Supernova explosion is a peculiar astronomical phenomenon,which has aroused great interest and extensive research by astronomers.At present,however,it is erroneously believed that the supernova explosion is a splendid...Supernova explosion is a peculiar astronomical phenomenon,which has aroused great interest and extensive research by astronomers.At present,however,it is erroneously believed that the supernova explosion is a splendid funeral of a dying star.In fact,new astronomical observations and the author’s theoretical studies have shown that in the process of a star’s never-ending evolution,numerous supernova explosions may occur,and supernova explosion will run through many stages of stellar evolution.Whenever the atmosphere of the star becomes very dense and its surface is covered with a thick layer of material again,a thermonuclear reaction can be ignited again,causing a supernova explosion.Especially,when the star has undergone a number of supernovae explosions and its surface is covered with multiple layers of supernova explosion remnants,the core of the massive star may undergo sudden gravitational collapse,causing a violent supernova;when a star is impacted by a falling celestial body,it also produces violent supernova explosions.展开更多
Based on the recently developed numerical approach to understand the formation and the chemical evolution of the milky-way galaxy in the solar neighborhood we study the influence of the supernova type SN Ia rates on t...Based on the recently developed numerical approach to understand the formation and the chemical evolution of the milky-way galaxy in the solar neighborhood we study the influence of the supernova type SN Ia rates on the galactic chemical evolution. Supernova SN Ia plays an important role in producing the iron inventory of the galaxy. We also study the dependence of the chemical evolution on the star formation rate prevailing during the initial one billion years of the evolution of the galaxy. This era marks the formation of the galactic halo and the thick disk. A comparison of the elemental abundance distributions of the dwarf stars in the solar neighborhood is made among the various models simulated in the present work. In order to explain the majority of the observed elemental evolutionary trends, specifically those related with the galactic evolution of iron and oxygen, it would be essential to incorporate a major component of prompt SN Ia to the galactic evolution. The prompt SN Ia would produce significant fraction of SN Ia within the initial ~100 million years from the time of star formation. The essential requirement of prompt SN Ia would result in a significant enhancement of SN Ia rates during the earliest epoch of the galaxy. The elemental evolutionary trends also favor an enhancement in the star formation rate during the initial one billion years of the galaxy at least by a factor of three compared to the trend prevailing during the latter evolutionary time of the galaxy.展开更多
The astrophysical reaction rate of 12C(α,γ)16O plays a key role in massive star evolution. However, this reaction rate and its uncertainties have not been well determined yet, especially at T9=0.2. The existing re...The astrophysical reaction rate of 12C(α,γ)16O plays a key role in massive star evolution. However, this reaction rate and its uncertainties have not been well determined yet, especially at T9=0.2. The existing results even disagree with each other to a certain extent. In this paper, the El, E2 and total (E1+E2) 12C(α,γ)16O reaction rates are calculated in the temperature range from T9=0.3 to 2 according to all the available cross section data. A new analytic expression of the 12C(α,γ)16O reaction rate is brought forward based on the reaction mechanism. In this expression, each part embodies the underlying physics of the reaction. Unlike previous works, some physical parameters are chosen from experimental results directly, instead of all the parameters obtained from fitting. These parameters in the new expression, with their 3σ fit errors, are obtained from fit to our calculated reaction rate from T9=0.3 to 2. Using the fit results, the analytic expression of 12C(α,γ)16Oreaction rate is extrapolated down to T9=0.05 based on the underlying physics. The 12C(α,γ)16O reaction rate at T9=0.2 is (8.78 ± 1.52) × 10^15 cm3s^-1mol^-1. Some comparisons and discussions about our new 12C(α,γ)16Oreaction rate are presented, and the contributions of the reaction rate correspond to the different part of reaction mechanism are given. The agreements of the reaction rate below T9=2 between our results and previous works indicate that our results are reliable, and they could be included in the astrophysical reaction rate network. Furthermore, we believe our method to investigate the 12C(α,γ)16O reaction rate is reasonable, and this method can also be employed to study the reaction rate of other astrophysical reactions. Finally, a new constraint of the supernovae production factor of some isotopes are illustrated according to our 12C(α,γ)16O reaction rates.展开更多
Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope...Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101.Fitting of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+422-258K.The luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion.In the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation.Combined with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.展开更多
Motivated by the fact that calibrated light curves of Type Ia supernovae (SNe Ia) have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observat...Motivated by the fact that calibrated light curves of Type Ia supernovae (SNe Ia) have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observations and models of these events over the past 15 years. Here, we summarize new observational constraints, address recent progress in modeling Type Ia supernovae by means of three-dimensional hydrodynamic simulations, and discuss several of the still open questions. It will be be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparing them be applied to study the origin of the diversity with observations and we show how such models can of SNe Ia.展开更多
The robotic supernova survey system of Beijing Astronomical Observatory (BAO) is based on the 60-cm telescope of BAO, which includes a CCD camera attached to the prime focus and a software system for facility control ...The robotic supernova survey system of Beijing Astronomical Observatory (BAO) is based on the 60-cm telescope of BAO, which includes a CCD camera attached to the prime focus and a software system for facility control and image reduction.展开更多
Six supernovae (SNe) discovered in 1996 by the Beijing Astronomical Observatory Supernova (SN) Survey (BAOSS) are reported. SN 1996W, the first supernova discovered by the survey, has been monitored photometrically an...Six supernovae (SNe) discovered in 1996 by the Beijing Astronomical Observatory Supernova (SN) Survey (BAOSS) are reported. SN 1996W, the first supernova discovered by the survey, has been monitored photometrically and spectroscopically for a long time. The spectra and photometry showed that it was a typical type Ⅱ-P supernova. SN 1996cb, the sixth SN discovered in 1996 and a peculiar one like SN 1993J, has also been observed intensively for a long time.展开更多
We review our understanding of the nucleosynthesis that occurs in thermonuclear supernovae and their contribution to Galactic Chemical evolution. We discuss the prospects to improve the modeling of the nucleosynthesis...We review our understanding of the nucleosynthesis that occurs in thermonuclear supernovae and their contribution to Galactic Chemical evolution. We discuss the prospects to improve the modeling of the nucleosynthesis within simulations of these events.展开更多
An annotation for the statement about Jing- Xing (Great Star) in the most famous Chinese ancient his- torical book Shi Ji (Historical Records) authored by Sima Qian reads as follows: “There was a red aureole (“Chi-F...An annotation for the statement about Jing- Xing (Great Star) in the most famous Chinese ancient his- torical book Shi Ji (Historical Records) authored by Sima Qian reads as follows: “There was a red aureole (“Chi-Fang-Qi”) which connected with a deep-color aureole (“Qing-Fang-Qi”). Two yellow stars were in the red aureole, one yellow star was in the deep-color aureole”. The author of the annotation was Meng Kang, an officer as well as a scholar of the Wei State in the Three Kingdoms period. The same records are to be found in two other Chinese historical books compiled by the authors of later ages in Tang Dy- nasty ――Jin History and Sui History. The scene illustrated by the record of “Chi-Fang-Qi” is very similar to the pictures of SN1987A taken by the Hubble Space Telescope. Let it be noted that although the ancient authors were often with se- rious wrong understandings of some astronomical phenom- ena such as supernovae, their depictions about natural phe- nomena they witnessed were mostly objective, and it was unlikely that they fictionally made the record of “Chi-Fang-Qi”. We infer that the ancient observers might have ever watched a very bright supernova with an aureole structure in its remnant and then left such a record. Meng Kang perhaps was the first to give the record about “Chi-Fang-Qi”, and he might have lived in the period from about AD 180 to AD250, very near to AD 185, so, here the supernova the ancient people watched was most likely the one in the year of AD 185. This supposition is consistent with the distance parameter of the most possible remnant of SN185 derived by some modern measurements. If the corre- lation between the record of “Chi-Fang-Qi” and the super- nova remnant can be further proven true, it would be an important verification of the modern theory about stellar evolution.展开更多
文摘Supernova explosion is a peculiar astronomical phenomenon,which has aroused great interest and extensive research by astronomers.At present,however,it is erroneously believed that the supernova explosion is a splendid funeral of a dying star.In fact,new astronomical observations and the author’s theoretical studies have shown that in the process of a star’s never-ending evolution,numerous supernova explosions may occur,and supernova explosion will run through many stages of stellar evolution.Whenever the atmosphere of the star becomes very dense and its surface is covered with a thick layer of material again,a thermonuclear reaction can be ignited again,causing a supernova explosion.Especially,when the star has undergone a number of supernovae explosions and its surface is covered with multiple layers of supernova explosion remnants,the core of the massive star may undergo sudden gravitational collapse,causing a violent supernova;when a star is impacted by a falling celestial body,it also produces violent supernova explosions.
文摘Based on the recently developed numerical approach to understand the formation and the chemical evolution of the milky-way galaxy in the solar neighborhood we study the influence of the supernova type SN Ia rates on the galactic chemical evolution. Supernova SN Ia plays an important role in producing the iron inventory of the galaxy. We also study the dependence of the chemical evolution on the star formation rate prevailing during the initial one billion years of the evolution of the galaxy. This era marks the formation of the galactic halo and the thick disk. A comparison of the elemental abundance distributions of the dwarf stars in the solar neighborhood is made among the various models simulated in the present work. In order to explain the majority of the observed elemental evolutionary trends, specifically those related with the galactic evolution of iron and oxygen, it would be essential to incorporate a major component of prompt SN Ia to the galactic evolution. The prompt SN Ia would produce significant fraction of SN Ia within the initial ~100 million years from the time of star formation. The essential requirement of prompt SN Ia would result in a significant enhancement of SN Ia rates during the earliest epoch of the galaxy. The elemental evolutionary trends also favor an enhancement in the star formation rate during the initial one billion years of the galaxy at least by a factor of three compared to the trend prevailing during the latter evolutionary time of the galaxy.
基金Project supported partially by the Innovation Program of Science and Technology of the Chinese Academy of Sciences (Grant Nos KJCX2.SW.N13 and KJCX3.SYW.N2)the National Natural Science Foundation of China (Grant Nos 10775167, 10675156 and 10610285)+2 种基金the Major State Basic Research Development Program (Grant No 2007CB815004)the Hundred Talent Project of the Chinese Academy of Sciences (Grant No 26010701)the Shanghai Development Foundation for Science and Technology (Grant No 06JC14082)
文摘The astrophysical reaction rate of 12C(α,γ)16O plays a key role in massive star evolution. However, this reaction rate and its uncertainties have not been well determined yet, especially at T9=0.2. The existing results even disagree with each other to a certain extent. In this paper, the El, E2 and total (E1+E2) 12C(α,γ)16O reaction rates are calculated in the temperature range from T9=0.3 to 2 according to all the available cross section data. A new analytic expression of the 12C(α,γ)16O reaction rate is brought forward based on the reaction mechanism. In this expression, each part embodies the underlying physics of the reaction. Unlike previous works, some physical parameters are chosen from experimental results directly, instead of all the parameters obtained from fitting. These parameters in the new expression, with their 3σ fit errors, are obtained from fit to our calculated reaction rate from T9=0.3 to 2. Using the fit results, the analytic expression of 12C(α,γ)16Oreaction rate is extrapolated down to T9=0.05 based on the underlying physics. The 12C(α,γ)16O reaction rate at T9=0.2 is (8.78 ± 1.52) × 10^15 cm3s^-1mol^-1. Some comparisons and discussions about our new 12C(α,γ)16Oreaction rate are presented, and the contributions of the reaction rate correspond to the different part of reaction mechanism are given. The agreements of the reaction rate below T9=2 between our results and previous works indicate that our results are reliable, and they could be included in the astrophysical reaction rate network. Furthermore, we believe our method to investigate the 12C(α,γ)16O reaction rate is reasonable, and this method can also be employed to study the reaction rate of other astrophysical reactions. Finally, a new constraint of the supernovae production factor of some isotopes are illustrated according to our 12C(α,γ)16O reaction rates.
基金supported by the National Natural Science Foundation of China(Grant Nos.12288102,12033003,and 11633002)the Ma Huateng Foundation+4 种基金the Scholar Program of Beijing Academy of Science and Technology(Grant No.DZ:BS202002)the Tencent Xplorer Prizesponsored(in part)by the Chinese Academy of Sciences(CAS)through a grant to the CAS South America Center for Astronomy(CASSACA)in Santiago,ChileFunding for the LJT has been provided by the CAS and the People’s Government of Yunnan Province。
文摘Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101.Fitting of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+422-258K.The luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion.In the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation.Combined with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.
文摘Motivated by the fact that calibrated light curves of Type Ia supernovae (SNe Ia) have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observations and models of these events over the past 15 years. Here, we summarize new observational constraints, address recent progress in modeling Type Ia supernovae by means of three-dimensional hydrodynamic simulations, and discuss several of the still open questions. It will be be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparing them be applied to study the origin of the diversity with observations and we show how such models can of SNe Ia.
文摘The robotic supernova survey system of Beijing Astronomical Observatory (BAO) is based on the 60-cm telescope of BAO, which includes a CCD camera attached to the prime focus and a software system for facility control and image reduction.
基金Project supported by the National Natural Science Foundation of China (Grant No. 19733020).
文摘Six supernovae (SNe) discovered in 1996 by the Beijing Astronomical Observatory Supernova (SN) Survey (BAOSS) are reported. SN 1996W, the first supernova discovered by the survey, has been monitored photometrically and spectroscopically for a long time. The spectra and photometry showed that it was a typical type Ⅱ-P supernova. SN 1996cb, the sixth SN discovered in 1996 and a peculiar one like SN 1993J, has also been observed intensively for a long time.
文摘We review our understanding of the nucleosynthesis that occurs in thermonuclear supernovae and their contribution to Galactic Chemical evolution. We discuss the prospects to improve the modeling of the nucleosynthesis within simulations of these events.
基金supported by the National Natural Science Foundation of China(Grant No.A0424304).
文摘An annotation for the statement about Jing- Xing (Great Star) in the most famous Chinese ancient his- torical book Shi Ji (Historical Records) authored by Sima Qian reads as follows: “There was a red aureole (“Chi-Fang-Qi”) which connected with a deep-color aureole (“Qing-Fang-Qi”). Two yellow stars were in the red aureole, one yellow star was in the deep-color aureole”. The author of the annotation was Meng Kang, an officer as well as a scholar of the Wei State in the Three Kingdoms period. The same records are to be found in two other Chinese historical books compiled by the authors of later ages in Tang Dy- nasty ――Jin History and Sui History. The scene illustrated by the record of “Chi-Fang-Qi” is very similar to the pictures of SN1987A taken by the Hubble Space Telescope. Let it be noted that although the ancient authors were often with se- rious wrong understandings of some astronomical phenom- ena such as supernovae, their depictions about natural phe- nomena they witnessed were mostly objective, and it was unlikely that they fictionally made the record of “Chi-Fang-Qi”. We infer that the ancient observers might have ever watched a very bright supernova with an aureole structure in its remnant and then left such a record. Meng Kang perhaps was the first to give the record about “Chi-Fang-Qi”, and he might have lived in the period from about AD 180 to AD250, very near to AD 185, so, here the supernova the ancient people watched was most likely the one in the year of AD 185. This supposition is consistent with the distance parameter of the most possible remnant of SN185 derived by some modern measurements. If the corre- lation between the record of “Chi-Fang-Qi” and the super- nova remnant can be further proven true, it would be an important verification of the modern theory about stellar evolution.