Pub Date : 2024-10-17DOI: 10.3847/1538-4357/ad6ccf
Satyajeet Moharana, B. P. Hema and Gajendra Pandey
Determining the He/H ratio in cool stars presents a fundamental astrophysical challenge. While this ratio is established for hot O and B stars, its extrapolation to cool stars remains uncertain due to the absence of helium lines in their observed spectra. We address this knowledge gap by focusing on the Sun as a representative cool star. We conduct spectroscopic analyses of the observed solar photospheric lines by utilizing a combination of MgH molecular lines and neutral Mg atomic lines including yet another combination of CH and C2 molecular lines with neutral C atomic lines. Our spectroscopic analyses were further exploited by adopting solar model atmospheres constructed for distinct He/H ratios to determine the solar photospheric helium abundance. The helium abundance is determined by enforcing the fact that for an adopted model atmosphere with an appropriate He/H ratio, the derived Mg abundance from the neutral Mg atomic lines and that from the MgH molecular lines must be the same. The same holds for the C abundance derived from neutral C atomic lines and that from CH lines of the CH molecular band and C2 lines from the C2 Swan band. The estimated He/H ratio for the Sun is discussed based on the one-dimensional local thermodynamic equilibrium model atmosphere. The helium abundance (He/H = ) obtained for the Sun serves as a critical reference point to characterize the He/H ratio of cool stars across the range in their effective temperature.
确定冷恒星中的氦/氢比率是一项基本的天体物理学挑战。虽然热 O 星和热 B 星的氦/氢比已经确定，但由于观测到的恒星光谱中没有氦线，因此推断冷恒星的氦/氢比仍然不确定。我们以太阳为代表的冷恒星为研究对象，填补了这一知识空白。我们利用 MgH 分子线和中性镁原子线的组合，包括 CH 和 C2 分子线与中性 C 原子线的另一种组合，对观测到的太阳光层线进行光谱分析。我们的光谱分析进一步利用了根据不同的氦/氢比构建的太阳模型大气，以确定太阳光层的氦丰度。确定氦丰度的方法是：对于所采用的具有适当 He/H 比值的模型大气，从中性镁原子线推导出的镁丰度和从 MgH 分子线推导出的镁丰度必须相同。从中性 C 原子线和 CH 分子波段的 CH 线以及 C2 天鹅波段的 C2 线得出的 C 丰度也是一样。根据一维局部热力学平衡模型大气，讨论了太阳的氦/氢比估计值。太阳的氦丰度（He/H = ）是描述不同有效温度范围内冷恒星氦/氢比的重要参考点。
{"title":"Helium Abundance of the Sun: A Spectroscopic Analysis","authors":"Satyajeet Moharana, B. P. Hema and Gajendra Pandey","doi":"10.3847/1538-4357/ad6ccf","DOIUrl":"https://doi.org/10.3847/1538-4357/ad6ccf","url":null,"abstract":"Determining the He/H ratio in cool stars presents a fundamental astrophysical challenge. While this ratio is established for hot O and B stars, its extrapolation to cool stars remains uncertain due to the absence of helium lines in their observed spectra. We address this knowledge gap by focusing on the Sun as a representative cool star. We conduct spectroscopic analyses of the observed solar photospheric lines by utilizing a combination of MgH molecular lines and neutral Mg atomic lines including yet another combination of CH and C2 molecular lines with neutral C atomic lines. Our spectroscopic analyses were further exploited by adopting solar model atmospheres constructed for distinct He/H ratios to determine the solar photospheric helium abundance. The helium abundance is determined by enforcing the fact that for an adopted model atmosphere with an appropriate He/H ratio, the derived Mg abundance from the neutral Mg atomic lines and that from the MgH molecular lines must be the same. The same holds for the C abundance derived from neutral C atomic lines and that from CH lines of the CH molecular band and C2 lines from the C2 Swan band. The estimated He/H ratio for the Sun is discussed based on the one-dimensional local thermodynamic equilibrium model atmosphere. The helium abundance (He/H = ) obtained for the Sun serves as a critical reference point to characterize the He/H ratio of cool stars across the range in their effective temperature.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448725","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 : 2024-10-17DOI: 10.3847/1538-4357/ad74ff
Emma M. Louden and Sarah C. Millholland
There is an intriguing and growing population of Neptune-sized planets with stellar obliquities near ∼90°. One previously proposed formation pathway is a disk-driven resonance, which can take place at the end stages of planet formation in a system containing an inner Neptune, outer cold Jupiter, and protoplanetary disk. This mechanism occurs within the first ∼10 Myr, but most of the polar Neptunes we see today are ∼Gyr old. Up until now, there has not been an extensive analysis of whether the polar orbits are stable over ∼Gyr timescales. Tidal realignment mechanisms are known to operate in other systems, and if they are active here, this would cause theoretical tension with a primordial misalignment story. In this paper, we explore the effects of tidal evolution on the disk-driven resonance theory. We use both N-body and secular simulations to study tidal effects on both the initial resonant encounter and long-term evolution. We find that the polar orbits are remarkably stable on ∼Gyr timescales. Inclination damping does not occur for the polar cases, although we do identify subpolar cases where it is important. We consider two case study polar Neptunes, WASP-107 b and HAT-P-11 b, and study them in the context of this theory, finding consistency with present-day properties if their tidal quality factors are Q ≳ 104 and Q ≳ 105, respectively.
{"title":"Polar Neptunes Are Stable to Tides","authors":"Emma M. Louden and Sarah C. Millholland","doi":"10.3847/1538-4357/ad74ff","DOIUrl":"https://doi.org/10.3847/1538-4357/ad74ff","url":null,"abstract":"There is an intriguing and growing population of Neptune-sized planets with stellar obliquities near ∼90°. One previously proposed formation pathway is a disk-driven resonance, which can take place at the end stages of planet formation in a system containing an inner Neptune, outer cold Jupiter, and protoplanetary disk. This mechanism occurs within the first ∼10 Myr, but most of the polar Neptunes we see today are ∼Gyr old. Up until now, there has not been an extensive analysis of whether the polar orbits are stable over ∼Gyr timescales. Tidal realignment mechanisms are known to operate in other systems, and if they are active here, this would cause theoretical tension with a primordial misalignment story. In this paper, we explore the effects of tidal evolution on the disk-driven resonance theory. We use both N-body and secular simulations to study tidal effects on both the initial resonant encounter and long-term evolution. We find that the polar orbits are remarkably stable on ∼Gyr timescales. Inclination damping does not occur for the polar cases, although we do identify subpolar cases where it is important. We consider two case study polar Neptunes, WASP-107 b and HAT-P-11 b, and study them in the context of this theory, finding consistency with present-day properties if their tidal quality factors are Q ≳ 104 and Q ≳ 105, respectively.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448747","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 : 2024-10-17DOI: 10.3847/1538-4357/ad77a9
Grant C. Weldon, Smadar Naoz and Bradley M. S. Hansen
Three-body systems are prevalent in nature, from planetary to stellar to supermassive black hole scales. In a hierarchical triple system, oscillations of the inner orbit’s eccentricity and inclination can be induced on secular timescales. Over many cycles, the octupole-level terms in the secular equations of motion can drive the system to extremely high eccentricities via the eccentric Kozai–Lidov (EKL) mechanism. The overall decrease in the inner orbit’s pericenter distance has potentially dramatic effects for realistic systems, such as tidal disruption events. We present an analytical approximation in the test-particle limit to describe individual stepwise increases in eccentricity of the inner orbit. A second approximation, also in the test-particle limit, is obtained by integrating the equations of motion and calibrating to numerical simulations to estimate the overall octupole-level time evolution of the eccentricity. The latter approach is then extended beyond the test particle to the general case. The three novel analytical approximations are compared to numerical solutions to show that the models accurately describe the form and timescale of the secular descent from large distances to a close-encounter distance (e.g., the Roche limit). By circumventing the need for numerical simulations to obtain the long-term behavior, these approximations can be used to readily estimate properties of close encounters and descent timescales for populations of systems. We demonstrate this by calculating rates of EKL-driven migration for Hot Jupiters in stellar binaries.
{"title":"Analytical Models for Secular Descents in Hierarchical Triple Systems","authors":"Grant C. Weldon, Smadar Naoz and Bradley M. S. Hansen","doi":"10.3847/1538-4357/ad77a9","DOIUrl":"https://doi.org/10.3847/1538-4357/ad77a9","url":null,"abstract":"Three-body systems are prevalent in nature, from planetary to stellar to supermassive black hole scales. In a hierarchical triple system, oscillations of the inner orbit’s eccentricity and inclination can be induced on secular timescales. Over many cycles, the octupole-level terms in the secular equations of motion can drive the system to extremely high eccentricities via the eccentric Kozai–Lidov (EKL) mechanism. The overall decrease in the inner orbit’s pericenter distance has potentially dramatic effects for realistic systems, such as tidal disruption events. We present an analytical approximation in the test-particle limit to describe individual stepwise increases in eccentricity of the inner orbit. A second approximation, also in the test-particle limit, is obtained by integrating the equations of motion and calibrating to numerical simulations to estimate the overall octupole-level time evolution of the eccentricity. The latter approach is then extended beyond the test particle to the general case. The three novel analytical approximations are compared to numerical solutions to show that the models accurately describe the form and timescale of the secular descent from large distances to a close-encounter distance (e.g., the Roche limit). By circumventing the need for numerical simulations to obtain the long-term behavior, these approximations can be used to readily estimate properties of close encounters and descent timescales for populations of systems. We demonstrate this by calculating rates of EKL-driven migration for Hot Jupiters in stellar binaries.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448749","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 : 2024-10-17DOI: 10.3847/1538-4357/ad7a64
Yi Feng, Di Li, Yong-Kun Zhang, Chao-Wei Tsai, Yuanhong Qu, Wei-Yang Wang, Yuan-Pei Yang, Pei Wang, Dengke Zhou, Jiarui Niu, Chenchen Miao, Mao Yuan, Jiaying Xu, Ryan S. Lynch, William Paul Armentrout, Brenne Gregory, Lingqi Meng, Shen Wang, Xianglei Chen, Shi Dai, Chen-Hui Niu, Mengyao Xue, Ju-Mei Yao, Bing Zhang, Junshuo Zhang, Weiwei Zhu, Jintao Xie and Yuhao Zhu
Fast radio bursts (FRBs) are bright radio bursts originating at cosmological distances. Only three repeating FRBs FRB 20121102A, FRB 20190520B, and FRB 20201124A among ∼60 known repeating FRBs have circular polarization. We observed the FRB 20220912A with the Robert C. Byrd Green Bank Telescope (GBT) at L-band on 2022 October 24 and detected 128 bursts in 1.4 hr, corresponding to a burst rate of about 90 hr−1, which is the highest yet for FRBs observed by the GBT. The average rotation measure (RM) was −0.4 ± 0.3 rad m−2 with negligible intraday RM change, indicating a likely nonmagneto-ionic environment. A total of 61% of bursts have a linear polarization fraction greater than 90%. Approximately 56% of the bright bursts have circular polarization. A downward drift in frequency and polarization angle swings were found in our sample. The characterization of FRB 20220912A indicates that the circular polarization is unlikely to be caused by the magneto-ionic environment for at least some of the repeating FRB population.
{"title":"An Extremely Active Repeating Fast Radio Burst Source in a Likely Nonmagneto-ionic Environment","authors":"Yi Feng, Di Li, Yong-Kun Zhang, Chao-Wei Tsai, Yuanhong Qu, Wei-Yang Wang, Yuan-Pei Yang, Pei Wang, Dengke Zhou, Jiarui Niu, Chenchen Miao, Mao Yuan, Jiaying Xu, Ryan S. Lynch, William Paul Armentrout, Brenne Gregory, Lingqi Meng, Shen Wang, Xianglei Chen, Shi Dai, Chen-Hui Niu, Mengyao Xue, Ju-Mei Yao, Bing Zhang, Junshuo Zhang, Weiwei Zhu, Jintao Xie and Yuhao Zhu","doi":"10.3847/1538-4357/ad7a64","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7a64","url":null,"abstract":"Fast radio bursts (FRBs) are bright radio bursts originating at cosmological distances. Only three repeating FRBs FRB 20121102A, FRB 20190520B, and FRB 20201124A among ∼60 known repeating FRBs have circular polarization. We observed the FRB 20220912A with the Robert C. Byrd Green Bank Telescope (GBT) at L-band on 2022 October 24 and detected 128 bursts in 1.4 hr, corresponding to a burst rate of about 90 hr−1, which is the highest yet for FRBs observed by the GBT. The average rotation measure (RM) was −0.4 ± 0.3 rad m−2 with negligible intraday RM change, indicating a likely nonmagneto-ionic environment. A total of 61% of bursts have a linear polarization fraction greater than 90%. Approximately 56% of the bright bursts have circular polarization. A downward drift in frequency and polarization angle swings were found in our sample. The characterization of FRB 20220912A indicates that the circular polarization is unlikely to be caused by the magneto-ionic environment for at least some of the repeating FRB population.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448755","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 : 2024-10-17DOI: 10.3847/1538-4357/ad6c3b
Elettra L. Piacentino, Aurelia Balkanski, Mahesh Rajappan and Karin I. Öberg
Aromatic structures are fundamental for key biological molecules such as RNA and metabolites and the abundances of aromatic molecules on young planets are therefore of high interest. Recent detections of benzonitrile and other aromatic compounds in interstellar clouds and comets have revealed a rich aromatic astrochemistry. In the cold phases of star and planet formation, most of these aromatic molecules are likely to reside in icy grain mantles, where they could be observed through IR spectroscopy. We present laboratory IR spectra of benzene and four monosubstituted benzene molecules—toluene, phenol, benzonitrile, and benzaldehyde—to determine their IR ice absorbances in undiluted aromatic ices, and in mixtures with water and CO. We also characterize the aromatic ice desorption rates, and extract binding energies and respective pre-exponential factors using temperature-programmed desorption experiments. We use these to predict at which protostellar and protoplanetary disk temperatures these molecules sublimate into the gas phase. We find that benzene and monosubstituted benzene derivatives are low-volatility with binding energies in the 5220–8390 K (43–70 kJ mol−1) range, which suggests that most of the chemistry of benzene and of functionalized aromatic molecules is to be expected to occur in the ice phase during star and planet formation.
芳香族结构是 RNA 和代谢物等关键生物分子的基础，因此年轻行星上芳香族分子的丰度备受关注。最近在星际云和彗星中探测到的苯甲腈和其他芳香族化合物揭示了丰富的芳香族天体化学。在恒星和行星形成的寒冷阶段，这些芳香族分子很可能大多存在于冰粒外壳中，可以通过红外光谱对它们进行观测。我们展示了苯和四种单取代苯分子--甲苯、苯酚、苯甲腈和苯甲醛--的实验室红外光谱，以确定它们在未稀释的芳香冰以及与水和 CO 的混合物中的红外冰吸收率。我们还利用温度编程解吸实验确定了芳香族冰解吸速率的特征，并提取了结合能和各自的预指数。我们利用这些来预测这些分子在原恒星和原行星盘的什么温度下升华为气相。我们发现苯和单取代苯衍生物的结合能在 5220-8390 K（43-70 kJ mol-1）范围内，属于低挥发性物质，这表明苯和官能化芳香分子的大部分化学反应预计会在恒星和行星形成过程中的冰相发生。
{"title":"Characterization of Monosubstituted Benzene Ices","authors":"Elettra L. Piacentino, Aurelia Balkanski, Mahesh Rajappan and Karin I. Öberg","doi":"10.3847/1538-4357/ad6c3b","DOIUrl":"https://doi.org/10.3847/1538-4357/ad6c3b","url":null,"abstract":"Aromatic structures are fundamental for key biological molecules such as RNA and metabolites and the abundances of aromatic molecules on young planets are therefore of high interest. Recent detections of benzonitrile and other aromatic compounds in interstellar clouds and comets have revealed a rich aromatic astrochemistry. In the cold phases of star and planet formation, most of these aromatic molecules are likely to reside in icy grain mantles, where they could be observed through IR spectroscopy. We present laboratory IR spectra of benzene and four monosubstituted benzene molecules—toluene, phenol, benzonitrile, and benzaldehyde—to determine their IR ice absorbances in undiluted aromatic ices, and in mixtures with water and CO. We also characterize the aromatic ice desorption rates, and extract binding energies and respective pre-exponential factors using temperature-programmed desorption experiments. We use these to predict at which protostellar and protoplanetary disk temperatures these molecules sublimate into the gas phase. We find that benzene and monosubstituted benzene derivatives are low-volatility with binding energies in the 5220–8390 K (43–70 kJ mol−1) range, which suggests that most of the chemistry of benzene and of functionalized aromatic molecules is to be expected to occur in the ice phase during star and planet formation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448724","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 : 2024-10-17DOI: 10.3847/1538-4357/ad77d5
J. R. Fuentes and Vanessa Graber
Neutron stars show a steady decrease in their rotational frequency, occasionally interrupted by sudden spin-up events called glitches. The dynamics of a neutron star after a glitch involve the transfer of angular momentum from the crust (where the glitch is presumed to originate) to the liquid core, causing the core to spin up. The crust–core coupling, which determines how quickly this spin-up proceeds, can be achieved through various physical processes, including Ekman pumping, superfluid vortex-mediated mutual friction, and magnetic fields. Although the complex nature of these mechanisms has made it difficult to study their combined effects, analytical estimations for individual processes reveal that spin-up timescales vary according to the relative strength of Coriolis, viscous, and mutual friction forces, as well as the magnetic field. However, experimental and numerical validations of those analytical predictions are limited. In this paper, we focus on viscous effects and mutual friction. We conduct nonlinear hydrodynamical simulations of the spin-up problem in a two-component fluid by solving the incompressible Hall–Vinen–Bekarevich–Khalatnikov equations in the full sphere (i.e., including r = 0) for the first time. We find that the viscous (normal) component accelerates due to Ekman pumping, although the mutual friction coupling to the superfluid component alters the spin-up dynamics compared to the single-fluid scenario. Close to the sphere’s surface, the response of the superfluid is accurately described by the mutual friction timescale irrespective of its coupling strength with the normal component. However, as we move deeper into the sphere, the superfluid accelerates on different timescales due to the slow viscous spin-up of the internal normal fluid layers. We discuss potential implications for neutron stars, and requirements for future work to build more realistic models.
中子星的旋转频率呈稳定下降趋势，偶尔会被称为 "突变 "的突然自旋上升事件打断。中子星在发生突变后的动力学过程涉及角动量从地壳（推测突变起源于地壳）向液态内核的转移，从而导致内核自旋上升。地壳-内核耦合决定了自旋上升的速度，可以通过各种物理过程实现，包括埃克曼泵、超流体涡旋介导的相互摩擦和磁场。虽然这些机制的复杂性使得研究它们的综合效应变得困难，但对单个过程的分析估计显示，自旋上升的时间尺度会根据科里奥利力、粘性力、相互摩擦力以及磁场的相对强度而变化。然而，这些分析预测的实验和数值验证是有限的。在本文中，我们将重点讨论粘性效应和相互摩擦力。我们首次在全球（即包括 r = 0）范围内求解不可压缩的 Hall-Vinen-Bekarevich-Khalatnikov 方程，对双组分流体中的自旋上升问题进行非线性流体力学模拟。我们发现，由于埃克曼泵的作用，粘性（法向）成分会加速，尽管与单流体情况相比，与超流体成分的相互摩擦耦合改变了自旋上升动力学。在靠近球面的地方，超流体的反应是由相互摩擦时间尺度精确描述的，而与法向分量的耦合强度无关。然而，当我们向球体深处移动时，由于内部法向流体层缓慢的粘性自旋，超流体在不同的时间尺度上加速。我们讨论了超流体对中子星的潜在影响，以及未来建立更逼真模型的工作要求。
{"title":"Superfluid Spin-up: Three-dimensional Simulations of Post-glitch Dynamics in Neutron Star Cores","authors":"J. R. Fuentes and Vanessa Graber","doi":"10.3847/1538-4357/ad77d5","DOIUrl":"https://doi.org/10.3847/1538-4357/ad77d5","url":null,"abstract":"Neutron stars show a steady decrease in their rotational frequency, occasionally interrupted by sudden spin-up events called glitches. The dynamics of a neutron star after a glitch involve the transfer of angular momentum from the crust (where the glitch is presumed to originate) to the liquid core, causing the core to spin up. The crust–core coupling, which determines how quickly this spin-up proceeds, can be achieved through various physical processes, including Ekman pumping, superfluid vortex-mediated mutual friction, and magnetic fields. Although the complex nature of these mechanisms has made it difficult to study their combined effects, analytical estimations for individual processes reveal that spin-up timescales vary according to the relative strength of Coriolis, viscous, and mutual friction forces, as well as the magnetic field. However, experimental and numerical validations of those analytical predictions are limited. In this paper, we focus on viscous effects and mutual friction. We conduct nonlinear hydrodynamical simulations of the spin-up problem in a two-component fluid by solving the incompressible Hall–Vinen–Bekarevich–Khalatnikov equations in the full sphere (i.e., including r = 0) for the first time. We find that the viscous (normal) component accelerates due to Ekman pumping, although the mutual friction coupling to the superfluid component alters the spin-up dynamics compared to the single-fluid scenario. Close to the sphere’s surface, the response of the superfluid is accurately described by the mutual friction timescale irrespective of its coupling strength with the normal component. However, as we move deeper into the sphere, the superfluid accelerates on different timescales due to the slow viscous spin-up of the internal normal fluid layers. We discuss potential implications for neutron stars, and requirements for future work to build more realistic models.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448451","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 : 2024-10-17DOI: 10.3847/1538-4357/ad5f1f
Tuomo Salmi, Devarshi Choudhury, Yves Kini, Thomas E. Riley, Serena Vinciguerra, Anna L. Watts, Michael T. Wolff, Zaven Arzoumanian, Slavko Bogdanov, Deepto Chakrabarty, Keith Gendreau, Sebastien Guillot, Wynn C. G. Ho, Daniela Huppenkothen, Renee M. Ludlam, Sharon M. Morsink and Paul S. Ray
We report an updated analysis of the radius, mass, and heated surface regions of the massive pulsar PSR J0740+6620 using Neutron Star Interior Composition Explorer (NICER) data from 2018 September 21 to 2022 April 21, a substantial increase in data set size compared to previous analyses. Using a tight mass prior from radio-timing measurements and jointly modeling the new NICER data with XMM-Newton data, the inferred equatorial radius and gravitational mass are km and M⊙, respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, with an estimated systematic error ≲ 0.1 km. This result was obtained using the best computationally feasible sampler settings providing a strong radius lower limit but a slightly more uncertain radius upper limit. The inferred radius interval is also close to the km obtained by Dittmann et al., when they require the radius to be less than 16 km as we do. The results continue to disfavor very soft equations of state for dense matter, with R < 11.15 km for this high-mass pulsar excluded at the 95% probability. The results do not depend significantly on the assumed cross-calibration uncertainty between NICER and XMM-Newton. Using simulated data that resemble the actual observations, we also show that our pipeline is capable of recovering parameters for the inferred models reported in this paper.
{"title":"The Radius of the High-mass Pulsar PSR J0740+6620 with 3.6 yr of NICER Data","authors":"Tuomo Salmi, Devarshi Choudhury, Yves Kini, Thomas E. Riley, Serena Vinciguerra, Anna L. Watts, Michael T. Wolff, Zaven Arzoumanian, Slavko Bogdanov, Deepto Chakrabarty, Keith Gendreau, Sebastien Guillot, Wynn C. G. Ho, Daniela Huppenkothen, Renee M. Ludlam, Sharon M. Morsink and Paul S. Ray","doi":"10.3847/1538-4357/ad5f1f","DOIUrl":"https://doi.org/10.3847/1538-4357/ad5f1f","url":null,"abstract":"We report an updated analysis of the radius, mass, and heated surface regions of the massive pulsar PSR J0740+6620 using Neutron Star Interior Composition Explorer (NICER) data from 2018 September 21 to 2022 April 21, a substantial increase in data set size compared to previous analyses. Using a tight mass prior from radio-timing measurements and jointly modeling the new NICER data with XMM-Newton data, the inferred equatorial radius and gravitational mass are km and M⊙, respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, with an estimated systematic error ≲ 0.1 km. This result was obtained using the best computationally feasible sampler settings providing a strong radius lower limit but a slightly more uncertain radius upper limit. The inferred radius interval is also close to the km obtained by Dittmann et al., when they require the radius to be less than 16 km as we do. The results continue to disfavor very soft equations of state for dense matter, with R < 11.15 km for this high-mass pulsar excluded at the 95% probability. The results do not depend significantly on the assumed cross-calibration uncertainty between NICER and XMM-Newton. Using simulated data that resemble the actual observations, we also show that our pipeline is capable of recovering parameters for the inferred models reported in this paper.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448722","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 : 2024-10-17DOI: 10.3847/1538-4357/ad7460
Anibal Sierra, Laura M. Pérez, Benjamín Sotomayor, Myriam Benisty, Claire J. Chandler, Sean Andrews, John Carpenter, Thomas Henning, Leonardo Testi, Luca Ricci and David Wilner
The physical origin of the large cavities observed in transition disks is to date still unclear. Different physical mechanisms (e.g., a companion, dead zones, enhanced grain growth) produce disk cavities of different depth, and the expected spatial distribution of gas and solids in each mechanism is not the same. In this work, we analyze the multiwavelength interferometric visibilities of dust continuum observations obtained with Atacama Large Millimeter/submillimeter Array and Very Large Array for six transition disks: CQTau, UXTau A, LkCa15, RXJ1615, SR24S, and DMTau, and calculate brightness radial profiles, where diverse emission morphology is revealed at different wavelengths. The multiwavelength data are used to model the spectral energy distribution and compute constraints on the radial profile of the dust surface density, maximum grain size, and dust temperature in each disk. They are compared with the observational signatures expected from various physical mechanisms responsible for disk cavities. The observational signatures suggest that the cavities observed in the disks around UXTau A, LkCa15, and RXJ1615 could potentially originate from a dust trap created by a companion. Conversely, in the disks around CQTau, SR24S, DMTau, the origin of the cavity remains unclear, although it is compatible with a pressure bump and grain growth within the cavity.
{"title":"Constraints on the Physical Origin of Large Cavities in Transition Disks from Multiwavelength Dust Continuum Emission","authors":"Anibal Sierra, Laura M. Pérez, Benjamín Sotomayor, Myriam Benisty, Claire J. Chandler, Sean Andrews, John Carpenter, Thomas Henning, Leonardo Testi, Luca Ricci and David Wilner","doi":"10.3847/1538-4357/ad7460","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7460","url":null,"abstract":"The physical origin of the large cavities observed in transition disks is to date still unclear. Different physical mechanisms (e.g., a companion, dead zones, enhanced grain growth) produce disk cavities of different depth, and the expected spatial distribution of gas and solids in each mechanism is not the same. In this work, we analyze the multiwavelength interferometric visibilities of dust continuum observations obtained with Atacama Large Millimeter/submillimeter Array and Very Large Array for six transition disks: CQTau, UXTau A, LkCa15, RXJ1615, SR24S, and DMTau, and calculate brightness radial profiles, where diverse emission morphology is revealed at different wavelengths. The multiwavelength data are used to model the spectral energy distribution and compute constraints on the radial profile of the dust surface density, maximum grain size, and dust temperature in each disk. They are compared with the observational signatures expected from various physical mechanisms responsible for disk cavities. The observational signatures suggest that the cavities observed in the disks around UXTau A, LkCa15, and RXJ1615 could potentially originate from a dust trap created by a companion. Conversely, in the disks around CQTau, SR24S, DMTau, the origin of the cavity remains unclear, although it is compatible with a pressure bump and grain growth within the cavity.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448746","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 : 2024-10-17DOI: 10.3847/1538-4357/ad7816
Yongmin Yoon, Jae-Woo Kim and Jongwan Ko
The most massive early-type galaxies (ETGs) are known to form through numerous galaxy mergers. Thus, it is intriguing to study whether their formation in low-density environments, where nearby companions are almost absent, is associated with mergers, which are directly traced by tidal features. Using the 436 most massive ETGs with Mstar > 1011.2M⊙ at z < 0.04, we determine the variation in the fraction of massive ETGs with tidal features (fT) across different environments and verify whether the most massive ETGs commonly have tidal features in very low density environments. Our main discovery is that the most massive ETGs exhibit tidal features more frequently in lower-density environments. In the highest-density environments, like galaxy clusters, fT is 0.21 ± 0.06, while in the lowest-density environments it triples to 0.62 ± 0.06. This trend is stronger for more extremely massive ETGs, with fT reaching 0.92 ± 0.08 in the lowest-density environments. One explanation for our finding is that the most massive ETGs in lower-density environments have genuinely experienced recent mergers more frequently than their counterparts in higher-density environments, suggesting that they possess extended formation histories that continue into the present. Another possibility is that tidal features last shorter in denser environments owing to external factors inherent in these environments. Our additional findings that massive ETGs with bluer u − r colors are a more dominant driver of our main discovery and that dust lanes are more commonly observed in massive ETGs in low-density environments imply that gas-abundant mergers primarily contribute to the increased rate of recent mergers in low-density environments.
众所周知，质量最大的早期型星系（ETG）是通过无数次星系合并形成的。因此，研究它们在几乎没有邻近伴星系的低密度环境中的形成是否与合并有关，并直接通过潮汐特征进行追踪，是很有意义的。我们利用 z < 0.04 时 Mstar > 1011.2M⊙ 的 436 个质量最大的 ETG，测定了不同环境下具有潮汐特征的质量最大的 ETG 的比例（fT）的变化，并验证了质量最大的 ETG 是否通常在极低密度环境下具有潮汐特征。我们的主要发现是，在密度较低的环境中，质量最大的ETG更频繁地表现出潮汐特征。在密度最高的环境中，比如星系团，fT为0.21 ± 0.06，而在密度最低的环境中，fT则增加了两倍，达到0.62 ± 0.06。这种趋势在质量更大的超大质量ETG中更为明显，在密度最低的环境中，fT达到了0.92 ± 0.08。对于我们的发现，一种解释是低密度环境中质量最大的ETG确实比高密度环境中的ETG更频繁地经历了最近的合并，这表明它们拥有延续至今的形成历史。另一种可能是，在密度较高的环境中，潮汐特征持续的时间较短，这是由于这些环境中固有的外部因素造成的。我们还发现，具有更蓝 u - r 颜色的大质量 ETG 是我们主要发现的一个更主要的驱动因素，而尘埃通道在低密度环境中的大质量 ETG 中更常被观测到，这意味着气体丰富的合并是导致低密度环境中最近合并率增加的主要原因。
{"title":"The Most Massive Early-type Galaxies Exhibit Tidal Features More Frequently in Lower-density Environments","authors":"Yongmin Yoon, Jae-Woo Kim and Jongwan Ko","doi":"10.3847/1538-4357/ad7816","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7816","url":null,"abstract":"The most massive early-type galaxies (ETGs) are known to form through numerous galaxy mergers. Thus, it is intriguing to study whether their formation in low-density environments, where nearby companions are almost absent, is associated with mergers, which are directly traced by tidal features. Using the 436 most massive ETGs with Mstar > 1011.2M⊙ at z < 0.04, we determine the variation in the fraction of massive ETGs with tidal features (fT) across different environments and verify whether the most massive ETGs commonly have tidal features in very low density environments. Our main discovery is that the most massive ETGs exhibit tidal features more frequently in lower-density environments. In the highest-density environments, like galaxy clusters, fT is 0.21 ± 0.06, while in the lowest-density environments it triples to 0.62 ± 0.06. This trend is stronger for more extremely massive ETGs, with fT reaching 0.92 ± 0.08 in the lowest-density environments. One explanation for our finding is that the most massive ETGs in lower-density environments have genuinely experienced recent mergers more frequently than their counterparts in higher-density environments, suggesting that they possess extended formation histories that continue into the present. Another possibility is that tidal features last shorter in denser environments owing to external factors inherent in these environments. Our additional findings that massive ETGs with bluer u − r colors are a more dominant driver of our main discovery and that dust lanes are more commonly observed in massive ETGs in low-density environments imply that gas-abundant mergers primarily contribute to the increased rate of recent mergers in low-density environments.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448752","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 : 2024-10-17DOI: 10.3847/1538-4357/ad710e
Yize Dong, 一泽 董, Stefano Valenti, Chris Ashall, Marc Williamson, David J. Sand, Schuyler D. Van Dyk, Alexei V. Filippenko, Saurabh W. Jha, Michael Lundquist, Maryam Modjaz, Jennifer E. Andrews, Jacob E. Jencson, Griffin Hosseinzadeh, Jeniveve Pearson, Lindsey A. Kwok, Teresa Boland, Eric Y. Hsiao, Nathan Smith, Nancy Elias-Rosa, Shubham Srivastav, Stephen Smartt, Michael Fulton, WeiKang Zheng, Thomas G. Brink, Melissa Shahbandeh, K. Azalee Bostroem, Emily Hoang, Daryl Janzen, Darshana Mehta, Nicolas Meza, Manisha Shrestha, Samuel Wyatt, Katie Auchettl, Christopher R. Burns, Joseph Farah, Lluís Galbany, Estefania Padilla Gonzalez, Joshua Haislip, Jason T. Hinkle, D. Andrew Howell, Thomas De Jaeger, Vladimir Kouprianov, Sahana Kumar, Jing Lu, Curtis McCully, Shane Moran, Nidia Morrell, Megan Newsome, Craig Pellegrino, Abigail Polin, Daniel E. Reichart, B. J. Shappee, Maximilian D. Stritzinger, Giacomo Terreran and M. A. Tucker
We present optical and near-infrared (NIR) observations of SN 2022crv, a stripped-envelope supernova in NGC 3054, discovered within 12 hr of explosion by the Distance Less Than 40 Mpc Survey. We suggest that SN 2022crv is a transitional object on the continuum between Type Ib supernovae (SNe Ib) and Type IIb supernovae (SNe IIb). A high-velocity hydrogen feature (∼ −20,000 to −16,000 km s−1) was conspicuous in SN 2022crv at early phases, and then quickly disappeared. We find that a hydrogen envelope of ∼10−3M⊙ can reproduce the observed behavior of the hydrogen feature. The lack of early envelope cooling emission implies that SN 2022crv had a compact progenitor with an extremely low amount of hydrogen. A nebular spectral analysis shows that SN 2022crv is consistent with the explosion of a He star with a final mass of ∼4.5–5.6 M⊙ that evolved from a ∼16 to 22 M⊙ zero-age main-sequence star in a binary system with ∼1.0–1.7 M⊙ of oxygen finally synthesized in the core. In order to retain such a small amount of hydrogen, the initial orbital separation of the binary system is likely larger than ∼1000 R⊙. The NIR spectra of SN 2022crv show a unique absorption feature on the blue side of the He i line at ∼1.005 μm. This is the first time such a feature has been observed in SNe Ib/IIb, and it could be due to Sr II. Further detailed modeling of SN 2022crv can shed light on the progenitor and the origin of the mysterious absorption feature in the NIR.
{"title":"Characterizing the Rapid Hydrogen Disappearance in SN 2022crv: Evidence of a Continuum between Type Ib and IIb Supernova Properties","authors":"Yize Dong, 一泽 董, Stefano Valenti, Chris Ashall, Marc Williamson, David J. Sand, Schuyler D. Van Dyk, Alexei V. Filippenko, Saurabh W. Jha, Michael Lundquist, Maryam Modjaz, Jennifer E. Andrews, Jacob E. Jencson, Griffin Hosseinzadeh, Jeniveve Pearson, Lindsey A. Kwok, Teresa Boland, Eric Y. Hsiao, Nathan Smith, Nancy Elias-Rosa, Shubham Srivastav, Stephen Smartt, Michael Fulton, WeiKang Zheng, Thomas G. Brink, Melissa Shahbandeh, K. Azalee Bostroem, Emily Hoang, Daryl Janzen, Darshana Mehta, Nicolas Meza, Manisha Shrestha, Samuel Wyatt, Katie Auchettl, Christopher R. Burns, Joseph Farah, Lluís Galbany, Estefania Padilla Gonzalez, Joshua Haislip, Jason T. Hinkle, D. Andrew Howell, Thomas De Jaeger, Vladimir Kouprianov, Sahana Kumar, Jing Lu, Curtis McCully, Shane Moran, Nidia Morrell, Megan Newsome, Craig Pellegrino, Abigail Polin, Daniel E. Reichart, B. J. Shappee, Maximilian D. Stritzinger, Giacomo Terreran and M. A. Tucker","doi":"10.3847/1538-4357/ad710e","DOIUrl":"https://doi.org/10.3847/1538-4357/ad710e","url":null,"abstract":"We present optical and near-infrared (NIR) observations of SN 2022crv, a stripped-envelope supernova in NGC 3054, discovered within 12 hr of explosion by the Distance Less Than 40 Mpc Survey. We suggest that SN 2022crv is a transitional object on the continuum between Type Ib supernovae (SNe Ib) and Type IIb supernovae (SNe IIb). A high-velocity hydrogen feature (∼ −20,000 to −16,000 km s−1) was conspicuous in SN 2022crv at early phases, and then quickly disappeared. We find that a hydrogen envelope of ∼10−3M⊙ can reproduce the observed behavior of the hydrogen feature. The lack of early envelope cooling emission implies that SN 2022crv had a compact progenitor with an extremely low amount of hydrogen. A nebular spectral analysis shows that SN 2022crv is consistent with the explosion of a He star with a final mass of ∼4.5–5.6 M⊙ that evolved from a ∼16 to 22 M⊙ zero-age main-sequence star in a binary system with ∼1.0–1.7 M⊙ of oxygen finally synthesized in the core. In order to retain such a small amount of hydrogen, the initial orbital separation of the binary system is likely larger than ∼1000 R⊙. The NIR spectra of SN 2022crv show a unique absorption feature on the blue side of the He i line at ∼1.005 μm. This is the first time such a feature has been observed in SNe Ib/IIb, and it could be due to Sr II. Further detailed modeling of SN 2022crv can shed light on the progenitor and the origin of the mysterious absorption feature in the NIR.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448728","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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