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Due to its powerful radiation over the entire electromagnetic spectrum andits radio jet activity, the blazar 3C273 offers the opportunity to study thephysics of $\gamma$-ray emission from active galactic nuclei. Since ahistorically strong outburst in 2009, 3C273 showed relatively weak emission inthe gamma-ray band over multiple years. However, recent Fermi-Large AreaTelescope observations indicate elevated activity during 2015-2019. We aim atconstraining the origin of the gamma-ray outbursts towards 3C273 andinvestigate their connection to the parsec-scale jet. We generate Fermi-LATgamma-ray light curves with multiple binning intervals and study the spectralproperties of the gamma-ray emission. Using a 3-mm ALMA light curve, we studythe correlation between radio and gamma-ray emission. Relevant activity in theparsec-scale jet of 3C273 is investigated with 7-mm VLBA observations obtainedclose in time to notable gamma-ray outbursts. We find two prominent gamma-rayoutbursts in 2016 (MJD 57382) and 2017 (MJD 57883) accompanied by mm-wavelengthflaring activity. The gamma-ray photon index time series show a weak hump-likefeature around the gamma-ray outbursts. The monthly gamma-ray flux-index plotindicates a transition from softer-when-brighter to harder-when-brighter at$1.03\times10^{-7}\rm\,ph\,cm^{-2}\,s^{-1}$. A significant correlation betweenthe gamma-ray and mm-wavelength emission is found, with the radio lagging thegamma-rays by about 105-112 days. The 43-GHz jet images reveal the knownstationary features (i.e., the core, S1, and S2) in a region upstream of thejet. We find indication for a propagating disturbance and a polarized knotbetween the stationary components around the times of both gamma-ray outbursts.

Investigating the connection between gamma-ray activity and relativistic jet in 3C273 during 2015-2019