The Astrophysical Journal最新文献_第2页

Measurement of the Forward Shock Velocities of the Supernova Remnant N132D Based on the Thermal X-Ray Emission

The Astrophysical Journal Pub Date : 2025-03-28 DOI: 10.3847/1538-4357/adb8cb

Yoshizumi Okada, Yuken Ohshiro, Shunsuke Suzuki, Hiromasa Suzuki, Paul P. Plucinsky, Ryo Yamazaki and Hiroya Yamaguchi

{"title":"Measurement of the Forward Shock Velocities of the Supernova Remnant N132D Based on the Thermal X-Ray Emission","authors":"Yoshizumi Okada, Yuken Ohshiro, Shunsuke Suzuki, Hiromasa Suzuki, Paul P. Plucinsky, Ryo Yamazaki and Hiroya Yamaguchi","doi":"10.3847/1538-4357/adb8cb","DOIUrl":"https://doi.org/10.3847/1538-4357/adb8cb","url":null,"abstract":"Measuring shock velocities is crucial for understanding the energy transfer processes at the shock fronts of supernova remnants (SNRs), including acceleration of cosmic rays. Here we present shock velocity measurements on the SNR N132D, based on the thermal properties of the shock-heated interstellar medium. We apply a self-consistent model developed in our previous work to X-ray data from deep Chandra observations with an effective exposure of ∼900 ks. In our model, both temperature and ionization relaxation processes in postshock plasmas are simultaneously calculated, so that we can trace back to the initial condition of the shock-heated plasma to constrain the shock velocity. We reveal that the shock velocity ranges from 800 to 1500 km s−1 with moderate azimuthal dependence. Although our measurement is consistent with the velocity determined by independent proper motion measurements in the south rim regions, a large discrepancy between the two measurements (up to a factor of 4) is found in the north rim regions. This implies that a substantial amount of the kinetic energy has been transferred to the nonthermal component through highly efficient particle acceleration. Our results are qualitatively consistent with the gamma-ray observations of this SNR.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143723275","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}

引用次数: 0

Barium Abundances of Common Stars in the Gaia-ESO Survey and the LAMOST Medium-resolution Survey

The Astrophysical Journal Pub Date : 2025-03-28 DOI: 10.3847/1538-4357/adbbe0

Tian-Yi Chen, Jian-Rong Shi, Hong-Liang Yan, Shuai Liu, Chun-Qian Li, Xiao-Jin Xie, Ze-Ming Zhou, Yao-Jia Tang and Ming-Yi Ding

{"title":"Barium Abundances of Common Stars in the Gaia-ESO Survey and the LAMOST Medium-resolution Survey","authors":"Tian-Yi Chen, Jian-Rong Shi, Hong-Liang Yan, Shuai Liu, Chun-Qian Li, Xiao-Jin Xie, Ze-Ming Zhou, Yao-Jia Tang and Ming-Yi Ding","doi":"10.3847/1538-4357/adbbe0","DOIUrl":"https://doi.org/10.3847/1538-4357/adbbe0","url":null,"abstract":"Barium (Ba) abundance has been used as a crucial tracer of both slow and rapid neutron-capture processes to constrain the evolutionary models of the Galaxy. In this study, we aim to establish a reference sample with high-resolution spectra and high-quality stellar parameters from the Gaia-ESO Survey (GES). This sample explores the non–local thermodynamic equilibrium (NLTE) effects on the Ba abundances and will support future measurements of Ba abundances for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution survey (MRS). The sample is composed of 85 common stars of LAMOST MRS DR9 and GES DR5.1, complemented by four metal-poor ([Fe/H] < −1 dex) stars from AMBRE-UVES. The stars cover the ranges of stellar parameters as 4152 K ≤ Teff ≤ 6866 K, 1.37 4.57, and −2.40 dex ≤ [Fe/H] ≤ +0.25 dex. We derive the Ba abundances from three Ba ii absorption lines at λλ5853, 6141, and 6496 Å of R = 47,000 UVES spectra through the spectral synthesis method using the local thermodynamic equilibrium (LTE) and NLTE assumptions. Compared to the GES catalog, the LTE Ba abundances obtained by us from the Ba ii λ5853 line are the closest to the GES LTE results. The NLTE hypothesis is found to show various impacts on the three lines. The maximum differences from LTE abundances are 0.2, 0.5, and 0.6 dex for the Ba ii lines at λλ5853, 6141, and 6496 Å, respectively. The NLTE corrections present opposite signs around [Fe/H] = −2.0 dex for the Ba ii line at λ5853. Stars with higher temperatures or higher Ba abundances suffer larger NLTE effects. A more consistent result of the three lines confirms the necessity of taking NLTE effects into account when determining the Ba abundances.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143723321","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}

引用次数: 0

Carbon Stars from Gaia Data Release 3 and the Space Density of Dwarf Carbon Stars

The Astrophysical Journal Pub Date : 2025-03-28 DOI: 10.3847/1538-4357/adba53

Benjamin R. Roulston, Naunet Leonhardes-Barboza, Paul J. Green and Evan Portnoi

{"title":"Carbon Stars from Gaia Data Release 3 and the Space Density of Dwarf Carbon Stars","authors":"Benjamin R. Roulston, Naunet Leonhardes-Barboza, Paul J. Green and Evan Portnoi","doi":"10.3847/1538-4357/adba53","DOIUrl":"https://doi.org/10.3847/1538-4357/adba53","url":null,"abstract":"Carbon stars (with atmospheric C/O > 1) range widely in temperature and luminosity, from low-mass dwarfs to asymptotic giant branch (AGB) stars. The main-sequence dwarf carbon (dC) stars have inherited carbon-rich material from an AGB companion, which has since transitioned to a white dwarf. The dC stars are far more common than C giants, but no reliable estimates of the dC space density have been published to date. We present results from an all-sky survey for carbon stars using the low-resolution XP spectra from Gaia Data Release 3. We developed and measured a set of spectral indices contrasting C2 and CN molecular band strengths in carbon stars against common absorption features found in normal (C/O < 1) stars, such as Ca i, TiO, and Balmer lines. We combined these indices with the XP spectral coefficients as inputs to supervised machine learning algorithms trained on a vetted sample of known C stars from LAMOST. We describe the selection of the carbon candidate sample and provide a catalog of 43,574 candidates dominated by cool C giants in the Magellanic Clouds and at low Galactic latitude in the Milky Way. We report the confirmation of candidate C stars using intermediate-resolution (R ∼ 1800) optical spectroscopy from the Fred Lawrence Whipple Observatory and provide estimates of the sample purity and completeness. From a carefully vetted sample of over 600 dCs, we measure their local space density to be (about one dC in every local disk volume of radius 50 pc), with a relatively large disk scale height of pc.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143723319","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}

引用次数: 0

A High-accuracy Alignment Approach for Solar Images of Different Wavelengths

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adbaec

Yun Wang, Kaifan Ji, Zhenyu Jin and Hui Liu

{"title":"A High-accuracy Alignment Approach for Solar Images of Different Wavelengths","authors":"Yun Wang, Kaifan Ji, Zhenyu Jin and Hui Liu","doi":"10.3847/1538-4357/adbaec","DOIUrl":"https://doi.org/10.3847/1538-4357/adbaec","url":null,"abstract":"Image alignment plays a crucial role in solar physics research, primarily involving translation, rotation, and scaling. The different wavelength images of the chromosphere and transition region have structural complexity and differences in similarity, which poses a challenge to their alignment. Therefore, a novel alignment approach based on dense optical flow (OF) and the RANSAC algorithm is proposed in this paper. It takes the OF vectors of similar regions between images to be used as feature points for matching. Then, it calculates scaling, rotation, and translation. The study selects three wavelengths for two groups of alignment experiments: the 304 Å of the Atmospheric Imaging Assembly (AIA), the 1216 Å of the Solar Disk Imager (SDI), and the 465 Å of the Solar Upper Transition Region Imager (SUTRI). Two methods are used to evaluate alignment accuracy: Monte Carlo simulation and Uncertainty Analysis Based on the Jacobian Matrix. The evaluation results indicate that this approach achieves subpixel accuracy in the alignment of AIA 304 Å and SDI 1216 Å, while demonstrating higher accuracy in the alignment of AIA 304 Å and SUTRI 465 Å, which have greater similarity.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143712891","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}

引用次数: 0

DIISC-VI (COS-DIISC): Ultraviolet Metal Absorption Relative to the H i Disk of Galaxies

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adb8ca

Brad Koplitz, Sanchayeeta Borthakur, Timothy Heckman, Mansi Padave, Tyler McCabe, Jason Tumlinson, Andrew J. Fox and Guinevere Kauffmann

{"title":"DIISC-VI (COS-DIISC): Ultraviolet Metal Absorption Relative to the H i Disk of Galaxies","authors":"Brad Koplitz, Sanchayeeta Borthakur, Timothy Heckman, Mansi Padave, Tyler McCabe, Jason Tumlinson, Andrew J. Fox and Guinevere Kauffmann","doi":"10.3847/1538-4357/adb8ca","DOIUrl":"https://doi.org/10.3847/1538-4357/adb8ca","url":null,"abstract":"As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the circumgalactic medium (CGM) near the H i gas disk (<4.5RHI) of 31 nearby galaxies through quasar absorption-line spectroscopy. Of the ions under study, Si iiiλ1206 was most frequently detected (18 of 31 sight lines), while C iiλ1334 and Si iiλ1260 were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models; most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters (ρ) normalized by the galaxy’s virial radius (Rvir) and H i radius (RHI) tend to have more components and larger rest-frame equivalent widths (Wr) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced by ρ/RHI rather than the traditional ρ/Rvir. Larger covering fractions are found closer to galaxies, with a radial decline that depends on the Wr limit used. Our results provide new insights into the spatial distribution of metals around the H i disks of low-redshift galaxies.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713060","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}

引用次数: 0

Hyperneutron Stars from an Ab Initio Calculation

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adba47

Hui Tong, Serdar Elhatisari and Ulf-G. Meißner

{"title":"Hyperneutron Stars from an Ab Initio Calculation","authors":"Hui Tong, Serdar Elhatisari and Ulf-G. Meißner","doi":"10.3847/1538-4357/adba47","DOIUrl":"https://doi.org/10.3847/1538-4357/adba47","url":null,"abstract":"The equation of state (EOS) of neutron matter plays a decisive role in understanding the neutron star properties and the gravitational waves from neutron star mergers. At sufficient densities, the appearance of hyperons generally softens the EOS, leading to a reduction in the maximum mass of neutron stars well below the observed values of about 2 M⊙. Even though repulsive three-body forces are known to solve this so-called “hyperon puzzle,” so far performing ab initio calculations with a substantial number of hyperons for neutron star properties has remained elusive. Starting from the newly developed auxiliary field quantum Monte Carlo algorithm to simulate hyperneutron matter without any sign oscillations, we derive three distinct EOSs by employing the state-of-the-art nuclear lattice effective field theory. We include NΛ, ΛΛ two-body forces, NNΛ, and NΛΛ three-body forces. Consequently, we determine essential astrophysical quantities such as the neutron star mass, radius, tidal deformability, and universal I–Love–Q relation. The maximum mass, radius, and tidal deformability of a 1.4 M⊙ neutron star are predicted to be 2.17(1)(1) M⊙, R1.4M⊙ = 13.10(1)(7) km, and , respectively, based on our most realistic EOS. These predictions are in good agreement with the latest astrophysical constraints derived from observations of massive neutron stars, gravitational waves, and joint mass–radius measurements. In addition, for the first time in ab initio calculations, we investigate both nonrotating and rotating neutron star configurations. The results indicate that the impact of rotational dynamics on the maximum mass is small, regardless of whether hyperons are present in the EOS or not.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143712884","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}

引用次数: 0

Aggressively Dissipative Dark Dwarfs: The Effects of Atomic Dark Matter on the Inner Densities of Isolated Dwarf Galaxies

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adb02b

Sandip Roy, Xuejian Shen, Jared Barron, Mariangela Lisanti, David Curtin, Norman Murray and Philip F. Hopkins

{"title":"Aggressively Dissipative Dark Dwarfs: The Effects of Atomic Dark Matter on the Inner Densities of Isolated Dwarf Galaxies","authors":"Sandip Roy, Xuejian Shen, Jared Barron, Mariangela Lisanti, David Curtin, Norman Murray and Philip F. Hopkins","doi":"10.3847/1538-4357/adb02b","DOIUrl":"https://doi.org/10.3847/1538-4357/adb02b","url":null,"abstract":"We present the first suite of cosmological hydrodynamical zoom-in simulations of isolated dwarf galaxies for a dark sector that consists of cold dark matter and a strongly dissipative subcomponent. The simulations are implemented in GIZMO and include standard baryons following the FIRE-2 galaxy formation physics model. The dissipative dark matter is modeled as atomic dark matter (aDM), which forms a dark hydrogen gas that cools in direct analogy to the Standard Model. Our suite includes seven different simulations of ∼1010M⊙ systems that vary over the aDM microphysics and the dwarf’s evolutionary history. We identify a region of aDM parameter space where the cooling rate is aggressive and the resulting halo density profile is universal. In this regime, the aDM gas cools rapidly at high redshifts, and only a small fraction survives in the form of a central dark gas disk; the majority collapses centrally into collisionless dark “clumps,” which are clusters of subresolution dark compact objects. These dark clumps rapidly equilibrate in the inner galaxy, resulting in an approximately isothermal distribution that can be modeled with a simple fitting function. Even when only a small fraction (∼5%) of the total dark matter is strongly dissipative, the central densities of classical dwarf galaxies can be enhanced by over an order of magnitude, providing a sharp prediction for observations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143723325","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}

引用次数: 0

Laboratory Detection of the Methoxymethyl Radical, CH3OCH2, Using Faraday Rotation and Chirped-pulse Techniques in the (Sub)millimeter Wave Range

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adba5c

Rosemonde Chahbazian, Marie-Aline Martin-Drumel and Olivier Pirali

{"title":"Laboratory Detection of the Methoxymethyl Radical, CH3OCH2, Using Faraday Rotation and Chirped-pulse Techniques in the (Sub)millimeter Wave Range","authors":"Rosemonde Chahbazian, Marie-Aline Martin-Drumel and Olivier Pirali","doi":"10.3847/1538-4357/adba5c","DOIUrl":"https://doi.org/10.3847/1538-4357/adba5c","url":null,"abstract":"Modeling the abundance of interstellar complex organic molecules in space is a major challenge for astrophysicists. The relative roles of gas-phase and grain-surface processes in the formation and destruction of such large molecules remain unclear. Methyl formate (CH3OCHO, MF) and dimethyl ether (CH3OCH3, DME) species have been detected at relatively high abundances in both warm and cold objects of the interstellar medium (ISM), challenging an initial hypothesis favoring grain-surface processes for their formation. In this context, the methoxymethyl radical (CH3OCH2, RDME) has been proposed as a key species linking the abundances of MF and DME in the gas phase. Its detection may provide crucial information to disentangle and quantify the different processes involved in the formation and destruction of MF and DME. To support the search for RDME in space, we present the laboratory detection of its pure rotational spectrum in the vibronic ground state. Special care was taken to measure the frequencies of transitions expected to be intense under cold interstellar conditions. In total, we assigned and fitted 1007 transitions of the RDME with and values up to 34 and 5, respectively. A reliable spectral catalog has been generated using the spectroscopic parameters derived from the fit and can be used confidently for future searches of the RDME radical in the ISM.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143712887","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}

引用次数: 0

Redshift Drift Effect through the Observation of the H I 21 cm Signal with SKA

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adae89

Jiangang Kang, Tong-Jie Zhang, Peng He and Ming Zhu

{"title":"Redshift Drift Effect through the Observation of the H I 21 cm Signal with SKA","authors":"Jiangang Kang, Tong-Jie Zhang, Peng He and Ming Zhu","doi":"10.3847/1538-4357/adae89","DOIUrl":"https://doi.org/10.3847/1538-4357/adae89","url":null,"abstract":"This study presents the findings of using the Square Kilometre Array (SKA) telescope to measure redshift drift via the H i 21 cm signal, employing semiannual observational intervals within a redshift of around z ∼ 1 with a main goal of directly gauging the Universe’s expansion acceleration rate with mm s−1 precision. The SKA can detect over 1 billion H i 21 cm emissions from individual galaxies to redshift z ∼ 2 and thousands of absorption lines from damped Lyα systems against bright quasars to redshift z ∼ 13 with a sensitivity limit of 100 mJy. By utilizing SKA’s high spectral resolution settings (0.001, 0.002, 0.005, 0.01 Hz) to detect redshift drift, particularly focusing on the 0.001 and 0.002 Hz configuration, one aims to achieve the necessary mm s−1 in precision measurement by the 0.5 yr observation period. The velocity drift rate, crucially determined by the two operational regimes within 0.01–0.21 mm s−1 and 0.031–0.17 mm s−1, exceeds the theoretical accuracy limit of 1.28 mm s−1. The analysis thoroughly restricts cosmological parameters related to dark energy using the Sandage–Loeb (SL) signal from the H i 21 cm emission and absorption lines. It estimates a H0 of about 70 km s−1 Mpc−1, Ωm near 0.3, and w close to −1, w0 around −1, and wa approaching −0.1. These results strongly endorse the SL effect as an effective method for confirming cosmic acceleration and exploring the dark sector in real-time cosmology with the SKA.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"183 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713057","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}

引用次数: 0

What Defines Stationarity in Space Plasmas

The Astrophysical Journal Pub Date : 2025-03-27 DOI: 10.3847/1538-4357/adb8d2

G. Livadiotis and D. J. McComas

{"title":"What Defines Stationarity in Space Plasmas","authors":"G. Livadiotis and D. J. McComas","doi":"10.3847/1538-4357/adb8d2","DOIUrl":"https://doi.org/10.3847/1538-4357/adb8d2","url":null,"abstract":"Starting from the concept of entropy defect in thermodynamics, we construct the entropy formulation of space plasmas, and then use it to develop a measure of their stationarity. In particular, we show that the statistics of this entropy results in two findings that improve our understanding of stationary and nonstationary systems: (i) variations of Boltzmann−Gibbs (BG) entropy do not exceed twice the value of the thermodynamic kappa, the parameter that provides a measure of the entropy defect in both stationary and nonstationary states, while becoming the shape parameter that labels the kappa distributions in stationary states; and (ii) the ratio of the deviation of the BG entropy with kappa scales with the kappa deviation via a power law, while the respective exponent provides the stationarity deviation index (SDI), which measures the natural tendency of the system to depart from stationarity. We confirm the validity of these findings in three different heliospheric plasma data sets observed from three missions: (1) a solar energetic particle event, recorded by the Integrated Science Investigation of the Sun instrument on board the Parker Solar Probe; (2) near-Earth solar wind protons recorded by the Solar Wind Experiment instrument on board Wind; and (3) plasma protons in the heliosheath, the source of energetic neutral atoms recorded by Interstellar Boundary Explorer. The full strength and capability of the entropic deviation ratio and SDI can now be used by the space physics community for analyzing and characterizing the stationarity of space plasmas, as well as other researchers for analyzing any other correlated systems.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143713062","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}

引用次数: 0