Astrophysics and Space Science最新文献

The presence of carbon-chain molecules in the interstellar medium (ISM) has been known since the early 1970s and (>130) such species have been identified to date, making up (sim 43)% of the total of detected ISM molecules. They are prevalent not only in star-forming regions in our Galaxy but also in other galaxies. These molecules provide important information on physical conditions, gas dynamics, and evolutionary stages of star-forming regions. Larger species of polycyclic aromatic hydrocarbons (PAHs) and fullerenes (C₆₀ and C₇₀), which may be related to the formation of the carbon-chain molecules, have been detected in circumstellar envelopes around carbon-rich Asymptotic Giant Branch (AGB) stars and planetary nebulae, while PAHs are also known to be a widespread component of the ISM in most galaxies. Recently, two line survey projects toward Taurus Molecular Cloud-1 with large single-dish telescopes have detected many new carbon-chain species, including molecules containing benzene rings. These new findings raise fresh questions about carbon-bearing species in the Universe. This article reviews various aspects of carbon-chain molecules, including observational studies, chemical simulations, quantum calculations, and laboratory experiments, and discusses open questions and how future facilities may answer them.

Significant association between flux emergence and the complexity of the involved processes in the solar corona could be substantial in estimating magnetic field activities and related driving mechanisms. In this study, we analysed solar magnetic activity in the time period between 1939 and 2022, covering solar cycles 17 to the present cycle 25. Our study was principally based on green coronal intensity, which was calculated using observations collected from a global network of coronal stations. Specifically, we utilized the homogenized Fe XIV 530.3 nm coronal emission line provided by the Astronomical Institute of the Slovak Academy of Sciences, as well as of the International Sunspot number index. The analyses were carried out using the Cross-Correlation and Empirical Mode Decomposition techniques. Firstly, the study found that there are strong and positive correlations between the two indices, with high coefficients specifically during the examined solar cycles. Secondly, the empirical mode decomposition technique reveals unique properties of the intrinsic mode functions (IMFs), highlighting distinctions between the emergence of sunspots and green coronal emissions based on their various modulations. Indeed, these IMFs are most likely closely linked to the magnetic flux rope structure and indirectly connected with the emergence of sunspot events. The observed lag between MCI and the SSN could potentially be linked to the dynamics between coronal response time and the evolutions of active regions. Furthermore, there is a steady decrease observed in the green coronal index from solar cycle 17 to the current cycle 25 that could be attributed to waning behaviour of solar magnetic field strength. This decline can also be regarded as evidence of the Centennial Gleissberg solar activity cycle during the descending phase. Interestingly, the green coronal index exhibits a significant degree of phase synchronization with sunspot numbers, suggesting that the intricate relationship between green coronal intensity and sunspot numbers can be potentially driven by processes such as heating, the formation of active coronal regions, and the emergence of magnetic flux.

The main aim of this paper is to study both the Interstellar Medium (ISM) and the young stellar population in the three star-forming regions, namely IRAS 05137+3919, 05168+3634, and 19110+1045. The study of the ISM includes determination of the hydrogen column density (N(H₂)) and dust temperature (T_d) in the regions using modified blackbody fitting. The main parameters of the identified and classified young stellar objects (YSOs) belonging to the regions were determined by comparing with the radiation-transfer models. We also constructed a color–magnitude diagram to compare the parameters of the YSOs with the results of the radiative-transfer models. The three stellar populations appear to have formed under different scenarios. In the cases of IRAS 05137+3919 and IRAS 05168+3634, the age spread is considerably wider, suggesting that the stellar population likely emerged from independent condensations. In contrast, the third region comprises a pair of ultracompact HII regions (UCHIIs), G45.12+0.13 and G45.07+0.13, with a notably smaller age spread. This hints at the possibility that these clusters originated from a single triggering event.

Polarization studies in blazars are effective tools for analyzing the emission composition and the relativistic jet. In this work, we collected photometric and polarization data from the Steward Observatory Blazar Monitoring Program and performed the following studies. (1) Among the 10 target sources, 8 sources exhibit correlations between the polarization variability ((P)) and (V)-lightcurves ((F_{V})). (2) When we use the multiorder power law function to fit (P) and (F_{V}), we obtain several parameters, including the brightening timescale ((Delta T_{b})) and the dimming timescale ((Delta T_{d})). In the brightening stage, (Delta T_{P|b}) and (Delta T_{F|b}) were correlated, with a correlation coefficient of (r=0.45), and a chance probability of (p=0.30%). In the dimming stage, (Delta T_{P|d}) and (Delta T_{F|d}) exhibited weak correlations. (3) To analyze the origin of the polarization, we study the dependence of polarization on spectral index.

Recently, we have seen a series of space missions to the Moon and asteroids, whether for exploratory or scientific purposes, with possibilities of a lot of profitability in a sustainable way. Given this scenario, the Garatéa-L Mission (from the Brazilian original people language Tupi-Guarani, “Search for Life”) stands out, a genuinely Brazilian mission, whose main objective is to place a 6U brazilian cubeSat in orbit around the Moon, in 2024 or 2025, with the aim of carrying out experiments in astrobiology and studying the Aitken Basin, a basin located at the lunar south pole. In this context, the main goal of the present work is to study the orbits that meet the needs of the mission, obeying the necessary parameters of 300 km of periselene and 3000 km of aposelene. The system is formed by the Moon (the central body) and its gravitational coefficients, (J_{2}), (J_{3}) and (C_{22}), the Earth as the perturbing body and a particle (cubesat). As a result, we obtained a sample of orbits that meets the requirements of the mission, their lifetimes in the region of interest and the evolution of the semi-major axis and eccentricity for each value of the inclination analysed. The results showed that the largest number of orbits with the longest lifetime have inclinations of 60° and 65°, with a semi-major axis of 3460 km and an eccentricity of approximately 0.38, remaining in the mission’s region of interest for an approximate period of 180 days.

The Alfvén resonance is an extensively observed phenomenon in astrophysics, playing a crucial role in understanding energy transfer, macroscopic structure, and evolutionary processes within celestial environments such as the magnetospheres of stars, planets, and other astrophysical objects. In this work, we investigate the spatial and temporal distribution of the Alfvén resonance points during the evolution of Kelvin-Helmholtz instability (KHI) at Earth’s dusk-flank magnetopause in numerical MHD simulation. The results show that, there is no appearance of the Alfvén resonance points (P_{AR}) during the linear phase. In the early nonlinear phase, the Alfvén resonance points (P_{AR}), whose duration time is approximately (Delta {t_{1}} sim 3{t_{A}}), looks like the “eyelid” of the KH vortex. During the nonlinear growth phase, the Alfvén resonance points (P_{AR}), whose duration time is about (Delta {t_{2}} sim 6{t_{A}}), appear at both the “eyelid” and the outer “corner” of the KH vortex. The Alfvén resonance phenomenon disappears with the decay of KH vortex.

In this paper, we consider the scenario of a pure quark star which is completely composed of quarks in the pseudo-Wigner phase. The equation of state (EoS) of deconfined quark stars is studied in the framework of the two-flavor NJL model, and the self-consistent mean field approximation is employed by introducing a parameter (alpha ) combining the original Lagrangian and the Fierz-transformed Lagrangian, (mathcal{L}_{R}= (1-alpha )mathcal{L}+alpha mathcal{L}_{F}), to measure the weights of different interaction channels. We assume deconfinement phase transition happens along with the chiral phase transition. Thus, due to the lack of description of confinement in the NJL model, the vacuum pressure is set to confine quarks at low densities, which is the pressure corresponding to the critical point of chiral phase transition. We find that the bag constant shifts from ((130text{ MeV})^{4}) to ((150 text{ MeV})^{4}) as (alpha ) grows. When (alpha ) is around 0.9, the mass-radius relations of deconfined quark stars can meet the requirement of pulsar observations. In addition, the tidal deformability (Lambda ) is found to range in 253 – 482, which satisfies the astronomical constraint of (Lambda <800) for 1.4-solar-mass neutron stars.

Purpose: The 1:1 spin-orbit resonance phenomenon is widely observed in binary asteroid systems. We aim to investigate the intrinsic dynamic mechanism behind the phenomenon under the coupled influence of the secondary’s rotation and orbital motion. Methods: The planar sphere–ellipsoid model is used to approximate the synchronous binary asteroid. The Lindstedt–Poincaré method is applied on the spin-orbit problem to find its explicit quasi-periodic solution. Results: Numerical simulations demonstrate that analytical solutions truncated at high orders are accurate enough to describe the orbital and rotational motions of the synchronous binary asteroid. With the help of the solution, we are able to identify in a more accurate way the stable region for the synchronous state by using the Lyapunov characteristic exponent. Moreover, the resonances that determine the boundary of the stability region are identified. Conclusion: The stable synchronous state requires a small eccentricity (e) of the mutual orbit but permits a large libration angle (theta ) of the secondary. The anti-correlation of (theta ) and (e) is confirmed. The stable region for a very elongated secondary is small, which helps explain the lack of such secondaries in observations (see Table 1 in Pravec et al. in Icarus 267:267–295, 2016). Findings of this study provide insights into the inherent dynamics that determine the rotational states of a synchronous binary asteroid.

Advancements in space weather forecasting have become crucial for understanding and mitigating the impacts of solar activity on Earth’s ionosphere. This research focuses on the prediction of Total Electron Content (TEC) during M-class solar flare events in 2023. TEC is a vital parameter for satellite communications and navigation, making accurate forecasting imperative. Two prediction models, Long Short-Term Memory (LSTM) neural networks and Surrogate Models based on Ordinary Kriging (OKSM), are employed. LSTM, known for capturing temporal dependencies, is contrasted with OKSM, a geostatistical interpolation technique capturing spatial autocorrelation. The study utilizes TEC measurements from the Hyderabad (HYDE) GPS station for model training and evaluation along with solar and geomagnetic parameters. The performance metrics for both models across various solar flare dates are measured using Root Mean Square Error (RMSE), Normalized RMSE, Correlation Coefficient (CC), and Symmetric Mean Absolute Percentage Error(sMAPE). The research interprets the results, highlighting the strengths and limitations of each model. Notable findings include LSTM’s proficiency in capturing temporal variations and OKSM’s unique spatial perspective. Different solar flare intensities are analyzed separately, demonstrating the model’s adaptability to varying space weather conditions. The average performance metrics during M 4.65 SF events for the OKSM model, in terms of Root Mean Square Error is 5.61, Normalized RMSE is 0.14, Correlation Coefficient is 0.9813, and Symmetric Mean Absolute Percentage Error is 14.90. Similarly, for LSTM, the corresponding averages are 10.03, 0.24, 0.9313, and 28.64. The research contributes valuable insights into the predictive capabilities of LSTM and OKSM for TEC during solar flare events. The outcomes aid in understanding the applicability of machine learning and geostatistical techniques in space weather prediction. As society’s reliance on technology susceptible to space weather effects grows, this research is pivotal for enhancing space weather forecasts and ensuring the robustness of critical technological infrastructure on Earth.

Satellite constellation deployment is a cohesive mission where the trajectories of satellites must be planned concurrently. This paper presents an Integrated Program for Optimal Deployment of a Satellite Constellation (PODSC) consisting of (m) non-identical satellites in any desired arrangement in (n) orbital planes. The PODSC can optimize the scheduling of mission timelines, ensuring effective coordination with the trajectory of each satellite. This involves meticulous planning that considers temporal constraints and regards collision avoidance constraint. Additionally, the PODSC can select the most favorable deployment strategy, considering the trade-offs between time and fuel consumption across all possible deployment methods. The PODSC also utilizes an innovative Perturbed Multi-impulsive Inclined transfer trajectory Amalgamated with a modified Lambert targeting problem (PMIAL). The main idea of designing the mentioned maneuver is to eliminate the defects of the Lambert Targeting Problem (LTP). The LTP cannot account for space perturbations. Moreover, the LTP faces challenges when attempting to align the transfer trajectory tangentially with the final orbit in situations where there exists a substantial disparity in inclination and right ascension between the initial and final orbits. The PMIAL establishes three consecutive steps to fix the mentioned defects. Balancing the trade-off between time and achieving optimal fuel consumption will be possible by applying a hybrid IWO/PSO (The hybrid Invasive Weed Optimization/Particle Swarm Optimization) optimization algorithm in both PMIAL and PODSC. The case study will involve simulating two constellation deployment missions, with a particular focus on considering the Earth’s oblateness as a notable perturbation; however, the proposed algorithms can consider any space perturbations.