I will present observations of blazar 3C273 using both the High Band Antennas and the Low Band Antennas of the LOFAR international stations. Blazars are active galactic nuclei which have a relativistic jet aligned towards Earth. Blazars radiate at all observable frequencies. 3C273 is one of the most heavily-researched blazars across the electromagnetic spectrum but remains poorly understood at low radio frequencies due to a lack of observational data below 200 MHz. We are conducting high-resolution observations between 10 MHz and 240 MHz to address this crucial gap in the literature and further our understanding of the emission mechanisms at work.

At radio frequencies, the jet is a core-dominated source of non-thermal radiation which is believed to be synchrotron in nature. There is still debate over the production mechanism behind the high-energy emission. Some models suggest that the X-ray emission is produced by the inverse-Compton scattering of cosmic microwave background photons (IC/CMB) off relativistic electrons. We assess the role the low-energy electron population plays with respect to the production of the high-energy emission and our results can test the viability of the IC/CMB model when combined with multiwavelength data.

We achieve sub-arcsecond angular resolution in the 10 MHz to 240 MHz frequency range using very-long-baseline interferometry data taken with the LOFAR international stations. Analysing a bright (67 Jy at 178 MHz) source with the international stations pushes the capabilities of LOFAR.