Bakos, G. Á., Hartman, J. D., Bhatti, W., Bieryla, A., de Val-Borro, M., Latham, D. W., Buchhave, L. A., Csubry, Z., Penev, K., Kovács, G., Béky, B., Falco, E., Kovács, T., Howard, A. W., Johnson, J. A., Isaacson, H., Marcy, G. W., Torres, G., Noyes, R. W., Berlind, P., Calkins, Michael L., Esquerdo, Gilbert A., Lázár, J., Papp, I., and Sári, P. 2015. "HAT-P-54b: A Hot Jupiter Transiting a 0.6 M? Star in Field 0 of the K2 Mission." The Astronomical Journal, 149 149. https://doi.org/10.1088/0004-6256/149/4/149.
We report the discovery of HAT-P-54b, a planet transiting a late K dwarf star in field 0 of the NASA K2 mission. We combine ground-based photometric light curves with radial velocity measurements to determine the physical parameters of the system. HAT-P-54b has a mass of 0.760\ /- 0.032 {{M}J}, a radius of 0.944 ± 0.028 {{R}J}, and an orbital period of 3.7998 days. The star has V=13.505\ /- 0.060, a mass of 0.645\ /- 0.020 {{M}}, a radius of 0.617\ /- 0.013 {{R}}, an effective temperature of {{T}eff\star }=4390\ /- 50, and a subsolar metallicity of [Fe/H]=-0.127\ /- 0.080. We also detect a periodic signal with P = 15.6 days and 5.6 mmag amplitude in the light curve, which we interpret as due to the rotation of the star. HAT-P-54b has a radius that is smaller than 92% of the known transiting planets with masses greater than that of Saturn, while HAT-P-54 is one of the lowest-mass stars known to host a hot Jupiter. Follow-up high-precision photometric observations by the
