HAT-P-20b-HAT-P-23b: Four massive transiting extrasolar planets

Abstract

We report the discovery of four relatively massive (2-7 M J) transiting extrasolar planets. HAT-P-20b orbits the moderately bright V = 11.339 K3 dwarf star GSC 1910-00239 on a circular orbit, with a period P = 2.875317 ± 0.000004days, transit epoch Tc = 2455080.92661± 0.00021 (BJDUTC), and transit duration 0.0770 0.0008days. The host star has a mass of 0.76 ±0.03 M ⊙, radius of 0.69± 0.02 R ⊙, effective temperature 4595 ±80K, and metallicity [Fe/H] = +0.35 0.08. The planetary companion has a mass of 7.246± 0.187M J and a radius of 0.867 ±0.033R J yielding a mean density of 13.78± 1.50g cm-3. HAT-P-21b orbits the V = 11.685 G3 dwarf star GSC 3013-01229 on an eccentric (e = 0.228± 0.016) orbit, with a period P = 4.124481± 0.000007days, transit epoch Tc = 2454996.41312± 0.00069, and transit duration 0.1530± 0.0027days. The host star has a mass of 0.95 ±0.04 M ⊙, radius of 1.10 0.08 R ⊙, effective temperature 5588 80K, and metallicity [Fe/H] = +0.01 0.08. The planetary companion has a mass of 4.063± 0.161M J and a radius of 1.024± 0.092R J yielding a mean density of 4.68 +1.59- 0.99g cm-3. HAT-P-21b is a borderline object between the pM and pL class planets, and the transits occur near apastron. HAT-P-22b orbits the bright V = 9.732 G5 dwarf star HD 233731 on a circular orbit, with a period P = 3.212220 ±0.000009days, transit epoch Tc = 2454930.22001 ±0.00025, and transit duration 0.1196 0.0014days. The host star has a mass of 0.92 0.03 M ⊙, radius of 1.04 0.04 R ⊙, effective temperature 5302 80K, and metallicity [Fe/H] = +0.24± 0.08. The planet has a mass of 2.147 0.061M J and a compact radius of 1.080 0.058R J yielding a mean density of 2.11+0.40- 0.29g cm-3. The host star also harbors an M-dwarf companion at a wide separation. Finally, HAT-P-23b orbits the V = 12.432 G0 dwarf star GSC 1632-01396 on a close to circular orbit, with a period P = 1.212884± 0.000002days, transit epoch Tc = 2454852.26464 ± 0.00018, and transit duration 0.0908 ±0.0007days. The host star has a mass of 1.13 ±0.04 M ⊙, radius of 1.20 ±0.07 R ⊙, effective temperature 5905± 80K, and metallicity [Fe/H] = +0.15± 0.04. The planetary companion has a mass of 2.090 0.111M J and a radius of 1.368± 0.090R J yielding a mean density of 1.01 ±0.18g cm-3. HAT-P-23b is an inflated and massive hot Jupiter on a very short period orbit, and has one of the shortest characteristic infall times (7.5+2.9- 1.8Myr) before it gets engulfed by the star. © 2011. The American Astronomical Society. All rights reserved.