Saturday, June 11, 2016

Inflated Hot-Jupiters by the Half-Dozen

Figure 1: Artist’s impression of a transiting planet.

Espinoza et al. (2016) present the discovery of six inflated hot-Jupiters identified as HATS-25b through HATS-30b. All six planets transit their host stars. The planets have masses between 0.5 to 0.7 times the mass of Jupiter, radii between 1.17 to 1.75 times the radius of Jupiter and orbital periods between 3.2 to 4.6 days. HATS-26b and HATS-27b stand out in having remarkably low densities of only 15.3 and 18.0 percent the density of water, respectively. All planets, with the exception of HATS-27b, appear to be good targets for future atmospheric characterisation. Nevertheless, HATS-27b is a good target for measuring the Rossiter-McLaughlin to determine its spin-orbit alignment due to the relatively high brightness and high stellar rotational velocity of its host star.

Figure 2: Mass-radius diagram for all the transiting hot-Jupiters discovered to date (grey points). Red points indicate the discovered exoplanets presented in this work. The black lines show the mass-radius relations of 4.5 billion year old planets at 0.045 AU from the Sun for core-free giant planets (solid line) and for giant planets with 100 Earth-mass cores (dashed line), which are appropriate for the insolation levels received by HATS-25b, HATS-28b, HATS-29b and HATS-30b. The blue lines show the same relations but for planets at 0.02 AU, more (but not exactly) appropriate for the insolation levels received by HATS-26b and HATS-27b. These relations imply insolation levels around 2500 times the solar insolation level at Earth, while the actual insolation levels for HATS-26b and HATS-27b are closer to 2250 and 1250 times the solar flux at Earth, respectively. Espinoza et al. (2016)

Figure 3: Equilibrium temperature-radius diagram for all the transiting hot-Jupiters discovered to date along with these six newly discovered ones. Espinoza et al. (2016)

Espinoza et al. (2016), "HATS-25b through HATS-30b: A Half-dozen New Inflated Transiting Hot Jupiters from the HATSouth Survey", arXiv:1606.00023 [astro-ph.EP