HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars

Details HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars

2010-07-27

arxiv.org/abs/1007.4850v2

Astronomy and Astrophysics

Astrophysics

Earth and Planetary Astrophysics

18 pages, 11 figures, 9 tables. Replaced with version accepted for publication in ApJ

Scientific paper

We report the discovery of two new transiting extrasolar planets. HAT-P-18b orbits the V=12.759 K2 dwarf star GSC 2594-00646, with a period P=5.508023+-0.000006 d, transit epoch Tc=2454715.02174+-0.00020 (BJD), and transit duration 0.1131+-0.0009 d. The host star has a mass of 0.77+-0.03 Msun, radius of 0.75+-0.04 Rsun, effective temperature 4803+-80 K, and metallicity [Fe/H]=+0.10+-0.08. The planetary companion has a mass of 0.197+-0.013 Mjup, and radius of 0.995+-0.052 Rjup yielding a mean density of 0.25+-0.04 g cm-3. HAT-P-19b orbits the V=12.901 K1 dwarf star GSC 2283-00589, with a period P=4.008778+-0.000006 d, transit epoch Tc=2455091.53417+-0.00034 (BJD), and transit duration 0.1182+-0.0014 d. The host star has a mass of 0.84+-0.04 Msun, radius of 0.82+-0.05 Rsun, effective temperature 4990+-130 K, and metallicity [Fe/H]=+0.23+-0.08. The planetary companion has a mass of 0.292+-0.018 Mjup, and radius of 1.132+-0.072 Rjup yielding a mean density of 0.25+-0.04 g cm-3. The radial velocity residuals for HAT-P-19 exhibit a linear trend in time, which indicates the presence of a third body in the system. Comparing these observations with theoretical models, we find that HAT-P-18b and HAT-P-19b are each consistent with a hydrogen-helium dominated gas giant planet with negligible core mass. HAT-P-18b and HAT-P-19b join HAT-P-12b and WASP-21b in an emerging group of low-density Saturn-mass planets, with negligible inferred core masses. However, unlike HAT-P-12b and WASP-21b, both HAT-P-18b and HAT-P-19b orbit stars with super-solar metallicity. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.

Affiliated with

Also associated with

No associations

Rating

HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-73393