In this work,we reanalyzed 11 years of spectral data from the Fermi Large Area Telescope(Fermi-LAT)of currently observed starburst galaxies(SBGs)and star-forming galaxies(SFGs).We used a one-zone model provided by NAI...In this work,we reanalyzed 11 years of spectral data from the Fermi Large Area Telescope(Fermi-LAT)of currently observed starburst galaxies(SBGs)and star-forming galaxies(SFGs).We used a one-zone model provided by NAIMA and the hadronic origin to explain the GeV observation data of the SBGs and SFGs.We found that a protonic distribution of a power-law form with an exponential cutoff can explain the spectra of most SBGs and SFGs.However,it cannot explain the spectral hardening components of NGC 1068 and NGC 4945 in the GeV energy band.Therefore,we considered the two-zone model to well explain these phenomena.We summarized the features of two model parameters,including the spectral index,cutoff energy,and proton energy budget.Similar to the evolution of supernova remnants(SNRs)in the Milky Way,we estimated the protonic acceleration limitation inside the SBGs to be the order of 10^(2) TeV using the one-zone model;this is close to those of SNRs in the Milky Way.展开更多
PMN J0218-2307(4 FGL J0218.9-2305) is classified as a blazar candidate with unknown type(BCU) in the fourth source catalog from the Fermi Large Area Telescope(Fermi-LAT).With the updated Fermi-LAT Pass 8 data,the γ-r...PMN J0218-2307(4 FGL J0218.9-2305) is classified as a blazar candidate with unknown type(BCU) in the fourth source catalog from the Fermi Large Area Telescope(Fermi-LAT).With the updated Fermi-LAT Pass 8 data,the γ-ray flaring activity toward PMN J0218-2307 is detected.The test statistic(TS) value of PMN J0218-2307 in energy band of 100 MeV-500 GeV is 133.893 with a significance level of 10.96σ.The maximum-likelihood photon flux is(8.131 ± 1.359) × 10^(-9) ph cm^(-2) s^(-1).A significantγ-ray flare in the period from 2008 August 4 to 2019 August 25 is found from the source.The spectral characteristics of GeV energy band of PMN J0218-2307 is similar to that of flat-spectrum radio quasars(FSRQs) in the local Universe.展开更多
The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three ...The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.展开更多
基金support for this work from the National Key R&D Program of China(Grant No.2018YFA0404204)the National Natural Science Foundation of China(Grant Nos.U1931113,U1738211 and U193110119)+1 种基金the Foundations of Yunnan Province(2018IC059 and 2018FY001(-003))the Scientific Research Fund of Yunnan Education Department(2020Y0039)。
文摘In this work,we reanalyzed 11 years of spectral data from the Fermi Large Area Telescope(Fermi-LAT)of currently observed starburst galaxies(SBGs)and star-forming galaxies(SFGs).We used a one-zone model provided by NAIMA and the hadronic origin to explain the GeV observation data of the SBGs and SFGs.We found that a protonic distribution of a power-law form with an exponential cutoff can explain the spectra of most SBGs and SFGs.However,it cannot explain the spectral hardening components of NGC 1068 and NGC 4945 in the GeV energy band.Therefore,we considered the two-zone model to well explain these phenomena.We summarized the features of two model parameters,including the spectral index,cutoff energy,and proton energy budget.Similar to the evolution of supernova remnants(SNRs)in the Milky Way,we estimated the protonic acceleration limitation inside the SBGs to be the order of 10^(2) TeV using the one-zone model;this is close to those of SNRs in the Milky Way.
基金the support for this work from National Key R&D Program of China under grant No.2018YFA0404204the National Natural Science Foundation of China(NSFC,U1931113,U1738211 and U193110119)+2 种基金the Foundations of Yunnan Province(2018IC059,2018FY001(-003))the Scientific Research Fund of the Yunnan Education Department(2020Y0039)the China Postdoctoral Science Foundation funded project(2019M661971)。
文摘PMN J0218-2307(4 FGL J0218.9-2305) is classified as a blazar candidate with unknown type(BCU) in the fourth source catalog from the Fermi Large Area Telescope(Fermi-LAT).With the updated Fermi-LAT Pass 8 data,the γ-ray flaring activity toward PMN J0218-2307 is detected.The test statistic(TS) value of PMN J0218-2307 in energy band of 100 MeV-500 GeV is 133.893 with a significance level of 10.96σ.The maximum-likelihood photon flux is(8.131 ± 1.359) × 10^(-9) ph cm^(-2) s^(-1).A significantγ-ray flare in the period from 2008 August 4 to 2019 August 25 is found from the source.The spectral characteristics of GeV energy band of PMN J0218-2307 is similar to that of flat-spectrum radio quasars(FSRQs) in the local Universe.
基金the support for this work from the National Key R&D Program of China under Grant No.2018YFA0404204the National Natural Science Foundation of China(NSFC U1931113 and U1738211)+1 种基金the Foundations of Yunnan Province(2018IC059 and 2018FY001(-003))the scientific research fund of Yunnan Education Department(2020Y0039)。
文摘The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.
