Pub Date : 2024-07-29DOI: 10.1007/s10509-024-04340-4
GuangZhen Wang, Xiaolei Li, Nan Liang
In this work, we investigate the phenomenologically emergent dark energy (PEDE) model and its generalized form, namely the generalized emergent dark energy (GEDE) model, which introduces a free parameter (Delta ) that can discriminate between the (Lambda )CDM model and the PEDE model. Fitting the emergent dark energy (EDE) models with the observational datasets including the cosmology-independent gamma-ray bursts (GRBs) and the observational Hubble data (OHD) at intermediate redshift, we find a large value of (H_{0}) which is close to the results of local measurement of (H_{0}) from the SH0ES Collaboration in both EDE models. In order to refine our analysis and tighten the constraints on cosmological parameters, we combine mid-redshift observations GRBs and OHD with baryon acoustic oscillations (BAOs). Finally, we constrain DE models by using the simultaneous fitting method, in which the parameters of DE models and the relation parameters of GRBs are fitted simultaneously. Our results suggest that PEDE and GEDE models can be possible alternative to the standard cosmological model, pending further theoretical explorations and observational verifications.
在这项工作中,我们研究了现象涌现暗能量(PEDE)模型及其广义形式,即广义涌现暗能量(GEDE)模型,它引入了一个自由参数(Delta ),可以区分(Lambda )CDM模型和PEDE模型。将新兴暗能量(EDE)模型与观测数据集(包括独立于宇宙学的伽玛射线暴(GRBs)和中红移时的哈勃观测数据(OHD))进行拟合,我们发现在两个EDE模型中,(H_{0})的值都很大,这与SH0ES合作组织对(H_{0})的本地测量结果很接近。为了完善我们的分析并加强对宇宙学参数的约束,我们把中红移观测GRBs和OHD与重子声振荡(BAOs)结合起来。最后,我们使用同时拟合法来约束 DE 模型,即同时拟合 DE 模型参数和 GRBs 的关系参数。我们的结果表明,PEDE 和 GEDE 模型有可能成为标准宇宙学模型的替代模型,这有待于进一步的理论探索和观测验证。
{"title":"Constraining the emergent dark energy models with observational data at intermediate redshift","authors":"GuangZhen Wang, Xiaolei Li, Nan Liang","doi":"10.1007/s10509-024-04340-4","DOIUrl":"https://doi.org/10.1007/s10509-024-04340-4","url":null,"abstract":"<p>In this work, we investigate the phenomenologically emergent dark energy (PEDE) model and its generalized form, namely the generalized emergent dark energy (GEDE) model, which introduces a free parameter <span>(Delta )</span> that can discriminate between the <span>(Lambda )</span>CDM model and the PEDE model. Fitting the emergent dark energy (EDE) models with the observational datasets including the cosmology-independent gamma-ray bursts (GRBs) and the observational Hubble data (OHD) at intermediate redshift, we find a large value of <span>(H_{0})</span> which is close to the results of local measurement of <span>(H_{0})</span> from the SH0ES Collaboration in both EDE models. In order to refine our analysis and tighten the constraints on cosmological parameters, we combine mid-redshift observations GRBs and OHD with baryon acoustic oscillations (BAOs). Finally, we constrain DE models by using the simultaneous fitting method, in which the parameters of DE models and the relation parameters of GRBs are fitted simultaneously. Our results suggest that PEDE and GEDE models can be possible alternative to the standard cosmological model, pending further theoretical explorations and observational verifications.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-26DOI: 10.1007/s10509-024-04338-y
Kanchan Devi, Ajay Kumar, Pankaj Kumar
We consider a recently modified version of holographic dark energy, known as Barrow holographic dark energy, in the framework of (f(R, T)) gravity and consider a flat Friedmann-Lemaitre-Robertson-Walker line element for our study. We solve the field equations of the model to obtain the values of Hubble parameter and scale factor of the universe. We obtain the values of deceleration parameter and effective equation of state to discuss the evolution of the universe. Further, we constrain the model parameters using various data sets like type Ia supernova, observational Hubble data, SH0ES data etc. We use the Monte Carlo Markov Chain method to obtain the best fit values of the model parameters. We observe that the best fit present values of Hubble parameter (H_{0}=67.764_{-1.354}^{+1.274}) and (H_{0}=70.440_{-0.869}^{+0.816}), obtained for two different combinations of observational data, are in agreement with recent observations. We also constrain the case in which our model converts to the Barrow holographic dark energy model in general relativity and compare the results of both models. We compare the results with (Lambda )-CDM model wherever required. We plot deceleration parameter against redshift parameter for best fit values of the model parameters. We observe a smooth phase transition of the universe from early time decelerated expansion to accelerated expansion which shows compatibility with recent observations. The values of equation of state parameter (omega _{h}) of Barrow holographic dark energy are found to be (-0.873_{-0.078}^{+0.115}) and (-0.866_{-0.130}^{+0.156}), and age of the universe are found to be 14.09 (Gyr) and 15.43 (Gyr) for two combination of data sets for Barrow holographic dark energy model in (f(R, T)) gravity. Furthermore, we apply statefinder and (Om) diagnostic to discriminate our model from existing dark energy models.
我们在(f(R, T))引力框架下考虑了最近修改过的全息暗能量,即巴罗全息暗能量,并考虑了平坦的弗里德曼-勒梅特-罗伯逊-沃克线元。我们求解了模型的场方程,得到了宇宙的哈勃参数和尺度因子值。我们获得了减速参数值和有效状态方程,以讨论宇宙的演化。此外,我们还利用各种数据集,如 Ia 型超新星、哈勃观测数据、SH0ES 数据等,对模型参数进行约束。我们使用蒙特卡罗马尔可夫链方法来获得模型参数的最佳拟合值。我们观察到,在两种不同的观测数据组合下得到的哈勃参数的最佳拟合现值(H_{0}=67.764_{-1.354}^{+1.274})和(H_{0}=70.440_{-0.869}^{+0.816})与最近的观测结果是一致的。我们还约束了我们的模型转换为广义相对论中巴罗全息暗能量模型的情况,并比较了两种模型的结果。在需要的地方,我们将结果与(Lambda)-CDM模型进行比较。我们绘制了模型参数最佳拟合值的减速参数与红移参数的关系图。我们观察到宇宙从早期减速膨胀到加速膨胀的平滑相变,这与最近的观测结果是一致的。发现巴罗全息暗能量的状态方程参数值(omega _{h})为(-0.873_{-0.078}^{+0.115})和(-0.866_{-0.130}^{+0.(f(R,T))引力下的巴罗全息暗能量模型的两组数据组合的宇宙年龄分别为14.09(Gyr)和15.43(Gyr)。此外,我们还应用状态探测器和(Om )诊断法来区分我们的模型和现有的暗能量模型。
{"title":"Barrow holographic dark energy model in $f(R, T)$ theory","authors":"Kanchan Devi, Ajay Kumar, Pankaj Kumar","doi":"10.1007/s10509-024-04338-y","DOIUrl":"https://doi.org/10.1007/s10509-024-04338-y","url":null,"abstract":"<p>We consider a recently modified version of holographic dark energy, known as Barrow holographic dark energy, in the framework of <span>(f(R, T))</span> gravity and consider a flat Friedmann-Lemaitre-Robertson-Walker line element for our study. We solve the field equations of the model to obtain the values of Hubble parameter and scale factor of the universe. We obtain the values of deceleration parameter and effective equation of state to discuss the evolution of the universe. Further, we constrain the model parameters using various data sets like type Ia supernova, observational Hubble data, SH0ES data etc. We use the Monte Carlo Markov Chain method to obtain the best fit values of the model parameters. We observe that the best fit present values of Hubble parameter <span>(H_{0}=67.764_{-1.354}^{+1.274})</span> and <span>(H_{0}=70.440_{-0.869}^{+0.816})</span>, obtained for two different combinations of observational data, are in agreement with recent observations. We also constrain the case in which our model converts to the Barrow holographic dark energy model in general relativity and compare the results of both models. We compare the results with <span>(Lambda )</span>-CDM model wherever required. We plot deceleration parameter against redshift parameter for best fit values of the model parameters. We observe a smooth phase transition of the universe from early time decelerated expansion to accelerated expansion which shows compatibility with recent observations. The values of equation of state parameter <span>(omega _{h})</span> of Barrow holographic dark energy are found to be <span>(-0.873_{-0.078}^{+0.115})</span> and <span>(-0.866_{-0.130}^{+0.156})</span>, and age of the universe are found to be 14.09 <span>(Gyr)</span> and 15.43 <span>(Gyr)</span> for two combination of data sets for Barrow holographic dark energy model in <span>(f(R, T))</span> gravity. Furthermore, we apply statefinder and <span>(Om)</span> diagnostic to discriminate our model from existing dark energy models.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141775206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we aim to study the consequences of presently observed accelerated expansion of the universe by assuming power-law based Starobinsky type metric (f(R)) gravity as the theory of gravity. We, here, focused on evolution of the universe by studying different cosmological parameters like Hubble parameter, Deceleration parameter and Jerk parameter etc. From our analysis, we found that the phenomenological constant of Starobinsky model ((M^{2})) has a very small value (0.6538t_{0}^{-2}), where (t_{0}) is the present age of the universe. Again, from the nature of variation of deceleration parameter and jerk parameter, we concluded that the universe has been undergoing an accelerated phase of expansion from (0.711t_{0}) and this will continue even upto the distant future.
{"title":"Cosmological parameters, accelerated expansion of the universe and metric $mathit{{f(R)}}$ gravity","authors":"Suraj Kumar Pati, Suryakanta Swain, Bibekananda Nayak","doi":"10.1007/s10509-024-04337-z","DOIUrl":"https://doi.org/10.1007/s10509-024-04337-z","url":null,"abstract":"<p>In this work, we aim to study the consequences of presently observed accelerated expansion of the universe by assuming power-law based Starobinsky type metric <span>(f(R))</span> gravity as the theory of gravity. We, here, focused on evolution of the universe by studying different cosmological parameters like Hubble parameter, Deceleration parameter and Jerk parameter etc. From our analysis, we found that the phenomenological constant of Starobinsky model <span>((M^{2}))</span> has a very small value <span>(0.6538t_{0}^{-2})</span>, where <span>(t_{0})</span> is the present age of the universe. Again, from the nature of variation of deceleration parameter and jerk parameter, we concluded that the universe has been undergoing an accelerated phase of expansion from <span>(0.711t_{0})</span> and this will continue even upto the distant future.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-23DOI: 10.1007/s10509-024-04335-1
Claudio Germanà
In this manuscript we pursue tidal disruption of magnetically confined clumps of matter as candidate to interpret the twin peak high-frequency quasiperiodic oscillations (HF QPOs) seen in low-mass x-ray binaries (LMXBs). In previews works we have proposed the upper HF QPO seen in neutron star (NS) LMXBs be linked to the energy released during tidal circularization of relativistic orbits. The lower HF QPO instead might come from the energy released during spiraling and tidal stretching of the clump. The observed behavior of the coherence (Q) of the lower HF QPO was related to both the tidal stretching time-scale of the clump along the orbit and the number of turns clumps make before reaching the innermost stable bound orbit. In this paper we focus on the maximum value of (Q) across LMXBs spanning two orders of magnitudes in luminosity. We show the (Q_{max}) behavior of the lower HF QPO seen across LMXBs luminosity might be related to tidal stretching time-scale as well, giving an estimate of the magnetic field in the plasma.
{"title":"Lower twin peak quasiperiodic oscillation coherence across luminosity and the tidal stretching time-scale","authors":"Claudio Germanà","doi":"10.1007/s10509-024-04335-1","DOIUrl":"https://doi.org/10.1007/s10509-024-04335-1","url":null,"abstract":"<p>In this manuscript we pursue tidal disruption of magnetically confined clumps of matter as candidate to interpret the twin peak high-frequency quasiperiodic oscillations (HF QPOs) seen in low-mass x-ray binaries (LMXBs). In previews works we have proposed the upper HF QPO seen in neutron star (NS) LMXBs be linked to the energy released during tidal circularization of relativistic orbits. The lower HF QPO instead might come from the energy released during spiraling and tidal stretching of the clump. The observed behavior of the coherence <span>(Q)</span> of the lower HF QPO was related to both the tidal stretching time-scale of the clump along the orbit and the number of turns clumps make before reaching the innermost stable bound orbit. In this paper we focus on the maximum value of <span>(Q)</span> across LMXBs spanning two orders of magnitudes in luminosity. We show the <span>(Q_{max})</span> behavior of the lower HF QPO seen across LMXBs luminosity might be related to tidal stretching time-scale as well, giving an estimate of the magnetic field in the plasma.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-12DOI: 10.1007/s10509-024-04331-5
S. V. Sinitsyn
For Galactic RRab stars 121 empirical and semiempirical metallicity–absolute magnitude relations known since 1990 are analyzed. For these variables, using their known empirical data, relations are determined between the mass, the radius, the effective surface temperature, the bolometric correction, the luminosity, the absolute magnitude, on the one hand, and the metallicity and the pulsation period, on the other hand. Using these relations, the empirical value of the Eddington pulsation constant is accurately determined for RRab stars for the first time.
{"title":"Parameters and the Eddington pulsation constant of Galactic RRab stars","authors":"S. V. Sinitsyn","doi":"10.1007/s10509-024-04331-5","DOIUrl":"https://doi.org/10.1007/s10509-024-04331-5","url":null,"abstract":"<p>For Galactic RRab stars 121 empirical and semiempirical metallicity–absolute magnitude relations known since 1990 are analyzed. For these variables, using their known empirical data, relations are determined between the mass, the radius, the effective surface temperature, the bolometric correction, the luminosity, the absolute magnitude, on the one hand, and the metallicity and the pulsation period, on the other hand. Using these relations, the empirical value of the Eddington pulsation constant is accurately determined for RRab stars for the first time.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141613662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1007/s10509-024-04333-3
M. Moscibrodzka
X-ray binaries are known to exhibit different spectral states which are often associated with different black hole accretion modes. The exact geometry and properties of these accretion modes is still uncertain. Recent IXPE measurements of linear polarization of X-ray emission in canonical X-ray binary system Cygnus X-1 allow us to test models for the hard spectral state of accretion in a unique way. We show that general relativistic radiative magnetohydrodynamic (GRRMHD) simulations of accreting stellar black hole in a hard X-ray state may be consistent with the new observational information. In the presented framework, where first-principle models have limited number of free parameters, the polarimetric X-ray observations put constraints on the viewing angle of the inner hot accretion flow.
众所周知,X射线双星会表现出不同的光谱状态,而这些光谱状态往往与不同的黑洞吸积模式有关。这些吸积模式的确切几何形状和特性仍不确定。最近在经典 X 射线双星系统天鹅座 X-1 中对 X 射线发射的线性偏振进行的 IXPE 测量,使我们能够以一种独特的方式检验吸积的硬光谱状态模型。我们的研究表明,对处于硬X射线状态的吸积恒星黑洞的广义相对论辐射磁流体动力学(GRRMHD)模拟可能与新的观测信息相一致。在提出的框架中,第一原理模型的自由参数数量有限,而偏振 X 射线观测则对内部热吸积流的视角施加了约束。
{"title":"What is the hard spectral state in X-ray binaries? Insights from GRRMHD accretion flows simulations and polarization of their X-ray emission","authors":"M. Moscibrodzka","doi":"10.1007/s10509-024-04333-3","DOIUrl":"https://doi.org/10.1007/s10509-024-04333-3","url":null,"abstract":"<p>X-ray binaries are known to exhibit different spectral states which are often associated with different black hole accretion modes. The exact geometry and properties of these accretion modes is still uncertain. Recent IXPE measurements of linear polarization of X-ray emission in canonical X-ray binary system Cygnus X-1 allow us to test models for the hard spectral state of accretion in a unique way. We show that general relativistic radiative magnetohydrodynamic (GRRMHD) simulations of accreting stellar black hole in a hard X-ray state may be consistent with the new observational information. In the presented framework, where first-principle models have limited number of free parameters, the polarimetric X-ray observations put constraints on the viewing angle of the inner hot accretion flow.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141574086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-08DOI: 10.1007/s10509-024-04329-z
José D. Gutiérrez, Eva Tresaco, Andrés Riaguas
This work studies the motion around irregular elongated asteroids through two approaches. Firstly, it revisits the dipole-segment model, identifying families of periodic orbits for asymmetric mass distribution. Additionally, a new model incorporating variable density for elongated asteroids is introduced and compared to the dipole-segment model. Several families of periodic orbits have been found through continuation of planar orbits and out-of-plane bifurcation processes, obtaining results in agreement with previous studies about the dynamics around irregular asteroids. This highlights the relevance of simple mathematical models in studying asteroid dynamics and the importance of accounting for density and geometric properties. Although the families of periodic orbits studied in this work are not comprehensively sampled, they constitute an example of the variety of orbits that can be followed by a particle orbiting the asteroid, helping us to better understand the dynamics around these elongated bodies.
{"title":"Orbital analysis in the gravitational potential of elongated asteroids","authors":"José D. Gutiérrez, Eva Tresaco, Andrés Riaguas","doi":"10.1007/s10509-024-04329-z","DOIUrl":"https://doi.org/10.1007/s10509-024-04329-z","url":null,"abstract":"<p>This work studies the motion around irregular elongated asteroids through two approaches. Firstly, it revisits the dipole-segment model, identifying families of periodic orbits for asymmetric mass distribution. Additionally, a new model incorporating variable density for elongated asteroids is introduced and compared to the dipole-segment model. Several families of periodic orbits have been found through continuation of planar orbits and out-of-plane bifurcation processes, obtaining results in agreement with previous studies about the dynamics around irregular asteroids. This highlights the relevance of simple mathematical models in studying asteroid dynamics and the importance of accounting for density and geometric properties. Although the families of periodic orbits studied in this work are not comprehensively sampled, they constitute an example of the variety of orbits that can be followed by a particle orbiting the asteroid, helping us to better understand the dynamics around these elongated bodies.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141574088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1007/s10509-024-04330-6
Y. P. Singh, Badruddin
We utilized the Forbush decreases (magnitude (>1.5%)) detected in cosmic ray neutron monitor data during continuous five solar cycles, viz., 20, 21, 22, 23 and 24 (1965 to 2019) and subjected them to wavelet analysis in order to obtain the possible periodicities in their occurrence. We also studied the periodicities separately during the odd and even solar activity cycles. In addition to solar activity, the solar magnetic polarity and its extension into the interplanetary space makes significant difference in the cosmic ray modulation in the helisphere, we have also applied the wavelet analysis procedure separately during positive (A > 0) and negative (A < 0) polarity states of the heliospheric magnetic fields. Observed periodicities in Forbush decreases have been discussed and compared with earlier detected periodicities in solar and geomagnetic activity indices, e.g., sunspot numbers, sunspot areas, sunspot groups, solar flares, coronal mass ejections, and various geomagnetic activity indices. Significant short-term periodic behaviour detected in the occurrence of Forbush decreases, which in general, corroborates the observed behaviour in solar (in particular, solar eruptive activity) and geomagnetic activity. Understanding the quasi-periodic process in magnetic field emergence from solar active regions and solar eruptive activity, as well as solar-terrestrial coupling and space weather effects, requires comparing the quasi-periodic behaviour between parameters representing solar and geomagnetic activity along with cosmic ray variability.
{"title":"Study of short-term periodicities in the occurrence of Forbush decreases: wavelet analysis","authors":"Y. P. Singh, Badruddin","doi":"10.1007/s10509-024-04330-6","DOIUrl":"https://doi.org/10.1007/s10509-024-04330-6","url":null,"abstract":"<p>We utilized the Forbush decreases (magnitude <span>(>1.5%)</span>) detected in cosmic ray neutron monitor data during continuous five solar cycles, viz., 20, 21, 22, 23 and 24 (1965 to 2019) and subjected them to wavelet analysis in order to obtain the possible periodicities in their occurrence. We also studied the periodicities separately during the odd and even solar activity cycles. In addition to solar activity, the solar magnetic polarity and its extension into the interplanetary space makes significant difference in the cosmic ray modulation in the helisphere, we have also applied the wavelet analysis procedure separately during positive (A > 0) and negative (A < 0) polarity states of the heliospheric magnetic fields. Observed periodicities in Forbush decreases have been discussed and compared with earlier detected periodicities in solar and geomagnetic activity indices, e.g., sunspot numbers, sunspot areas, sunspot groups, solar flares, coronal mass ejections, and various geomagnetic activity indices. Significant short-term periodic behaviour detected in the occurrence of Forbush decreases, which in general, corroborates the observed behaviour in solar (in particular, solar eruptive activity) and geomagnetic activity. Understanding the quasi-periodic process in magnetic field emergence from solar active regions and solar eruptive activity, as well as solar-terrestrial coupling and space weather effects, requires comparing the quasi-periodic behaviour between parameters representing solar and geomagnetic activity along with cosmic ray variability.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1007/s10509-024-04334-2
Stephen L. Adler
We have proposed that galaxy formation is catalyzed by the collision of infalling and outstreaming particles from leaky, horizonless astrophysical black holes, most likely gravastars, and based on this gave a model for the disk galaxy scale length. In this paper we modify our original scale length formula by including an activation probability (P) for a collision to lead to nucleation of star formation. The revised formula extrapolates from early universe JWST data to late time data to within a factor of five, and suggests that galaxy dimensions should systematically get smaller as the observed redshift z increases. We also show that particles recycling through gravastars can lead to a reduction in the temperature of the surrounding gas, through a “heat pump” refrigeration effect. This can trigger galaxy formation through enhanced star formation in the vicinity of the gravastar.
{"title":"Galaxy formation catalyzed by gravastars and the JWST, revisited","authors":"Stephen L. Adler","doi":"10.1007/s10509-024-04334-2","DOIUrl":"https://doi.org/10.1007/s10509-024-04334-2","url":null,"abstract":"<p>We have proposed that galaxy formation is catalyzed by the collision of infalling and outstreaming particles from leaky, horizonless astrophysical black holes, most likely gravastars, and based on this gave a model for the disk galaxy scale length. In this paper we modify our original scale length formula by including an activation probability <span>(P)</span> for a collision to lead to nucleation of star formation. The revised formula extrapolates from early universe JWST data to late time data to within a factor of five, and suggests that galaxy dimensions should systematically get smaller as the observed redshift z increases. We also show that particles recycling through gravastars can lead to a reduction in the temperature of the surrounding gas, through a “heat pump” refrigeration effect. This can trigger galaxy formation through enhanced star formation in the vicinity of the gravastar.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1007/s10509-024-04325-3
O. Ahmed, B. Badruddin, M. Derouich
In this work we have studied about the characteristics and dynamical changes during the recovery time of moderate and strong geomagnetic storms of ((mathrm{Dst}<-50text{ nT})). In our investigation of 57 storms triggered by CMEs/CIRs, we concentrated on the solar wind’s influence on their decay phases. Selected storms were classified into distinct groups based on their recovery characteristics. Employing the superposed epoch analysis and best fit methods, we scrutinized several interplanetary solar wind plasma and field parameters and their various functions. The analysis encompassed various single, dual, and multiple interplanetary plasma and field parameters/functions. We determined the most representative characteristic time for the storm’s recovery profile by carefully fitting an exponential curve. A correlation analysis between Dst and solar wind parameters/functions led us to isolate a coupling function ((rho ^{frac{1}{2}}mathrm{Ey})) which best described the decay rate of the ring current. It shows that electric field term (Ey) coupled with a viscus term ((rho ^{frac{1}{2}})) plays pivotal role in determining the recovery rate of a geomagnetic storms. Additionally, we modeled the complex patterns of Dst recovery in relation to solar wind parameters and functions using a second-order polynomial. Remarkably, during the recovery phase, a dynamic correlation between Dst and solar wind parameters/functions was revealed. The three-parameter solar wind-magnetosphere electrodynamical coupling functions, which combines the viscus term ((rho ^{frac{1}{2}})) and the electric field-related function ((mathrm{v}^{frac{4}{3}}mathrm{B})) ((rho ^{frac{1}{2}}mathrm{v}^{frac{4}{3}}mathrm{B})), significantly impacts the recovery phase of geomagnetic disturbances. Our investigation extended to the relationship between main and recovery phase durations, providing valuable insights into the solar wind’s intricate control over the decay of the geomagnetic disturbances. These findings contribute significantly to advancing our comprehension of the complex relationship between solar wind dynamics and the evolution of geomagnetic disturbances.
{"title":"Dynamics and solar wind control of the recovery of strong geomagnetic storms","authors":"O. Ahmed, B. Badruddin, M. Derouich","doi":"10.1007/s10509-024-04325-3","DOIUrl":"https://doi.org/10.1007/s10509-024-04325-3","url":null,"abstract":"<p>In this work we have studied about the characteristics and dynamical changes during the recovery time of moderate and strong geomagnetic storms of (<span>(mathrm{Dst}<-50text{ nT})</span>). In our investigation of 57 storms triggered by CMEs/CIRs, we concentrated on the solar wind’s influence on their decay phases. Selected storms were classified into distinct groups based on their recovery characteristics. Employing the superposed epoch analysis and best fit methods, we scrutinized several interplanetary solar wind plasma and field parameters and their various functions. The analysis encompassed various single, dual, and multiple interplanetary plasma and field parameters/functions. We determined the most representative characteristic time for the storm’s recovery profile by carefully fitting an exponential curve. A correlation analysis between Dst and solar wind parameters/functions led us to isolate a coupling function (<span>(rho ^{frac{1}{2}}mathrm{Ey})</span>) which best described the decay rate of the ring current. It shows that electric field term (Ey) coupled with a viscus term (<span>(rho ^{frac{1}{2}})</span>) plays pivotal role in determining the recovery rate of a geomagnetic storms. Additionally, we modeled the complex patterns of Dst recovery in relation to solar wind parameters and functions using a second-order polynomial. Remarkably, during the recovery phase, a dynamic correlation between Dst and solar wind parameters/functions was revealed. The three-parameter solar wind-magnetosphere electrodynamical coupling functions, which combines the viscus term (<span>(rho ^{frac{1}{2}})</span>) and the electric field-related function (<span>(mathrm{v}^{frac{4}{3}}mathrm{B})</span>) (<span>(rho ^{frac{1}{2}}mathrm{v}^{frac{4}{3}}mathrm{B})</span>), significantly impacts the recovery phase of geomagnetic disturbances. Our investigation extended to the relationship between main and recovery phase durations, providing valuable insights into the solar wind’s intricate control over the decay of the geomagnetic disturbances. These findings contribute significantly to advancing our comprehension of the complex relationship between solar wind dynamics and the evolution of geomagnetic disturbances.</p>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}