A Candidate Massive Saturn Analog Orbiting HD 30177 Authors:

The Anglo-Australian Planet Search XXV: A Candidate Massive Saturn Analog Orbiting HD 30177

Authors:

Wittenmyer et al

Abstract:

We report the discovery of a second long-period giant planet orbiting HD 30177, a star previously known to host a massive Jupiter analog (HD 30177b: a=3.8±0.1 au, m sin i=9.7±0.5 Mjup). HD 30177c can be regarded as a massive Saturn analog in this system, with a=9.9±1.0 au and m sin i=7.6±3.1 Mjup. The formal best fit solution slightly favours a closer-in planet at a∼7 au, but detailed n-body dynamical simulations show that configuration to be unstable. A shallow local minimum of longer-period, lower-eccentricity solutions was found to be dynamically stable, and hence we adopt the longer period in this work. The proposed ∼32 year orbit remains incomplete; further monitoring of this and other stars is necessary to reveal the population of distant gas giant planets with orbital separations a∼10 au, analogous to that of Saturn.

Relfected Light Curves of Jupiter and Saturn like Exoplanets

Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

Authors:

Dyudina et al

Abstract:

We estimate how the light curve and total stellar heating of a planet depend on forward and backward scattering clouds. To do that, we construct light curves for Jupiter- and Saturn-like planet based on observations. We fit analytical functions to the reflected brightness of Jupiter's and Saturn's surface versus planet's phase. We use Pioneer and Cassini spacecraft images to estimate these functions. These observations cover broad bands at 0.59-0.72 microns and 0.39-0.5 microns, and narrow bands at 0.938 microns (atmospheric window), 0.889 microns (CH4 absorption band), and 0.24-0.28 microns. We simulate the images of the planets at different phases with ray-tracing model of a planet by Dyudina et al. (2005). The full-disk luminosity of these simulated images changes with planet's phase producing the full-orbit light curves. We also derive total planet's reflection integrated in all directions (spherical albedos) for Jupiter, Saturn, and for planets with Lambertian and Rayleigh-scattering atmosphere. For Jupiter, we tune the model to fit the observed full-disk brightness at several phase angles. Jupiter-like atmosphere can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo (and likely the wavelengh-integrated Bond albedo) is lower than for a Lambertian planet. Corresponding absorption of the stellar light and the planet's heating rate would be higher than for a grey Lambertian planet. Lambertian assumption can overestimate spherical albedo by up to a factor of ~ 1.5.

MOA-2010-BLG-353Lb: A Possible Saturn Revealed

MOA-2010-BLG-353Lb A Possible Saturn Revealed

Authors:

Rattenbury et al

Abstract:

We report the discovery of a possible planet in microlensing event MOA-2010-BLG-353. This event was only recognised as having a planetary signal after the microlensing event had finished, and following a systematic analysis of all archival data for binary lens microlensing events collected to date. Data for event MOA-2010-BLG-353 were only recorded by the high cadence observations of the OGLE and MOA survey groups. If we make the assumptions that the probability of the lens star hosting a planet of the measured mass ratio is independent of the lens star mass or distance, and that the source star is in the Galactic bulge, a probability density analysis indicates the planetary system comprises a 0.9^{+1.6}_{-0.53} M_{Saturn} mass planet orbiting a 0.18^{+0.32}_{-0.11} M_{sun} red dwarf star, 6.43^{+1.09}_{-1.15} kpc away. The projected separation of the planet from the host star is 1.72^{+0.56}_{-0.48} AU. Under the additional assumption that the source is on the far side of the Galactic bulge, the probability density analysis favours a lens system comprising a slightly lighter planet.

OGLE-2012-BLG-0563Lb: a Saturn-mass gas Giant Orbiting .75 AU Around a M Dwarf Star

OGLE-2012-BLG-0563Lb: a Saturn-mass Planet around an M Dwarf with the Mass Constrained by Subaru AO imaging

Authors:

Fukui et al

Abstract:

We report the discovery of a microlensing exoplanet OGLE-2012-BLG-0563Lb with the planet-star mass ratio ~1 x 10^{-3}. Intensive photometric observations of a high-magnification microlensing event allow us to detect a clear signal of the planet. Although no parallax signal is detected in the light curve, we instead succeed at detecting the flux from the host star in high-resolution JHK'-band images obtained by the Subaru/AO188 and IRCS instruments, allowing us to constrain the absolute physical parameters of the planetary system. With the help of a spectroscopic information of the source star obtained during the high-magnification state by Bensby et al. (2013), we find that the lens system is located at 1.3^{+0.6}_{-0.8} kpc from us, and consists of an M dwarf (0.34^{+0.12}_{-0.20} M_sun) orbited by a Saturn-mass planet (0.39^{+0.14}_{-0.23} M_Jup) at the projected separation of 0.74^{+0.26}_{-0.42} AU (close model) or 4.3^{+1.5}_{-2.5} AU (wide model). The probability of contamination in the host star's flux, which would reduce the masses by a factor of up to 3, is estimated to be 17%. This possibility can be tested by future high-resolution imaging. We also estimate the (J-Ks) and (H-Ks) colors of the host star, which are marginally consistent with a low-metallicity mid-to-early M dwarf, although further observations are required for the metallicity to be conclusive. This is the fifth sub-Jupiter-mass (0.2 less than m_p/M_Jup less than 1) microlensing planet around an M dwarf with the mass well constrained. The relatively rich harvest of sub-Jupiters around M dwarfs is contrasted with a possible paucity of ~1--2 Jupiter-mass planets around the same type of star, which can be explained by the planetary formation process in the core accretion scheme.

The Jupiter and Saturn Analogs Two More Gaia-like Missions Could Detect

Exo-Jupiters and Saturns from two Gaia-like missions

Author:

Høg et al

Abstract:

Detection and orbit determination for thousands of planets with periods up to about 40 years would be obtained by astrometry from two Gaia-like missions, results which cannot be obtained by any other mission, planned or proposed. A billion stars of all spectral types will be surveyed. A comprehensive knowledge about heavy planets with these periods, reaching well beyond the snow line of any system, will lead to a better understanding of the formation and evolution of planets, also in the habitable zone.