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 ± 0.10 and Teff =5679 ± 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 ± 0.019 MJ 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) RJ, resulting in a bulk density of just 0.259 ± 0.091 g.cm−3. The metallicity of the host star is super-Solar ([Fe/H]=0.210 ± 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.
@article{arxiv.1506.01334,
title = {HATS-8b: A Low-Density Transiting Super-Neptune},
author = {D. Bayliss and J. D. Hartman and G. Á. Bakos and K. Penev and G. Zhou and R. Brahm and M. Rabus and A. Jordán and L. Mancini and M. de Val-Borro and W. Bhatti and N. Espinoza and Z. Csubry and A. W. Howard and B. J. Fulton and L. A. Buchhave and T. Henning and B. Schmidt and S. Ciceri and R. W. Noyes and H. Isaacson and G. W. Marcy and V. Suc and J. Lázár and I. Papp and P. Sári},
journal= {arXiv preprint arXiv:1506.01334},
year = {2015}
}
Comments
11 pages, 7 figures, accepted for publication in AJ