HAT-P-12b: A LOW-DENSITY SUB-SATURN MASS PLANET TRANSITING A METAL-POOR K DWARF

Abstract

We report on the discovery of HAT-P-12b, a transiting extrasolar planet orbiting the moderately bright V ≈ 12.8 K4 dwarf GSC 03033−00706, with a period P = 3.2130598 ± 0. 05. We find a slight correlation between the observed spectral line bisector spans and the radial velocity, so we consider, and rule out, various blend configurations including a blend with a background eclipsing binary, and hierarchical triple systems where the eclipsing body is a star or a planet. We conclude that a model consisting of a single star with a transiting planet best fits the observations, and show that a likely explanation for the apparent correlation is contamination from scattered moonlight. Based on this model, the planetary companion has a mass of 0.211 ± 0.012 M J and radius of 0.959 +0.029 −0.021 R J yielding a mean density of 0.295 ± 0.025 g cm −3 . Comparing these observations with recent theoretical models, we find that HAT-P-12b is consistent with a ∼1-4.5 Gyr, mildly irradiated, H/He-dominated planet with a core mass M C 10 M ⊕ . HAT-P-12b is thus the least massive H/He-dominated gas giant planet found to date. This record was previously held by Saturn.

Exoplanet Transits Registered at the Universidad de Monterrey Observatory. I. HAT-P-12b, HAT-P-13b, HAT-P-16b, HAT-P-23b, and WASP-10b

“…Our observations also show that the host star did not vary in brightness with respect to the comparison stars when out of transit, which lends confidence to combining the individual light curves. For the calculation of the period and epoch we used, aside from our six observations, four mid-transit times of Hartman et al (2009; as presented by Lee et al 2012), three from Lee et al (2012) and one from Sada et al (2012). Our result (P = 3.2130589 ± 0.0000003 days and T c = 2454419.19584 ± 0.00009 BJD_TDB) agrees with the one obtained by Lee et al (2012) and with the one by Todorov et al (2013), both of which also included reanalyzed amateur light curves from the ETD website.…”

HAT-P-34b-HAT-P-37b: FOUR TRANSITING PLANETS MORE MASSIVE THAN JUPITER ORBITING MODERATELY BRIGHT STARS

“…A bisector (BS) analysis for each system based on the Keck and TRES spectra was done as described in Section 5 of Bakos et al (2007a). For HAT-P-35, which is relatively faint, we found that the measured BSs were significantly affected by scattered moonlight and applied an empirical correction for this effect following Hartman et al (2009;see also Kovács et al 2010). For HAT-P-34 the BS scatter is fairly high (∼25 m s −1 ), but this is in line with the high RV jitter (∼60 m s −1 ), which is typical of an F star with v sin i = 24.0 ± 0.5 km s −1 (Saar et al 2003;Hartman et al 2011b).…”

WASP-21b: a hot-Saturn exoplanet transiting a thick disc star

“…Figure 5 shows the mass-radius diagram of known gas-giant transiting exoplanets (with a mass of more than 0.1 M Jup ). WASP-21b is one of the only five transiting gas-giant planets with a mass below 0.4 M Jup including HAT-P-12b (Hartman et al 2009), HD 149026b (Sato et al 2005), CoRoT-8b (Bordé et al 2010) and WASP-29b (Hellier et al 2010). Figure 6 shows the density histogram of transiting gas-giant planets with a mass between 0.2 and 1.5 Jupiter masses (totaling 50 exoplanets).…”