查看更多>>摘要：The time series of daily data on solar activity proxies,namely the sunspot number(SSN),sunspot area(SSA),solar radio flux(F10.7),modified coronal index(MCI),solar flare index(FI),and cosmic ray intensity(CRI),were analyzed to understand the solar activity modulations and short-term periodicities therein.Rieger-type and other short-term periods include the solar rotational period that covers the maximum activity phase period(maximum phase of solar cycle 24).The wavelet power spectra and Periodogram of SSN,SSA,F10.7,MCI,FI,and CRI exhibited a significant short-term period.The heliospheric effects exist for a particular period(～27 days)and they are related to the solar activity phenomena.The cross-correlation coefficients and time lags between the CRI and solar activity parameters were estimated to be～200,46,281,39,and 47 days for SSN,SSA,F10.7,MCI,and FI respectively during the time series 2012-2015(maximum phase of solar cycle 24).
查看更多>>摘要：The δ-Cancrid meteoroid stream forms four active meteor showers which are observable on the Earth annually during January-February and August-September.The stream's definite parent comet has not been established.We performed a search for near-Earth asteroids(NEAs)associated with this stream.We have followed the backward evolution of the orbital elements of a sample of NEAs and found their orbits at the Earth-crossing positions.Using these orbits,we calculated the theoretical parameters of meteor showers associated with the considered NEAs.We carried out our search for observable active showers that match theoretically predicted ones with published data,and the result turned out that the predicted meteor showers of 13 NEAs were identified with the active showers produced by the δ-Cancrid meteoroid stream.The comet-like orbits of NEAs and established association with active meteor showers indicate their common cometary origin.The NEAs considered are moving within the stream and likely represent the dormant remnants of a parent comet of the δ-Cancrid asteroid-meteoroid complex that disintegrated more than 12 thousand years ago.
查看更多>>摘要：In this paper,we utilize recent observational data from gamma-ray bursts(GRBs)and Pantheon+supernovae Ia(SNe Ia)samples to explore the interacting dark energy(IDE)model in a phenomenological scenario.Results from GRBs alone,SNe Ia and GRBs+SNe Ia indicate that the energy is transferred from dark energy to dark matter and the coincidence problem is alleviated.The value of H0 from GRBs+SNe Ia in the IDE scenario shows agreement with the SH0ES measurement.Considering the age estimate of the quasar APM 08279+5255 at z=3.91,we find that the phenomenological IDE scenario can predict a cosmic age greater than that of the ACDM model,thus the cosmic age problem can be alleviated.
查看更多>>摘要：In recent astronomical discussions,attempts have been made to link the known dwarf nova Z Cam to historical celestial events,particularly the"guest star"phenomenon reported in China in 77 BCE.Despite other suggestions and the problems with regard to the location of the event in 77 BCE,its identification with Z Cam is used in the Variable Star Index of the AAVSO and in several research papers that aim to derive knowledge on the evolution of cataclysmic variables.Through the reconstruction of the super-constellation of the Purple Palace in the Han Dynasty,we found that Z Cam is actually located outside this enclosure,contradicting the records of the 77 BCE guest star being"within the Purple Palace."With newly found text versions of the guest star in 77 BCE,we narrowed down the position given therein.Combining with a new analysis of accompanying divination text leads to the conclusion that this guest star was actually a comet.Finally,through meticulous examination and comparison,we conclude that the guest star of 369 CE appears the most plausible candidate for Z Cam's historical counterpart,aligning with both textual evidence and modern astronomical observations.
查看更多>>摘要：The solar coronal magnetic field is a pivotal element in the study of eruptive phenomena,and understanding its dynamic evolution has long been a focal point in solar physics.Numerical models,driven directly by observation data,serve as indispensable tools in investigating the dynamics of the coronal magnetic field.This paper presents a new approach to electric field inversion,which involves modifying the electric field derived from the DAVE4VM velocity field using ideal Ohm's law.The time series of the modified electric field is used as a boundary condition to drive a magnetohydrodynamics model,which is applied to simulate the magnetic field evolution of active region 12673.The simulation results demonstrate that our method enhances the magnetic energy injection through the bottom boundary,as compared with energy injection calculated directly from the DAVE4VM code,and reproduces the evolution of the photospheric magnetic flux.The coronal magnetic field structure is also in morphological similarity to the coronal loops.This new approach will be applied to the high-accuracy simulation of eruption phenomena and provide more details on the dynamical evolution of the coronal magnetic field.
查看更多>>摘要：A Very High-energy(VHE)flare was observed by Major Atmospheric Gamma Imaging Cherenkov Telescopes on MJD 57788.This VHE flare was characterized by increased VHE flux and short timescales.In this study,we used one-zone synchrotron self-Compton,two-zone,and spine/layer models to explore this VHE flare's origin.The results indicate that this γ-ray flare can be explained by Inverse Compton Scattering radiation from the layer contributed gamma radiation and results in the γ-ray flare in a different way than the two-zone model.The difference between the two models lies in the performance of spectral energy distribution after γ-ray flare as well as a possible difference in the timescales of the flare.
查看更多>>摘要：We studied the latitudinal and solar cycle distribution of extreme(≥X5)solar flares spanning 1976-2018.We found that all such flares were confined within the latitudinal range of[S30,N35].Nonetheless,the majority of these flares during different solar cycles were confined in different latitudinal scopes.Statistical results showed that the southeast quadrant experienced the highest activity of extreme flares.47.5％of the extreme flares occurred within the latitudes ≤15° of the two hemispheres,with 26.2％,31.1％,and 42.6％in the latitudinal bands[5°,10°],＞20° and[11°,20°]of both hemispheres,respectively.Significant N-S asymmetries were observed in the ascending phase of SC 21,the descending phase of SC 23,and both phases of SC 24.Other phases showed asymmetries primarily in latitudinal distribution.The proportion of extreme flares in the ascending phases of SCs 21-24 was 22.2％,33.3％,38.9％,and 50％,respectively.Stronger flares(≥X10)were more likely to occur in the descending phase,with 39％of X5-X9 flares and 20％of(≥X10)flares occurring in the ascending phase.On average,83.6％of extreme flares occurred within a period extending from two years prior to three years following the solar peak,according to our statistical analysis,with specific percentages for each cycle being 88.9％,100％,61.1％,and 75％.
查看更多>>摘要：We have examined most of the astrophysical properties of the two star clusters,FSR-163 and Majaess 215,using the third data release of the Gaia space mission(Gaia DR3).We utilized the pyUPMASK method to allocate the probabilities of stars'membership candidates.Using the clusters'trigonometric parallaxes of the members with probabilities P＞50％,we calculated the distance to the clusters of 3290(±140)and 2833(±140)pc,respectively,which match well with our isochrone fitting results on the color-magnitude diagrams.We determined the age of the clusters,and they are 1.00(±0.15)and 3.55(±0.15)Gyr for FSR-163 and Majaess 215,respectively.We evaluated the following photometric parameters:reddenings,distances,galactic geometrical distances,luminosity-mass functions,and total masses of the two clusters.On studying the dynamic state of the two clusters,we found that Majaess 215 is more relaxed than FSR-163.
查看更多>>摘要：The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula,where comets are formed.From the cometary atmospheres,the atoms and gas-phase molecules arise mainly in three ways:(ⅰ)the outgassing from the nucleus,(ⅱ)the photochemical process,and(ⅲ)the sublimation of icy grains from the nucleus.In this paper,we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3(ZTF)using the Giant Metrewave Radio Telescope(GMRT)band L and the Atacama Large Millimeter/submillimeter Array(ALMA)band 6.We do not detect continuum emissions and an emission line of atomic hydrogen(HI)at rest frequency 1420 MHz from this comet using the GMRT.Based on ALMA observations,we detect the dust continuum emission and rotational emission lines of methanol(CH3OH)from comet C/2022 E3(ZTF).From the dust continuum emission,the dust production(Afρ)activity of comet ZTF is 2280±50 cm.Based on LTE spectral modeling,the column density and excitation temperature of CH3OH toward C/2022 E3(ZTF)are(4.50±0.25)×1014 cm-2 and 70±3K respectively.The integrated emission maps show that CH3OH was emitted from the coma region of the comet.The production rate of CH3OH toward C/2022 E3(ZTF)is(7.32±0.64)× 1026 molecules s-1.The fractional abundance of CH3OH with respect to H2O in the coma of the comet is 1.52％.We also compare our derived abundance of CH3OH with the existence modeled value,and we see the observed and modeled values are quite similar.We claim that CH3OH is formed via the subsequential hydrogenation of formaldehyde(H2CO)on the grain surface of comet C/2022 E3(ZTF).
查看更多>>摘要：An extreme ultraviolet(EUV)close-up view of the Sun offers unprecedented detail of heating events in the solar corona.Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perihelion enabled us to identify clustered EUV bright tadpoles(CEBTs)occurring near the footpoints of coronal loops.Combining SDO/AIA observations,we determine the altitudes of six distinct CEBTs by stereoscopy,ranging from～1300 to 3300 km.We then notice a substantial presence of dark,cooler filamentary structures seemingly beneath the CEBTs,displaying periodic up-and-down motions lasting 3-5 minutes.This periodic behavior suggests an association of the majority of CEBTs with Type I spicules.Out of the ten selected CEBTs with fast downward velocity,six exhibit corrected velocities close to or exceeding 50kms-1.These velocities notably surpass the typical speeds of Type Ⅰ spicules.We explore the generation of such velocities.It indicates that due to the previous limited observations of spicules in the EUV wavelengths,they may reveal novel observational features beyond our current understanding.Gaining insights into these features contributes to a better comprehension of small-scale coronal heating dynamics.
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