W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITA...W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITAS in 2008. It is the first TeV intermediate-frequency-peaked BL Lacertae source. I find that both the broadband spectral energy distributions （SEDs） which were quasi-simultaneously obtained during the TeV flare and during the optical/X-ray outburst are well fit by using a single-zone synchrotron ＋ synchrotron-self-Compton model. The satisfactory fitting requires a large beaming factor, i.e., δ- 25 and δ- 20 for the TeV flare and the optical/X-ray outburst, respectively, suggesting that both the optical/X-ray outburst and the TeV flare are from a relativistic jet. The size of the emission region of the TeV flare is three times larger than that of the optical/X-ray outburst, and the strength of the magnetic field for the TeV flare is - 14 times smaller than that of the X-ray/optical outburst, likely indicating that the region of the TeV flare is more distant from the core than that of the X-ray/optical outburst. The inverse Compton component of the TeV flare peaks around 1.3 GeV, but it is around 20 MeV for the X-ray/optical outburst, lower than that for the TeV flare by two orders of magnitude. The model predicts that the optical/X-ray outburst might be accompanied by a strong MeV/GeV emission, but the TeV flare may be not associated with the X-ray/optical outburst. The GeV emission is critical for characterizing the SEDs of the optical/X-ray outburst and the TeV flare. The predicted GeV flux is above the sensitivity of Fermi/LAT, and it could be verified with the observations by Fermi/LAT in the near future.展开更多
Divalent metal clusters have received great attention due to the interesting size-induced nonmetal-to-metal transition and fascinating properties dependent on cluster size,shape,and doping.In this work,the combination...Divalent metal clusters have received great attention due to the interesting size-induced nonmetal-to-metal transition and fascinating properties dependent on cluster size,shape,and doping.In this work,the combination of the CALYPSO code and density functional theory(DFT)optimization is employed to explore the structural properties of neutral and anionic Mg_(n+1) and SrMgn(n=2-12)clusters.The results exhibit that as the atomic number of Mg increases,Sr atoms are more likely to replace Mg atoms located in the skeleton convex cap.By analyzing the binding energy,second-order energy difference and the charge transfer,it can be found the SrMg9 cluster with tower framework presents outstanding stability in a studied size range.Further,bonding characteristic analysis reveals that the stability of SrMg9 can be improved due to the strong s-p interaction among the atomic orbitals of Sr and Mg atoms.展开更多
The stable structures and stabilities of AgnH2S（n = 1-10） clusters have been calculated using the B3P86-DFT method. The results predicate that the stable geometries of AgnH2 S clusters can be got by directly adding ...The stable structures and stabilities of AgnH2S（n = 1-10） clusters have been calculated using the B3P86-DFT method. The results predicate that the stable geometries of AgnH2 S clusters can be got by directly adding the H2 S molecule on different sites of Agn clusters. Agn clusters would like to bond with sulfur atom and the H2 S molecules are partial to adsorb at the top site in the clusters. After adsorption, the structures of Agn clusters and H2 S molecule keep the original structures except Ag9. The binding energy of AgnH2 S is distinctly larger than that of pure Agn clusters. The second difference in energy and the HOMO and LUMO gaps of Agn and AgnH2 S exhibit an obvious odd-even oscillation, which demonstrate that the stabilities of even-numbered silver clusters are relatively more stable than the neighboring odd-numbered silver clusters. Mulliken population analysis shows that charges always transfer from the H2 S molecule to Agn clusters in all clusters.展开更多
基金supported by the National Natural Science Foundation of China under grants 10533050the National Basic Research Program ("973" Program) of China under Grant 2009CB824800
文摘W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITAS in 2008. It is the first TeV intermediate-frequency-peaked BL Lacertae source. I find that both the broadband spectral energy distributions （SEDs） which were quasi-simultaneously obtained during the TeV flare and during the optical/X-ray outburst are well fit by using a single-zone synchrotron ＋ synchrotron-self-Compton model. The satisfactory fitting requires a large beaming factor, i.e., δ- 25 and δ- 20 for the TeV flare and the optical/X-ray outburst, respectively, suggesting that both the optical/X-ray outburst and the TeV flare are from a relativistic jet. The size of the emission region of the TeV flare is three times larger than that of the optical/X-ray outburst, and the strength of the magnetic field for the TeV flare is - 14 times smaller than that of the X-ray/optical outburst, likely indicating that the region of the TeV flare is more distant from the core than that of the X-ray/optical outburst. The inverse Compton component of the TeV flare peaks around 1.3 GeV, but it is around 20 MeV for the X-ray/optical outburst, lower than that for the TeV flare by two orders of magnitude. The model predicts that the optical/X-ray outburst might be accompanied by a strong MeV/GeV emission, but the TeV flare may be not associated with the X-ray/optical outburst. The GeV emission is critical for characterizing the SEDs of the optical/X-ray outburst and the TeV flare. The predicted GeV flux is above the sensitivity of Fermi/LAT, and it could be verified with the observations by Fermi/LAT in the near future.
基金the National Natural Science Foundation of China(Grant No.11404008)the Artificial Intelligence Key Laboratory of Sichuan Province,China(Grant No.2018RYJ07)+2 种基金the Innovation Fund of Postgraduate Sichuan University of Science&Engineering,China(Grant Nos.y202007 and y2021008)the Innovation and Entrepreneurship Training Program of Sichuan Province,China(Grant Nos.S202010622080 and S202010622082)the Innovation and Entrepreneurship Training Program of Sichuan University of Science&Engineering,China(Grant No.cx2019005)。
文摘Divalent metal clusters have received great attention due to the interesting size-induced nonmetal-to-metal transition and fascinating properties dependent on cluster size,shape,and doping.In this work,the combination of the CALYPSO code and density functional theory(DFT)optimization is employed to explore the structural properties of neutral and anionic Mg_(n+1) and SrMgn(n=2-12)clusters.The results exhibit that as the atomic number of Mg increases,Sr atoms are more likely to replace Mg atoms located in the skeleton convex cap.By analyzing the binding energy,second-order energy difference and the charge transfer,it can be found the SrMg9 cluster with tower framework presents outstanding stability in a studied size range.Further,bonding characteristic analysis reveals that the stability of SrMg9 can be improved due to the strong s-p interaction among the atomic orbitals of Sr and Mg atoms.
基金supported by the National Natural Science Foundation of China(11247229,11304246)the Scientific Research Program Fund by Shaanxi Provincial Education Department(2013JK0629)+1 种基金the Natural Science Basic Research Plan in Shaanxi Province of China(2014JQ6206)the Innovation and Entrepreneurship Training Project of Provincial College Students
文摘The stable structures and stabilities of AgnH2S（n = 1-10） clusters have been calculated using the B3P86-DFT method. The results predicate that the stable geometries of AgnH2 S clusters can be got by directly adding the H2 S molecule on different sites of Agn clusters. Agn clusters would like to bond with sulfur atom and the H2 S molecules are partial to adsorb at the top site in the clusters. After adsorption, the structures of Agn clusters and H2 S molecule keep the original structures except Ag9. The binding energy of AgnH2 S is distinctly larger than that of pure Agn clusters. The second difference in energy and the HOMO and LUMO gaps of Agn and AgnH2 S exhibit an obvious odd-even oscillation, which demonstrate that the stabilities of even-numbered silver clusters are relatively more stable than the neighboring odd-numbered silver clusters. Mulliken population analysis shows that charges always transfer from the H2 S molecule to Agn clusters in all clusters.
