Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model f...Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model for the radio eclipse by calculating the geometry of the bow shock between the winds of the pulsar and companion,where the shock shapes the eclipsing medium but had not been described in detail in previous works.The model is further used to explain the variations of the flux density and dispersion measure of three BW pulsars(i.e.,PSR B1957+20,J2055+3829,and J2051-0827)detected by the Five-hundred-meter Aperture Spherical radio Telescope.Consequently,we constrained the parameters of the three BW systems such as the inclination angles and true anomalies of the observer as well as the mass-loss rates and wind velocity of the companion stars.With the help of these constraints,it is expected that magnetic fields of companion stars and even masses of pulsars could further be determined as some extra observation can be achieved in the future.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
Modern wide-field high-cadence surveys have revealed the significant diversity of optical transient phenomena in their luminosity and timescale distributions,which led to the discovery of some mysterious fast optical ...Modern wide-field high-cadence surveys have revealed the significant diversity of optical transient phenomena in their luminosity and timescale distributions,which led to the discovery of some mysterious fast optical transients(FOTs).These FOTs can usually rise and decline remarkably in a timescale of a few days to weeks,which are obviously much rapider than ordinary supernovae.SN2019 bkc/ATLAS19 dqr is one of the fastest detected FOTs so far and,meanwhile,it was found to be unassociated with a host galaxy.These discoveries provide a good chance to explore the possible origins of FOTs.So,we model the light curves of SN 2019 bkc in details.It is found that SN 2019 bkc can be well explained by the thermal emission of an explosion ejecta that is powered by a long-lasting central engine.The engine could be a spinning-down millisecond magnetar or a fallback accretion onto a compact object.Combining the engine property,the mass of the ejecta,and the hostlessness of SN 2019 bkc,we suggest that this FOT is likely to originate from a merger of a white dwarf and a neutron star.展开更多
基金supported by the National SKA program of China(2020SKA0120300)the National Key R&D Program of China(2021YFA0718500)+2 种基金the National Natural Science Foundation of China(grant Nos.11833003,12033001)the China Postdoctoral Science Foundation(No.2023T160410)the Opening Foundation of Xinjiang Key Laboratory(No.2021D04016)。
文摘Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model for the radio eclipse by calculating the geometry of the bow shock between the winds of the pulsar and companion,where the shock shapes the eclipsing medium but had not been described in detail in previous works.The model is further used to explain the variations of the flux density and dispersion measure of three BW pulsars(i.e.,PSR B1957+20,J2055+3829,and J2051-0827)detected by the Five-hundred-meter Aperture Spherical radio Telescope.Consequently,we constrained the parameters of the three BW systems such as the inclination angles and true anomalies of the observer as well as the mass-loss rates and wind velocity of the companion stars.With the help of these constraints,it is expected that magnetic fields of companion stars and even masses of pulsars could further be determined as some extra observation can be achieved in the future.
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 Ministry of Science and Technology of the People’s Republic of China (2020SKA0120300)the National Natural Science Foundation of China (Grant Nos.11822302 and 11833003)。
文摘Modern wide-field high-cadence surveys have revealed the significant diversity of optical transient phenomena in their luminosity and timescale distributions,which led to the discovery of some mysterious fast optical transients(FOTs).These FOTs can usually rise and decline remarkably in a timescale of a few days to weeks,which are obviously much rapider than ordinary supernovae.SN2019 bkc/ATLAS19 dqr is one of the fastest detected FOTs so far and,meanwhile,it was found to be unassociated with a host galaxy.These discoveries provide a good chance to explore the possible origins of FOTs.So,we model the light curves of SN 2019 bkc in details.It is found that SN 2019 bkc can be well explained by the thermal emission of an explosion ejecta that is powered by a long-lasting central engine.The engine could be a spinning-down millisecond magnetar or a fallback accretion onto a compact object.Combining the engine property,the mass of the ejecta,and the hostlessness of SN 2019 bkc,we suggest that this FOT is likely to originate from a merger of a white dwarf and a neutron star.
