Chandra and optical/IR observations of CXOJ1415.2+3610, a massive, newly discovered galaxy cluster at z~1.5

(Abridged) We report the discovery of CXO J1415.2+3610, a distant (z~1.5) galaxy cluster serendipitously detected in a deep, high-resolution Chandra observation targeted to study the cluster WARP J1415.1+3612 at z=1.03. This is the highest-z cluster discovered with Chandra so far. Moreover, the total exposure time of 280 ks with ACIS-S provides the deepest X-ray observation currently achieved on a cluster at z>1.5. We perform an X-ray spectral fit of the extended emission of the intracluster medium (ICM) with XSPEC, and we detect at a 99.5% confidence level the rest frame 6.7-6.9 keV Iron K_alpha line complex, from which we obtain z_X=1.46pm0.025. The analysis of the z-3.6mu m color-magnitude diagram shows a well defined sequence of red galaxies within 1 from the cluster X-ray emission peak with a color range [5 < z-3.6 mu m < 6]. The photometric redshift obtained by spectral energy distribution (SED) fitting is z_phot=1.47pm 0.25. After fixing the redshift to z=1.46, we perform the final spectral analysis and measure the average gas temperature with a 20% error, kT=5.8^{+1.2}_{-1.0} keV, and the Fe abundance Z_Fe = 1.3_{-0.5}^{+0.8}Z_odot. We fit the background subtracted surface brightness with a single beta--model out to 35 and derive the deprojected electron density profile. The ICM mass is 1.09_{-0.2}^{+0.3}times 10^{13} M_odot within 300 kpc. The total mass is M_{2500}= 8.6_{-1.7}^{+2.1} times 10 ^{13} M_odot for R_{2500}=(220pm 55) kpc. Extrapolating the profile at larger radii we find M_{500}= 2.1_{-0.5}^{+0.7} times 10 ^{14} M_odot for R_{500} = 510_{-50}^{+55}$ kpc. This analysis establishes CXOJ1415.2+3610 as one of the best characterized distant galaxy clusters based on X-ray data alone.