Research On The Multi-Bands Observation Characteristics Of Gaia-Quasars

Quasars are very bright active galactic nuclei,the variabilities are important features of this kind of sources,and variabilities in some electromagnetic observation bands are correlated with other band.There are variabilities in almost all electromagnetic bands and correlated in each band.This paper firstly introduces the basic features of quasars,the unified model and the typical subclasses of active galactic nuclei.Then the Gaia satellite and the release of its three band observations data are introduced.Finally,we introduce our two research works on Gaia quasars as follow.?1?Basing on the Gaia's second release?Gaia DR2?and the?-ray flux of blazars in Fermi 3FGL catalog,we obtained Gaia-blazars samples by cross matching.By comparing the results of the correlation analysis of the multi-band data of the three subsamples,it can be seen that the correlation between the quasars and the gamma ray multi-bands.We found that BL Lac had the strongest correlation,followed by flat-spectrum radio quasars,while undetermined subtypes of BCUs had the weakest,and some of the correlations were even positive.This trend may be due to the fact that the gamma ray and optical radiation of BL Lac objects is mainly from jets,the gamma ray radiation of flat spectrum radio quasars is from jets,but the optical radiation may be from jet and accretion disk and the broad emission line region.?2?Quasars usually harden in their energy spectrum as their luminosity increases,these results suggest that quasars generally turn blue when they bright?BWB?.Basing on high-precision simultaneous photometric observations of Gaia DR2,we were able to study the multi-band color index of Gaia quasar and found that Gaia quasar has similar Hertzsprung-Russell Diagram?HRD?.We also see that the relationship between the color index of G_BP-G_RP and the G band of Gaia indicates that when the G band brightens,the color index decreases,that is,the color turns blue.We found the light curves of 115 Gaia quasars brighter than 19 magnitude in G band by cross-matching the samples.The fitting of a single source in this sample also indicates that the trend of the most Gaia quasar is bluer when brighter?BWB?.At the same time,we found that the collective synchrotron radiation of the electrons in the accretion disk and the jet could explain this behavior.To some extent,the optical phenomena of quasars can reflect their physical nature.The unprecedented high precision optical data of Gaia provides an opportunity to further study the observation characteristics of quasars,although the radiation region and radiation mechanism still need to be further confirmed.