J/AJ/153/138 Radial velocity curve of 51 Peg (Birkby+, 2017) ================================================================================ Discovery of water at high spectral resolution in the atmosphere of 51 Peg b. Birkby J.L., de Kok R.J., Brogi M., Schwarz H., Snellen I.A.G. =2017AJ....153..138B (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Stars, double and multiple ; Planets ; Radial velocities Keywords: planetary systems - planets and satellites: composition - planets and satellites: gaseous planets - planets and satellites: individual: 51 Peg b Abstract: We report the detection of water absorption features in the day side spectrum of the first-known hot Jupiter, 51 Peg b, confirming the star-planet system to be a double-lined spectroscopic binary. We use high-resolution (R{approx}100000), 3.2{mu}m spectra taken with CRIRES/VLT to trace the radial-velocity shift of the water features in the planet's day side atmosphere during 4 hr of its 4.23 day orbit after superior conjunction. We detect the signature of molecular absorption by water at a significance of 5.6{sigma} at a systemic velocity of V_sys_=-33+/-2km/s, coincident with the 51 Peg host star, with a corresponding orbital velocity K_P_=133_-3.5_^+4.3^km/s. This translates directly to a planet mass of M_p_=0.476_-0.031_^+0.032^M_J_, placing it at the transition boundary between Jovian and Neptunian worlds. We determine upper and lower limits on the orbital inclination of the system of 70{deg}