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Register a new userHATS-8b: A Low-Density Transiting Super-Neptune
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HATS-8b is a low density transiting super-Neptune discovered as part of the HATSouth project. The planet orbits its solar-like G dwarf host (V=14.03 $pm$ 0.10 and T$_{eff}$ =5679 $pm$ 50 K) with a period of 3.5839 d. HATS-8b is the third lowest mass transiting exoplanet to be discovered from a wide-field ground based search, and with a mass of 0.138 $pm$ 0.019 M$_J$ it is approximately half-way between the masses of Neptune and Saturn. However HATS-8b has a radius of 0.873 (+0.123,-0.075) R$_J$, resulting in a bulk density of just 0.259 $pm$ 0.091 g.cm$^{-3}$. The metallicity of the host star is super-Solar ([Fe/H]=0.210 $pm$ 0.080), arguing against the idea that low density exoplanets form from metal-poor environments. The low density and large radius of HATS-8b results in an atmospheric scale height of almost 1000 km, and in addition to this there is an excellent reference star of near equal magnitude at just 19 arcsecond separation on the sky. These factors make HATS-8b an exciting target for future atmospheric characterization studies, particularly for long-slit transmission spectroscopy.
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IW ../submit_V2/abstract.txt ( Row 1 Col 1 6:48 Ctrl-K H for help We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120+/-0.012MJ, a radius of 0.563+/-(0.046,0.034)RJ, and an orbital period of 3.1853days. The host star is a moderately bright (V=13.340+/-0.010mag, K_S=10.976+/-0.026mag) K dwarf star with a mass of 0.849+/-0.027Msun , a radius of 0.815+/-(0.049,-0.035)Rsun, and a metallicity of [Fe/H]=+0.250+/-0.080. The star is photometrically quiet to within the precision of the HATSouth measurements and has low RV jitter. HATS-7b is the second smallest radius planet discovered by a wide-field ground-based transit survey, and one of only a handful of Neptune-size planets with mass and radius determined to 10% precision. Theoretical modeling of HATS-7b yields a hydrogen-helium fraction of 18+/-4% (rock-iron core and H2-He envelope), or 9+/-4% (ice core and H2-He envelope), i.e.it has a composition broadly similar to that of Uranus and Neptune, and very different from that of Saturn, which has 75% of its mass in H2-He. Based on a sample of transiting exoplanets with accurately (<20%) determined parameters, we establish approximate power-law relations for the envelopes of the mass-density distribution of exoplanets. HATS-7b, which, together with the recently discovered HATS-8b, is one of the first two transiting super-Neptunes discovered in the Southern sky, is a prime target for additional follow-up observations with Southern hemisphere facilities to characterize the atmospheres of Super-Neptunes (which we define as objects with mass greater than that of Neptune, and smaller than halfway between that of Neptune and Saturn, i.e. 0.054 MJ<Mp<0.18 MJ).
We present results for the inflated super-Neptune HATS-8b from MOPSS, The Michigan Optical Planetary Spectra Survey. This program is aimed at creating a database of optical planetary transmission spectra all observed, reduced, and analyzed with a uniform method for the benefit of enabling comparative exoplanet studies. HATS-8b orbits a G dwarf and is a low density super-Neptune, with a radius of 0.873 R$_{Jup}$, a mass of 0.138 M$_{Jup}$, and a density of 0.259 g/cm$^3$. Two transits of HATS-8b were observed in July and August of 2017 with the IMACS instrument on the Magellan Baade 6.5m telescope. We find an enhanced scattering slope that differs between our two nights. These slopes are stronger than one due only to Rayleigh scattering and cannot be fully explained by unocculted star spots. We explore the impact of condensates on the scattering slope and determine that MnS particulates smaller than 10$^{-2}mu$m can explain up to 80% of our measured slope if the planet is warmer than equilibrium, or 50% of the slope at the equilibrium temperature of the planet for a low mean molecular weight atmosphere. The scattering slope that we observe is thus beyond even the most extreme case predicted by theory. We suggest further follow up on this target and host star to determine if the temporal variation of the slope is primarily due to stellar or planetary effects, and to better understand what these effects may be.
We report the discovery of four transiting hot Jupiters from the HATSouth survey: HATS-39b, HATS-40b, HATS41b and HATS-42b. These discoveries add to the growing number of transiting planets orbiting moderately bright (12.5 < V < 13.7) F dwarf stars on short (2-5 day) periods. The planets have similar radii, ranging from 1.33(+0.29/-0.20) R_J for HATS-41b to 1.58(+0.16/-0.12) R_J for HATS-40b. Their masses and bulk densities, however, span more than an order of magnitude. HATS-39b has a mass of 0.63 +/- 0.13 M_J, and an inflated radius of 1.57 +/- 0.12 R_J, making it a good target for future transmission spectroscopic studies. HATS-41b is a very massive 9.7 +/- 1.6 M_J planet and one of only a few hot Jupiters found to date with a mass over 5 M_J. This planet orbits the highest metallicity star ([Fe/H] = 0.470 +/- 0.010) known to host a transiting planet and is also likely on an eccentric orbit. The high mass, coupled with a relatively young age (1.34 +0.31/-0.51 Gyr) for the host star, are factors that may explain why this planets orbit has not yet circularised.
We report the discovery of four short period extrasolar planets transiting moderately bright stars from photometric measurements of the HATSouth network coupled to additional spectroscopic and photometric follow-up observations. While the planet masses range from 0.26 to 0.90 M$_J$, the radii are all approximately a Jupiter radii, resulting in a wide range of bulk densities. The orbital period of the planets range from 2.7d to 4.7d, with HATS-43b having an orbit that appears to be marginally non-circular (e= 0.173$pm$0.089). HATS-44 is notable for a high metallicity ([Fe/H]= 0.320$pm$0.071). The host stars spectral types range from late F to early K, and all of them are moderately bright (13.3<V<14.4), allowing the execution of future detailed follow-up observations. HATS-43b and HATS-46b, with expected transmission signals of 2350 ppm and 1500 ppm, respectively, are particularly well suited targets for atmospheric characterisation via transmission spectroscopy.
We report the discovery of three moderately high-mass transiting hot Jupiters from the HATSouth survey: HATS-22b, HATS-23b and HATS-24b. These planets add to the numbers of known planets in the ~2MJ regime. HATS-22b is a 2.74+/-0.11 MJ mass and 0.953+0.048/-0.029 RJ radius planet orbiting a V = 13.455 +/- 0.040 sub-silar mass (M_star = 0.759+/-0.019 M_sun; R_star = 0.759+/-0.019 R_sun) K-dwarf host star on an eccentric (e = 0.079 +/- 0.026) orbit. This planets high planet-to-stellar mass ratio is further evidence that migration mechanisms for hot Jupiters may rely on exciting orbital eccentricities that bring planets closer to their parent stars followed by tidal circularisation. HATS-23b is a 1.478 +/- 0.080 MJ mass and 1.69 +/- 0.24 RJ radius planet on a grazing orbit around a V = 13.901 +/- 0.010 G-dwarf with properties very similar to those of the Sun (M_star = 1.115 +/- 0.054 M_sun; R_star = 1.145 +/- 0.070 R_sun). HATS-24b orbits a moderately bright V = 12.830 +/- 0.010 F-dwarf star (M_star = 1.218 +/- 0.036 M_sun; R_star = 1.194+0.066/-0.041 R_sun). This planet has a mass of 2.39 +0.21/-0.12 MJ and an inflated radius of 1.516 +0.085/-0.065 RJ.
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