SN 2018xx and SN 2019gbx light curves

The B-band light curve decline rate for SN 2018xx is estimated to be 1.48+/-0.07mag and for SN 2019gbx it is 1.37+/-0.07mag. Despite the similarities in photometric evolution, quasi-bolometric luminosity, and spectroscopy between these two SNe Ia, SN 2018xx has been found to be fainter by about 0.38mag in the Bband and has a lower 56Ni yield.

Their host galaxies have similar metallicities at the SN location, indicating that the differences between these two SNe Ia may be associated with the higher progenitor metallicity of SN 2018xx. Further inspection of the near maximum-light spectra has revealed that SN 2018xx has relatively strong absorption features near 4300{AA} relative to SN 2019gbx. The application of the code TARDIS fitting to the above features indicates that the absorption features near 4300{AA} appear to be related to not only FeII/MgII abundance but possibly to the other element abundances as well.