Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit timing measurements spanning more than a decade have revealed that the orbital period is decreasing at a rate of dP/dt ≈ 10 −9 , corresponding to a reduced tidal quality factor of about 2 × 10 5 . Here, we present a compilation of transit-timing data for WASP-12 and eleven other systems which are especially favorable for detecting orbital decay: 19, 43, 72, 103, 114, and 122; HAT-P-23; HATS-18; and OGLE-TR-56. For most of these systems we present new data that extend the time baseline over which observations have been performed. None of the systems besides WASP-12 displays convincing evidence for period changes, with typical upper limits on dP/dt on the order of 10 −9 or 10 −10 , and lower limits on the reduced tidal quality factor on the order of 10 5 . One possible exception is WASP-19, which shows a statistically significant trend, although it may be a spurious effect of starspot activity. Further observations are encouraged.

We present optical (g ′ , R c , and I c ) to near-infrared (J) simultaneous photometric observations for a primary transit of GJ3470b, a Uranus-mass transiting planet around a nearby M dwarf, by using the 50-cm MITSuME telescope and the 188-cm telescope both at Okayama Astrophysical Observatory. From these data, we derive the planetary mass, radius, and density as 14.1 ± 1.3 M ⊕ , 4.32 +0.21 −0.10 R ⊕ , and 0.94 ± 0.12 g cm −3 , respectively, thus confirming the low density that was reported by Demory et al. based on the Spitzer/IRAC 4.5-µm photometry (0.72 +0.13 −0.12 g cm −3 ). Although the planetary radius is about 10% smaller than that reported by Demory et al., this difference does not alter their conclusion that the planet possesses a hydrogen-rich envelope whose mass is approximately 10% of the planetary total mass. On the other hand, we find that the planet-to-star radius ratio (R p /R s ) in the J band (0.07577 +0.00072 −0.00075 ) is smaller than that in the I c (0.0802 ± 0.0013) and 4.5-µm (0.07806 +0.00052 −0.00054 ) bands by 5.8% ± 2.0% and 2.9% ± 1.1%, respectively. A plausible explanation for the differences is that the planetary atmospheric opacity varies with wavelength due to absorption and/or scattering by atmospheric molecules. Although the significance of the observed R p /R s variations is low, if confirmed, this fact would suggest that GJ3470b does not have a thick cloud layer in the atmosphere. This property would offer a wealth of opportunity for future transmission-spectroscopic observations of this planet to search for certain molecular features, such as H 2 O, CH 4 , and CO, without being prevented by clouds. Subject headings: planetary systems -planets and satellites: atmosphere -planets and satellites:individual(GJ3470b) -stars: individual(GJ3470) -techniques: photometric

We present 5 new transit light curves of GJ 1214b taken in BJHK s -bands. Two transits were observed in B-band using the Suprime-Cam and the FOCAS instruments onboard the Subaru 8.2m telescope, and one transit was done in JHK s -bands simultaneously with the SIRIUS camera on the IRSF 1.4m telescope. MCMC analyses show that the planet-to-star radius ratios are,R p /R s = 0.11654±0.00080 (J-band, IRSF/SIRIUS), R p /R s = 0.11550 +0.00142 −0.00153 (H-band, IRSF/SIRIUS), and R p /R s = 0.11547 ± 0.00127 (K s -band, IRSF/SIRIUS). The Subaru Suprime-Cam transit photometry shows a possible spot-crossing feature. Comparisons of the new transit depths and those from previous studies with the theoretical models by Howe & Burrows (2012) suggest that the high molecular weight atmosphere (e.g., 1% H 2 O + 99% N 2 ) models are most likely, however, the low molecular weight (hydrogen

We present the discovery of three small planets transiting K2-136 (LP 358 348, EPIC 247589423), a late K dwarf in the Hyades. The planets have orbital periods of 7.9757±0.0011, 17.30681 0.00036 0.00034 -+ , and 25.5715 days 0.0040 0.0038 -+ , and radii of 1.05±0.16, 3.14±0.36, and R 1.55 0.21 0.24 -+ Å , respectively. With an age of 600-800 Myr, these planets are some of the smallest and youngest transiting planets known. Due to the relatively bright (J=9.1) host star, the planets are compelling targets for future characterization via radial velocity mass measurements and transmission spectroscopy. As the first known star with multiple transiting planets in a cluster, the system should be helpful for testing theories of planet formation and migration.

No abstract