DOI

https://doi.org/10.48717/8rz2-mp48

Project

RSY08

Title

e-EVN: EA065G, EM162A, EC082D, RSY08

Abstract

BL Lacertae (BL Lac) is a prototype of the BL Lac objects. As a nearby blazar at redshift z=0.0686, its pc and sub-pc-scale jet has been well studied for decades. Because it is a highly variable source from GeV to radio regimes, its high-brightness radio core shows significant frequency- and luminosity-dependent positional shifts. However, the variability of the core shift cannot be accurately investigated at the higher observing frequencies because of the absence of a nearby stable calibrator. Recently, we have found a promising candidate calibrator. Based on the flux densities reported in some radio surveys, it does not have a very steep spectrum between 1.4 and 5 GHz. To probe its compactness, we propose to run 0.5-h e-VLBI observations at 5 GHz with the default frequency setup. The short phase-referencing observations can allow us image its structure, derive its peak brightness, and measure its position. With these inputs, we could answer whether it could help us to run differential astrometry with a precision of < 0.01 mas per epoch.