"Leveraging SN Ia spectroscopic similarity to improve the measurement of H0"

[RedshiftDrift]

Y.S. Murakami, A.G. Riess, B.E. Stahl et al. arXiv:2306.00070

Recent studies suggest spectroscopic differences explain a fraction of the variation in Type Ia supernova (SN Ia) luminosities after light-curve/color standardization. In this work, (i) we empirically characterize the variations of standardized SN Ia luminosities, and (ii) we use a spectroscopically inferred parameter to improve the precision of SNe Ia along the distance ladder and the determination of the Hubble constant ($H_0$).

We report an updated local Hubble constant with ∼1.2% uncertainty, $H_0 = 73.29 \pm 0.90$ km/s/Mpc. We conclude that spectroscopic differences among photometrically standardized SNe Ia do not explain the ``Hubble tension." Rather, accounting for such differences increases its significance, as the discrepancy against ΛCDM calibrated by the Planck 2018 measurement rises to 5.7σ. (Accepted to JCAP)