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Register a new userFrom dense hot Jupiter to low-density Neptune: The discovery of WASP-127b, WASP-136b and WASP-138b
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Added by
Kristine Wai Fun Lam
Publication date
2016
fields
Physics
and research's language is
English
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We report three newly discovered exoplanets from the SuperWASP survey. WASP-127b is a heavily inflated super-Neptune of mass 0.18 +/- 0.02 M_J and radius 1.37 +/- 0.04 R_J. This is one of the least massive planets discovered by the WASP project. It orbits a bright host star (Vmag = 10.16) of spectral type G5 with a period of 4.17 days. WASP-127b is a low-density planet that has an extended atmosphere with a scale height of 2500 +/- 400 km, making it an ideal candidate for transmission spectroscopy. WASP-136b and WASP-138b are both hot Jupiters with mass and radii of 1.51 +/- 0.08 M_J and 1.38 +/- 0.16 R_J, and 1.22 +/- 0.08 M_J and 1.09 +/- 0.05 R_J, respectively. WASP-136b is in a 5.22-day orbit around an F9 subgiant star with a mass of 1.41 +/- 0.07 M_sun and a radius of 2.21 +/- 0.22 R_sun. The discovery of WASP-136b could help constrain the characteristics of the giant planet population around evolved stars. WASP-138b orbits an F7 star with a period of 3.63 days. Its radius agrees with theoretical values from standard models, suggesting the presence of a heavy element core with a mass of ~10 M_earth. The discovery of these new planets helps in exploring the diverse compositional range of short-period planets, and will aid our understanding of the physical characteristics of both gas giants and low-density planets.
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We report the discovery of WASP-190b, an exoplanet on a 5.37-day orbit around a mildly-evolved F6 IV-V star with V = 11.7, T_eff = 6400 $pm$ 100 K, M$_{*}$ = 1.35 $pm$ 0.05 M_sun and R$_{*}$ = 1.6 $pm$ 0.1 R_sun. The planet has a radius of R_p = 1.15 $pm$ 0.09 R_Jup and a mass of M_p = 1.0 $pm$ 0.1 M_Jup, making it a mildly inflated hot Jupiter. It is the first hot Jupiter confirmed via Doppler tomography with an orbital period >5 days. The orbit is also marginally misaligned with respect to the stellar rotation, with $lambda$ = 21 $pm$ 6$^{circ}$ measured using Doppler tomography.
We report on four new transiting hot Jupiters discovered by the WASP-South survey. WASP-178b transits a V = 9.9, A1V star with Teff = 9350 +/- 150 K, the second-hottest transit host known. It has a highly bloated radius of 1.81 +/- 0.09 Rjup, in line with the known correlation between high irradiation and large size. With an estimated temperature of 2470 +/- 60 K, the planet is one of the best targets for studying ultra-hot Jupiters that is visible from the Southern hemisphere. The three host stars WASP-184, WASP-185 and WASP-192 are all post-main-sequence G0 stars of ages 4-8 Gyr. The larger stellar radii (1.3-1.7 Msun) mean that the transits are relatively shallow (0.7-0.9%) even though the planets have moderately inflated radii of 1.2-1.3 Rjup. WASP-185b has an eccentric orbit (e = 0.24) and a relatively long orbital period of 9.4 d. A star that is 4.6 arcsec from WASP-185 and 4.4 mag fainter might be physically associated.
We report the discovery of two transiting exoplanets from the WASP survey, WASP-150b and WASP-176b. WASP-150b is an eccentric ($e$ = 0.38) hot Jupiter on a 5.6 day orbit around a $V$ = 12.03, F8 main-sequence host. The host star has a mass and radius of 1.4 $rm M_{odot}$ and 1.7 $rm R_{odot}$ respectively. WASP-150b has a mass and radius of 8.5 $rm M_J$ and 1.1 $rm R_J$, leading to a large planetary bulk density of 6.4 $rm rho_J$. WASP-150b is found to be $sim3$ Gyr old, well below its circularisation timescale, supporting the eccentric nature of the planet. WASP-176b is a hot Jupiter planet on a 3.9 day orbit around a $V$ = 12.01, F9 sub-giant host. The host star has a mass and radius of 1.3 $rm M_{odot}$ and 1.9 $rm R_{odot}$. WASP-176b has a mass and radius of 0.86 $rm M_J$ and 1.5 $rm R_J$ respectively, leading to a planetary bulk density of 0.23 $rm rho_J$.
We report the discovery by WASP of five planets orbiting moderately bright ($V$ = 11.0-12.9) Solar-type stars. WASP-137b, WASP-143b and WASP-146b are typical hot Jupiters in orbits of 3-4 d and with masses in the range 0.68--1.11 $M_{rm Jup}$. WASP-134 is a metal-rich ([Fe/H] = +0.40 $pm$ 0.07]) G4 star orbited by two warm Jupiters: WASP-134b ($M_{rm pl}$ = 1.41 $M_{rm Jup}$; $P = 10.1$ d; $e = 0.15 pm 0.01$; $T_{rm eql}$ = 950 K) and WASP-134c ($M_{rm pl} sin i$ = 0.70 $M_{rm Jup}$; $P = 70.0$ d; $e = 0.17 pm 0.09$; $T_{rm eql}$ = 500 K). From observations of the Rossiter-McLaughlin effect of WASP-134b, we find its orbit to be misaligned with the spin of its star ($lambda = -44 pm 10^circ$). WASP-134 is a rare example of a system with a short-period giant planet and a nearby giant companion. In-situ formation or disc migration seem more likely explanations for such systems than does high-eccentricity migration.
We present three newly discovered sub-Jupiter mass planets from the SuperWASP survey: WASP-54b is a heavily bloated planet of mass 0.636$^{+0.025}_{-0.024}$ mj and radius 1.653$^{+0.090}_{-0.083}$ rj. It orbits a F9 star, evolving off the main sequence, every 3.69 days. Our MCMC fit of the system yields a slightly eccentric orbit ($e=0.067^{+0.033}_{-0.025}$) for WASP-54b. We investigated further the veracity of our detection of the eccentric orbit for WASP-54b, and we find that it could be real. However, given the brightness of WASP-54 V=10.42 magnitudes, we encourage observations of a secondary eclipse to draw robust conclusions on both the orbital eccentricity and the thermal structure of the planet. WASP-56b and WASP-57b have masses of 0.571$^{+0.034}_{-0.035}$ mj and $0.672^{+0.049}_{-0.046}$ mj, respectively; and radii of $1.092^{+0.035}_{-0.033}$ rj for WASP-56b and $0.916^{+0.017}_{-0.014}$ rj for WASP-57b. They orbit main sequence stars of spectral type G6 every 4.67 and 2.84 days, respectively. WASP-56b and WASP-57b show no radius anomaly and a high density possibly implying a large core of heavy elements; possibly as high as $sim$50 M$_{oplus}$ in the case of WASP-57b. However, the composition of the deep interior of exoplanets remain still undetermined. Thus, more exoplanet discoveries such as the ones presented in this paper, are needed to understand and constrain giant planets physical properties.
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