TDCOSMO XXVIII. The Hubble constant from the quadruply lensed quasar J1537 - 3010 with precise time delays

We present the first measurement of the Hubble constant (H 0) from the quadruply-lensed quasar J1537 - 3010, which has optically-measured time delays at about2 % precision. We combine these delays with multi-band imaging data from the Hubble Space Telescope (HST) and model the system with two independent software and teams. We adopt a mass profile that is maximally degenerate with H 0 to fully incorporate the mass-sheet degeneracy in the error budget, with nuisance parameters constrained by spatially resolved stellar kinematics from the Multi Unit Spectroscopic Explorer (MUSE) and a line-of-sight (LoS) analysis using the Euclid Flagship simulation. The entire analysis is performed blindly to H 0, distances and mass density slope of the main deflector. After unblinding, we measure H 0 = 75.5+9.3-5.8 km,s-1,Mpc-1, corresponding to a 10% precision measurement from a single system. This precision is driven by conservative lens modeling assumptions including differences between lens modeling methods and the limited stellar kinematics constraints, from which we infer a total mass-sheet parameter λ (1-κ ext)λ int = 0.89+0.11-0.06 (λ int=0.89+0.09-0.07) that is consistent with current results for elliptical galaxies (λ about 1). Our lensing constraints, stellar kinematic measurements and LoS characterization will be included in subsequent population-level measurements of H 0. Moreover, our lens models combined with future near-infrared spectroscopy and imaging from the James Webb Space Telescope will further reduce the uncertainties on H 0 from J1537 - 3010 alone, bringing it closer to the few percents precision of the time delays.