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Possible γ-ray emission of radio intermediate AGN Ⅲ Zw 2 and its implication on the evolution of jets in AGNs

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Research in Astronomy and Astrophysics 2010年第8期10卷 707-712页

作者： Liang Chen jin-ming bai jin Zhang Hong-Tao Liu National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China College of Physics and Electronic Engineering Guangxi Teachers Education University Nanning 530001 China

AGNs with hard γ-ray emission identified so far are radio-loud. Ⅲ Zw 2 is a radio intermediate AGN with a relativistic jet. We study its spectral energy distribution （SED） and find that the broad band emissions are dominated by the nonthermal emissions from the jet. We model its SED through a synchrotron ＋ inverse Compton （IC） model. The results show that the IC component of Ⅲ Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index F 3.3 above 0.1 GeV. The predicted flux is slightly over the sensitivity of Fermi/LAT, but it was not included in the first Fermi/LAT AGN catalog. The reason for this may be： 1） that the IC peak is low and the spectrum is very steep above 0.1 GeV, 2） that Ⅲ Zw 2 is in the low state during the period of the Fermi/LAT operation. We also find that Ⅲ Zw 2 follows similar jet processes as those in γ-ray AGNs, e.g., the relation between jet power and radiation power, which is called the blazar sequence. We suggest that Ⅲ Zw 2 may be a young source at an earlier stage of jet activity.

关键词： galaxies active -- galaxies Seyfert- galaxies jets -- radiation mechanisms non-thermal

What determines the observational differences of blazars？

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Research in Astronomy and Astrophysics 2016年第11期16卷 61-70页

作者： Xu-Liang Fan jin-ming bai Ji-Rong Mao Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China University of Chinese Academy of Sciences Beijing 100049 China

We examine the scenario that the Doppler factor determines the observational differences of blazars. Significantly negative correlations are found between the observational synchrotron peak frequency and the Doppler factor. After correcting the Doppler boosting, the intrinsic peak frequency has a tight linear relation with the Doppler factor. It is interesting that this relation is consistent with the scenario that the black hole mass governs both the bulk Lorentz factor and the synchrotron peak frequency. In addition, the distinction between the kinetic jet powers of BL Lac objects and fiat spectrum radio quasars disappears after the boosting factor δ2 is considered. The negative correlation between the peak frequency and the observational isotropic luminosity, known as the blazar sequence, also disappears after the Doppler boosting is corrected. We also find that the correlation between the Compton dominance and the Doppler factor exists for all types of blazars. Therefore, this correlation is unsuitable for examining the external Compton emission dominance.

关键词： galaxies: jets - BL Lacertae objects: general - quasars: general - radiation mechanisms:non-thermal

Time Lags between the 22 and 37 GHz Bursts of 48 Radio-loud AGNs

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Chinese Journal of Astronomy and Astrophysics 2008年第2期8卷 195-203页

作者： Wen-Guo Deng jin-ming bai Li Zhang Xian Yang National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Physics Department Yunnan University Kunming 650091

Based on the light curves at 22 and 37 GHz from the Metsahovi monitoring program, we investigate the time lags between the two radio bands for 48 radio-loud AGNs. DCF and ZDCF analyses are applied to the data. Our results show that there is a strong correlation between the two radio frequencies for all the sources, with the variations in the light curves at 37 GHz leading the ones at 22 GHz in general. There is no obvious differences between different sub-class AGNs as regards the time lag. In two sources, it was found that the bursts at the lower frequency lead the ones at the higher frequency. One possible explanation is that electron acceleration dominates the light curve until the radiation reaches the maximum. Some sources, such as 3C 273, 3C 279, 3C 345 and 3C 454.3, have good enough data, so we can calculate their lags burst-by-burst. Our calculations show that different outbursts have dif- ferent lags. Some bursts have positive lags, most of bursts have no clear lags, and a few have negative lags. This result means that different bursts are triggered by different mechanisms, and the interpretation for the result involves both an intrinsic and a geometric mechanism. The positive lags are well consistent with the shock model, and we use these lags to calculate the typical magnetic field strength of the radiating region.

关键词： galaxies: active -- galaxies: individual (3C 273 3C 279 3C 345 3C 454.3) --methods: data analysis

Radial stellar populations of AGN-host dwarf galaxies in SDSS-Ⅳ MaNGA survey

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Research in Astronomy and Astrophysics 2021年第8期21卷 203-219页

作者： Wei Cai Ying-He Zhao jin-ming bai Yunnan Observatories Chinese Academy of SciencesKunming 652016China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China

Based on MaNGA integral field unit(IFU) spectroscopy we search 60 AGN candidates,which have stellar masses M*≤5 × 10^(9) M⊙ and show AGN ionization signatures in the BPT *** these AGN candidates,we derive the spatially resolved stellar population with the stellar population synthesis code STARLIGHT and measure the gradients of the mean stellar age and *** find that the gradients of mean stellar age(metallicity) of individual AGN-host dwarfs are diverse in 0-0.5 Re,0.5-1 Re and 0-1 ***,the overall behavior of the mean stellar age(metallicity) profiles tend to be flat,as the median values of the gradients are close to *** further study the overall behavior of the mean stellar age(metallicity) by plotting the co-added radial profiles for the AGN sample and compare with a control sample with similar stellar *** find that the median values of light-weighted mean stellar ages of the AGN sample are as old as 2-3 Gyr within 2 Re,which are about 4-7 times older than those of the control ***,most of the AGN candidates are low-level AGNs,as only eight sources have L[OⅢ]>1039.5 erg s^(-1).Hence,the AGNs in dwarf galaxies might accelerate the evolution of galaxies by accelerating the consumption of the gas,resulting in an overall quenching of the dwarf galaxies,and the AGNs also become weak due to the lack of *** median values of mass-weighted mean stellar age of both samples within 2 Re are similar and as old as about 10 Gyr,indicating that the stellar mass is mainly contributed by old stellar *** gradients of co-added mean stellar metallicity for both samples tend to be negative but close to zero,and the similar mean stellar metallicity profiles for both samples indicate that the chemical evolution of the host galaxy is not strongly influenced by the AGN.

关键词： galaxies:dwarf galaxies:active galaxies:galaxies stellar content

An explanation for 13 consecutive day activities of Mrk 421

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Research in Astronomy and Astrophysics 2021年第1期21卷 75-86页

作者： Yong-Gang Zheng Chu-Yuan Yang Shi-Ju Kang jin-ming bai Yunnan Observatories Chinese Academy of SciencesKunming 650011China Department of Physics Yunnan Normal UniversityKunming 650092China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment-Shandong University Weihai 264209China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China Department of Physics and Electronics Science Liupanshui Normal UniversityLiupanshui 553004China

It is surprising to find an instance of migration in the peak positions of synchrotron spectral energy distribution components during the activity epochs of Markarian 421(Mrk 421),accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands.A geometric interpretation and standard shock or stochastic acceleration models of blazar emission have difficulty reproducing these observed *** present paper introduces a linear acceleration by integrating the reconnection electric field into the particle transport model for the observed behaviors of Mrk *** note that strong evidence for evolution in characteristic of multi-wavelength spectral energy distribution including shifting the peak frequency,accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands provides an important electrostatic acceleration diagnostic in a blazar *** suitable model parameters,we apply the results of the simulation to the 13-day flaring event in March 2010 of Mrk 421,concentrating on the evolution of multiwavelength spectral energy distribution characteristic by shifting the peak *** is clear that the ratio of the electric field and magnetic field strength plays an important role in temporal evolution of the peak frequency of synchrotron spectral energy distribution *** suggest it is reasonable that the electrostatic acceleration is responsible for the evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak *** on the model results,we assert that the peak frequency of the synchrotron spectral energy distribution component may signify a temporary characteristic of blazars,rather than a permanent one.

关键词： radiation mechanisms:non-thermal BL Lacertae objects:individual:(Mrk 421) acceleration of particles

The afterglow emission from a stratified jet in GRB 170817A

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Research in Astronomy and Astrophysics 2021年第7期21卷 223-233页

作者： Kang-Fa Cheng Xiao-Hong Zhao Bin-Bin Zhang jin-ming bai Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of the Chinese Academy of Sciences Beijing 100049China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China School of Astronomy and Space Science Nanjing UniversityNanjing 210093China Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210046China Department of Physics and Astronomy University of Nevada Las VegasNV 89154USA

The afterglow of GRB 170817 A has been detected for more than three years,but the origin of the multi-band afterglow light curves remains under debate.A classical top-hat jet model is faced with difficulties in producing a shallow rise of the afterglow light curves as observed(E_(v) ∝ T^(0.8)).Here we reconsider the model of stratified ejecta with an energy profile of E(> Γβ)=E_0(Γβ)^(-k) as the origin of the afterglow light curves of the burst,where Γ and β are the Lorentz factor and speed of the ejecta,respectively.k is the power-law slope of the energy *** consider that the ejecta are collimated into *** kinds of jet evolutions are investigated,including a lateral-spreading jet and a non-lateral-spreading *** fit the multi-band afterglow light curves,including the X-ray data at one thousand days post-burst,and find that both the models of the spreading and non-spreading jets can fit the light curves well,but the observed angular size of the source and the apparent velocity of the flux centroid for the spreading jet model are beyond the observation limits,while the non-spreading jet model meets the observation *** of the best-fit parameters for the non-spreading jet model,such as the number density of the circumburst medium~10^(-2) cm^(-3) and the total jet kinetic energy E ~ 4.8 × 10^(51) erg,also appear *** best-fit slope of the jet energy profile is k ~*** results suggest that the afterglow of GRB 170817 A may arise from the stratified jet and that the lateral spreading of the jet is not significant.

关键词： gamma-ray burst:general stars:jets relativistic processes

Statistical Properties of a Blazar Sample and Comparison of HBLs, LBLs and FSRQs

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Chinese Journal of Astronomy and Astrophysics 2005年第5期5卷 471-486页

作者： Li-Sheng Mao Guang-Zhong Xie jin-ming bai Hong-Tao Liu Yunnan Observatory National Astronomical Observatories Chinese Academy of SciencesKunming 650011 Graduate University of Chinese Academy of Sciences Beijing 100049 Yunnan Astrophysics Center Yunnan University Kunming 650091

Making use of the 2MASS Data Release, we have searched for nearinfrared （JHK） counterparts to 268 blazars from Donato et al. and obtained 238 counterparts within 5＇＇ in the area covered by 2MASS. It provides us a sample with infrared data several times larger than the previous one of the same kind. Based on our sample and the sample by Donato et al., we have compared in detail the properties of HBLs, LBLs and FSRQs from five aspects and found that HBLs are significantly different from LBLs and FSRQs while LBLs are not obviously different from FSRQs. Our results strongly support the division of BL Lac objects into the high-frequency peaked （HBL） and low-frequency peaked （LBL） objects introduced by Padovani ＆ Giommi and show that HBLs and LBLs are two kinds of blazar having different physical properties.

关键词： BL Lacertae objects: general-infrared: galaxies - methods: statistical

Optical multi-color monitoring of OJ 287 from 2006 to 2012

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Research in Astronomy and Astrophysics 2017年第8期17卷 57-68页

作者： Qian Guo Ding-Rong Xiong jin-ming bai Xu-Liang Fan Wei-Min Yi Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China University of Chinese Academy of Sciences Beijing 100049 China

We present our optical multi-color monitoring of the BL Lac object OJ 287 from January 2006to December 2012 in the V,R and I bands.A relatively active state in OJ 287 has been found over all monitored epochs,among which the variations of average magnitude in V/R/I bands were measured with ?V=1.956 mag,?R=2.067 mag and ?I=2.115 mag,*** reliable intraday variability is detected,but possible variability is detected on 16 *** relative variation amplitudes fall into the range between 1% and 8%,with the majority between 2% and 4%.No time lags have been detected,but strong correlations exist among light curves in the three *** bluer-when-brighter trend is dominant over intraday timescales,which supports the shock-in-jet *** combining with additional V/R band data obtained from SMARTS and the Steward Observatory,we also find a bluer-when-brighter trend over a long-term *** possible periods of 513,176,36,30,26,17 and 14 d are found in all time-series data sets from 2006 to *** explanations about these periods are given.

关键词： BL Lacertae objects individual(OJ 287)—galaxies active—galaxies photometry

The connection between radio and γ-ray emission in Fermi/LAT blazars

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Research in Astronomy and Astrophysics 2012年第11期12卷 1475-1485页

作者： Xu-Liang Fan jin-ming bai Hong-Tao Liu Liang Chen Neng-Hui Liao National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy ofSciences Kunming 650011 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical ObservatoriesChinese Academy of Sciences Shanghai 200030 China Graduate University of Chinese Acaciemy of Sciences Beijing 100049 China

We collect the second Large Area Telescope AGN catalog （2LAC） and Monitor of Jets in AGN with VLBA Equipment （MOJAVE） quasi-simultaneous data to investigate the radio-γ connection of blazars. The cross sample contains 166 sources. The statistical analysis based on this sample confirms positive correlations between these two bands, but the correlations become weaker as the γ-ray energy increases. The statistical results between various parameters show negative correla- tions of γ-ray photon spectral index with γ-ray loudness for both Flat Spectrum Radio Quasars （FSRQs） and BL Lacertae objects, positive correlations of γ-ray variability index with the γ-ray loudness for FSRQs, a negative correlation of the γ-ray variabil- ity index with the γ-ray photon spectral index for FSRQs, and negative correlations of γ-ray photon spectral index with γ-ray luminosity for FSRQs. These results suggest that the γ-ray variability may be due to changes inside the γ-ray emission region like the injected power, rather than changes in the photon density of the external radiation fields, and the variability amplitude tends to be larger as the γ-rays are closer to the high energy peak of the spectral energy distribution （SED）. No correlation of variabil- ity index found for BL Lacertae objects implies that variability behavior may differ below and above the peak energy.

关键词： BL Lacertae objects general -- galaxies: jets -- quasars general -- radio continuum galaxies -- gamma rays observations