We report g, V, and r photometric time series of HD 149026 spanning predicted times of transit of the Saturn-mass planetary companion, which was recently discovered by Sato and collaborators. We present a joint analysis of our observations and the previously reported photometry and radial velocities of the central star. We refine the estimate of the transit ephemeris to T c = (2,453,527.87455-0.00091+0.00085) + (2.87598-0.00017+0.00012)N (HJD). Assuming that the star has a radius of 1.45 ± 0.10 R⊙ and a mass of 1.30 ±, 0.10 M⊙ we estimate the planet radius to be (0.726 ± 0.064)RJup, which implies a mean density of 1.07 -0.30+0.42 g cm-3. This density is significantly greater than predicted for models that include the effects of stellar insolation and in which the planet has only a small core of solid material. Thus, we confirm that this planet likely contains a large core and that the ratio of core mass to total planet mass is more akin to that of Uranus and Neptune than to either Jupiter or Saturn.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Planetary systems
- Stars: individual (HD 149026)
- Techniques: photometric Online material: machine-readable table