银河系中心的Sgr A lobes是一对垂直于银盘、关于银心对称的气泡结构,高度约为15 pc。X射线观测表明,这对气泡具有清晰的边界,很可能是由某种能量爆发现象产生的激波扫过银心附近的气体介质所形成。银心黑洞的活动产生的外流是一个可以...银河系中心的Sgr A lobes是一对垂直于银盘、关于银心对称的气泡结构,高度约为15 pc。X射线观测表明,这对气泡具有清晰的边界,很可能是由某种能量爆发现象产生的激波扫过银心附近的气体介质所形成。银心黑洞的活动产生的外流是一个可以作为该气泡形成原因的机制,因此该气泡的形成历史对理解银河系中心的演化和高能天体物理过程具有重要意义。通过流体力学模拟研究了短时标的活动星系核喷流作为气泡成因的模型。数值模拟研究结果表明,一次持续500 a的喷流可以较好地还原该气泡的形态、密度、温度、X射线辐射等性质。基于目前结果还不能排除其他的气泡成因模型,例如潮汐撕裂事件产生的外流模型。未来通过多波段联合观测,将能对气泡成因施加更严格的约束。展开更多
We use the Fe Kα emission in X-rays from non-equilibrium ionizing plasmas as a probe to explore the dust in supernova remnants(SNRs). We applied our model to Cassiopeia A(Cas A), a well-studied SNR with plenty of obs...We use the Fe Kα emission in X-rays from non-equilibrium ionizing plasmas as a probe to explore the dust in supernova remnants(SNRs). We applied our model to Cassiopeia A(Cas A), a well-studied SNR with plenty of observational data as a test. We use Chandra Advanced CCD Imaging Spectrometer 980 ks data of Cas A, and AtomDB v3.0.9, an atomic database for X-ray plasma spectral modeling, to fit 248 spectra. A two-temperature model is adopted to describe the physical conditions of shocked ejecta and iron-rich plasma. We measure the Fe Kα flux ratio and the centroid difference of the dust and gas contributions. We find strong 6.4 keV line emission components, which indicates that iron-rich dust can survive within Cas A's shocked ejecta. We also find that the Fe Kα complex demonstrates an apparent double-hump structure in some Fe–K rich regions, which may be caused by both dust and multi-ejecta structure in Cas A. The results of Fe Kα structures are consistent with our model for a dust cloud embedded in multi-phase ejecta and suggest the presence of both dust sputtering and drag effects in those regions. It is currently still limited by the low spatial and spectrum resolution for the current X-ray detectors, but should be more useful when the new generation, high-resolution X-ray telescopes come into service.展开更多
Type Ia supernovae(SNe Ia)are among the most extreme phenomena in the Universe and play a crucial role in the studies of stellar evolution,galactic chemical evolution and cosmology.However,the progenitors of SNe Ia ar...Type Ia supernovae(SNe Ia)are among the most extreme phenomena in the Universe and play a crucial role in the studies of stellar evolution,galactic chemical evolution and cosmology.However,the progenitors of SNe Ia are still under debate.It has been suggested that SNe Ia could be produced by helium(He)novae in the singledegenerate channel.Recently,a He nova named[HP99]159 was proposed to be a progenitor candidate for SNe Ia,in which the white dwarf(WD)has a mass of 1.2_(0.4)^(+0.18)M_(⊙),the He star’s mass ranges from 0.8M_(⊙)to 2.0M_(⊙)and the orbital period was suggested to be 2.33 or 1.16 days.In the present work,we evolved a large number of primordial binaries to the formation of WD+He star systems and investigated their future evolution.We provided a representative evolutionary track of[HP99]159 and found that[HP99]159 may originate from a primordial binary with a 6.16M_(⊙)primary and a 4.32M_(⊙)secondary with an initial orbital period of 5110 days.We also found that[HP99]159 might evolve to an SN Ia explosion as suggested by previous studies,or it may also form an accretion-induced collapse event or a wide double WD.Further detailed observations are needed in future studies to provide more information about the precise nature of[HP99]159.展开更多
We present the discovery of TCP J07222683+6220548,a new ultracompact binary system of the AM CVn type.This system was first identified displaying aΔV=7.6 mag outburst on 2025-01-20.9416 UTC by the New Milky Way wide-...We present the discovery of TCP J07222683+6220548,a new ultracompact binary system of the AM CVn type.This system was first identified displaying aΔV=7.6 mag outburst on 2025-01-20.9416 UTC by the New Milky Way wide-field survey for transients and later independently detected by ASAS-SN and ZTF.The outburst peaked at V_(max)=12.45 and lasted for seven days,followed by a series of rebrightenings.No previous outbursts are found in archival data.Positive superhumps with a period of 0.032546±0.000084 day(46.87±0.12 minutes),barely detectable during the main outburst,became clearly visible during the first rebrightening that lasted from day 18 to day 24 after the initial outburst.No convincing change in the superhump period was detected.Dense time-series photometry follow-up by a pair of 0.5 m INASAN robotic telescopes,together with VSNET and AAVSO observers,was essential for identifying TCP J07222683+6220548 as an AM CVn system and triggering confirmation spectroscopy with the 2.5 m CMO SAI telescope.Some outbursting AM CVn systems lacking such detailed follow-up may remain unrecognized among the newly discovered cataclysmic variable candidates.展开更多
We identify a point-symmetric morphology of three pairs of ears/clumps in the core-collapse supernova remnant(CCSNR)Puppis A,supporting the jittering jets explosion mechanism(JJEM).In the JJEM,the three pairs of jets ...We identify a point-symmetric morphology of three pairs of ears/clumps in the core-collapse supernova remnant(CCSNR)Puppis A,supporting the jittering jets explosion mechanism(JJEM).In the JJEM,the three pairs of jets that shaped the three pairs of ears/clumps in Puppis A are part of a large set,about 10–30 pairs of jets,that exploded Puppis A.Some similarities in morphological features between CCSNR Puppis A and three multipolar planetary nebulae considered to have been shaped by jets solidify the claim for shaping by jets.Puppis A has a prominent dipole structure,where one side is bright with a well-defined boundary,while the other is faint and defused.The neutron star(NS)has a natal kick velocity in the opposite direction to the denser part of the dipole structure.We propose a new mechanism in the frame of the JJEM that imparts a natal kick to the NS,the kick-byearly asymmetrical pair(kick-BEAP)mechanism.At the early phase of the explosion process,the NS launches a pair of jets where one jet is much more energetic than the counter jet.The more energetic jet compresses a dense side to the CCSNR,and,by momentum conservation,the NS recoils in the opposite direction.Our study supports the JJEM as the primary explosion mechanism of core-collapse supernovae and enriches this explosion mechanism by introducing the novel kick-BEAP mechanism.展开更多
The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio tele...The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio telescopes.Previous studies searched for axion DM-induced signals from the isolated NS J0806.4-4123 using observations of the Meer KAT UHF band(544–1088 MHz),but excluded the 1051–1088 MHz subband to mitigate potential sideband contamination.To probe this unexplored parameter space,we reprocessed the 1000–1088 MHz subband data using optimized radio frequency interference(RFI)flagging and meticulous sideband calibration.The flux stability of the calibrators and the consistency with Meer KAT’s system equivalent flux density confirmed the reliability of the data within the 1000–1080 MHz range,while the 1080–1088 MHz subband was omitted due to flux anomalies.No significant signals exceeding 5σsignificance were detected within the axion mass range of 4.136–4.467μe V(1000–1080 MHz),including the previously unprobed range 4.347–4.467μe V(1051–1080 MHz).Our null detection sets new stringent constraints with Meer KAT NS data,excluding axion-photon couplings|g_(aγγ)|?8.2×10^(-12)Ge V^(-1)at the 95%confidence level for DM masses between 4.347 and 4.467μe V.展开更多
A kilonova is an optical-infrared transient powered by the radioactive decay of heavy nuclei from a binary neutron star merger.Its observational characteristics depend on the mass and the nuclide composition of merger...A kilonova is an optical-infrared transient powered by the radioactive decay of heavy nuclei from a binary neutron star merger.Its observational characteristics depend on the mass and the nuclide composition of merger ejecta,which are sensitive to the equation of state(EoS)of the neutron star.We use astrophysical conditions derived from different EoSs as nucleosynthesis inputs to explore the impact of various EoS on the r-process nucleosynthesis and the kilonova emission.Our results show that both the abundance patterns of merger ejecta and kilonova light curves are strongly dependent on the neutron star EoSs.Given the mass of two neutron stars,the merger with a softer EoS tends to generate a larger amount of ejected material,and may lead to a brighter kilonova peak luminosity.The relationship between the neutron star EoS and the peak luminosity provides a probe for constraining the properties of EoS in multi-messenger observations of neutron star mergers.展开更多
Binary millisecond pulsars with a massive white dwarf(WD)companion are intermediate-mass binary pulsars(IMBPs).They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with a...Binary millisecond pulsars with a massive white dwarf(WD)companion are intermediate-mass binary pulsars(IMBPs).They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with an orbital period of less than 1 day.They are fairly rare in the known pulsar population;only five such IMBPs have been discovered before,and one of them is in a globular cluster.Here we report six IMBPs in compact orbits:PSRs J0416+5201,J0520+3722,J1919+1341,J1943+2210,J1947+2304 and J2023+2853,discovered during the Galactic Plane Pulsar Snapshot survey by using the Five-hundred-meter Aperture Spherical radio Telescope,doubling the number of such IMBPs due to the high survey sensitivity in the short survey time of 5 minutes.Follow-up timing observations show that they all have either a CO WD or an ONeMg WD companion with a mass greater than about 0.8M_(⊙)in a very circular orbit with an eccentricity in the order of10^(−5).PSR J0416+5201 should be an ONeMg WD companion with a remarkable minimum mass of 1.28M_(⊙).These massive WD companions lead to a detectable Shapiro delay for PSRs J0416+5201,J0520+3722,J1943+2210,and J2023+2853,indicating that their orbits are highly inclined.From the measurement of the Shapiro delay,the pulsar mass of J1943+2210 was constrained to be 1.84^(+0.11)_(-0.09)M_(⊙),and that of PSR J2023+2853 to be 1.28^(+0.06)_(-0.05)M_(⊙).展开更多
Mergers of binary neutron stars (BNSs) produce kilonovae,powered by decay of r-process heavy nuclei in their ejecta.Searching and finding kilonovae,associated with gravitational wave (GW) detected BNS mergers,is cruci...Mergers of binary neutron stars (BNSs) produce kilonovae,powered by decay of r-process heavy nuclei in their ejecta.Searching and finding kilonovae,associated with gravitational wave (GW) detected BNS mergers,is crucial for multimessenger studies of BNS mergers and their astrophysical and cosmological applications.In this paper,we investigate the detectability of kilonovae by several electromagnetic surveys,including SiTian,the Chinese Space Station Telescope (CSST),the Rubin Observatory,Euclid and the Nancy Grace Roman Space Telescope (RST).We consider BNS mergers detected by both the network of the Laser Interferometer Gravitational-Wave Observatory(LIGO),Virgo and KAGRA (LVK),and of the Einstein Telescope and Cosmic Explorer (ET&2CE).We adopt a binary population synthesis model to obtain a mock sample of BNS mergers with known properties,and a phenomenological kilonova model to predict multiband light curve of the kilonova associated with each BNS merger.We predict the detection rate or efficiency of kilonovae by Rubin and SiTian,CSST,Euclid and RST,associated with BNS mergers either detected by LVK operation 5 (O5) or ET&2CE,under either the wide fast deep survey or time of opportunity strategy.We also predict the parameter (total mass,mass ratio,localization area) distributions of BNS systems jointly detected by GW and EM observations.We emphasize that kilonovae associated with massive BNS mergers like GW190425 (with total mass■3.3M⊙) can be detected in a significant fraction■20%–30%for ET&2CE or■30%–40%for LVK O5 by Si Tian with a shallow observational depth or other survey telescopes,providing crucial information for kilonova physics and the equation of state of neutron stars.展开更多
Most massive stars reside in binary or multi-object systems.Short gamma-ray bursts(sGRBs),the product of the merger of double compact objects,may originate from massive common-envelope binaries.In contrast,the progeni...Most massive stars reside in binary or multi-object systems.Short gamma-ray bursts(sGRBs),the product of the merger of double compact objects,may originate from massive common-envelope binaries.In contrast,the progenitors of long GRBs(lGRBs)are typically considered isolated massive stars.However,no effective method has yet been established to identify potential companions from current observations.Recent studies have demonstrated that quasi-periodic oscillation signatures can serve as a promising tool to probe the properties of GRB central engines.In this study,by drawing an analogy to periodicity in X-ray binaries,we explore the precession periods of companion-induced disk precession for lGRBs born in the ultra-compact binary scenario.Our results suggest that the periodicity observed in lGRB afterglows,measured in units of 1000 s or more,may indicate that lGRBs originate within binary systems.GRB 050904 could represent a rare case where the burst occurred in a binary system,leaving behind a black hole–black hole binary at redshift z=6.29.展开更多
Superluminous supernovae(SLSNe)and luminous supernovae(LSNe)exhibit extreme luminosities,which require additional energy supply mechanisms such as central engines or circumstellar interaction.In the centralengine scen...Superluminous supernovae(SLSNe)and luminous supernovae(LSNe)exhibit extreme luminosities,which require additional energy supply mechanisms such as central engines or circumstellar interaction.In the centralengine scenario,jets inject energy into the polar ejecta,modifying its evolution and shaping the explosion geometry.This study investigates the polarization signatures of jet-driven bipolar explosions in SLSNe/LSNe,where the asymmetric ejecta structure and differential photospheric evolution imprint distinct observational features.We develop a two-component ejecta model,consisting of fast-expanding polar ejecta(powered by jets)and slower equatorial ejecta.We find that polarization exhibits complex temporal evolution,where the ejecta geometry and flux asymmetry between the two regions jointly produce a double-peaked feature.In addition,the line opacity in the polar region further enhances the wavelength dependence of the polarization.Spectropolarimetric observations,particularly during early phases,can constrain the geometry and energy sources of SLSNe/LSNe,advancing our understanding of their explosion mechanisms.展开更多
We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to...We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to the 10th harmonic of the bright pulsar M15A(~11.06647 ms)that it was missed in a previous pulsar search.We suggest adding the spectrum in the pulsar candidate diagnostic plot to identify new signals near the harmonics.M15O has the first spin frequency derivative and the second spin frequency derivative,being 1.79191(5)×10^(-14)Hz s^(-1)and 3.3133(6)×10^(-23)Hz s^(-2),respectively.Its projected distance from the optical center of M15 is the closest among all the pulsars in M15.The origin can be something from the center of the massive and core-collapsed globular cluster M15.展开更多
White dwarfs(WDs)are the final stage for most low and intermediate mass stars,which play an important role in understanding stellar evolution and galactic history.Here we performed an asteroseismological analysis on T...White dwarfs(WDs)are the final stage for most low and intermediate mass stars,which play an important role in understanding stellar evolution and galactic history.Here we performed an asteroseismological analysis on TIC 231277791 based on 10 independent modes reported by Romero et al.Two groups of modes were identified with frequency splitting:mode identification_1 with one l=1,m=0 mode,two l=2,m=0 modes,and three l=1 or 2,m=0 modes,and mode identification_2 with one l=1,m=0 mode,three l=2,m=0 modes,and one l=1 or 2,m=0 mode.The rotation period is derived to be 41.64±2.73 hr for TIC 231277791.We established a large sample(7,558,272)of DAV star models using the White Dwarf Evolution Code(WDEC;2018,v16),resulting of optimal models with model_1(mode identification_1):M_(*)=0.570±0.005 M⊙,Teff=11300±10 K,-log(MH/M_(*))=9.15±0.01,-log(M_(He)/M_(*))=4.94±0.01,andσrms=0.06 s,and model_2(mode identification_2):M_(*)=0.720±0.005 M⊙,Teff=1910±10 K,-log(M_(H)/M_(*))=6.11±0.01,-log(M_(He)/M_(*))=3.09±0.01,andσrms=0.04 s.The central oxygen abundances are 0.71(optimal model_1)and 0.72(optimal model_2),respectively,which are consistent with the results of stellar structure and evolution theory.展开更多
文摘银河系中心的Sgr A lobes是一对垂直于银盘、关于银心对称的气泡结构,高度约为15 pc。X射线观测表明,这对气泡具有清晰的边界,很可能是由某种能量爆发现象产生的激波扫过银心附近的气体介质所形成。银心黑洞的活动产生的外流是一个可以作为该气泡形成原因的机制,因此该气泡的形成历史对理解银河系中心的演化和高能天体物理过程具有重要意义。通过流体力学模拟研究了短时标的活动星系核喷流作为气泡成因的模型。数值模拟研究结果表明,一次持续500 a的喷流可以较好地还原该气泡的形态、密度、温度、X射线辐射等性质。基于目前结果还不能排除其他的气泡成因模型,例如潮汐撕裂事件产生的外流模型。未来通过多波段联合观测,将能对气泡成因施加更严格的约束。
基金supported by a GRF grant of the Hong Kong Government under HKU 17304524.
文摘We use the Fe Kα emission in X-rays from non-equilibrium ionizing plasmas as a probe to explore the dust in supernova remnants(SNRs). We applied our model to Cassiopeia A(Cas A), a well-studied SNR with plenty of observational data as a test. We use Chandra Advanced CCD Imaging Spectrometer 980 ks data of Cas A, and AtomDB v3.0.9, an atomic database for X-ray plasma spectral modeling, to fit 248 spectra. A two-temperature model is adopted to describe the physical conditions of shocked ejecta and iron-rich plasma. We measure the Fe Kα flux ratio and the centroid difference of the dust and gas contributions. We find strong 6.4 keV line emission components, which indicates that iron-rich dust can survive within Cas A's shocked ejecta. We also find that the Fe Kα complex demonstrates an apparent double-hump structure in some Fe–K rich regions, which may be caused by both dust and multi-ejecta structure in Cas A. The results of Fe Kα structures are consistent with our model for a dust cloud embedded in multi-phase ejecta and suggest the presence of both dust sputtering and drag effects in those regions. It is currently still limited by the low spatial and spectrum resolution for the current X-ray detectors, but should be more useful when the new generation, high-resolution X-ray telescopes come into service.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12288102,12225304,and 12090040/12090043)the National Key R&D Program of China(No.2021YFA1600404)+3 种基金the Western Light Project of CAS(No.XBZG-ZDSYS-202117)the Yunnan Revitalization Talent Support Program(Yunling Scholar Project)the Yunnan Fundamental Research Project(No.202201BC070003)the International Centre of Supernovae,Yunnan Key Laboratory(No.202302AN360001).
文摘Type Ia supernovae(SNe Ia)are among the most extreme phenomena in the Universe and play a crucial role in the studies of stellar evolution,galactic chemical evolution and cosmology.However,the progenitors of SNe Ia are still under debate.It has been suggested that SNe Ia could be produced by helium(He)novae in the singledegenerate channel.Recently,a He nova named[HP99]159 was proposed to be a progenitor candidate for SNe Ia,in which the white dwarf(WD)has a mass of 1.2_(0.4)^(+0.18)M_(⊙),the He star’s mass ranges from 0.8M_(⊙)to 2.0M_(⊙)and the orbital period was suggested to be 2.33 or 1.16 days.In the present work,we evolved a large number of primordial binaries to the formation of WD+He star systems and investigated their future evolution.We provided a representative evolutionary track of[HP99]159 and found that[HP99]159 may originate from a primordial binary with a 6.16M_(⊙)primary and a 4.32M_(⊙)secondary with an initial orbital period of 5110 days.We also found that[HP99]159 might evolve to an SN Ia explosion as suggested by previous studies,or it may also form an accretion-induced collapse event or a wide double WD.Further detailed observations are needed in future studies to provide more information about the precise nature of[HP99]159.
基金support of the Foundation for the Development of Theoretical Physics and Mathematics BASIS(project 24-2-1-6-1)supported by the UKRI Science and Technology Facilities Council and is a collaboration between the University of Edinburgh(grant ST/N002512/1)and Queen’s University Belfast(grant ST/N002520/1)within the LSST:UK Science Consortium+4 种基金supported by the National Science Foundation under grants No.AST-1440341 and AST-2034437primarily funded to search for near earth asteroids through NASA grants NN12AR55G,80NSSC18K0284,and80NSSC18K1575partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889STFC grants ST/T000198/1 and ST/S006109/1made use of the Astrophysics Data System,funded by NASA under Cooperative Agreement 80NSSC21M00561。
文摘We present the discovery of TCP J07222683+6220548,a new ultracompact binary system of the AM CVn type.This system was first identified displaying aΔV=7.6 mag outburst on 2025-01-20.9416 UTC by the New Milky Way wide-field survey for transients and later independently detected by ASAS-SN and ZTF.The outburst peaked at V_(max)=12.45 and lasted for seven days,followed by a series of rebrightenings.No previous outbursts are found in archival data.Positive superhumps with a period of 0.032546±0.000084 day(46.87±0.12 minutes),barely detectable during the main outburst,became clearly visible during the first rebrightening that lasted from day 18 to day 24 after the initial outburst.No convincing change in the superhump period was detected.Dense time-series photometry follow-up by a pair of 0.5 m INASAN robotic telescopes,together with VSNET and AAVSO observers,was essential for identifying TCP J07222683+6220548 as an AM CVn system and triggering confirmation spectroscopy with the 2.5 m CMO SAI telescope.Some outbursting AM CVn systems lacking such detailed follow-up may remain unrecognized among the newly discovered cataclysmic variable candidates.
基金A grant from the Pazy Foundation supported this research。
文摘We identify a point-symmetric morphology of three pairs of ears/clumps in the core-collapse supernova remnant(CCSNR)Puppis A,supporting the jittering jets explosion mechanism(JJEM).In the JJEM,the three pairs of jets that shaped the three pairs of ears/clumps in Puppis A are part of a large set,about 10–30 pairs of jets,that exploded Puppis A.Some similarities in morphological features between CCSNR Puppis A and three multipolar planetary nebulae considered to have been shaped by jets solidify the claim for shaping by jets.Puppis A has a prominent dipole structure,where one side is bright with a well-defined boundary,while the other is faint and defused.The neutron star(NS)has a natal kick velocity in the opposite direction to the denser part of the dipole structure.We propose a new mechanism in the frame of the JJEM that imparts a natal kick to the NS,the kick-byearly asymmetrical pair(kick-BEAP)mechanism.At the early phase of the explosion process,the NS launches a pair of jets where one jet is much more energetic than the counter jet.The more energetic jet compresses a dense side to the CCSNR,and,by momentum conservation,the NS recoils in the opposite direction.Our study supports the JJEM as the primary explosion mechanism of core-collapse supernovae and enriches this explosion mechanism by introducing the novel kick-BEAP mechanism.
基金supported by the National Natural Science Foundation of China(NSFC,grant No.12220101003)the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(grant No.2023R01008)the National Key R&D Program of China No.2023YFE0110500。
文摘The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio telescopes.Previous studies searched for axion DM-induced signals from the isolated NS J0806.4-4123 using observations of the Meer KAT UHF band(544–1088 MHz),but excluded the 1051–1088 MHz subband to mitigate potential sideband contamination.To probe this unexplored parameter space,we reprocessed the 1000–1088 MHz subband data using optimized radio frequency interference(RFI)flagging and meticulous sideband calibration.The flux stability of the calibrators and the consistency with Meer KAT’s system equivalent flux density confirmed the reliability of the data within the 1000–1080 MHz range,while the 1080–1088 MHz subband was omitted due to flux anomalies.No significant signals exceeding 5σsignificance were detected within the axion mass range of 4.136–4.467μe V(1000–1080 MHz),including the previously unprobed range 4.347–4.467μe V(1051–1080 MHz).Our null detection sets new stringent constraints with Meer KAT NS data,excluding axion-photon couplings|g_(aγγ)|?8.2×10^(-12)Ge V^(-1)at the 95%confidence level for DM masses between 4.347 and 4.467μe V.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12403043,12347172,and 12133003)M.H.C.also acknowledges support from the China Postdoctoral Science Foundation(grant Nos.GZB20230029 and 2024M750057)supported by the Guangxi Talent Program(Highland of Innovation Talents).
文摘A kilonova is an optical-infrared transient powered by the radioactive decay of heavy nuclei from a binary neutron star merger.Its observational characteristics depend on the mass and the nuclide composition of merger ejecta,which are sensitive to the equation of state(EoS)of the neutron star.We use astrophysical conditions derived from different EoSs as nucleosynthesis inputs to explore the impact of various EoS on the r-process nucleosynthesis and the kilonova emission.Our results show that both the abundance patterns of merger ejecta and kilonova light curves are strongly dependent on the neutron star EoSs.Given the mass of two neutron stars,the merger with a softer EoS tends to generate a larger amount of ejected material,and may lead to a brighter kilonova peak luminosity.The relationship between the neutron star EoS and the peak luminosity provides a probe for constraining the properties of EoS in multi-messenger observations of neutron star mergers.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101,12133004 and 11833009)the Research Program of the Chinese Academy of Sciences(grant No.QYZDJ-SSW-SLH021 and JZHKYPT-2021-06).
文摘Binary millisecond pulsars with a massive white dwarf(WD)companion are intermediate-mass binary pulsars(IMBPs).They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with an orbital period of less than 1 day.They are fairly rare in the known pulsar population;only five such IMBPs have been discovered before,and one of them is in a globular cluster.Here we report six IMBPs in compact orbits:PSRs J0416+5201,J0520+3722,J1919+1341,J1943+2210,J1947+2304 and J2023+2853,discovered during the Galactic Plane Pulsar Snapshot survey by using the Five-hundred-meter Aperture Spherical radio Telescope,doubling the number of such IMBPs due to the high survey sensitivity in the short survey time of 5 minutes.Follow-up timing observations show that they all have either a CO WD or an ONeMg WD companion with a mass greater than about 0.8M_(⊙)in a very circular orbit with an eccentricity in the order of10^(−5).PSR J0416+5201 should be an ONeMg WD companion with a remarkable minimum mass of 1.28M_(⊙).These massive WD companions lead to a detectable Shapiro delay for PSRs J0416+5201,J0520+3722,J1943+2210,and J2023+2853,indicating that their orbits are highly inclined.From the measurement of the Shapiro delay,the pulsar mass of J1943+2210 was constrained to be 1.84^(+0.11)_(-0.09)M_(⊙),and that of PSR J2023+2853 to be 1.28^(+0.06)_(-0.05)M_(⊙).
基金supported by the Strategic Priority Program of the Chinese Academy of Sciences(grant No.XDB0550300)the National Natural Science Foundation of China(NSFC,Grant Nos.12273050 and 11991052).
文摘Mergers of binary neutron stars (BNSs) produce kilonovae,powered by decay of r-process heavy nuclei in their ejecta.Searching and finding kilonovae,associated with gravitational wave (GW) detected BNS mergers,is crucial for multimessenger studies of BNS mergers and their astrophysical and cosmological applications.In this paper,we investigate the detectability of kilonovae by several electromagnetic surveys,including SiTian,the Chinese Space Station Telescope (CSST),the Rubin Observatory,Euclid and the Nancy Grace Roman Space Telescope (RST).We consider BNS mergers detected by both the network of the Laser Interferometer Gravitational-Wave Observatory(LIGO),Virgo and KAGRA (LVK),and of the Einstein Telescope and Cosmic Explorer (ET&2CE).We adopt a binary population synthesis model to obtain a mock sample of BNS mergers with known properties,and a phenomenological kilonova model to predict multiband light curve of the kilonova associated with each BNS merger.We predict the detection rate or efficiency of kilonovae by Rubin and SiTian,CSST,Euclid and RST,associated with BNS mergers either detected by LVK operation 5 (O5) or ET&2CE,under either the wide fast deep survey or time of opportunity strategy.We also predict the parameter (total mass,mass ratio,localization area) distributions of BNS systems jointly detected by GW and EM observations.We emphasize that kilonovae associated with massive BNS mergers like GW190425 (with total mass■3.3M⊙) can be detected in a significant fraction■20%–30%for ET&2CE or■30%–40%for LVK O5 by Si Tian with a shallow observational depth or other survey telescopes,providing crucial information for kilonova physics and the equation of state of neutron stars.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDB0550400)the National Key Research and Development Program of China(Nos.2024YFA1611704 and 2021YFA0718500)the National Natural Science Foundation of China(NSFC,Nos.12473049,12041301,12121003,and 12225305).
文摘Most massive stars reside in binary or multi-object systems.Short gamma-ray bursts(sGRBs),the product of the merger of double compact objects,may originate from massive common-envelope binaries.In contrast,the progenitors of long GRBs(lGRBs)are typically considered isolated massive stars.However,no effective method has yet been established to identify potential companions from current observations.Recent studies have demonstrated that quasi-periodic oscillation signatures can serve as a promising tool to probe the properties of GRB central engines.In this study,by drawing an analogy to periodicity in X-ray binaries,we explore the precession periods of companion-induced disk precession for lGRBs born in the ultra-compact binary scenario.Our results suggest that the periodicity observed in lGRB afterglows,measured in units of 1000 s or more,may indicate that lGRBs originate within binary systems.GRB 050904 could represent a rare case where the burst occurred in a binary system,leaving behind a black hole–black hole binary at redshift z=6.29.
基金supported by the National Natural Science Foundation of China(Projects 12373040 and 12021003)the National SKA Program of China(2022SKA0130100)the Fundamental Research Funds for the Central Universities.
文摘Superluminous supernovae(SLSNe)and luminous supernovae(LSNe)exhibit extreme luminosities,which require additional energy supply mechanisms such as central engines or circumstellar interaction.In the centralengine scenario,jets inject energy into the polar ejecta,modifying its evolution and shaping the explosion geometry.This study investigates the polarization signatures of jet-driven bipolar explosions in SLSNe/LSNe,where the asymmetric ejecta structure and differential photospheric evolution imprint distinct observational features.We develop a two-component ejecta model,consisting of fast-expanding polar ejecta(powered by jets)and slower equatorial ejecta.We find that polarization exhibits complex temporal evolution,where the ejecta geometry and flux asymmetry between the two regions jointly produce a double-peaked feature.In addition,the line opacity in the polar region further enhances the wavelength dependence of the polarization.Spectropolarimetric observations,particularly during early phases,can constrain the geometry and energy sources of SLSNe/LSNe,advancing our understanding of their explosion mechanisms.
基金supported by the National Key R&D Program of China No.2022YFC2205202,No.2020SKA0120100the National Natural Science Foundation of China(NSFC,grant Nos.12373032,12003047,11773041,U2031119,12173052,and 12173053)+2 种基金supported by the Youth Innovation Promotion Association of CAS(id.2018075,Y2022027 and 2023064)the CAS“Light of West China”Programsupported by the Science and Technology Program of Guizhou Province under project No.QKHPTRC-ZDSYS[2023]003 and QKHFQ[2023]003。
文摘We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to the 10th harmonic of the bright pulsar M15A(~11.06647 ms)that it was missed in a previous pulsar search.We suggest adding the spectrum in the pulsar candidate diagnostic plot to identify new signals near the harmonics.M15O has the first spin frequency derivative and the second spin frequency derivative,being 1.79191(5)×10^(-14)Hz s^(-1)and 3.3133(6)×10^(-23)Hz s^(-2),respectively.Its projected distance from the optical center of M15 is the closest among all the pulsars in M15.The origin can be something from the center of the massive and core-collapsed globular cluster M15.
基金supported by the International Centre of Supernovae,Yunnan Key Laboratory(No.202302AN36000101)supported by the Yunnan Province Youth Talent Project(2019-182)。
文摘White dwarfs(WDs)are the final stage for most low and intermediate mass stars,which play an important role in understanding stellar evolution and galactic history.Here we performed an asteroseismological analysis on TIC 231277791 based on 10 independent modes reported by Romero et al.Two groups of modes were identified with frequency splitting:mode identification_1 with one l=1,m=0 mode,two l=2,m=0 modes,and three l=1 or 2,m=0 modes,and mode identification_2 with one l=1,m=0 mode,three l=2,m=0 modes,and one l=1 or 2,m=0 mode.The rotation period is derived to be 41.64±2.73 hr for TIC 231277791.We established a large sample(7,558,272)of DAV star models using the White Dwarf Evolution Code(WDEC;2018,v16),resulting of optimal models with model_1(mode identification_1):M_(*)=0.570±0.005 M⊙,Teff=11300±10 K,-log(MH/M_(*))=9.15±0.01,-log(M_(He)/M_(*))=4.94±0.01,andσrms=0.06 s,and model_2(mode identification_2):M_(*)=0.720±0.005 M⊙,Teff=1910±10 K,-log(M_(H)/M_(*))=6.11±0.01,-log(M_(He)/M_(*))=3.09±0.01,andσrms=0.04 s.The central oxygen abundances are 0.71(optimal model_1)and 0.72(optimal model_2),respectively,which are consistent with the results of stellar structure and evolution theory.
