia金属性低至-4.0 dex的模拟3M巨星样本，目的是去污。为此，我们构建了一个尽可能没有虚假光度估计的样本，这是在高$V_贫金属恒星中经常遇到的问题。我们利用 APOGEE 和 LAMOST 数据（增加了 GALAH 和 GSP-spec 用于验证），建立了一个模拟 36000 颗 Pristine-Gaia 极贫金属（Fe/H <-1.7）巨星的统计稳健样本，以估计和去除污染。我们利用$V_和作用空间研究了去污样本的空间和运动特性，它们都是区分恒星群的有力工具。我们样本中极度贫金属恒星的总体分布显示出典型的运动学、轨道特性和光环的空间分布；然而，与之前的研究一样，我们发现在$L_z$和$V_的分布上存在明显的不对称，这有利于逆行恒星。我们的研究表明，这种过量主要是由顺行星造成的（占极贫金属星群的10%），在2σ置信水平下，可以探测到低至Fe/H = -2.9的顺行星。这个平级星群包含了$V_ $和$Z_ max $ < 1.5,kpc 的恒星。虽然我们样本的总体轨道构型（max $ - $R_ max $或作用空间分布）与光环相匹配，但高度顺行和平面子集（极度贫金属星群中的2 $$）也具有与厚圆盘相关的典型特征：(i) 空间分布与短尺度厚圆盘相匹配，(ii) $Z_ max $ - $R_ max $ 分布与盖亚宇宙模型快照预测的厚圆盘分布相似，(iii) 假定 V_ phi $ sim 30-40 km 的静止或顺行光环，其特征难以消除。s$^ $.总之，这些结果似乎排除了这些高顺行和平面恒星是薄圆盘星群的一部分的可能性，而支持来自弱金属厚圆盘的贡献。要完全弄清这些星群的起源，还需要更高分辨率的光谱。
{"title":"The Pristine survey. XXIV. The Galactic underdogs: Dynamic tales of a Milky Way metal-poor population","authors":"Isaure Gonz'alez Rivera de La Vernhe, Vanessa Hill, G. Kordopatis, Felipe Gran, Emma Fern'andez-Alvar, Anke Ardern-Arentsen, Guillaume F. Thomas, F. Sestito, Camila Navarrete, N. Martin, E. Starkenburg, Akshara Viswanathan, G. Battaglia, K. Venn, S. Vitali","doi":"10.1051/0004-6361/202450513","DOIUrl":"https://doi.org/10.1051/0004-6361/202450513","url":null,"abstract":"Metal-poor stars hold key information on the early Milky Way.\u0000 Through the identification and characterisation of substructures, one can understand internal mechanisms (including merger and accretion events), which are indispensable to reconstruct the formation history of the Galaxy. To allow an investigation of a population of very metal-poor stars ( Fe/H < -1.7) with disc-like orbits (planar and prograde), high angular momenta ($L_z$/$J_ tot $ > 0.5) and rotational velocities ($V_ $) proposed in the literature, we used a sample of sim 3M giant stars with Gaia DR3 BP/RP information and Pristine-Gaia metallicities down to -4.0 dex that we aimed to decontaminate. To achieve this, we constructed a sample as free as possible from spurious photometric estimates, an issue commonly encountered for high $V_ metal-poor stars. We created a statistically robust sample of sim 36 000 Pristine-Gaia very metal-poor ( Fe/H < -1.7) giant stars, using APOGEE and LAMOST data (adding GALAH and GSP-spec for verification) to estimate and remove contamination. We investigated the spatial and kinematic properties of the decontaminated sample, making use of $V_ as well as the action space, which are both powerful tools to disentangle stellar populations. The global distribution of very metal-poor stars in our sample shows the typical kinematics, orbital properties, and spatial distributions of a halo; however, as in previous works, we found a pronounced asymmetry in the $L_z$ and $V_ distributions, in favour of prograde stars. We showed that this excess is predominantly due to prograde-planar stars (10 $$ of the very metal-poor population), which can be detected down to Fe/H = -2.9 at a 2sigma confidence level. This prograde-planar population contains stars with $V_ $ and $Z_ max $ < 1.5,kpc. While the overall orbital configurations max $ - $R_ max $ or action space distributions) of our sample match that of a halo, the highly prograde and planar subset (2 $$ of the very metal-poor population) also bears characteristics classically associated with a thick disc: (i) a spatial distribution compatible with a short-scaled thick disc, (ii) a $Z_ max $ - $R_ max $ distribution similar to the one expected from the thick disc prediction of the Gaia Universe Model Snapshot, and (iii) a challenge to erase its signature assuming a stationary or prograde halo with $ V_ phi $ sim 30-40 km.s$^ $. Altogether, these results seem to rule out that these highly prograde and planar stars are part of a thin disc population and, instead, support a contribution from a metal-weak thick disc. Higher resolution spectra are needed to fully disentangle the origin(s) of the population.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"66 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141806499","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: 10.1051/0004-6361/202449965
Marion Galoy, François Lignières, J'erome Ballot
The space missions Kepler and TESS provided a large number of highly detailed time series for main-sequence stars, including gamma Doradus stars. Additionally, numerous gamma Doradus stars are to be observed in the near future thanks to the upcoming PLATO mission. In gamma Doradus stars, gravito-inertial modes in the radiative zone and inertial modes in the convective core can interact resonantly, which translates into the appearance of dip structures in the period spacing of modes. Those dips are information-rich, as they are related to the star core characteristics. Our aim is to characterise these dips according to stellar properties and thus to develop new seismic diagnostic tools to constrain the internal structure of gamma Doradus stars, especially their cores. We used the two-dimensional oscillation code TOP to compute sectoral prograde and axisymmetric dipolar modes in gamma Doradus stars at different rotation rates and evolutionary stages. We then characterised the dips we obtained by their width and location on the period spacing diagram. We found that the width and the location of the dips depend quasi-linearly on the ratio of the rotation rate and the Brunt-Väisälä frequency at the core interface. This allowed us to determine empirical relations between the width and location of dips as well as the resonant inertial mode frequency in the core and the Brunt-Väisälä frequency at the interface between the convective core and the radiative zone. We propose an approximate theoretical model to support and discuss these empirical relations. The empirical relations we established could be applied to dips observed in data, which would allow for the estimation of frequencies of resonant inertial modes in the core and of the Brunt-Väisälä jump at the interface between the core and the radiative zone. As those two parameters are both related to the evolutionary stage of the star, their determination could lead to more accurate estimations of stellar ages.
{"title":"Properties of observable mixed inertial and gravito-inertial modes in gamma Doradus stars","authors":"Marion Galoy, François Lignières, J'erome Ballot","doi":"10.1051/0004-6361/202449965","DOIUrl":"https://doi.org/10.1051/0004-6361/202449965","url":null,"abstract":"The space missions Kepler and TESS provided a large number of highly detailed time series \u0000 for \u0000 main-sequence stars, including gamma Doradus stars. Additionally, numerous gamma Doradus stars are to be observed in the near future thanks to the upcoming PLATO mission. \u0000 \u0000 In gamma Doradus stars, gravito-inertial modes in the radiative zone and inertial modes in the convective core can interact resonantly, \u0000 \u0000 which translates into the appearance of dip structures in the period spacing of modes. Those dips are information-rich, as they are related to the star core characteristics. Our aim is to characterise these dips according to stellar properties and thus to develop new\u0000 seismic diagnostic tools to constrain the internal structure of gamma Doradus stars, especially their cores. We used the two-dimensional oscillation code TOP to compute sectoral prograde and axisymmetric dipolar modes in gamma Doradus stars at different rotation rates and evolutionary stages. We then characterised the dips we obtained by their width and location on the period spacing diagram. We found that the width and the location of the dips \u0000 depend quasi-linearly on the ratio of the rotation rate and the Brunt-Väisälä frequency at the core interface. This allowed us to determine empirical relations between the width and location of dips as well as the resonant inertial mode frequency in the core\u0000 and the Brunt-Väisälä frequency at the interface between the convective core and the radiative zone. \u0000 We propose an approximate theoretical model to support and discuss these empirical relations. The empirical relations we established could be applied to dips observed in data, which would allow for the estimation of frequencies of resonant inertial modes in the core and of the Brunt-Väisälä jump at the interface between the core and the radiative zone. As those two parameters are both related to the evolutionary stage of the star, their determination could lead to more accurate estimations of stellar ages.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"67 21","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141806783","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: 10.1051/0004-6361/202449228
Samaresh Mondal, G. Ponti, Luke Filor, Tong Bao, F. Haberl, Ciro Salcedo, S. Campana, C. Hailey, K. Mori, N. Rea
We aim to characterise the population of low-luminosity X-ray sources in the Galactic plane by studying their X-ray spectra and periodic signals in the light curves. We are performing an X-ray survey of the Galactic disc using and the source XMMU J173029.8--330920 was serendipitously discovered in our campaign. We performed a follow-up observation of the source using our pre-approved target of opportunity time. We used various phenomenological models in xspec for the X-ray spectral modelling. We also computed the Lomb-Scargle periodogram to search for X-ray periodicity. A Monte Carlo method was used to simulate 1000 artificial light curves in order to estimate the significance of the detected period. We also searched for X-ray, optical, and infrared counterparts of the source in various catalogues. The spectral modelling indicates the presence of an intervening cloud with $N_ H $ that partially absorbs the incoming X-ray photons. The X-ray spectra are best fit by a model representing emission from a collisionally ionised diffuse gas with a plasma temperature of $kT=26^ $ keV. Furthermore, an Fe $K_ alpha $ line at $6.47^ $ keV was detected with an equivalent width of the line of $312 eV. We discovered a coherent pulsation with a period of $521.7 s. The 3--10 keV pulsed fraction of the source is around sim 50--60. The hard X-ray emission with plasma temperature $kT=26^ $ keV, iron $K_ alpha $ emission at 6.4 keV, and a periodic behaviour of $521.7 s suggest XMMU J173029.8--33092 to be an intermediate polar. We estimated the mass of the central white dwarf to be $0.94-1.4 odot $ by assuming a distance to the source of $ kpc.
我们的目标是通过研究银河面上低亮度 X 射线源的 X 射线光谱和光变曲线中的周期性信号来确定其特征。我们正在对银河盘进行 X 射线巡天，XMMU J173029.8--330920 源就是在我们的巡天活动中偶然发现的。我们利用事先批准的机会时间目标对该源进行了跟踪观测。我们使用 xspec 中的各种现象学模型进行 X 射线光谱建模。我们还计算了 Lomb-Scargle 周期图，以寻找 X 射线周期性。我们使用蒙特卡洛方法模拟了 1000 条人造光曲线，以估计探测到的周期的重要性。我们还在各种星表中搜索了该源的 X 射线、光学和红外线对应天体。光谱建模表明，存在一个含有 $N_ H $ 的中间云团，它部分吸收了射入的 X 射线光子。X 射线光谱与等离子体温度为 $kT=26^ $ keV 的碰撞电离弥漫气体发射模型的拟合效果最佳。此外，还探测到了一条 6.47^ $ keV 的铁 $K_ alpha $ 线，其等效线宽为 312 eV。我们发现了一个周期为 521.7 秒的相干脉冲。该源的 3-10 keV 脉冲部分约为 sim 50--60。等离子体温度为 kT=26^ $ keV 的硬 X 射线发射、6.4 keV 的铁 $K_ alpha $ 发射以及 521.7 s 的周期行为表明 XMMU J173029.8--33092 是一个中间极。我们假定与源的距离为 $ kpc，估计中央白矮星的质量为 $0.94-1.4 odot $。
{"title":"XMM-Newton and NuSTAR discovery of a likely IP candidate XMMU J173029.8--330920 in the Galactic disc","authors":"Samaresh Mondal, G. Ponti, Luke Filor, Tong Bao, F. Haberl, Ciro Salcedo, S. Campana, C. Hailey, K. Mori, N. Rea","doi":"10.1051/0004-6361/202449228","DOIUrl":"https://doi.org/10.1051/0004-6361/202449228","url":null,"abstract":"We aim to characterise the population of low-luminosity X-ray sources in the Galactic plane by studying their X-ray spectra and periodic signals in the light curves. We are performing an X-ray survey of the Galactic disc using and the source XMMU J173029.8--330920 was serendipitously discovered in our campaign. We performed a follow-up observation of the source using our pre-approved target of opportunity time. We used various phenomenological models in xspec for the X-ray spectral modelling. We also computed the Lomb-Scargle periodogram to search for X-ray periodicity. A Monte Carlo method was used to simulate 1000 artificial light curves in order to estimate the significance of the detected period. We also searched for X-ray, optical, and infrared counterparts of the source in various catalogues. The spectral modelling indicates the presence of an intervening cloud with $N_ H $ that partially absorbs the incoming X-ray photons. The X-ray spectra are best fit by a model representing emission from a collisionally ionised diffuse gas with a plasma temperature of $kT=26^ $ keV. Furthermore, an Fe $K_ alpha $ line at $6.47^ $ keV was detected with an equivalent width of the line of $312 eV. We discovered a coherent pulsation with a period of $521.7 s. The 3--10 keV pulsed fraction of the source is around sim 50--60. The hard X-ray emission with plasma temperature $kT=26^ $ keV, iron $K_ alpha $ emission at 6.4 keV, and a periodic behaviour of $521.7 s suggest XMMU J173029.8--33092 to be an intermediate polar. We estimated the mass of the central white dwarf to be $0.94-1.4 odot $ by assuming a distance to the source of $ kpc.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"56 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807010","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: 10.1051/0004-6361/202450355
M. Temmink, F. Ewine van Dishoeck, D. Gasman, L. Sierra Grant, B. Tabone, M. Gudel, Thomas K. Henning, D. Barrado, A. Caratti o Garatti, M. Adrian Glauser, I. Kamp, M. Aditya Arabhavi, H. Jang, N. Kurtovic, G. Perotti, K. Schwarz, M. Vlasblom
The Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) gives insights into the chemical richness and complexity of the inner regions of planet-forming disks. Several disks that are compact in the millimetre dust emission have been found by Spitzer to be particularly bright in H_2O which is thought to be caused by the inward drift of icy pebbles. Here, we analyse the H_2O -rich spectrum of the compact disk DR Tau using high-quality JWST-MIRI observations. We infer the H_2O column densities (in cm$^ $) using methods presented in previous works, as well as introducing a new method to fully characterise the pure rotational spectrum. We aim to further characterise the abundances of H_2O in the inner regions of this disk and its abundance relative to CO . We also search for emission of other molecular species, such as CH_4 NH_3 CS H_2 SO_2 and larger hydrocarbons; commonly detected species, such as CO CO_2 HCN and C_2H_2 have been investigated in our previous paper. We first use 0D local thermodynamic equilibrium (LTE) slab models to investigate the excitation properties observed in different wavelength regions across the entire spectrum, probing both the ro-vibrational and rotational transitions. To further analyse the pure rotational spectrum (geq 10 $ mu $m), we use the spectrum of a large, structured disk (CI Tau) as a template to search for differences with our compact disk. Finally, we fit multiple components to characterise the radial (and vertical) temperature gradient(s) present in the spectrum of DR Tau. The 0D slab models indicate a radial gradient in the disk, as the excitation temperature (emitting radius) decreases (increases) with increasing wavelength, which is confirmed by the analysis involving the large disk template. To explain the derived emitting radii, we need a larger inclination for the inner disk ($i agreeing with our previous analysis on CO . From our multi-component fit, we find that at least three temperature components ($T_1 K, $T_2 K, and $T_3 K) are required to reproduce the observed rotational spectrum of H_2O arising from the inner $R_ em au. By comparing line ratios, we derived an upper limit on the column densities (in $) for the first two components of $ (N) within sim 1.2 au. We note that the models with a pure temperature gradient provide as robust results as the more complex models, which include spatial line shielding. No robust detection of the isotopologue H_2 ^ O can be made and upper limits are provided for other molecular species. Our analysis confirms the presence of a pure radial temperature gradient present in the inner disk of DR Tau, which can be described by at least three components. This gradient scales roughly as $ R_ em $ in the emitting layers, in the inner 2 au. As the observed H_2O is mainly optically thick, a lower limit on the abundance ratio of H_2O CO sim 0.17 is derived, suggesting a potential depletion of H_2O . Similarly to
詹姆斯-韦伯太空望远镜（JWST）上的中红外光谱仪（MIRI）的中分辨率分光计（MRS）让人们了解到行星形成盘内部区域丰富而复杂的化学成分。斯皮策发现，一些在毫米尘埃发射中比较紧凑的星盘在 H_2O 中特别明亮，这被认为是冰卵石向内漂移造成的。在这里，我们利用高质量的 JWST-MIRI 观测数据分析了紧凑盘 DR Tau 的富含 H_2O 的光谱。我们利用以前工作中提出的方法推断出 H_2O 柱密度（单位：cm$^ $），并引入一种新方法来全面描述纯旋转光谱的特征。我们的目标是进一步确定该圆盘内部区域的 H_2O 丰度及其相对于 CO 的丰度。我们还搜索了其他分子物种的发射，如 CH_4 NH_3 CS H_2 SO_2 和更大的碳氢化合物；在我们之前的论文中已经研究了通常检测到的物种，如 CO CO_2 HCN 和 C_2H_2。我们首先使用 0D 局域热力学平衡 (LTE) 板坯模型来研究在整个光谱的不同波长区域观察到的激发特性，同时探究了旋转振动和旋转跃迁。为了进一步分析纯旋转光谱（geq 10 $ mu $m），我们使用了一个大型结构化圆盘（CI Tau）的光谱作为模板，以寻找与我们的紧凑圆盘的差异。最后，我们拟合了多个分量来描述 DR Tau 光谱中存在的径向（和垂直）温度梯度。0D板块模型表明，随着波长的增加，激发温度（发射半径）会降低（增加），因此在磁盘中存在径向梯度，这一点在涉及大磁盘模板的分析中得到了证实。为了解释得出的发射半径，我们需要一个更大的内盘倾角（$i 与我们之前对 CO .通过多成分拟合，我们发现至少需要三个温度成分（$T_1 K、$T_2 K 和 $T_3 K）才能重现观测到的来自内部 $R_ em au 的 H_2O 旋转光谱。通过比较线比，我们得出了模拟 1.2 au 范围内 $ (N) 的前两个分量的柱密度（单位：$）上限。我们注意到，纯温度梯度模型与包含空间线屏蔽的更复杂模型一样，都能提供可靠的结果。对同素异形体 H_2 ^ O 无法进行可靠的探测，但对其他分子种类提供了上限。我们的分析证实，DR Tau 的内盘存在纯径向温度梯度，至少可以用三个部分来描述。这个梯度在内部 2 au 的发射层中与 $ R_ em $ 大致成比例。由于观测到的 H_2O 主要是光厚型的，因此得出了 H_2O CO sim 0.17 的丰度比下限，这表明 H_2O 可能存在耗竭。与之前的工作类似，我们探测到了来自雪线附近的冷 H_2O 成分（$T K），现在是多成分分析。然而，我们还不能断定在径向漂移之后是否观测到 H_2O 储层的增强。要研究漂移对提高 H_2O 丰度的重要性，需要对更大的样本进行一致的分析。
{"title":"MINDS: The DR Tau disk. II. Probing the hot and cold H_2O reservoirs in the JWST-MIRI spectrum","authors":"M. Temmink, F. Ewine van Dishoeck, D. Gasman, L. Sierra Grant, B. Tabone, M. Gudel, Thomas K. Henning, D. Barrado, A. Caratti o Garatti, M. Adrian Glauser, I. Kamp, M. Aditya Arabhavi, H. Jang, N. Kurtovic, G. Perotti, K. Schwarz, M. Vlasblom","doi":"10.1051/0004-6361/202450355","DOIUrl":"https://doi.org/10.1051/0004-6361/202450355","url":null,"abstract":"The Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) gives insights into the chemical richness and complexity of the inner regions of planet-forming disks. Several disks that are compact in the millimetre dust emission have been found by Spitzer to be particularly bright in H_2O which is thought to be caused by the inward drift of icy pebbles. Here, we analyse the H_2O -rich spectrum of the compact disk DR Tau using high-quality JWST-MIRI observations. We infer the H_2O column densities (in cm$^ $) using methods presented in previous works, as well as introducing a new method to fully characterise the pure rotational spectrum. We aim to further characterise the abundances of H_2O in the inner regions of this disk and its abundance relative to CO . We also search for emission of other molecular species, such as CH_4 NH_3 CS H_2 SO_2 and larger hydrocarbons; commonly detected species, such as CO CO_2 HCN and C_2H_2 have been investigated in our previous paper. We first use 0D local thermodynamic equilibrium (LTE) slab models to investigate the excitation properties observed in different wavelength regions across the entire spectrum, probing both the ro-vibrational and rotational transitions. To further analyse the pure rotational spectrum (geq 10 $ mu $m), we use the spectrum of a large, structured disk (CI Tau) as a template to search for differences with our compact disk. Finally, we fit multiple components to characterise the radial (and vertical) temperature gradient(s) present in the spectrum of DR Tau. The 0D slab models indicate a radial gradient in the disk, as the excitation temperature (emitting radius) decreases (increases) with increasing wavelength, which is confirmed by the analysis involving the large disk template. To explain the derived emitting radii, we need a larger inclination for the inner disk ($i agreeing with our previous analysis on CO . From our multi-component fit, we find that at least three temperature components ($T_1 K, $T_2 K, and $T_3 K) are required to reproduce the observed rotational spectrum of H_2O arising from the inner $R_ em au. By comparing line ratios, we derived an upper limit on the column densities (in $) for the first two components of $ (N) within sim 1.2 au. We note that the models with a pure temperature gradient provide as robust results as the more complex models, which include spatial line shielding. No robust detection of the isotopologue H_2 ^ O can be made and upper limits are provided for other molecular species. Our analysis confirms the presence of a pure radial temperature gradient present in the inner disk of DR Tau, which can be described by at least three components. This gradient scales roughly as $ R_ em $ in the emitting layers, in the inner 2 au. As the observed H_2O is mainly optically thick, a lower limit on the abundance ratio of H_2O CO sim 0.17 is derived, suggesting a potential depletion of H_2O . Similarly to","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"86 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807830","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: 10.1051/0004-6361/202451016
Michal Švanda, Daniel Chmúrny
Helioseismic inversions largely rely on sensitivity kernels, in which 3D spatial functions describe how the changes in the solar interior translate into the change in helioseismic observables. These sensitivity kernels in most cases come from the forward modelling that is used in the most advanced solar models. We aim to test the sensitivity kernels by comparing their volume integrals with measured values from helioseismic travel times. By manipulating the tracking rate, we mimicked the additional zonal velocity in the Dopplergram datacubes. These datacubes were then processed by a standard travel-time measurements pipeline. We investigated the dependence of the east-west travel time averaged over a box around the disc centre on the implanted tracking velocity. The slope of this dependence is directly proportional to the total volume integral of the sensitivity kernel that corresponds to the travel-time geometry that is used. The agreement between measurements and models for travel times that are computed with a ridge filtering is very good to acceptable. The dependence we sought to determine indeed resembles a linear function, and its slope agrees with the expected volume integral from the forward-modelled sensitivity kernel. The agreement is poorer for the phase-speed filtered datacubes. The disagreement is particularly strong for the slowest phase speeds (filters td1--td4). For the higher phase speeds, our result indicates that the measured kernel integrals are systematically larger than expected from the forward modelling. We admit our testing procedure may not be appropriate for high phase speeds and higher radial modes.
{"title":"Testing the volume integrals of travel-time sensitivity kernels for flows","authors":"Michal Švanda, Daniel Chmúrny","doi":"10.1051/0004-6361/202451016","DOIUrl":"https://doi.org/10.1051/0004-6361/202451016","url":null,"abstract":"Helioseismic inversions largely rely on sensitivity kernels, in which 3D spatial functions describe how the changes in the solar interior translate into the change in helioseismic observables. These sensitivity kernels in most cases come from the forward modelling that is used in the most advanced solar models. We aim to test the sensitivity kernels by comparing their volume integrals with measured values from helioseismic travel times. By manipulating the tracking rate, we mimicked the additional zonal velocity in the Dopplergram datacubes. These datacubes were then processed by a standard travel-time measurements pipeline. We investigated the dependence of the east-west travel time averaged over a box around the disc centre on the implanted tracking velocity. The slope of this dependence is directly proportional to the total volume integral of the sensitivity kernel that corresponds to the travel-time geometry that is used. The agreement between measurements and models for travel times that are computed with a ridge filtering is very good to acceptable. The dependence we sought to determine indeed resembles a linear function, and its slope agrees with the expected volume integral from the forward-modelled sensitivity kernel. The agreement is poorer for the phase-speed filtered datacubes. The disagreement is particularly strong for the slowest phase speeds (filters td1--td4). For the higher phase speeds, our result indicates that the measured kernel integrals are systematically larger than expected from the forward modelling. We admit our testing procedure may not be appropriate for high phase speeds and higher radial modes.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"27 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809019","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: 10.1051/0004-6361/202449987
Elie Leroy, Jérôme Bobin, Herve Moutarde
The space-based gravitational wave observatory LISA will provide a wealth of information to analyze massive black hole binaries with high chirp masses, beyond $10^5$ solar masses. The large number of expected MBHBs (one event a day on average) increases the risk of overlapping between events. As well, the data will be contaminated with non-stationary artifacts, such as glitches and data gaps, which are expected to strongly impact the MBHB analysis, which mandates the development of dedicated detection and retrieval methods on long time intervals. Building upon a methodological approach we introduced for galactic binaries, in this article we investigate an original non-parametric recovery of MBHB signals from measurements with instrumental noise typical of LISA in order to tackle detection and signal reconstruction tasks on long time intervals. We investigated different approaches based on sparse signal modeling and machine learning. In this framework, we focused on recovering MBHB waveforms on long time intervals, which is a building block to further tackling more general signal recovery problems, from gap mitigation to unmixing overlapped signals. To that end, we introduced a hybrid method called SCARF (sparse chirp adaptive representation in Fourier), which combines a deep learning modeling of the merger of the MBHB with a specific adaptive time-frequency representation of the inspiral. Numerical experiments have been carried out on simulations of single MBHB events that account for the LISA response and with realistic realizations of noise. We checked the performances of the proposed hybrid method for the fast detection and recovery of the MBHB.
天基引力波观测站 LISA 将为分析具有高啁啾质量（超过 10^5$ 太阳质量）的大质量黑洞双星提供大量信息。预期的大量 MBHB（平均每天一个）增加了事件之间重叠的风险。此外，数据还将受到非稳态假象的污染，如闪烁和数据缺口，这些假象预计将对 MBHB 分析产生严重影响，这就要求开发专门的长时间跨度检测和检索方法。基于我们为星系双星引入的方法，我们在本文中研究了一种从具有典型 LISA 仪器噪声的测量中恢复 MBHB 信号的原创非参数方法，以解决长时间跨度上的探测和信号重建任务。我们研究了基于稀疏信号建模和机器学习的不同方法。在这一框架中，我们重点研究了在长时间跨度上恢复 MBHB 波形的问题，这是进一步解决更多一般信号恢复问题（从间隙缓解到解除混合重叠信号）的基石。为此，我们引入了一种名为 SCARF（傅里叶稀疏啁啾自适应表示）的混合方法，它将 MBHB 合并的深度学习建模与吸气的特定自适应时频表示相结合。我们在模拟单个 MBHB 事件时进行了数值实验，这些事件考虑到了 LISA 的响应和现实中的噪声。我们检验了所提出的混合方法在快速探测和恢复 MBHB 方面的性能。
{"title":"Low-dimensional signal representations for massive black hole binary signals analysis from LISA data","authors":"Elie Leroy, Jérôme Bobin, Herve Moutarde","doi":"10.1051/0004-6361/202449987","DOIUrl":"https://doi.org/10.1051/0004-6361/202449987","url":null,"abstract":"The space-based gravitational wave observatory LISA will provide a wealth of information to analyze massive black hole binaries with high chirp masses, beyond $10^5$ solar masses. The large number of expected MBHBs (one event a day on average) increases the risk of overlapping between events. As well, the data will be contaminated with non-stationary artifacts, such as glitches and data gaps, which are expected to strongly impact the MBHB analysis, which mandates the development of dedicated detection and retrieval methods on long time intervals. Building upon a methodological approach we introduced for galactic binaries, in this article we investigate an original non-parametric recovery of MBHB signals from measurements with instrumental noise typical of LISA in order to tackle detection and signal reconstruction tasks on long time intervals. We investigated different approaches based on sparse signal modeling and machine learning. In this framework, we focused on recovering MBHB waveforms on long time intervals, which is a building block to further tackling more general signal recovery problems, from gap mitigation to unmixing overlapped signals. To that end, we introduced a hybrid method called SCARF (sparse chirp adaptive representation in Fourier), which combines a deep learning modeling of the merger of the MBHB with a specific adaptive time-frequency representation of the inspiral. Numerical experiments have been carried out on simulations of single MBHB events that account for the LISA response and with realistic realizations of noise. We checked the performances of the proposed hybrid method for the fast detection and recovery of the MBHB.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"23 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141810298","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: 10.1051/0004-6361/202450550
S.M. Hejazi, S. Vasheghani Farahani, K. Hajisharifi, H. Mehdian
We model solar atmospheric structures characterised by parallel structuring. We focus on Alfv'en waves in the weakly non-linear regime to highlight the efficiency of non-linear wave steepening when dissipative effects are prominent. We also consider the local and equilibrium conditions involved in shock formation and the shock's contributions to coronal seismology. Coronal plumes were modelled analytically by implementing the magnetohydrodynamic (MHD) theory in cylindrical geometry. Here, the stratification and viscosity are present internal to the plume, whilst effects of the external medium, together with equilibrium conditions, are implied where the magnetic fields are parallel to the plume axis. We implemented a second-order thin flux tube approximation to obtain a wave equation that points to effects tied to non-linear, dissipative, and stratification terms, as well as terms representing atmospheric conditions. The impact of shear viscosity on non-linear Alfv'en waves extracted by the Cohen-Kulsrud-Burgers-type equation proves more efficient when propagated to higher altitudes. The dissipative effects linked to the dimensionless viscosity indicate that the dissipative effects are not linear. Meanwhile, the delay in shock formation enables energy conversions at higher altitudes, thereby maintaining coronal heating at higher levels. The efficiency of parallel structuring and viscous damping is enhanced by such transverse structuring, as it is directly proportional to the external plasma-beta . It is observed that Alfv'en pulses may undergo a backward shock, either in the lower levels of coronal plasma or as they propagate toward higher regions, implying a conversion of energy occurring at various altitudes. A peak was observed, indicating that the interplay reverses at heights around $1.5$ solar radii. Such effects are shown to play a key role in the context of coronal seismology.
{"title":"Non-linear torsional Alfv'en waves evolving in stratified viscous plasmas: Coronal hole plumes","authors":"S.M. Hejazi, S. Vasheghani Farahani, K. Hajisharifi, H. Mehdian","doi":"10.1051/0004-6361/202450550","DOIUrl":"https://doi.org/10.1051/0004-6361/202450550","url":null,"abstract":"We model solar atmospheric structures characterised by parallel structuring. We focus on Alfv'en waves in the weakly non-linear regime to highlight the efficiency of non-linear wave steepening when dissipative effects are prominent. We also consider the local and equilibrium conditions involved in shock formation and the shock's contributions to coronal seismology. Coronal plumes were modelled analytically by implementing the magnetohydrodynamic (MHD) theory in cylindrical geometry. Here, the stratification and viscosity are present internal to the plume, whilst effects of the external medium, together with equilibrium conditions, are implied where the magnetic fields are parallel to the plume axis. We implemented a second-order thin flux tube approximation to obtain a wave equation that points to effects tied to non-linear, dissipative, and stratification terms, as well as terms representing atmospheric conditions. The impact of shear viscosity on non-linear Alfv'en waves extracted by the Cohen-Kulsrud-Burgers-type equation proves more efficient when propagated to higher altitudes. The dissipative effects linked to the dimensionless viscosity indicate that the dissipative effects are not linear. Meanwhile, the delay in shock formation enables energy conversions at higher altitudes, thereby maintaining coronal heating at higher levels. The efficiency of parallel structuring and viscous damping is enhanced by such transverse structuring, as it is directly proportional to the external plasma-beta . It is observed that Alfv'en pulses may undergo a backward shock, either in the lower levels of coronal plasma or as they propagate toward higher regions, implying a conversion of energy occurring at various altitudes. A peak was observed, indicating that the interplay reverses at heights around $1.5$ solar radii. Such effects are shown to play a key role in the context of coronal seismology.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"14 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807352","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: 10.1051/0004-6361/202450365
A. Spasic, H. Edler, Y. Su, M. Brüggen, F. de Gasperin, T. Pasini, V. Heesen, M. Simonte, A. Boselli, H. Röttgering, M. Fossati
The evolution of active galactic nuclei (AGNs) is closely connected to their host galaxies and surroundings. Via feedback processes, AGNs can counteract the cooling of the intracluster medium (ICM) and suppress star formation in their host galaxies. Radio observations at low frequencies provide a glimpse into the history of AGN activity. The Virgo cluster is a substantial reservoir of nearby galaxies and provides an ideal laboratory for the study of AGNs as well as their feedback mechanisms. The aim of our work is to characterise the AGN population within the Virgo cluster down to low radio luminosities, constrain the AGN duty cycle, and investigate environmental feedback in cluster member galaxies. We analysed 144,MHz and 1.3,GHz radio observations of early-type galaxies from the ACS Virgo Cluster Survey (ACSVCS) taken with LOFAR and MeerKAT. We detect 12 of these galaxies at 144,MHz, five of which show clearly extended radio emission. The radio luminosity shows a strong dependence on the stellar mass of the host galaxy, in agreement with previous results. As a notable outlier, the massive elliptical galaxy NGC,4365 ($M_*=2.2 ,M_ is not detected as compact source in the LOFAR observations. Instead, it is surrounded by diffuse, low-surface brightness emission, which hints towards a past phase of stronger nuclear activity. Furthermore, we find a cavity in NGC,4472 (= M,49) inflated by the wide-angle tail only visible in the LOFAR data, which implies that the cavity was created by a past outburst. The corresponding cavity power is of the same order of magnitude as the jet power in the present duty cycle of the AGN.
{"title":"ViCTORIA project: The LOFAR-MeerKAT view of active galactic nuclei in Virgo cluster early-type galaxies","authors":"A. Spasic, H. Edler, Y. Su, M. Brüggen, F. de Gasperin, T. Pasini, V. Heesen, M. Simonte, A. Boselli, H. Röttgering, M. Fossati","doi":"10.1051/0004-6361/202450365","DOIUrl":"https://doi.org/10.1051/0004-6361/202450365","url":null,"abstract":"The evolution of active galactic nuclei (AGNs) is closely connected to their host galaxies and surroundings. Via feedback processes, AGNs can counteract the cooling of the intracluster medium (ICM) and suppress star formation in their host galaxies. Radio observations at low frequencies provide a glimpse into the history of AGN activity. The Virgo cluster is a substantial reservoir of nearby galaxies and provides an ideal laboratory for the study of AGNs as well as their feedback mechanisms. The aim of our work is to characterise the AGN population within the Virgo cluster down to low radio luminosities, constrain the AGN duty cycle, and investigate environmental feedback in cluster member galaxies. We analysed 144,MHz and 1.3,GHz radio observations of early-type galaxies from the ACS Virgo Cluster Survey (ACSVCS) taken with LOFAR and MeerKAT. We detect 12 of these galaxies at 144,MHz, five of which show clearly extended radio emission. The radio luminosity shows a strong dependence on the stellar mass of the host galaxy, in agreement with previous results. As a notable outlier, the massive elliptical galaxy NGC,4365 ($M_*=2.2 ,M_ is not detected as compact source in the LOFAR observations. Instead, it is surrounded by diffuse, low-surface brightness emission, which hints towards a past phase of stronger nuclear activity. Furthermore, we find a cavity in NGC,4472 (= M,49) inflated by the wide-angle tail only visible in the LOFAR data, which implies that the cavity was created by a past outburst. The corresponding cavity power is of the same order of magnitude as the jet power in the present duty cycle of the AGN.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"2 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807484","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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