Accepted Manuscripts

Long period variable stars (LPVs) are very promising distance indicators in the infrared bands. We selected asymptotic giant branch (AGB) stars in the Large and Small Magellanic Cloud (LMC and SMC) from the Gaia Data Release 3 (DR3) LPV catalog, and classified them into oxygen-rich (O-rich) and carbon-rich (C-rich) AGB stars. Using the WISE database, we determined the $W1$- and $W2$-bands Period--Luminosity relations (PLRs) for each pulsation-mode sequence of AGB stars. The dispersion of the PLRs of O-rich AGB stars in sequences $\rm{C^{'}}$ and C is relatively small, around 0.14 mag. The PLRs of LMC and SMC are consistent in each sequence. 
% while due to selection effect, {\bf the PLR zero points} of Milky Way are significantly underestimated.
In the $W2$ band, the PLR of large-amplitude C-rich AGB stars is steeper than that of small-amplitude C-rich AGB stars, due to their more circumstellar dust. By two methods, we find that some PLR sequences of O-rich AGB stars in the LMC are dependent on metallicity. The coefficients of the metallicity effect are $\beta = -0.533 \pm 0.213 $ mag/dex and $\beta= -0.767 \pm 0.158$ mag/dex for sequence C in $W1$ and $W2$ bands, respectively. The significance of the metallicity effect in $W1$ band for the four sequences is $2.2-3.5 \sigma$. Both of these imply that distance measurements using O-rich Mira maybe need to take the metallicity effect into account.

Using an effective adiabatic index $\gamma_{\mathrm{eff}}$ to mimic the feedback of efficient shock acceleration, we simulate the temporal evolution of a young type Ia supernova remnant (SNR) with two different background magnetic field (BMF) topologies: a uniform and a turbulent BMF. The density distribution and magnetic-field characteristics of our benchmark SNR are studied with two-dimensional cylindrical magnetohydrodynamic (MHD) simulations. When $\gamma_{\mathrm{eff}}$ is considered, we find that: (1) the two-shock structure shrinks and the downstream magnetic-field orientation is dominated by the Rayleigh-Taylor instability structures; (2) \del{for the uniform case, }there exists more quasi-radial magnetic fields inside the shocked region.\del{ While for the turbulent case, owing to the turbulence in BMF, the downstream magnetic-field orientation is time-dependent}; and 
(3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in radial direction, with $\gamma_{\mathrm{eff}}=$1.1, they are amplified \add{about 10-26 times more than} those with $\gamma_{\mathrm{eff}}=$5/3. While in angular direction, the total magnetic energy densities could be amplified \add{about 350 times more than} those with $\gamma_{\mathrm{eff}}=$5/3, \add{and there are more grid cells within the intershock region where the magnetic energy density is amplified by a factor greater than 100.(3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in radial direction, with $\gamma_{\mathrm{eff}}=$1.1, they are amplified about 6-9 times those with $\gamma_{\mathrm{eff}}=$5/3. While in angular direction, the total magnetic energy densities could be amplified more than 125 times those with $\gamma_{\mathrm{eff}}=$5/3. More grid cells within the intershock region manifest magnetic energy densities surpassing the background magnetic energy density by a factor $>$ 100.

In October 2022, the magnetar SGR J1935+2154 entered the active outburst state. During the episode, the Insight-HXMT satellite carried out a long observation that lasted for 20 days. More than 300 bursts were detected, and a certain amount of persistent radiation signals were also accumulated. This paper mainly introduces the results of persistent radiation profile folding and period search based on Insight-HXMT data. At the same time, the burst phase distribution characteristics, spectral lag results of burst, the spectral characteristics of zero-lag bursts and the time-resolved spectral evolution characteristics of high-flux bursts are reported. We found that there is no significant delay feature during different energy band for the bursts of SGR J1935+2154. The observed zero-lag burst does not have a unique spectrum. The time-resolved spectrum of individual burst has consistent spectral types and spectral parameters at different time periods of the burst. We also find that the burst number phase distribution and the burst photons phase distribution have the same tendency to concentrate in specific regions of persistent emission profile.

The Van Hoof effect is a phase shift existing between the radial velocity curves of hydrogen and metallic lines within the atmosphere of pulsating stars. In this article, we present a study of this phenomenon through the spectra of the brightest pulsating star RR Lyr of RR Lyrae stars recorded for 22 years. We based ourselves, on the one hand, on 1268 spectra (41 nights of observation) recorded between the years 1994 and 1997 at the Observatory of Haute Provence OHP (France) previously observed by Chadid and Gillet, and on the other hand on 1569 spectra (46 nights of observation) recorded at our Oukaimeden observatory (Morocco) between 2015 and 2016. Through this study, we have detected information on atmospheric dynamics that had not previously been detected. Indeed, the Van Hoof effect which results in a clear correlation between the radial velocities of hydrogen and those of the metallic lines has been observed and analyzed at different Blazhko phases. A correlation between the radial velocities of different metallic lines located in the lower atmosphere has been observed as well. For the first time, we were able to show that the amplitude of the radial velocity curves deduced from the lines of hydrogen and that of FeII (λ4923.921Å) increases towards the minimum of the Blazhko cycle and decreases towards the maximum of the same Blazhko cycle. Furthermore, we found that the Van Hoof effect is also modulated by the Blazhko effect. Thus, towards the minimum of the Blazhko cycle the Van Hoof effect is more visible and at the maximum of the Blazhko cycle, this effect is minimal. We also observed the temporal evolution of the amplitudes of the radial velocities of the lower and upper atmosphere. When observed over a long time, we can interpret it as a function of the Blazhko phases.

Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the moon and becomes polarized. This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the moon. We obtained the linear degree of polarization (DOP) parameters of white light by observation from the eastern and western hemispheres of the moon. The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall. Combining the analysis of lunar soil samples, we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide (FeO) on the moon. This study may serve as a new diagnostic tool for the moon.

With great advance of ground-based extensive air shower array, such as LHAASO and HAWC, many very high energy (VHE) gamma-ray sources have been discovered and are been monitored regardless of the day and the night. Hence, the Sun and Moon would have some compact on the observation of gamma-ray sources, which have not been taken into account in previous analysis. In this paper, the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated. The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period. The absorption of very high energy gamma-ray by sunlight is estimated with detailed method and some usefully conclusions are achieved. The main influence is the block of the Sun and Moon on gamma-ray and their shadow on the cosmic ray background. The influence is investigated considering the detector angular resolution and some strategy on data analysis are proposed to avoid the underestimation of the gamma-ray emission.

The next generation of very long baseline interferometry (VLBI) is stepping into the era of microarcsecond ($\mu$as) astronomy, and pushing astronomy, especially astrometry, to new heights. VLBI with the Square Kilometre Array (SKA), SKA-VLBI, will increase current sensitivity by an order of magnitude, and reach astrometric precision routinely below 10 $\mu$as, even challenging 1 $\mu$as. This advancement allows precise parallax and proper motion measurements of various celestial objects. Such improvements can be used to study objects (including isolated objects, and binary or multiple systems) in different stellar stages (such as star formation, main-sequence stars, asymptotic giant branch stars, pulsars, black holes, white dwarfs, etc.), unveil the structure and evolution of complex systems (such as the Milky Way), benchmark the international celestial reference frame, and reveal cosmic expansion. Furthermore, the theory of general relativity can also be tested with SKA-VLBI using precise measurements of light deflection under the gravitational fields of different solar system objects and the perihelion precession of solar system objects.

A possible quasi-periodic oscillation (QPO) at frequency $7.045\times10^{-5}$ Hz is found in the narrow-line seyfert 1 (NLS1) galaxy Mrk 142 in the data of XMM-Newton collected on 2020 April 11. We obtain that the QPO signal is statistically significant larger than the $5\sigma$ level and highly coherent with quality factor $Q > 5$ at the 0.3-10 keV band by using the method of the Lomb-Scargle Periodogram (LSP), the Weighted Wavelet Z-transform (WWZ) and the REDFIT. We analyse the data in 0.3-0.6 keV, 0.6-1 keV, 1-3 keV and 3-10 keV energy bands, and find obvious QPO signals at 0.3-0.6 keV and 1-3 keV bands. We then analyze the time-average spectra and time variability at the QPO frequency of $7.045\times10^{-5}$ Hz, and use a model to fit them. We find that the QPO signal mainly comes from the X-ray hot corona.

The location of $\gamma$-ray emission of blazars remains a contested topic, inspiring the development of numerous investigative techniques to address this issue.
In this work, we analyzed \textit{Fermi} $\gamma$-ray lightcurves in the GeV and MeV bands, employing the discrete cross-correlation function (DCF) method to discern time lags between the two bands.
For 4C +21.35, Ton 599, B2 1420+32, and PKS 1510-089, we identified a time lag spanning several days, while for PKS 1441+25, the time lag was not statistically found.
The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus (DT) in the first four sources, whereas for PKS 1441+25, they seem to be sourced mainly from the BLR.
Further analysis of the opacity ($\tau_{\gamma \gamma}$) and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption. 
Notably, for PKS 1441+25, the emission region is also posited to lie outside yet proximate to the BLR.
The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution (SED) with contemporaneous observation data.
Our findings suggest that for the five TeV FSRQs, during TeV flaring events, the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources, with the exceptions of 4C +21.35 and PKS 1441+25.
In terms of the overall jet power, particle energy is the dominant contributor, and the observed blazar radiation cannot be solely attributed to the magnetic field, except in the case of 4C +21.35. 
Consequently, magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.

We fit various colour--magnitude diagrams (CMDs) of the high-latitude Galactic globular clusters NGC\,5024 (M53), NGC\,5053, NGC\,5272 (M3), NGC\,5466, and NGC\,7099 (M30) by isochrones from the Dartmouth Stellar Evolution Database and Bag of Stellar Tracks and Isochrones for $\alpha$--enrichment [$\alpha$/Fe]$=+0.4$. For the CMDs, we use data sets from {\it Hubble Space Telescope}, {\it Gaia}, and other sources utilizing, at least, 25 photometric filters for each cluster. We obtain the following characteristics with their statistic uncertainties for NGC\,5024, NGC\,5053, NGC\,5272, NGC\,5466, and NGC\,7099, respectively: metallicities [Fe/H]$=-1.93\pm0.02$, $-2.08\pm0.03$, $-1.60\pm0.02$, $-1.95\pm0.02$, and $-2.07\pm0.04$ dex with their systematic uncertainty 0.1 dex; ages $13.00\pm0.11$, $12.70\pm0.11$, $11.63\pm0.07$, $12.15\pm0.11$, and $12.80\pm0.17$ Gyr with their systematic uncertainty 0.8 Gyr; distances (systematic uncertainty added) $18.22\pm0.06\pm0.60$, $16.99\pm0.06\pm0.56$, $10.08\pm0.04\pm0.33$, $15.59\pm0.03\pm0.51$, and $8.29\pm0.03\pm0.27$ kpc;
reddenings $E(B-V)=0.023\pm0.004$, $0.017\pm0.004$, $0.023\pm0.004$, $0.023\pm0.003$, and $0.045\pm0.002$ mag with their systematic uncertainty 0.01 mag; extinctions $A_\mathrm{V}=0.08\pm0.01$, $0.06\pm0.01$, $0.08\pm0.01$, $0.08\pm0.01$, and $0.16\pm0.01$ mag with their systematic uncertainty 0.03 mag, which suggest the total Galactic extinction $A_\mathrm{V}=0.08$ across the whole Galactic dust to extragalactic objects at the North Galactic pole. The horizontal branch morphology difference of these clusters is explained by their different metallicity, age, mass-loss efficiency, and loss of low-mass members in the evolution of the core-collapse cluster NGC\,7099 and loose clusters NGC\,5053 and NGC\,5466.