Expansion rate of the young, oxygen-rich supernova remnant G292.0+1.8

Core-collapse supernova remnants (CCSNRs) are ideal targets for studying ejecta--interstellar-medium interactions, shock dynamics, and explosion characteristics. G292.0+1.8 is a classic CCSNR featuring oxygen-rich ejecta, circumstellar material, a rapidly moving pulsar, and a pulsar wind nebula (PWN). We examine its expansion rate using deep Chandra ACIS-I observations over two nearly independent about 10 yr baselines (2006--2016). After applying astrometric corrections based on Gaia DR3 sources, we extracted radial profiles in 19 sectors around the forward shock. The weighted-mean expansion rate is 0.016% plus or minus 0.001%, yr-1 in the broadband, implying an expansion age of about 2500 yr for a uniform ambient medium, consistent with previous estimates of 2000--3700 yr. For a 1/r squared circumstellar density profile (Wolf-Rayet progenitor wind), the inferred age is about 4100 yr. Narrow-band analysis of alpha elements (O-Ne, Mg, Si-S) shows that lighter elements follow the broadband behaviour, while heavier elements expand more slowly, consistent with their origin in deeper stellar layers. We discuss the pronounced azimuthal asymmetry of the expansion, the apparent paradox that some sectors expand (with about 2500 km/s) preferentially in the direction of the neutron-star kick, and the role of reflected shocks from the reverse-shock--PWN interaction.