New Astronomy最新文献

The mass–radius relationship of white dwarfs (WDs) is one of their defining characteristics, largely derived from electron degeneracy pressure. We present a model-independent study of the observed mass–radius relationship in WD binaries of Parsons et al. (2017), listing data over a broad temperature range up to about 60,000 K (5 eV). The data show an appreciable temperature sensitivity with pronounced intrinsic scatter (beyond measurement uncertainty) for the canonical He-models with proton$-$to$-$neutron ratio 1:1. We characterize temperature sensitivity by a temperature scale $T_0$ in model-agnostic power-law relations with temperature normalized radius. For low-mass WDs, the results identify a remarkably modest $T_0=1\sim 2$  eV. We comment on a potential interpretation for atmospheres insulating super-Eddington temperature cores from the sub-Eddington photospheres of low-mass WDs.

The decrease rate of dust mass due to strong shock waves ($v_s\ge 150$ km s⁻¹) from supernovae (SNe) estimated for the Milky Way interstellar medium significantly exceeds the overall production rate by both asymptotic giant branch stars and core collapse SNe. The interplay between the production and destruction rates is critically important for evaluation of the net dust outcome from SNe at different conditions. In light of this, we study the dynamics of initially polydisperse dust grains pre-existing in an ambient medium swept up the SN shock front depending on magnitude of inhomogeneity (clumpiness) in the medium. We find that dust destruction inside the bubble is inhibited in more inhomogeneous medium: the larger amount of dust survives for the higher dispersion of density. This trend is set by the interrelation between radiative gas cooling and dust sputtering in different environment. After several radiative times the mass fraction of the survived dust saturates at the level almost independent on the gas mean density. We note that for more clumpy medium the distributions of dust over thermal phases of a gas inside the bubble and over sizes are smoother and flatter in comparison with those in a nearly homogeneous medium.

In this paper, we present an analytical solution for the interacting generalized holographic dark energy model, assuming a linear interaction rate between dark energy and dark matter. We determine the equation of state parameter, the generalized holographic Ricci dark energy density, the matter density, and the deceleration parameter. By analyzing the behavior of these cosmological parameters, we demonstrate that our model aligns with recent observations and reproduces the late-time accelerated expansion of the Universe. To compare our model with the $\Lambda$CDM model, we use various diagnostic tools including statefinder, $Om\left(z\right)$-diagnostic, statefinder hierarchy, growth rate analysis, and ${\omega }_H$-${\omega }_H^{\prime }$ plane. We also analyze the stability of the model by examining the speed of sound. These methods show that the dynamics of the Universe remain very close to that of the standard cosmological model.

Planets and their host stars undergo evolutionary changes over time, resulting in variations in internal temperature and incoming radiation, which significantly impact the temperature structure and composition of their atmospheres. These evolving conditions give rise to distinctive features in planetary spectra that are observable only during specific stages of planetary evolution. We aim to understand how the composition of planets with H₂-dominated atmospheres changes over longer timescales due to their thermal evolution. We also investigate time-dependent features in the transmission spectra. These features could provide insights in both the formation and evolution of these gaseous planets, as well as the timescales of these changes, enabling us to study the potential variability of exoplanets over time. We evolve a $\sim$0.04 M${}_{\mathrm{Jup}}$ and $\sim$0.45 M${}_{\mathrm{Jup}}$ planet around a 1.0 M${}_{\odot }$ and 1.3 M${}_{\odot }$ star respectively for 10${}^{9.5}$ years. In both systems, the planets are considered at semi-major axes of 0.1 AU and 1.0 AU. The star-planet systems are evolved by making use of Modules for Experiments in Stellar Astrophysics (MESA). The temperature–pressure profiles are obtained at selected time-steps using an analytical approximation based on the internal and irradiation temperature of the planet at each time step. We then use VULCAN, a photochemical kinetics code, to see how the composition changes with time in the atmosphere due to the thermal evolution of the planets. By making use of the radiative transfer code petitRADTrans, we also simulate the evolution of the transmission spectra of the planets to find potential time-dependent spectral features. Our findings show a prominent change in the CO${}_2$ feature at $\sim 4.3\mu m$. For the 0.45 M${}_{\mathrm{Jup}}$ case, this feature is visible in the pre-main-sequence phase of the host star, regardless of orbital distance from the host star. In the case of the $\sim$0.04 M${}_{\mathrm{Jup}}$ planet, this CO₂ feature is visible until t $\le$ 10⁶ years, and then it reappears after t $\ge$ 10⁸ years when the planet is 0.1 AU away the host star. The CH₄ features