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ksp:ksp [2017/09/27 10:58]
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ksp:ksp [2017/11/01 15:46]
sslee
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 ====== Origins of Gamma-ray Flares in AGNs ====== ====== Origins of Gamma-ray Flares in AGNs ======
 ==== Science Goals  ==== ==== Science Goals  ====
 +
 +**[[:​KSP:​iMOGABA:​]]** (being updated)
 +
 A KVN Key Science Program with the title of **Origins of Gamma-ray flares in AGNs** (PI: Sang-Sung Lee, sslee@kasi.re.kr) is a three-year project consisting of VLBI monitoring observations (or iMOGABA) and single dish (SD) rapid response observations (RRO, or MOGABA). The VLBI monitoring observations are comprised of ten 24-hr observations per year (every month) of about 30 gamma-ray brigt active galactic nuclei (AGNs)(see [[http://​radio.kasi.re.kr/​sslee]]) with Korea VLBI Network (KVN) at 22, 43, 86, and 129 GHz. The SD RROs may consist of twelve 7-hr observations per source (every week for 3 months after triggering) of gamma-ray flaring sources with two KVN SD telescopes at 22, 43, and 86 GHz (and/or 129 GHz)in dual polarization. We expect one or two sources per year for the SD RROs. Gamma-ray flares of AGNs are known to be occured in innermost regions of relativistic jets which radiate in whole ranges of electromagnetic spectra due to synchrotron radiation, syschrotron self absorption, inverse-compton scttering, doppler boosting etc. Here we may eraise two questions on the natures of the gamma-ray flares of AGN such as: a) What is the basic casue of the gamma-ray flares from AGNs? b) What is the physical process of the causes? For the first question, there are several suggestions like 1) a relativistic jet of high energy plasma (Marscher et al. 2008), 2) Doppler boosting of synchrotron radiation of the jet (Dermer 1995), 3) inverse Compton scattering by relativistic electrons, etc. For the second question, we may find some candidates and detail mechanism for the gamma-ray flares such as 1) compression and heating of the plasma in the relativistic jets, 2) generation of the relativistic particles, 3) rapid variability in flux and magnetic field. In order to answer to the questions, we may conduct either 1) studies of large samples of flaring AGNs for investigating statistics and correlation of observed properties (Lister et al. 2011), 2) multi-wavelength observations of individual objects for testing time profiles of flares (Jorstad et al. 2010), for studying physical properties of emission features (jet knots) (Agudo et al. 2011), and studying evolution of SEDs (Wehrle et al. 2013), or 3) polarization observations for looking at magnetic field environments (Jorstad et al. 2013). Possible explanations of the gamma-ray flares in AGNs are a) shocks-in-jets propagating within jet flow and b) bending of the whole jets. For both cases, we should expect changes in polarization,​ luminosity, particle distribution,​ and structures of jets at mas-scale. The multifrequency simultaneous VLBI/SD observations with KVN are the best tool for detecting such changes correlated with gamma-ray flares. This KSP aims to answer the fundamental questions about the basic nature of the flares of AGN. A KVN Key Science Program with the title of **Origins of Gamma-ray flares in AGNs** (PI: Sang-Sung Lee, sslee@kasi.re.kr) is a three-year project consisting of VLBI monitoring observations (or iMOGABA) and single dish (SD) rapid response observations (RRO, or MOGABA). The VLBI monitoring observations are comprised of ten 24-hr observations per year (every month) of about 30 gamma-ray brigt active galactic nuclei (AGNs)(see [[http://​radio.kasi.re.kr/​sslee]]) with Korea VLBI Network (KVN) at 22, 43, 86, and 129 GHz. The SD RROs may consist of twelve 7-hr observations per source (every week for 3 months after triggering) of gamma-ray flaring sources with two KVN SD telescopes at 22, 43, and 86 GHz (and/or 129 GHz)in dual polarization. We expect one or two sources per year for the SD RROs. Gamma-ray flares of AGNs are known to be occured in innermost regions of relativistic jets which radiate in whole ranges of electromagnetic spectra due to synchrotron radiation, syschrotron self absorption, inverse-compton scttering, doppler boosting etc. Here we may eraise two questions on the natures of the gamma-ray flares of AGN such as: a) What is the basic casue of the gamma-ray flares from AGNs? b) What is the physical process of the causes? For the first question, there are several suggestions like 1) a relativistic jet of high energy plasma (Marscher et al. 2008), 2) Doppler boosting of synchrotron radiation of the jet (Dermer 1995), 3) inverse Compton scattering by relativistic electrons, etc. For the second question, we may find some candidates and detail mechanism for the gamma-ray flares such as 1) compression and heating of the plasma in the relativistic jets, 2) generation of the relativistic particles, 3) rapid variability in flux and magnetic field. In order to answer to the questions, we may conduct either 1) studies of large samples of flaring AGNs for investigating statistics and correlation of observed properties (Lister et al. 2011), 2) multi-wavelength observations of individual objects for testing time profiles of flares (Jorstad et al. 2010), for studying physical properties of emission features (jet knots) (Agudo et al. 2011), and studying evolution of SEDs (Wehrle et al. 2013), or 3) polarization observations for looking at magnetic field environments (Jorstad et al. 2013). Possible explanations of the gamma-ray flares in AGNs are a) shocks-in-jets propagating within jet flow and b) bending of the whole jets. For both cases, we should expect changes in polarization,​ luminosity, particle distribution,​ and structures of jets at mas-scale. The multifrequency simultaneous VLBI/SD observations with KVN are the best tool for detecting such changes correlated with gamma-ray flares. This KSP aims to answer the fundamental questions about the basic nature of the flares of AGN.
  
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