Pub Date : 2025-01-02DOI: 10.3847/2041-8213/ad9f5e
Chunyi Zhang, Junfeng Wang and Tian-Wen Cao
The cold and hot interstellar medium in star-forming galaxies resembles the reservoir for star formation and associated heating by stellar winds and explosions during stellar evolution, respectively. We utilize data from deep Chandra observations and archival millimeter surveys to study the interconnection between these two phases and the relation to star formation activities in M51 on kiloparsec scales. A sharp radial decrease is present in the hot gas surface brightness profile within the inner 2 kpc of M51. The ratio between the total infrared luminosity (LIR) and the hot gas luminosity ( ) shows a positive correlation with the galactic radius in the central region. For the entire galaxy, a twofold correlation is revealed in the –LIR diagram, where sharply increases with LIR in the center but varies more slowly in the disk. The best fit gives a steep relation of for the center of M51. The similar twofold correlations are also found in the –molecular line luminosity ( ) relations for the four molecular emission lines CO(1–0), CO(2–1), HCN(1–0), and HCO+(1–0). We demonstrate that the core-collapse supernovae (SNe) are the primary source of energy for heating gas in the galactic center of M51, leading to the observed steep –LIR and – relations, as their X-ray radiation efficiencies (η ≡ / ) increase with the star formation rate surface densities (ΣSFR), where is the SN mechanical energy input rate.
{"title":"Fire and Ice in the Whirlpool: Spatially Resolved Scaling Relations between X-Ray-emitting Hot Gas and Cold Molecular Gas in M51","authors":"Chunyi Zhang, Junfeng Wang and Tian-Wen Cao","doi":"10.3847/2041-8213/ad9f5e","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9f5e","url":null,"abstract":"The cold and hot interstellar medium in star-forming galaxies resembles the reservoir for star formation and associated heating by stellar winds and explosions during stellar evolution, respectively. We utilize data from deep Chandra observations and archival millimeter surveys to study the interconnection between these two phases and the relation to star formation activities in M51 on kiloparsec scales. A sharp radial decrease is present in the hot gas surface brightness profile within the inner 2 kpc of M51. The ratio between the total infrared luminosity (LIR) and the hot gas luminosity ( ) shows a positive correlation with the galactic radius in the central region. For the entire galaxy, a twofold correlation is revealed in the –LIR diagram, where sharply increases with LIR in the center but varies more slowly in the disk. The best fit gives a steep relation of for the center of M51. The similar twofold correlations are also found in the –molecular line luminosity ( ) relations for the four molecular emission lines CO(1–0), CO(2–1), HCN(1–0), and HCO+(1–0). We demonstrate that the core-collapse supernovae (SNe) are the primary source of energy for heating gas in the galactic center of M51, leading to the observed steep –LIR and – relations, as their X-ray radiation efficiencies (η ≡ / ) increase with the star formation rate surface densities (ΣSFR), where is the SN mechanical energy input rate.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142911543","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 : 2024-12-30DOI: 10.3847/2041-8213/ad9f3c
Chun Huang
Traditional methods for determining the radius of a 1.4 M⊙ neutron star (R1.4) rely on specific equation-of-state (EOS) models that describe various types of dense nuclear matter. This dependence on EOS models can introduce substantial systematic uncertainties, which may exceed the measurement uncertainties when constraining R1.4. In this study, we explore a novel approach to constraining R1.4 using data from Neutron Star Interior Composition Explorer observations of PSR J0030+0451 (J0030) and PSR J0437-4715 (J0437). However, this work presents a more data-driven analysis framework, substantially decreasing the need for EOS assumptions. By analyzing the mass–radius measurements of these two neutron stars, we infer R1.4 using statistical methods based mostly on observational data. We examine various hotspot configurations for J0030, along with new J0437 observations, and their effects on the inferred radius. Our results are consistent with X-ray timing, gravitational-wave, and nuclear physics constraints, while avoiding EOS-related biases. The same method has also been applied to a simulated mass–radius data set, based on our knowledge of future X-ray telescopes, demonstrating the model's ability to recover the injected R1.4 value in certain cases. This method provides a data-driven pathway for extracting neutron star properties and offers a new approach for future observational efforts in neutron star astrophysics.
{"title":"Equation of State Independent Determination on the Radius of a 1.4 M ⊙ Neutron Star Using Mass–Radius Measurements","authors":"Chun Huang","doi":"10.3847/2041-8213/ad9f3c","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9f3c","url":null,"abstract":"Traditional methods for determining the radius of a 1.4 M⊙ neutron star (R1.4) rely on specific equation-of-state (EOS) models that describe various types of dense nuclear matter. This dependence on EOS models can introduce substantial systematic uncertainties, which may exceed the measurement uncertainties when constraining R1.4. In this study, we explore a novel approach to constraining R1.4 using data from Neutron Star Interior Composition Explorer observations of PSR J0030+0451 (J0030) and PSR J0437-4715 (J0437). However, this work presents a more data-driven analysis framework, substantially decreasing the need for EOS assumptions. By analyzing the mass–radius measurements of these two neutron stars, we infer R1.4 using statistical methods based mostly on observational data. We examine various hotspot configurations for J0030, along with new J0437 observations, and their effects on the inferred radius. Our results are consistent with X-ray timing, gravitational-wave, and nuclear physics constraints, while avoiding EOS-related biases. The same method has also been applied to a simulated mass–radius data set, based on our knowledge of future X-ray telescopes, demonstrating the model's ability to recover the injected R1.4 value in certain cases. This method provides a data-driven pathway for extracting neutron star properties and offers a new approach for future observational efforts in neutron star astrophysics.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"83 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142901658","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9eb1
Cindy N. Luu, Xinting Yu, 馨婷 余, Christopher R. Glein, Hamish Innes, Artyom Aguichine, Joshua Krissansen-Totton, Julianne I. Moses, Shang-Min Tsai, Xi Zhang, Ngoc Truong and Jonathan J. Fortney
Temperate exoplanets between the sizes of Earth and Neptune, known as “sub-Neptunes,” have emerged as intriguing targets for astrobiology. It is unknown whether these planets resemble Earth-like terrestrial worlds with a habitable surface, Neptune-like giant planets with deep atmospheres and no habitable surface, or something exotic in between. Recent JWST transmission spectroscopy observations of the canonical sub-Neptune, K2-18 b, revealed ~1% CH4, ~1% CO2, and a nondetection of CO in the atmosphere. While previous studies proposed that the observed atmospheric composition could help constrain the lower atmosphere's conditions and determine the interior structure of sub-Neptunes like K2-18 b, the possible interactions between the atmosphere and a hot, supercritical water ocean at its base remain unexplored. In this work, we investigate whether a global supercritical water ocean, resembling a planetary-scale hydrothermal system, can explain these observations on K2-18 b–like sub-Neptunes through equilibrium aqueous geochemical calculations. We find that the observed atmospheric CH4/CO2 ratio implies a minimum ocean temperature of ~710 K, whereas the corresponding CO/CO2 ratio allows ocean temperatures up to ~1070 K. These results indicate that a global supercritical water ocean on K2-18 b is plausible. While life cannot survive in such an ocean, this work represents the first step toward understanding how a global supercritical water ocean may influence observable atmospheric characteristics on volatile-rich sub-Neptunes. Future observations with better-constrained CO and NH3 mixing ratios could further help distinguish between possible interior compositions of K2-18 b.
{"title":"Volatile-rich Sub-Neptunes as Hydrothermal Worlds: The Case of K2-18 b","authors":"Cindy N. Luu, Xinting Yu, 馨婷 余, Christopher R. Glein, Hamish Innes, Artyom Aguichine, Joshua Krissansen-Totton, Julianne I. Moses, Shang-Min Tsai, Xi Zhang, Ngoc Truong and Jonathan J. Fortney","doi":"10.3847/2041-8213/ad9eb1","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9eb1","url":null,"abstract":"Temperate exoplanets between the sizes of Earth and Neptune, known as “sub-Neptunes,” have emerged as intriguing targets for astrobiology. It is unknown whether these planets resemble Earth-like terrestrial worlds with a habitable surface, Neptune-like giant planets with deep atmospheres and no habitable surface, or something exotic in between. Recent JWST transmission spectroscopy observations of the canonical sub-Neptune, K2-18 b, revealed ~1% CH4, ~1% CO2, and a nondetection of CO in the atmosphere. While previous studies proposed that the observed atmospheric composition could help constrain the lower atmosphere's conditions and determine the interior structure of sub-Neptunes like K2-18 b, the possible interactions between the atmosphere and a hot, supercritical water ocean at its base remain unexplored. In this work, we investigate whether a global supercritical water ocean, resembling a planetary-scale hydrothermal system, can explain these observations on K2-18 b–like sub-Neptunes through equilibrium aqueous geochemical calculations. We find that the observed atmospheric CH4/CO2 ratio implies a minimum ocean temperature of ~710 K, whereas the corresponding CO/CO2 ratio allows ocean temperatures up to ~1070 K. These results indicate that a global supercritical water ocean on K2-18 b is plausible. While life cannot survive in such an ocean, this work represents the first step toward understanding how a global supercritical water ocean may influence observable atmospheric characteristics on volatile-rich sub-Neptunes. Future observations with better-constrained CO and NH3 mixing ratios could further help distinguish between possible interior compositions of K2-18 b.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888174","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 : 2024-12-27DOI: 10.3847/2041-8213/ad99d9
Chunyang Cao, F. K. Liu, Xian Chen and Shuo Li
Quasiperiodic eruptions (QPEs) are a novel class of transients recently discovered in a few extragalactic nuclei. It has been suggested that a QPE can be produced by a main-sequence star undergoing repeated partial disruptions by the tidal field of a supermassive black hole (SMBH) immediately after getting captured on a tightly bound orbit through the Hills mechanism. In this Letter, we investigate the period-dependent formation rate of QPEs for this scenario, utilizing scattering experiments and the loss-cone theory. We calculate the QPE formation rates in both a single-SMBH and a dual-SMBH system, motivated by the overrepresentation of postmerger galaxies as QPE hosts. We find that for SMBHs of mass 106–107M⊙, most QPEs formed in this scenario have periods longer than ≃ 100 days. A single-SMBH system generally produces QPEs at a negligible rate of 10−10–10−8 yr−1 due to inefficient two-body relaxation. Meanwhile, in a dual-SMBH system, the QPE rate is enhanced by 3–4 orders of magnitude, mainly due to a boosted angular momentum evolution under tidal perturbation from the companion SMBH (galaxy). The QPE rate in a postmerger galactic nucleus hosting two equal-mass SMBHs separated by a few parsecs could reach 10−6–10−5 yr−1. Our results suggest that a nonnegligible fraction (≃10%–90%) of long-period QPEs should come from postmerger galaxies.
{"title":"Formation Rate of Quasiperiodic Eruptions in Galactic Nuclei Containing Single and Dual Supermassive Black Holes","authors":"Chunyang Cao, F. K. Liu, Xian Chen and Shuo Li","doi":"10.3847/2041-8213/ad99d9","DOIUrl":"https://doi.org/10.3847/2041-8213/ad99d9","url":null,"abstract":"Quasiperiodic eruptions (QPEs) are a novel class of transients recently discovered in a few extragalactic nuclei. It has been suggested that a QPE can be produced by a main-sequence star undergoing repeated partial disruptions by the tidal field of a supermassive black hole (SMBH) immediately after getting captured on a tightly bound orbit through the Hills mechanism. In this Letter, we investigate the period-dependent formation rate of QPEs for this scenario, utilizing scattering experiments and the loss-cone theory. We calculate the QPE formation rates in both a single-SMBH and a dual-SMBH system, motivated by the overrepresentation of postmerger galaxies as QPE hosts. We find that for SMBHs of mass 106–107M⊙, most QPEs formed in this scenario have periods longer than ≃ 100 days. A single-SMBH system generally produces QPEs at a negligible rate of 10−10–10−8 yr−1 due to inefficient two-body relaxation. Meanwhile, in a dual-SMBH system, the QPE rate is enhanced by 3–4 orders of magnitude, mainly due to a boosted angular momentum evolution under tidal perturbation from the companion SMBH (galaxy). The QPE rate in a postmerger galactic nucleus hosting two equal-mass SMBHs separated by a few parsecs could reach 10−6–10−5 yr−1. Our results suggest that a nonnegligible fraction (≃10%–90%) of long-period QPEs should come from postmerger galaxies.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888118","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9c78
Erick Powell, Merav Opher, Ethan Bair, Matthew Hill, Romina Nikoukar, Joe Giacalone, Konstantinos Dialynas, John D. Richardson, Pontus C. Brandt, Kelsi N. Singer, S. Alan Stern, Elena Provornikova, Anne J. Verbiscer, Andrew R. Poppe, Joel Wm. Parker and New Horizons Heliospheric Team
A couple years before Voyager 1 and Voyager 2 (V2) crossed the termination shock (TS), instruments on board both spacecraft observed high intensities of accelerated termination shock particles (TSPs) beaming in opposite directions. This phenomenon was explained by magnetic field lines connecting the spacecraft to the TS prior to the crossings. The opposite streaming of TSPs is due to an east–west asymmetry of the TS caused by the interstellar magnetic field building up on the outside of the heliopause. Here, we examine the magnetic connectivity for New Horizons (NH) ahead of the TS with a global MHD model with steady solar wind conditions. Our model predicts that NH will observe particles streaming in the same direction as V2 (+T direction in the RTN coordinate system), 1.0 ± 0.7 au from the TS. We then estimate the average speed of the TS during the V2 TS crossing to be 2.5 au yr−1 outward, based on the timing and distance of the TS at the onset of the TSP observations and the crossing itself. Using this speed, we find that NH will have a 0.2 yr warning prior to crossing the TS if the TS is moving inward at the time of the crossing and a 2.4 yr warning if the TS is moving outward.
在旅行者1号和旅行者2号（V2）穿越终端激波（TS）的几年前，两艘飞船上的仪器都观测到高强度的加速终端激波粒子（tsp）向相反方向发射。这一现象的解释是，在穿越之前，连接航天器和TS的磁力线。由于星际磁场在日球层顶的外部形成，导致了日球层顶的东西不对称。在这里，我们使用具有稳定太阳风条件的全球MHD模型来研究TS之前新视野（NH）的磁连通性。我们的模型预测NH将观测到与V2方向相同的粒子流（RTN坐标系中的+T方向），距离TS 1.0±0.7 au .然后，根据TSP观测开始时TS的时间和距离以及穿越本身，我们估计在V2 TS穿越期间TS的平均速度为向外2.5 au / yr - 1。使用这个速度，我们发现如果TS在穿越时向内移动，NH在穿越TS之前将有0.2年的警告，如果TS向外移动，则有2.4年的警告。
{"title":"Termination Shock Particle Streaming Upstream at New Horizons","authors":"Erick Powell, Merav Opher, Ethan Bair, Matthew Hill, Romina Nikoukar, Joe Giacalone, Konstantinos Dialynas, John D. Richardson, Pontus C. Brandt, Kelsi N. Singer, S. Alan Stern, Elena Provornikova, Anne J. Verbiscer, Andrew R. Poppe, Joel Wm. Parker and New Horizons Heliospheric Team","doi":"10.3847/2041-8213/ad9c78","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9c78","url":null,"abstract":"A couple years before Voyager 1 and Voyager 2 (V2) crossed the termination shock (TS), instruments on board both spacecraft observed high intensities of accelerated termination shock particles (TSPs) beaming in opposite directions. This phenomenon was explained by magnetic field lines connecting the spacecraft to the TS prior to the crossings. The opposite streaming of TSPs is due to an east–west asymmetry of the TS caused by the interstellar magnetic field building up on the outside of the heliopause. Here, we examine the magnetic connectivity for New Horizons (NH) ahead of the TS with a global MHD model with steady solar wind conditions. Our model predicts that NH will observe particles streaming in the same direction as V2 (+T direction in the RTN coordinate system), 1.0 ± 0.7 au from the TS. We then estimate the average speed of the TS during the V2 TS crossing to be 2.5 au yr−1 outward, based on the timing and distance of the TS at the onset of the TSP observations and the crossing itself. Using this speed, we find that NH will have a 0.2 yr warning prior to crossing the TS if the TS is moving inward at the time of the crossing and a 2.4 yr warning if the TS is moving outward.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888121","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9dd7
Jin Guo, San Lu, Quanming Lu, Junyi Ren, Jiuqi Ma, James A. Slavin, Weijie Sun, Jun Zhong, Xinliang Gao, Rajkumar Hajra and Rongsheng Wang
Plasma high-speed jets are common in Earth’s magnetosheath, and they significantly perturb the magnetosheath and affect the magnetosphere. The space environment of Mercury, characterized by the bow shock, magnetosheath, and magnetosphere, shares many similarities with that of Earth, so high-speed jets may also be formed in Mercury’s magnetosheath. Here we examine the formation of magnetosheath jets using a three-dimensional global hybrid simulation. The simulation results demonstrate that magnetosheath jets may be formed by the passage of upstream compressive structures through the bow shock. The number and size of the jets are significantly smaller than those at Earth because of Mercury’s smaller magnetosphere size. Under the impact of magnetosheath jets, Mercury’s magnetopause undergoes significant deformation up to ( is Mercury’s radius). These simulation results are expected to be tested by the BepiColombo mission.
{"title":"Three-dimensional Global Hybrid Simulation of Magnetosheath Jets at Mercury","authors":"Jin Guo, San Lu, Quanming Lu, Junyi Ren, Jiuqi Ma, James A. Slavin, Weijie Sun, Jun Zhong, Xinliang Gao, Rajkumar Hajra and Rongsheng Wang","doi":"10.3847/2041-8213/ad9dd7","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9dd7","url":null,"abstract":"Plasma high-speed jets are common in Earth’s magnetosheath, and they significantly perturb the magnetosheath and affect the magnetosphere. The space environment of Mercury, characterized by the bow shock, magnetosheath, and magnetosphere, shares many similarities with that of Earth, so high-speed jets may also be formed in Mercury’s magnetosheath. Here we examine the formation of magnetosheath jets using a three-dimensional global hybrid simulation. The simulation results demonstrate that magnetosheath jets may be formed by the passage of upstream compressive structures through the bow shock. The number and size of the jets are significantly smaller than those at Earth because of Mercury’s smaller magnetosphere size. Under the impact of magnetosheath jets, Mercury’s magnetopause undergoes significant deformation up to ( is Mercury’s radius). These simulation results are expected to be tested by the BepiColombo mission.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888123","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9aaa
H. N. Smitha, Alexander I. Shapiro, Veronika Witzke, Nadiia M. Kostogryz, Yvonne C. Unruh, Tanayveer S. Bhatia, Robert Cameron, Sara Seager and Sami K. Solanki
Accurate calculations of starspot spectra are essential for multiple applications in astronomy. The current standard is to represent starspot spectra by spectra of stars that are cooler than the quiet star regions. This implies approximating a starspot as a nonmagnetic 1D structure in radiative–convective equilibrium, parametrizing convective energy transport by mixing-length theory. It is the inhibition of convection by the starspot magnetic field that is emulated by using a lower spot temperature relative to the quiet stellar regions. Here, we take a different approach, avoiding the approximate treatment of convection and instead self-consistently accounting for the interaction between matter, radiation, and the magnetic field. We simulate spots on G2V, K0V, and M0V stars with the 3D radiative magnetohydrodynamics code MURaM and calculate spectra (R ≈ 500 from 250 to 6000 nm) using ray-by-ray radiative transfer with the MPS-ATLAS code. We find that the 1D models fail to return accurate umbral and penumbral spectra on K0V and M0V stars, where convective and radiative transfer of energy is simultaneously important over a broad range of atmospheric heights, rendering mixing-length theory inaccurate. However, 1D models work well for G2V stars, where both radiation and convection significantly contribute to energy transfer only in a narrow region near the stellar surface. Quantitatively, the 1D approximation leads to errors longward of 500 nm of about 50% for both umbral and penumbral flux contrast relative to quiet star regions on M0V stars and less than 2% (for umbrae) and 10% (for penumbrae) for G2V stars.
{"title":"First Calculations of Starspot Spectra Based on 3D Radiative Magnetohydrodynamics Simulations","authors":"H. N. Smitha, Alexander I. Shapiro, Veronika Witzke, Nadiia M. Kostogryz, Yvonne C. Unruh, Tanayveer S. Bhatia, Robert Cameron, Sara Seager and Sami K. Solanki","doi":"10.3847/2041-8213/ad9aaa","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9aaa","url":null,"abstract":"Accurate calculations of starspot spectra are essential for multiple applications in astronomy. The current standard is to represent starspot spectra by spectra of stars that are cooler than the quiet star regions. This implies approximating a starspot as a nonmagnetic 1D structure in radiative–convective equilibrium, parametrizing convective energy transport by mixing-length theory. It is the inhibition of convection by the starspot magnetic field that is emulated by using a lower spot temperature relative to the quiet stellar regions. Here, we take a different approach, avoiding the approximate treatment of convection and instead self-consistently accounting for the interaction between matter, radiation, and the magnetic field. We simulate spots on G2V, K0V, and M0V stars with the 3D radiative magnetohydrodynamics code MURaM and calculate spectra (R ≈ 500 from 250 to 6000 nm) using ray-by-ray radiative transfer with the MPS-ATLAS code. We find that the 1D models fail to return accurate umbral and penumbral spectra on K0V and M0V stars, where convective and radiative transfer of energy is simultaneously important over a broad range of atmospheric heights, rendering mixing-length theory inaccurate. However, 1D models work well for G2V stars, where both radiation and convection significantly contribute to energy transfer only in a narrow region near the stellar surface. Quantitatively, the 1D approximation leads to errors longward of 500 nm of about 50% for both umbral and penumbral flux contrast relative to quiet star regions on M0V stars and less than 2% (for umbrae) and 10% (for penumbrae) for G2V stars.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888119","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9c79
J. Davelaar
Polarized synchrotron emission is a fundamental process in high-energy astrophysics, particularly in the environments around black holes and pulsars. Accurate modeling of this emission requires precise computation of the emission, absorption, rotation, and conversion coefficients, which are critical for radiative transfer simulations. Traditionally, these coefficients are derived using fit functions based on precomputed ground truth values. However, these fit functions often lack accuracy, particularly in specific plasma conditions not well represented in the data sets used to generate them. In this work, we introduce MLody, a deep neural network designed to compute polarized synchrotron coefficients with high accuracy across a wide range of plasma parameters. We demonstrate MLody's capabilities by integrating it with a radiative transfer code to generate synthetic polarized synchrotron images for an accreting black hole simulation. Our results reveal significant differences, up to a factor of 2, in both linear and circular polarization compared to traditional methods. These differences could have important implications for parameter estimation in Event Horizon Telescope observations, suggesting that MLody could enhance the accuracy of future astrophysical analyses.
{"title":"MLody—Deep Learning–generated Polarized Synchrotron Coefficients","authors":"J. Davelaar","doi":"10.3847/2041-8213/ad9c79","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9c79","url":null,"abstract":"Polarized synchrotron emission is a fundamental process in high-energy astrophysics, particularly in the environments around black holes and pulsars. Accurate modeling of this emission requires precise computation of the emission, absorption, rotation, and conversion coefficients, which are critical for radiative transfer simulations. Traditionally, these coefficients are derived using fit functions based on precomputed ground truth values. However, these fit functions often lack accuracy, particularly in specific plasma conditions not well represented in the data sets used to generate them. In this work, we introduce MLody, a deep neural network designed to compute polarized synchrotron coefficients with high accuracy across a wide range of plasma parameters. We demonstrate MLody's capabilities by integrating it with a radiative transfer code to generate synthetic polarized synchrotron images for an accreting black hole simulation. Our results reveal significant differences, up to a factor of 2, in both linear and circular polarization compared to traditional methods. These differences could have important implications for parameter estimation in Event Horizon Telescope observations, suggesting that MLody could enhance the accuracy of future astrophysical analyses.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888122","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9c69
Samantha L. Garza, Jessica K. Werk, Trystyn A. M. Berg, Yakov Faerman, Benjamin D. Oppenheimer, Rongmon Bordoloi and Sara L. Ellison
This paper investigates C iv absorption in the circumgalactic medium (CGM) of L⋆ galaxies and its relationship with galaxy star formation rates. We present new observations from the C iv in L⋆ galaxies survey (PID#17076) using the Hubble Space Telescope/Cosmic Origins Spectrograph. By combining these measurements with archival C iv data (46 observations total), we estimate detection fractions for star-forming (sSFR > 10−11 yr−1) and passive galaxies (sSFR ≤ 10−11 yr−1 ) to be 72 % [21/29] and 23 % [3/13], respectively. This indicates a significant dichotomy in C iv presence between L⋆ star-forming and passive galaxies, with over 99% confidence. This finding aligns with J. Tumlinson et al., which noted a similar dichotomy in O vi absorption. Our results imply a substantial carbon reservoir in the CGM of L⋆ galaxies, suggesting a minimum carbon mass of ≳3.03 × 106M⊙ out to 120 kpc. Together, these findings highlight a strong connection between star formation in galaxies and the state of their CGM, providing insight into the mechanisms governing galaxy evolution.
{"title":"The CIViL* Survey: The Discovery of a C iv Dichotomy in the Circumgalactic Medium of L* Galaxies","authors":"Samantha L. Garza, Jessica K. Werk, Trystyn A. M. Berg, Yakov Faerman, Benjamin D. Oppenheimer, Rongmon Bordoloi and Sara L. Ellison","doi":"10.3847/2041-8213/ad9c69","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9c69","url":null,"abstract":"This paper investigates C iv absorption in the circumgalactic medium (CGM) of L⋆ galaxies and its relationship with galaxy star formation rates. We present new observations from the C iv in L⋆ galaxies survey (PID#17076) using the Hubble Space Telescope/Cosmic Origins Spectrograph. By combining these measurements with archival C iv data (46 observations total), we estimate detection fractions for star-forming (sSFR > 10−11 yr−1) and passive galaxies (sSFR ≤ 10−11 yr−1 ) to be 72 % [21/29] and 23 % [3/13], respectively. This indicates a significant dichotomy in C iv presence between L⋆ star-forming and passive galaxies, with over 99% confidence. This finding aligns with J. Tumlinson et al., which noted a similar dichotomy in O vi absorption. Our results imply a substantial carbon reservoir in the CGM of L⋆ galaxies, suggesting a minimum carbon mass of ≳3.03 × 106M⊙ out to 120 kpc. Together, these findings highlight a strong connection between star formation in galaxies and the state of their CGM, providing insight into the mechanisms governing galaxy evolution.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888120","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 : 2024-12-27DOI: 10.3847/2041-8213/ad9ea7
J. A. Morales and C. J. Horowitz
Neutron stars are not observed to spin faster than about half their breakup rate. This limiting rotational frequency may be related to the strength of their crusts. As a star spins up from accretion, centrifugal forces stress the crust. We perform finite-element simulations of rotating neutron stars and find that the crust fails at rotation rates about half the breakup rate. Given uncertainties in microphysics, we have not determined the crust configuration after this failure. Instead, we argue that the crust may fail in an asymmetric way and could produce a configuration with a significant ellipticity (fractional difference in moments of inertia). If the ellipticity is large, a rotating star will radiate gravitational waves that may limit further spin-up. These stars may be promising sources for LIGO/VIRGO and next-generation gravitational-wave detectors.
{"title":"Limiting Rotation Rate of Neutron Stars from Crust Breaking and Gravitational Waves","authors":"J. A. Morales and C. J. Horowitz","doi":"10.3847/2041-8213/ad9ea7","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9ea7","url":null,"abstract":"Neutron stars are not observed to spin faster than about half their breakup rate. This limiting rotational frequency may be related to the strength of their crusts. As a star spins up from accretion, centrifugal forces stress the crust. We perform finite-element simulations of rotating neutron stars and find that the crust fails at rotation rates about half the breakup rate. Given uncertainties in microphysics, we have not determined the crust configuration after this failure. Instead, we argue that the crust may fail in an asymmetric way and could produce a configuration with a significant ellipticity (fractional difference in moments of inertia). If the ellipticity is large, a rotating star will radiate gravitational waves that may limit further spin-up. These stars may be promising sources for LIGO/VIRGO and next-generation gravitational-wave detectors.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"87 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888124","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：