Pub Date : 2024-10-16DOI: 10.3847/1538-4357/ad7375
Arpit Arora, Nicolás Garavito-Camargo, Robyn E. Sanderson, Emily C. Cunningham, Andrew Wetzel, Nondh Panithanpaisal and Megan Barry
Dark matter subhalos are predicted to perturb stellar streams; stream morphologies and dynamics can, therefore, constrain the mass distribution of subhalos. Using FIRE-2 simulations of Milky Way–mass galaxies, we demonstrate that the presence of an LMC analog significantly changes stream–subhalo encounter rates. The LMC analog brings in many subhalos, increasing encounter rates for streams near the massive satellite by 10%–40%. Additionally, the LMC analog displaces the host from its center of mass (inducing reflex motion), which causes a north–south asymmetry in the density and radial velocity distributions of subhalos. This asymmetry, combined with the presence of LMC-analog subhalos, causes encounter rates at the same distance to vary by 50%–70% across the sky, particularly in regions opposite the LMC analog. Furthermore, the LMC analog induces a density wake in the host's dark matter halo, further boosting the encounter rates near the LMC analog. We also explore how stream orbital properties affect encounter rates, finding up to a 50% increase for streams moving retrograde to the LMC analog’s orbit in the opposite quadrant. Finally, we report the encounter rates for Milky Way streams within the context of our simulations, both with and without the presence of an LMC analog. The dependence of encounter rates on stream location, orbit, and their position relative to the LMC has important implications for where to search for streams with spurs and gaps in the Milky Way.
{"title":"LMC-driven Anisotropic Boosts in Stream–Subhalo Interactions","authors":"Arpit Arora, Nicolás Garavito-Camargo, Robyn E. Sanderson, Emily C. Cunningham, Andrew Wetzel, Nondh Panithanpaisal and Megan Barry","doi":"10.3847/1538-4357/ad7375","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7375","url":null,"abstract":"Dark matter subhalos are predicted to perturb stellar streams; stream morphologies and dynamics can, therefore, constrain the mass distribution of subhalos. Using FIRE-2 simulations of Milky Way–mass galaxies, we demonstrate that the presence of an LMC analog significantly changes stream–subhalo encounter rates. The LMC analog brings in many subhalos, increasing encounter rates for streams near the massive satellite by 10%–40%. Additionally, the LMC analog displaces the host from its center of mass (inducing reflex motion), which causes a north–south asymmetry in the density and radial velocity distributions of subhalos. This asymmetry, combined with the presence of LMC-analog subhalos, causes encounter rates at the same distance to vary by 50%–70% across the sky, particularly in regions opposite the LMC analog. Furthermore, the LMC analog induces a density wake in the host's dark matter halo, further boosting the encounter rates near the LMC analog. We also explore how stream orbital properties affect encounter rates, finding up to a 50% increase for streams moving retrograde to the LMC analog’s orbit in the opposite quadrant. Finally, we report the encounter rates for Milky Way streams within the context of our simulations, both with and without the presence of an LMC analog. The dependence of encounter rates on stream location, orbit, and their position relative to the LMC has important implications for where to search for streams with spurs and gaps in the Milky Way.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443965","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 : 2024-10-16DOI: 10.3847/1538-4357/ad737c
Brendan T. Reed, Rahul Somasundaram, Soumi De, Cassandra L. Armstrong, Pablo Giuliani, Collin Capano, Duncan A. Brown and Ingo Tews
Gravitational-wave observations of binary neutron-star (BNS) mergers have the potential to revolutionize our understanding of the nuclear equation of state (EOS) and the fundamental interactions that determine its properties. However, Bayesian parameter estimation frameworks do not typically sample over microscopic nuclear-physics parameters that determine the EOS. One of the major hurdles in doing so is the computational cost involved in solving the neutron-star structure equations, known as the Tolman–Oppenheimer–Volkoff (TOV) equations. In this paper, we explore approaches to emulating solutions for the TOV equations: multilayer perceptrons (MLPs), Gaussian processes, and a data-driven variant of the reduced basis method (RBM). We implement these emulators for three different parameterizations of the nuclear EOS, each with a different degree of complexity represented by the number of model parameters. We find that our MLP-based emulators are generally more accurate than the other two algorithms, whereas the RBM results in the largest speedup with respect to the full high-fidelity TOV solver. We employ these emulators for a simple parameter inference using a potentially loud BNS observation and show that the posteriors predicted by our emulators are in excellent agreement with those obtained from the full TOV solver.
对双中子星（BNS）合并的引力波观测有可能彻底改变我们对核状态方程（EOS）以及决定其性质的基本相互作用的理解。然而，贝叶斯参数估计框架通常不会对决定 EOS 的微观核物理参数进行采样。这样做的主要障碍之一是求解中子星结构方程（即托尔曼-奥本海默-沃尔科夫（Tolman-Oppenheimer-Volkoff，TOV）方程）所涉及的计算成本。在本文中，我们探索了模拟 TOV 方程求解的方法：多层感知器 (MLP)、高斯过程和还原基方法 (RBM) 的数据驱动变体。我们针对核 EOS 的三种不同参数化实现了这些仿真器，每种仿真器的复杂程度不同，由模型参数的数量表示。我们发现，基于 MLP 的模拟器通常比其他两种算法更精确，而相对于完整的高保真 TOV 求解器，RBM 的求解速度最快。我们利用这些仿真器对潜在的高噪声 BNS 观测结果进行了简单的参数推断，结果表明我们的仿真器预测的后验结果与完整 TOV 求解器预测的后验结果非常一致。
{"title":"Toward Accelerated Nuclear-physics Parameter Estimation from Binary Neutron Star Mergers: Emulators for the Tolman–Oppenheimer–Volkoff Equations","authors":"Brendan T. Reed, Rahul Somasundaram, Soumi De, Cassandra L. Armstrong, Pablo Giuliani, Collin Capano, Duncan A. Brown and Ingo Tews","doi":"10.3847/1538-4357/ad737c","DOIUrl":"https://doi.org/10.3847/1538-4357/ad737c","url":null,"abstract":"Gravitational-wave observations of binary neutron-star (BNS) mergers have the potential to revolutionize our understanding of the nuclear equation of state (EOS) and the fundamental interactions that determine its properties. However, Bayesian parameter estimation frameworks do not typically sample over microscopic nuclear-physics parameters that determine the EOS. One of the major hurdles in doing so is the computational cost involved in solving the neutron-star structure equations, known as the Tolman–Oppenheimer–Volkoff (TOV) equations. In this paper, we explore approaches to emulating solutions for the TOV equations: multilayer perceptrons (MLPs), Gaussian processes, and a data-driven variant of the reduced basis method (RBM). We implement these emulators for three different parameterizations of the nuclear EOS, each with a different degree of complexity represented by the number of model parameters. We find that our MLP-based emulators are generally more accurate than the other two algorithms, whereas the RBM results in the largest speedup with respect to the full high-fidelity TOV solver. We employ these emulators for a simple parameter inference using a potentially loud BNS observation and show that the posteriors predicted by our emulators are in excellent agreement with those obtained from the full TOV solver.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443967","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 : 2024-10-16DOI: 10.3847/1538-4357/ad77bb
Simon de Wet, Tanmoy Laskar, Paul J. Groot, Rodolfo Barniol Duran, Edo Berger, Shivani Bhandari, Tarraneh Eftekhari, Cristiano Guidorzi, Shiho Kobayashi, Daniel A. Perley, Re’em Sari and Genevieve Schroeder
We present X-ray to radio frequency observations of the bright long gamma-ray burst GRB 210702A. Our Atacama Large Millimeter/submillimeter Array 97.5 GHz observations show a significant rebrightening by a factor of ≈2 beginning at 8.2 days post-burst and rising to peak brightness at 18.1 days before declining again. This is the first such rebrightening seen in a millimeter afterglow light curve. A standard forward shock model in a stellar wind circumburst medium can explain most of our X-ray, optical, and millimeter observations prior to the rebrightening, but significantly overpredicts the self-absorbed radio emission, and cannot explain the millimeter rebrightening. We investigate possible explanations for the millimeter rebrightening, and find that energy injection or a reverse shock from a late-time shell collision are plausible causes. Similar to other bursts, our radio data may require alternative scenarios such as a thermal electron population or a structured jet to explain the data. Our observations demonstrate that millimeter light curves can exhibit some of the rich features more commonly seen in optical and X-ray afterglow light curves, motivating further millimeter wavelength studies of GRB afterglows.
我们展示了对明亮的长伽马射线暴 GRB 210702A 的 X 射线到射频观测结果。我们的阿塔卡马大型毫米波/亚毫米波阵列 97.5 GHz 观测结果表明，从爆发后 8.2 天开始，亮度出现了显著的回升，回升系数≈2，并在 18.1 天达到峰值亮度，然后再次下降。这是在毫米余辉光曲线中首次看到的这种再增亮现象。恒星风环流介质中的标准前向冲击模型可以解释回亮之前的大部分 X 射线、光学和毫米波观测结果，但对自吸收射电辐射的预测明显偏高，而且无法解释毫米波回亮现象。我们对毫米波重亮的可能解释进行了研究，发现能量注入或晚期壳碰撞产生的反向冲击是可信的原因。与其他爆发类似，我们的射电数据可能需要热电子群或结构喷流等其他方案来解释。我们的观测结果表明，毫米波长的光变曲线可以表现出光学和 X 射线余辉光变曲线中常见的一些丰富特征，这促使我们对 GRB 余辉进行进一步的毫米波长研究。
{"title":"A Millimeter Rebrightening in GRB 210702A","authors":"Simon de Wet, Tanmoy Laskar, Paul J. Groot, Rodolfo Barniol Duran, Edo Berger, Shivani Bhandari, Tarraneh Eftekhari, Cristiano Guidorzi, Shiho Kobayashi, Daniel A. Perley, Re’em Sari and Genevieve Schroeder","doi":"10.3847/1538-4357/ad77bb","DOIUrl":"https://doi.org/10.3847/1538-4357/ad77bb","url":null,"abstract":"We present X-ray to radio frequency observations of the bright long gamma-ray burst GRB 210702A. Our Atacama Large Millimeter/submillimeter Array 97.5 GHz observations show a significant rebrightening by a factor of ≈2 beginning at 8.2 days post-burst and rising to peak brightness at 18.1 days before declining again. This is the first such rebrightening seen in a millimeter afterglow light curve. A standard forward shock model in a stellar wind circumburst medium can explain most of our X-ray, optical, and millimeter observations prior to the rebrightening, but significantly overpredicts the self-absorbed radio emission, and cannot explain the millimeter rebrightening. We investigate possible explanations for the millimeter rebrightening, and find that energy injection or a reverse shock from a late-time shell collision are plausible causes. Similar to other bursts, our radio data may require alternative scenarios such as a thermal electron population or a structured jet to explain the data. Our observations demonstrate that millimeter light curves can exhibit some of the rich features more commonly seen in optical and X-ray afterglow light curves, motivating further millimeter wavelength studies of GRB afterglows.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443974","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 : 2024-10-16DOI: 10.3847/1538-4357/ad794c
Min-Yu Li, Sheng-Bang Qian, Ai-Ying Zhou, Li-Ying Zhu, Wen-Ping Liao, Er-Gang Zhao, Xiang-Dong Shi, Fu-Xing Li and Qi-Bin Sun
Heartbeat stars (HBSs) with tidally excited oscillations (TEOs) are ideal astrophysical laboratories for studying the internal properties of the systems. In this paper, five new HBSs exhibiting TEOs are discovered using TESS photometric data. The orbital parameters are derived using a corrected version of Kumar et al.'s model based on the Markov Chain Monte Carlo method. The TEOs in these objects are examined, and their pulsation phases and modes are identified. The pulsation phases of the TEOs in TIC 266809405, TIC 266894805, and TIC 412881444 are consistent with the dominant l = 2, m = 0, or ±2 spherical harmonic. For TIC 11619404, although the TEO phase is close to the m = +2 mode, the m = 0 mode cannot be excluded because of the low inclination in this system. The TEO phase in TIC 447927324 shows a large deviation (>2σ) from the adiabatic expectations, suggesting that it is expected to be a traveling wave or that the pulsations are nonadiabatic. In addition, these TEOs occur at relatively low orbital harmonics, and we cautiously suggest that this may be an observational bias. These objects are valuable sources for studying the structure and evolution of eccentricity orbit binaries and extending the TESS HBS catalog with TEOs.
具有潮汐激发振荡（TEOs）的心跳星（HBSs）是研究系统内部特性的理想天体物理实验室。本文利用 TESS 的测光数据，发现了五颗表现出 TEO 的新 HBS。这些天体的轨道参数是使用基于马尔可夫链蒙特卡罗方法的库马尔等人模型的修正版得出的。对这些天体中的 TEO 进行了研究，并确定了它们的脉动相位和模式。TIC 266809405、TIC 266894805 和 TIC 412881444 中的近地天体的脉动相位与主要的 l = 2、m = 0 或 ±2 球谐波相一致。至于 TIC 11619404，虽然 TEO 相位接近 m = +2 模式，但由于该系统倾角较低，因此不能排除 m = 0 模式。TIC 447927324中的TEO相位与绝热预期有很大偏差（>2σ），这表明它可能是一个行波，或者脉动是非绝热的。此外，这些近地天体的轨道谐波相对较低，我们谨慎地认为这可能是一种观测偏差。这些天体对于研究偏心轨道双星的结构和演化，以及用 TEOs 来扩展 TESS HBS 星表都是非常有价值的来源。
{"title":"Five New Heartbeat Star Systems with Tidally Excited Oscillations Discovered Based on TESS Data","authors":"Min-Yu Li, Sheng-Bang Qian, Ai-Ying Zhou, Li-Ying Zhu, Wen-Ping Liao, Er-Gang Zhao, Xiang-Dong Shi, Fu-Xing Li and Qi-Bin Sun","doi":"10.3847/1538-4357/ad794c","DOIUrl":"https://doi.org/10.3847/1538-4357/ad794c","url":null,"abstract":"Heartbeat stars (HBSs) with tidally excited oscillations (TEOs) are ideal astrophysical laboratories for studying the internal properties of the systems. In this paper, five new HBSs exhibiting TEOs are discovered using TESS photometric data. The orbital parameters are derived using a corrected version of Kumar et al.'s model based on the Markov Chain Monte Carlo method. The TEOs in these objects are examined, and their pulsation phases and modes are identified. The pulsation phases of the TEOs in TIC 266809405, TIC 266894805, and TIC 412881444 are consistent with the dominant l = 2, m = 0, or ±2 spherical harmonic. For TIC 11619404, although the TEO phase is close to the m = +2 mode, the m = 0 mode cannot be excluded because of the low inclination in this system. The TEO phase in TIC 447927324 shows a large deviation (>2σ) from the adiabatic expectations, suggesting that it is expected to be a traveling wave or that the pulsations are nonadiabatic. In addition, these TEOs occur at relatively low orbital harmonics, and we cautiously suggest that this may be an observational bias. These objects are valuable sources for studying the structure and evolution of eccentricity orbit binaries and extending the TESS HBS catalog with TEOs.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443975","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 : 2024-10-16DOI: 10.3847/1538-4357/ad71d4
Wenwen Zuo, Hengxiao Guo, Jingbo Sun, Qi Yuan, Paulina Lira, Minfeng Gu, Philip G. Edwards, Alok C. Gupta, Shubham Kishore, Jamie Stevens, Tao An, Zhen-Yi Cai, Hai-Cheng Feng, Luis C. Ho, Dragana Ilić, Andjelka B. Kovačević, Sha-Sha Li, Mar Mezcua, Luka Č. Popović, Mouyuan Sun, Tushar Tripathi, Vivian U, Oliver Vince, Jianguo Wang, Junxian Wang, Shu Wang, Xuebing Wu and Zhenya Zheng
To investigate the short-term variability and determine the size of the optical continuum emitting region of intermediate-mass black holes (IMBHs), we carried out high-cadence, multiband photometric monitoring of a Seyfert 1 galaxy J0249−0815 across two nights, together with a one-night single-band preliminary test. The presence of the broad Hα component in our target was confirmed by recent Palomar/P200 spectroscopic observations, 23 yr after the Sloan Digital Sky Survey, ruling out the supernovae origin of the broad Hα line. The photometric experiment was primarily conducted utilizing four-channel imagers MuSCAT 3 and 4 mounted on 2 m telescopes within the Las Cumbres Observatory Global Telescope Network. Despite the expectation of variability, we observed no significant variation (<1.4%) on timescales of 6–10 hr. This nondetection is likely due to substantial host galaxy light diluting the subtle active galactic nucleus (AGN) variability. Additionally, we cannot rule out that the target was in a relatively quiescent state without intranight variability during our monitoring, owing to the stochastic nature of AGN variations. To enhance the possibility of detecting subtle variability signals and lag in future IMBH reverberation campaigns, it may be beneficial to select targets with a higher AGN-to-host flux ratio, and conduct dual-band preliminary tests and tailored simulations.
{"title":"Optical Continuum Reverberation Mapping of a Candidate IMBH in a Nearby Seyfert 1 Galaxy","authors":"Wenwen Zuo, Hengxiao Guo, Jingbo Sun, Qi Yuan, Paulina Lira, Minfeng Gu, Philip G. Edwards, Alok C. Gupta, Shubham Kishore, Jamie Stevens, Tao An, Zhen-Yi Cai, Hai-Cheng Feng, Luis C. Ho, Dragana Ilić, Andjelka B. Kovačević, Sha-Sha Li, Mar Mezcua, Luka Č. Popović, Mouyuan Sun, Tushar Tripathi, Vivian U, Oliver Vince, Jianguo Wang, Junxian Wang, Shu Wang, Xuebing Wu and Zhenya Zheng","doi":"10.3847/1538-4357/ad71d4","DOIUrl":"https://doi.org/10.3847/1538-4357/ad71d4","url":null,"abstract":"To investigate the short-term variability and determine the size of the optical continuum emitting region of intermediate-mass black holes (IMBHs), we carried out high-cadence, multiband photometric monitoring of a Seyfert 1 galaxy J0249−0815 across two nights, together with a one-night single-band preliminary test. The presence of the broad Hα component in our target was confirmed by recent Palomar/P200 spectroscopic observations, 23 yr after the Sloan Digital Sky Survey, ruling out the supernovae origin of the broad Hα line. The photometric experiment was primarily conducted utilizing four-channel imagers MuSCAT 3 and 4 mounted on 2 m telescopes within the Las Cumbres Observatory Global Telescope Network. Despite the expectation of variability, we observed no significant variation (<1.4%) on timescales of 6–10 hr. This nondetection is likely due to substantial host galaxy light diluting the subtle active galactic nucleus (AGN) variability. Additionally, we cannot rule out that the target was in a relatively quiescent state without intranight variability during our monitoring, owing to the stochastic nature of AGN variations. To enhance the possibility of detecting subtle variability signals and lag in future IMBH reverberation campaigns, it may be beneficial to select targets with a higher AGN-to-host flux ratio, and conduct dual-band preliminary tests and tailored simulations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444033","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 : 2024-10-16DOI: 10.3847/1538-4357/ad76a1
Yuanze Ding, Javier A. Garcıa, Timothy R. Kallman, Claudio Mendoza, Manuel Bautista, Fiona A. Harrison, John A. Tomsick and Jameson Dong
Luminous accretion disks around black holes are expected to have densities of ∼1015−1022 cm−3, which are high enough that plasma physics effects become important. Many of these effects have been traditionally neglected in the calculation of atomic parameters, and therefore in photoionization models and ultimately also in X-ray reflection models. In this paper, we describe updates to the atomic rates used by the xstar code, which is in turn part of the xillver disk reflection model. We discuss the effect of adding necessary high-density corrections into the xillver code. Specifically, we find that the change of recombination rates plays an important role, dominating the differences between model versions. With synthetic spectra, we show that, even in a highly ionized state, high-density slabs can produce strong iron (∼6.5–9 keV) and oxygen (∼0.6–0.8 keV) resonance features. The significant iron emission could address the problem of the supersolar iron abundances found in some sources.
{"title":"Next-generation Accretion Disk Reflection Model: High-density Plasma Effects","authors":"Yuanze Ding, Javier A. Garcıa, Timothy R. Kallman, Claudio Mendoza, Manuel Bautista, Fiona A. Harrison, John A. Tomsick and Jameson Dong","doi":"10.3847/1538-4357/ad76a1","DOIUrl":"https://doi.org/10.3847/1538-4357/ad76a1","url":null,"abstract":"Luminous accretion disks around black holes are expected to have densities of ∼1015−1022 cm−3, which are high enough that plasma physics effects become important. Many of these effects have been traditionally neglected in the calculation of atomic parameters, and therefore in photoionization models and ultimately also in X-ray reflection models. In this paper, we describe updates to the atomic rates used by the xstar code, which is in turn part of the xillver disk reflection model. We discuss the effect of adding necessary high-density corrections into the xillver code. Specifically, we find that the change of recombination rates plays an important role, dominating the differences between model versions. With synthetic spectra, we show that, even in a highly ionized state, high-density slabs can produce strong iron (∼6.5–9 keV) and oxygen (∼0.6–0.8 keV) resonance features. The significant iron emission could address the problem of the supersolar iron abundances found in some sources.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443972","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 : 2024-10-16DOI: 10.3847/1538-4357/ad7eab
Lin Nie, Xiang-Li Qian, Yi-Qing Guo and Si-Ming Liu
Since the discovery of cosmic rays (CRs) over a century ago, their origin has remained a mystery and a key research question. Recently, the LHAASO experiment identified the first CR superacceleration source, the Cygnus bubble, which can accelerate CRs to energies exceeding 10 PeV. A pertinent question is how much the Cygnus bubble contributes to the CR spectrum observed on Earth. With the aim of answering that question, a 3D propagation analysis was conducted on CRs in this study. The Cygnus bubble was incorporated into our propagation model in order to determine its contributions to the observed spectra. First, we calculated the spectrum and spatial morphology of the Cygnus bubble to reproduce the observed LHAASO data. Subsequently, we calculated the diffuse γ-ray emissions produced by the CRs from the Cygnus bubble and the energy spectrum of the CR particles near Earth after propagation. Finally, we utilized a CR spatial-dependent propagation model to calculate the large-scale CR energy spectrum and the resulting diffuse γ-ray emissions. Our results indicate that (1) the Cygnus bubble contributes minimally to the CR spectrum observed on Earth, (2) the emissions produced by the CR particles from the Cygnus bubble dominate the diffuse γ-ray emissions in that region, and (3) the structural fluctuations of the diffuse γ-ray emissions observed by LHAASO are likely due to the local CR halo. We anticipate that LHAASO will identify more CR halo sources to validate our model.
{"title":"Contribution of the Cygnus Bubble to the Galactic Cosmic Ray Spectrum and Diffuse γ-Ray Emissions","authors":"Lin Nie, Xiang-Li Qian, Yi-Qing Guo and Si-Ming Liu","doi":"10.3847/1538-4357/ad7eab","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7eab","url":null,"abstract":"Since the discovery of cosmic rays (CRs) over a century ago, their origin has remained a mystery and a key research question. Recently, the LHAASO experiment identified the first CR superacceleration source, the Cygnus bubble, which can accelerate CRs to energies exceeding 10 PeV. A pertinent question is how much the Cygnus bubble contributes to the CR spectrum observed on Earth. With the aim of answering that question, a 3D propagation analysis was conducted on CRs in this study. The Cygnus bubble was incorporated into our propagation model in order to determine its contributions to the observed spectra. First, we calculated the spectrum and spatial morphology of the Cygnus bubble to reproduce the observed LHAASO data. Subsequently, we calculated the diffuse γ-ray emissions produced by the CRs from the Cygnus bubble and the energy spectrum of the CR particles near Earth after propagation. Finally, we utilized a CR spatial-dependent propagation model to calculate the large-scale CR energy spectrum and the resulting diffuse γ-ray emissions. Our results indicate that (1) the Cygnus bubble contributes minimally to the CR spectrum observed on Earth, (2) the emissions produced by the CR particles from the Cygnus bubble dominate the diffuse γ-ray emissions in that region, and (3) the structural fluctuations of the diffuse γ-ray emissions observed by LHAASO are likely due to the local CR halo. We anticipate that LHAASO will identify more CR halo sources to validate our model.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443981","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 : 2024-10-16DOI: 10.3847/1538-4357/ad6c4e
Emma T. Whelan, Miriam Keppler, Neal J. Turner, Ilaria Pascucci, Erika Hamden, Keri Hoadley and Min Fang
2MASS J16075796-2040087 is an ∼5 Myr young star in Upper Sco with evidence for accretion bursts on a timescale of about 15 days and, uncommonly for its age, outflows traced by multicomponent forbidden emission lines (FELs). The accretion bursts may be triggered by a companion at ∼4.6 au. We analyze HIRES spectra optimised for spectro-astrometry to better understand the origin of the several FEL velocity components and determine whether a magnetohydrodynamic (MHD) disk wind is present. The FEL high-velocity component (HVC) traces an asymmetric, bipolar jet ∼700 au long. The jet’s position angle ∼ 277° is not perpendicular to the disk. The lower-velocity emission, classified previously as a disk wind low-velocity component, is found to have more in common with the HVC and overall it is not possible to identify an MHD disk wind component. The spectro-astrometric signal of the low-velocity emission resembles those of jets and its density and ionisation fraction fall into the range of HVCs. We suggest a scenario where the accretion bursts due to the close companion power the jets past the age where such activity ends around most stars. The low-velocity emission here could come from a slow jet launched near the close companion and this emission would be blended with emission from the MHD wind.
{"title":"Jets from the Upper Scorpius Variable Young Star System 2MASS J16075796-2040087 via KECK/HIRES Spectro-astrometry","authors":"Emma T. Whelan, Miriam Keppler, Neal J. Turner, Ilaria Pascucci, Erika Hamden, Keri Hoadley and Min Fang","doi":"10.3847/1538-4357/ad6c4e","DOIUrl":"https://doi.org/10.3847/1538-4357/ad6c4e","url":null,"abstract":"2MASS J16075796-2040087 is an ∼5 Myr young star in Upper Sco with evidence for accretion bursts on a timescale of about 15 days and, uncommonly for its age, outflows traced by multicomponent forbidden emission lines (FELs). The accretion bursts may be triggered by a companion at ∼4.6 au. We analyze HIRES spectra optimised for spectro-astrometry to better understand the origin of the several FEL velocity components and determine whether a magnetohydrodynamic (MHD) disk wind is present. The FEL high-velocity component (HVC) traces an asymmetric, bipolar jet ∼700 au long. The jet’s position angle ∼ 277° is not perpendicular to the disk. The lower-velocity emission, classified previously as a disk wind low-velocity component, is found to have more in common with the HVC and overall it is not possible to identify an MHD disk wind component. The spectro-astrometric signal of the low-velocity emission resembles those of jets and its density and ionisation fraction fall into the range of HVCs. We suggest a scenario where the accretion bursts due to the close companion power the jets past the age where such activity ends around most stars. The low-velocity emission here could come from a slow jet launched near the close companion and this emission would be blended with emission from the MHD wind.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444031","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 : 2024-10-16DOI: 10.3847/1538-4357/ad7466
K. Munakata, Y. Hayashi, M. Kozai, C. Kato, N. Miyashita, R. Kataoka, A. Kadokura, S. Miyake, K. Iwai, E. Echer, A. Dal Lago, M. Rockenbach, N. J. Schuch, J. V. Bageston, C. R. Braga, H. K. Al Jassar, M. M. Sharma, M. L. Duldig, J. E. Humble, I. Sabbah, P. Evenson, T. Kuwabara and J. Kóta
This paper presents the global analysis of two extended decreases in the galactic cosmic-ray intensity observed by worldwide networks of ground-based detectors in 2012. This analysis is capable of separately deriving the cosmic-ray density (or omnidirectional intensity) and anisotropy, each as a function of time and rigidity. A simple diffusion model along the spiral field line between Earth and a cosmic-ray barrier indicates the long duration of these events, resulting from about 190° eastern extent of a barrier such as an interplanetary shock followed by the sheath region and/or the corotating interaction region (CIR). It is suggested that the coronal mass ejection merging with and compressing the preexisting CIR at its flank can produce such an extended barrier. The derived rigidity spectra of the density and anisotropy both vary in time during each event period. In particular we find that the temporal feature of the “phantom Forbush decrease (FD)” reported in an analyzed period is dependent on rigidity, and looks quite different at different rigidities. From these rigidity spectra of the density and anisotropy, we derive the rigidity spectrum of the average parallel mean free path of pitch angle scattering along the spiral field line and infer the power spectrum of the magnetic fluctuation and its temporal variation. The possible physical cause of the strong rigidity dependence of the phantom FD is also discussed. These results demonstrate the high-energy cosmic rays observed at Earth responding to remote space weather.
{"title":"Global Analysis of the Extended Decreases in Cosmic Rays Observed with Worldwide Networks of Neutron Monitors and Muon Detectors: Temporal Variation of the Rigidity Spectrum and Its Implication","authors":"K. Munakata, Y. Hayashi, M. Kozai, C. Kato, N. Miyashita, R. Kataoka, A. Kadokura, S. Miyake, K. Iwai, E. Echer, A. Dal Lago, M. Rockenbach, N. J. Schuch, J. V. Bageston, C. R. Braga, H. K. Al Jassar, M. M. Sharma, M. L. Duldig, J. E. Humble, I. Sabbah, P. Evenson, T. Kuwabara and J. Kóta","doi":"10.3847/1538-4357/ad7466","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7466","url":null,"abstract":"This paper presents the global analysis of two extended decreases in the galactic cosmic-ray intensity observed by worldwide networks of ground-based detectors in 2012. This analysis is capable of separately deriving the cosmic-ray density (or omnidirectional intensity) and anisotropy, each as a function of time and rigidity. A simple diffusion model along the spiral field line between Earth and a cosmic-ray barrier indicates the long duration of these events, resulting from about 190° eastern extent of a barrier such as an interplanetary shock followed by the sheath region and/or the corotating interaction region (CIR). It is suggested that the coronal mass ejection merging with and compressing the preexisting CIR at its flank can produce such an extended barrier. The derived rigidity spectra of the density and anisotropy both vary in time during each event period. In particular we find that the temporal feature of the “phantom Forbush decrease (FD)” reported in an analyzed period is dependent on rigidity, and looks quite different at different rigidities. From these rigidity spectra of the density and anisotropy, we derive the rigidity spectrum of the average parallel mean free path of pitch angle scattering along the spiral field line and infer the power spectrum of the magnetic fluctuation and its temporal variation. The possible physical cause of the strong rigidity dependence of the phantom FD is also discussed. These results demonstrate the high-energy cosmic rays observed at Earth responding to remote space weather.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443969","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 : 2024-10-16DOI: 10.3847/1538-4357/ad7583
Riouhei Nakatani, Neal J. Turner and Shinsuke Takasao
Photoevaporation driven by hydrogen-ionizing extreme-ultraviolet (EUV) radiation profoundly shapes the lives of diverse astrophysical objects. We construct an analytical model accounting for the finite timescales of photoheating and photoionization and apply it to the dispersal of protoplanetary disks. The model yields improved estimates for the ionization, temperature, and velocity versus distance from the central source when compared to the classical picture of fully ionized and isothermal winds with temperatures ≈104 K and speeds ≈10 km s−1. In contrast to the classical picture, the photoevaporative winds take on several distinct hydrodynamical and thermochemical states depending on the central star’s EUV emission rate and spectral hardness: T Tauri stars with EUV luminosities around 1030 erg s−1 drive nonisothermal ionized disk winds at lower temperatures than the classical value if the spectrum is soft, with an average deposited energy per photoionization less than about 3.7 eV. If, however, the spectrum is hard, the winds tend to be atomic and isothermal at most disk radii. For lower EUV intensities, even with soft spectra, atomic winds can emerge beyond ∼10 au through advection. We show that these predictions are in general agreement with detailed radiation hydrodynamics calculations. The model furthermore illustrates how the energy efficiency of photoevaporation varies with the intensity and spectral hardness of the EUV illumination, as well as addressing discrepancies in the literature around the effectiveness of X-ray photoevaporation. The findings highlight the importance of the photoheating and photoionization timescales both for modeling and for understanding winds’ observed behavior.
由氢电离极紫外辐射（EUV）驱动的光蒸发现象深刻地影响着各种天体物理天体的生命。我们构建了一个考虑到光热和光离子化有限时间尺度的分析模型，并将其应用于原行星盘的散布。与温度≈104 K、速度≈10 km s-1的完全电离和等温风的经典图景相比，该模型对电离、温度和速度与中心源距离的关系有更好的估计。与经典图景不同的是，光蒸发风有几种不同的流体力学和热化学状态，这取决于中心恒星的超紫外辐射率和光谱硬度：如果光谱是软的，每次光电离的平均沉积能量小于约 3.7 eV，那么 EUV 光度约为 1030 erg s-1 的金牛座恒星会以低于经典值的温度驱动非等温电离盘风。然而，如果光谱较硬，在大多数磁盘半径上，风往往是原子风和等温风。对于较低的超紫外强度，即使光谱较软，原子风也会通过平流出现在 ∼10 au 以外的地方。我们证明这些预测与详细的辐射流体力学计算基本一致。该模型还进一步说明了光汽化的能量效率如何随超紫外光照射强度和光谱硬度的变化而变化，并解决了文献中围绕 X 射线光汽化有效性的差异。研究结果强调了光热和光离子化时间尺度对于建模和理解风的观测行为的重要性。
{"title":"Broadening the Canonical Picture of EUV-driven Photoevaporation of Accretion Disks","authors":"Riouhei Nakatani, Neal J. Turner and Shinsuke Takasao","doi":"10.3847/1538-4357/ad7583","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7583","url":null,"abstract":"Photoevaporation driven by hydrogen-ionizing extreme-ultraviolet (EUV) radiation profoundly shapes the lives of diverse astrophysical objects. We construct an analytical model accounting for the finite timescales of photoheating and photoionization and apply it to the dispersal of protoplanetary disks. The model yields improved estimates for the ionization, temperature, and velocity versus distance from the central source when compared to the classical picture of fully ionized and isothermal winds with temperatures ≈104 K and speeds ≈10 km s−1. In contrast to the classical picture, the photoevaporative winds take on several distinct hydrodynamical and thermochemical states depending on the central star’s EUV emission rate and spectral hardness: T Tauri stars with EUV luminosities around 1030 erg s−1 drive nonisothermal ionized disk winds at lower temperatures than the classical value if the spectrum is soft, with an average deposited energy per photoionization less than about 3.7 eV. If, however, the spectrum is hard, the winds tend to be atomic and isothermal at most disk radii. For lower EUV intensities, even with soft spectra, atomic winds can emerge beyond ∼10 au through advection. We show that these predictions are in general agreement with detailed radiation hydrodynamics calculations. The model furthermore illustrates how the energy efficiency of photoevaporation varies with the intensity and spectral hardness of the EUV illumination, as well as addressing discrepancies in the literature around the effectiveness of X-ray photoevaporation. The findings highlight the importance of the photoheating and photoionization timescales both for modeling and for understanding winds’ observed behavior.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443971","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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