The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade.Benefitting from that,our global understanding of the planet formation processes has been substantiall...The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade.Benefitting from that,our global understanding of the planet formation processes has been substantially improved.In this review,we first summarize the cutting-edge states of the exoplanet and disk observations.We further present a comprehensive panoptic view of modern core accretion planet formation scenarios,including dust growth and radial drift,planetesimal formation by the streaming instability,core growth by planetesimal accretion and pebble accretion.We discuss the key concepts and physical processes in each growth stage and elaborate on the connections between theoretical studies and observational revelations.Finally,we point out the critical questions and future directions of planet formation studies.展开更多
It is well known from the Butcher-Oemler effect that galaxies in dense environment are mostly red with little star formation and the fraction of blue galaxies in galaxy groups/clusters also declines rapidly with redsh...It is well known from the Butcher-Oemler effect that galaxies in dense environment are mostly red with little star formation and the fraction of blue galaxies in galaxy groups/clusters also declines rapidly with redshifts.A recent work by Hashimoto et al.reported a local ‘blue cluster’ with a high fraction of blue galaxies(∼0.57),higher than the model predictions.They ascribed this blue cluster to the feeding of gas along a filamentary structure around the cluster.In this work we use group catalog from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and the state-of-art of semi-analytic model(SAM) to investigate the formation of blue clusters in the local Universe.In total,we find four blue clusters with halo mass ∼10^14 M⊙ at 0.02 <z<0.082,while only the one found by Hashimoto et al.is in a filamentary structure.The SAM predicts that blue clusters have later formation time and most blue satellite galaxies are recently accreted.We conclude that the formation of blue clusters is mainly governed by newly accreted blue satellites,rather than the effect of large-scale environment.展开更多
In this paper,we introduce a new algorithm,fiDrizzle-MU,to coadd multiple exposures with multiplicative updates in each iteration instead of the difference correction terms of the preceding version.We find that multip...In this paper,we introduce a new algorithm,fiDrizzle-MU,to coadd multiple exposures with multiplicative updates in each iteration instead of the difference correction terms of the preceding version.We find that multiplicative update mechanisms demonstrate superior performance in decorrelating adjacent pixels compared to additive approaches,reducing noise complexity in the final stacked images.After applying fiDrizzle-MU to the JWST-NIRCam F277W band data,we obtain a comprehensive reconstruction of a potential gravitational lensing candidate substantially blurred by the JWST pipeline’s resampling process.展开更多
Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the rem...Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars.We study rigidly rotating strangeon stars in the slowly rotating approximation,using the Lennard-Jones model for the equation of state.Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers,enlarging the mass-range of long-lived strangeon stars.During spin-down after merger,the decrease of radius of the remnant will lead to the release of gravitational energy.Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity,we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow.The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.展开更多
The state of supranuclear matter in compact stars remains puzzling,and it is argued that pulsars could be strangeon stars.The consequences of merging double strangeon stars are worth exploring,especially in the new er...The state of supranuclear matter in compact stars remains puzzling,and it is argued that pulsars could be strangeon stars.The consequences of merging double strangeon stars are worth exploring,especially in the new era of multi-messenger astronomy.To develop the"strangeon kilonova"scenario proposed in Paper I,we make a qualitative description about the evolution of ejecta and light curves for merging double strangeon stars.In the hot environment of the merger,the strangeon nuggets ejected by tidal disruption and hydrodynamical squeezing would suffer from evaporation,in which process particles,such as strangeons,neutrons and protons,are emitted.Taking into account both the evaporation of strangeon nuggets and the decay of strangeons,most of the strangeon nuggets would turn into neutrons and protons,within dozens of milliseconds after being ejected.The evaporation rates of different particles depend on temperature,and we find that the ejecta could end up with two components,with high and low opacity respectively.The high opacity component would be in the directions around the equatorial plane,and the low opacity component would be in a broad range of angular directions.The bolometric light curves show that the spin-down power of the long-lived remnant would account for the whole emission of kilonova AT2017gfo associated with GW170817,if the total ejected mass 10^(-3)M⊙.The detailed picture of merging double strangeon stars is expected to be tested by future numerical simulations.展开更多
The equilibrium configuration of a solid strange star in the final inspiral phase with another compact object is generally discussed,and the starquake-related issue is revisited,for a special purpose to understand the...The equilibrium configuration of a solid strange star in the final inspiral phase with another compact object is generally discussed,and the starquake-related issue is revisited,for a special purpose to understand the precursor emission of binary compact star merger events(e.g.,that of GRB211211A).As the binary system inspirals inward due to gravitational wave radiation,the ellipticity of the solid strangeon star increases due to the growing tidal field of its compact companion.Elastic energy is hence accumulated during the inspiral stage which might trigger a starquake before the merger when the energy exceeds a critical value.The energy released during such starquakes is calculated and compared to the precursor observation of GRB211211 A.The result shows that the energy might be insufficient for binary strangeon-star case unless the entire solid strangeon star shatters,and hence favors a black hole-strangeon star scenario for GRB211211A.The timescale of the precursor as well as the frequency of the observed quasi-periodic-oscillation have also been discussed in the starquake model.展开更多
We have developed a novel method for co-adding multiple under-sampled images that combines the iteratively reweighted least squares and divide-and-conquer algorithms.Our approach not only allows for the anti-aliasing ...We have developed a novel method for co-adding multiple under-sampled images that combines the iteratively reweighted least squares and divide-and-conquer algorithms.Our approach not only allows for the anti-aliasing of the images but also enables Point-Spread Function(PSF)deconvolution,resulting in enhanced restoration of extended sources,the highest peak signal-to-noise ratio,and reduced ringing artefacts.To test our method,we conducted numerical simulations that replicated observation runs of the China Space Station Telescope/the VLT Survey Telescope(VST)and compared our results to those obtained using previous algorithms.The simulation showed that our method outperforms previous approaches in several ways,such as restoring the profile of extended sources and minimizing ringing artefacts.Additionally,because our method relies on the inherent advantages of least squares fitting,it is more versatile and does not depend on the local uniformity hypothesis for the PSF.However,the new method consumes much more computation than the other approaches.展开更多
We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curv...We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curves of seven pulsars: four HMXBPs, two MSBPs and the ultraluminous X-ray pulsar M82 X-2. We discuss the physics of their flaring activities or lack thereof, paying special attention to their emission properties when they are found on the propeller line, inside the Corbet gap or near the light-cylinder barrier. We provide guiding principles for future interpretations of faint X-ray observations, as well as a method of constraining the propeller lines and the dipolar surface magnetic fields of pulsars using a variety of quiescent states. In the process, we clarify some disturbing inaccuracies that have made their way into the published literature.展开更多
The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray （ULX） sources have finally enabled us to recognize a subclass within the ULX class： the great pretenders, neutron stars （NSs） that ap...The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray （ULX） sources have finally enabled us to recognize a subclass within the ULX class： the great pretenders, neutron stars （NSs） that appear to emit X-ray radiation at isotropic luminosities Lx = 7 × 10^39 erg s-1 _ 1 ×10^41 erg s-i only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II ＆ IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars： the three NSs reveal modest magnetic fields of about 0.3-0.4TG and beamed propeller-line X-ray luminosities of 1036 - 1037 erg s-1, substantially below the Eddington limit.展开更多
The adoption of Conservation Agriculture(CA)in Europe varies according to the ecological regions of the continent.Although Europe is behind other countries in adoption of CA,the indicators for future progress are enco...The adoption of Conservation Agriculture(CA)in Europe varies according to the ecological regions of the continent.Although Europe is behind other countries in adoption of CA,the indicators for future progress are encouraging.The area where CA is applied is growing rapidly because of increasing environmental awareness,including soil protection,and because of the need to reduce production costs.The European Conservation Agriculture Federation(ECAF)plays an important role in the adoption and dissemination of CA practices,and in discussions involving CA and the EU Common Agricultural Policy(CAP)reform.Yield performance and stability,operating costs,environmental policies and programs of the Common Agricultural Policy(CAP),and climate change will likely be the major driving forces defining the direction and for the extension of CA in Europe.The role of agriculture in climate change mitigation in the EU is discussed in the paper.展开更多
基金supported by the European Research Council(ERC Consolidator Grant 724687-PLANETESYS)the Swedish Walter Gyllenberg Foundation+3 种基金start-up grant of Bairen program from Zhejiang Universitysupported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the National Natural Science Foundation of China(Grant Nos.12033010 and 11773081)CAS Interdisciplinary Innovation Team and Foundation of Minor Planets of the Purple Mountain Observatory。
文摘The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade.Benefitting from that,our global understanding of the planet formation processes has been substantially improved.In this review,we first summarize the cutting-edge states of the exoplanet and disk observations.We further present a comprehensive panoptic view of modern core accretion planet formation scenarios,including dust growth and radial drift,planetesimal formation by the streaming instability,core growth by planetesimal accretion and pebble accretion.We discuss the key concepts and physical processes in each growth stage and elaborate on the connections between theoretical studies and observational revelations.Finally,we point out the critical questions and future directions of planet formation studies.
基金funded by the 973 program(No.2015CB857003)the NSFC(Nos.11825303,11861131006,11333008 and 11703091)。
文摘It is well known from the Butcher-Oemler effect that galaxies in dense environment are mostly red with little star formation and the fraction of blue galaxies in galaxy groups/clusters also declines rapidly with redshifts.A recent work by Hashimoto et al.reported a local ‘blue cluster’ with a high fraction of blue galaxies(∼0.57),higher than the model predictions.They ascribed this blue cluster to the feeding of gas along a filamentary structure around the cluster.In this work we use group catalog from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and the state-of-art of semi-analytic model(SAM) to investigate the formation of blue clusters in the local Universe.In total,we find four blue clusters with halo mass ∼10^14 M⊙ at 0.02 <z<0.082,while only the one found by Hashimoto et al.is in a filamentary structure.The SAM predicts that blue clusters have later formation time and most blue satellite galaxies are recently accreted.We conclude that the formation of blue clusters is mainly governed by newly accreted blue satellites,rather than the effect of large-scale environment.
基金supported by the Foundation for Distinguished Young Scholars of Jiangsu Province(No.BK20140050)the National Key R&D Program of China(No.2022YFF0503403)+7 种基金the National Natural Science Foundation of China(Nos.11973070,11988101,11333008,11273061,11825303,and 11673065)the China Manned Space Project(Nos.CMS-CSST-2021-A01,CMS-CSST-2021-A03,and CMS-CSST-2021-B01)the Joint Funds of the National Natural Science Foundation of China(No.U1931210).H.Y.S.acknowledges the support from the Key Research Program of Frontier Sciences,CAS,grant No.ZDBS-LY-7013Program of Shanghai Academic/Technology Research Leader.R.L.acknowledges the science research grants from the China Manned Space Project,CAS Project for Young Scientists in Basic Research(No.YSBR-062)the support from K.C.Wong Education Foundationsupport from the science research grants from the China Manned Space Project with CMS-CSST-2021-A04 and CMS-CSST-2021-A07supported by the GHfund A(202302017475).
文摘In this paper,we introduce a new algorithm,fiDrizzle-MU,to coadd multiple exposures with multiplicative updates in each iteration instead of the difference correction terms of the preceding version.We find that multiplicative update mechanisms demonstrate superior performance in decorrelating adjacent pixels compared to additive approaches,reducing noise complexity in the final stacked images.After applying fiDrizzle-MU to the JWST-NIRCam F277W band data,we obtain a comprehensive reconstruction of a potential gravitational lensing candidate substantially blurred by the JWST pipeline’s resampling process.
基金supported by the National SKA Program of China(Nos.2020SKA0120300,2020SKA0120100)the Outstanding Young and Middle-aged Science and Technology Innovation Teams from Hubei colleges and universities(No.T2021026)the Young Top-notch Talent Cultivation Program of Hubei Province,and the Key Laboratory Opening Fund(MOE)of China(grant No.QLPL2021P01)。
文摘Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars.We study rigidly rotating strangeon stars in the slowly rotating approximation,using the Lennard-Jones model for the equation of state.Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers,enlarging the mass-range of long-lived strangeon stars.During spin-down after merger,the decrease of radius of the remnant will lead to the release of gravitational energy.Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity,we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow.The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.
基金supported by the National SKA Program of China(Grant No.2020SKA0120300)the National Key R&D Program of China(Grant No.2017YFA0402602)+3 种基金the National Natural Science Foundation of China(Grant Nos.U1831104,11673002,U1531243,11705163,11822302 and 11803007)the Strategic Priority Research Program of CAS(Grant No.XDB23010200)Ningbo Natural Science Foundation(Grant No.2019A610066)provided by China Scholarship Council during a visit by C.-J.X to JAEA is acknowledged。
文摘The state of supranuclear matter in compact stars remains puzzling,and it is argued that pulsars could be strangeon stars.The consequences of merging double strangeon stars are worth exploring,especially in the new era of multi-messenger astronomy.To develop the"strangeon kilonova"scenario proposed in Paper I,we make a qualitative description about the evolution of ejecta and light curves for merging double strangeon stars.In the hot environment of the merger,the strangeon nuggets ejected by tidal disruption and hydrodynamical squeezing would suffer from evaporation,in which process particles,such as strangeons,neutrons and protons,are emitted.Taking into account both the evaporation of strangeon nuggets and the decay of strangeons,most of the strangeon nuggets would turn into neutrons and protons,within dozens of milliseconds after being ejected.The evaporation rates of different particles depend on temperature,and we find that the ejecta could end up with two components,with high and low opacity respectively.The high opacity component would be in the directions around the equatorial plane,and the low opacity component would be in a broad range of angular directions.The bolometric light curves show that the spin-down power of the long-lived remnant would account for the whole emission of kilonova AT2017gfo associated with GW170817,if the total ejected mass 10^(-3)M⊙.The detailed picture of merging double strangeon stars is expected to be tested by future numerical simulations.
基金supported by the National SKA Program of China(2020SKA01201000,2020SKA0120300)supported by the National Natural Science Foundation of China(NSFC)grant No.12203017+7 种基金supported by the NSFC(11975027,11991053)the NSFC(grant No.12273042)supported by NSFC grant No.42174059supported by NSFC grant No.12247180the Max Planck Partner Group Program funded by the Max Planck Societysupported by the National Key R&D Program of China(2021YFA0718500)the support by the Young Top-notch Talent Cultivation Program of Hubei Provincethe support from the Chinese Academy of Sciences(grant No.E329A3M1)。
文摘The equilibrium configuration of a solid strange star in the final inspiral phase with another compact object is generally discussed,and the starquake-related issue is revisited,for a special purpose to understand the precursor emission of binary compact star merger events(e.g.,that of GRB211211A).As the binary system inspirals inward due to gravitational wave radiation,the ellipticity of the solid strangeon star increases due to the growing tidal field of its compact companion.Elastic energy is hence accumulated during the inspiral stage which might trigger a starquake before the merger when the energy exceeds a critical value.The energy released during such starquakes is calculated and compared to the precursor observation of GRB211211 A.The result shows that the energy might be insufficient for binary strangeon-star case unless the entire solid strangeon star shatters,and hence favors a black hole-strangeon star scenario for GRB211211A.The timescale of the precursor as well as the frequency of the observed quasi-periodic-oscillation have also been discussed in the starquake model.
基金supported by the GHfund A(202302017475)supported by the Foundation for Distinguished Young Scholars of Jiangsu Province(No.BK20140050)+5 种基金the National Natural Science Foundation of China(Nos.11973070,11333008,11273061,11825303,and 11673065)the China Manned Space Project with No.CMS-CSST-2021-A01,CMSCSST-2021-A03,CMS-CSST-2021-B01the Joint Funds of the National Natural Science Foundation of China(No.U1931210)the support from Key Research Program of Frontier Sciences,CAS,grant No.ZDBS-LY-7013Program of Shanghai Academic/Technology Research Leaderthe support from the science research grants from the China Manned Space Project with CMS-CSST-2021-A04,CMS-CSST-2021-A07。
文摘We have developed a novel method for co-adding multiple under-sampled images that combines the iteratively reweighted least squares and divide-and-conquer algorithms.Our approach not only allows for the anti-aliasing of the images but also enables Point-Spread Function(PSF)deconvolution,resulting in enhanced restoration of extended sources,the highest peak signal-to-noise ratio,and reduced ringing artefacts.To test our method,we conducted numerical simulations that replicated observation runs of the China Space Station Telescope/the VLT Survey Telescope(VST)and compared our results to those obtained using previous algorithms.The simulation showed that our method outperforms previous approaches in several ways,such as restoring the profile of extended sources and minimizing ringing artefacts.Additionally,because our method relies on the inherent advantages of least squares fitting,it is more versatile and does not depend on the local uniformity hypothesis for the PSF.However,the new method consumes much more computation than the other approaches.
基金supported by NASA grant NNX14-AF77Gsupported by a NASA ADAP grant
文摘We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curves of seven pulsars: four HMXBPs, two MSBPs and the ultraluminous X-ray pulsar M82 X-2. We discuss the physics of their flaring activities or lack thereof, paying special attention to their emission properties when they are found on the propeller line, inside the Corbet gap or near the light-cylinder barrier. We provide guiding principles for future interpretations of faint X-ray observations, as well as a method of constraining the propeller lines and the dipolar surface magnetic fields of pulsars using a variety of quiescent states. In the process, we clarify some disturbing inaccuracies that have made their way into the published literature.
基金DMC,SGTL and RC were supported by NASA grant NNX14-AF77GDK was supported by a NASA ADAP grant
文摘The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray （ULX） sources have finally enabled us to recognize a subclass within the ULX class： the great pretenders, neutron stars （NSs） that appear to emit X-ray radiation at isotropic luminosities Lx = 7 × 10^39 erg s-1 _ 1 ×10^41 erg s-i only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II ＆ IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars： the three NSs reveal modest magnetic fields of about 0.3-0.4TG and beamed propeller-line X-ray luminosities of 1036 - 1037 erg s-1, substantially below the Eddington limit.
文摘The adoption of Conservation Agriculture(CA)in Europe varies according to the ecological regions of the continent.Although Europe is behind other countries in adoption of CA,the indicators for future progress are encouraging.The area where CA is applied is growing rapidly because of increasing environmental awareness,including soil protection,and because of the need to reduce production costs.The European Conservation Agriculture Federation(ECAF)plays an important role in the adoption and dissemination of CA practices,and in discussions involving CA and the EU Common Agricultural Policy(CAP)reform.Yield performance and stability,operating costs,environmental policies and programs of the Common Agricultural Policy(CAP),and climate change will likely be the major driving forces defining the direction and for the extension of CA in Europe.The role of agriculture in climate change mitigation in the EU is discussed in the paper.
