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HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star

Bakos, G. Á. and Howard, A. W. and Fulton, B. J. (2015) HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star. Astrophysical Journal, 813 (2). Art. No. 111. ISSN 0004-637X.

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We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120 ± 0.012 M_J, a radius of 0.563_(-0.034)^(+0.046) R_J, and an orbital period of 3.1853 days. The host star is a moderately bright (V = 13.340 ± 0.010 mag, K_S = 10.976 ± 0.026 mag) K dwarf star with a mass of 0.849 ± 0.027 M_⊙, a radius of 0.815_(-0.035)^(+0.049) R_⊙, and a metallicity of [Fe/H] = + 0.250 ± 0.080. The star is photometrically quiet to within the precision of the HATSouth measurements, has low RV jitter, and shows no evidence for chromospheric activity in its spectrum. 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 H_2–He envelope), or 9 ± 4% (ice core and H_2–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 H_2–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 M_J < M_p < 0.18 M_J).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Bakos, G. Á.0000-0001-7204-6727
Howard, A. W.0000-0001-8638-0320
Fulton, B. J.0000-0003-3504-5316
Additional Information:© 2015. The American Astronomical Society. Received 2015 July 3. Accepted 2015 September 14. Published 2015 November 4. Development of the HATSouth project was funded by NSF MRI grant NSF/AST-0723074, operations have been supported by NASA grants NNX09AB29G and NNX12AH91H, and follow-up observations received partial support from grant NSF/AST-1108686. A.J. acknowledges support from FONDECYT project 1130857, BASAL CATA PFB-06, and project IC120009 "Millennium Institute of Astrophysics (MAS)" of the Millenium Science Initiative, Chilean Ministry of Economy. R.B. and N.E. are supported by CONICYT-PCHA/Doctorado Nacional. R.B. and N.E. acknowledge additional support from project IC120009 "Millenium Institute of Astrophysics (MAS)" of the Millennium Science Initiative, Chilean Ministry of Economy. V.S. acknowledges support form BASAL CATA PFB-06. This work is based on observations made with ESO Telescopes at the La Silla Observatory. This paper also uses observations obtained with facilities of the Las Cumbres Observatory Global Telescope. Work at the Australian National University is supported by ARC Laureate Fellowship Grant FL0992131. We acknowledge the use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund, and the SIMBAD database, operated at CDS, Strasbourg, France. Operations at the MPG 2.2 m Telescope are jointly performed by the Max Planck Gesellschaft and the European Southern Observatory. The imaging system GROND has been built by the high-energy group of MPE in collaboration with the LSW Tautenburg and ESO. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. G. Á. B. wishes to thank the warm hospitality of Adèle and Joachim Cranz at the farm Isabis, supporting the operations and service missions of HATSouth.
Funding AgencyGrant Number
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1130857
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Australian Research CouncilFL0992131
Robert Martin Ayers Sciences FundUNSPECIFIED
Subject Keywords:stars: individual (HATS-7) ; techniques: photometric; techniques: radial velocities; techniques: spectroscopic
Issue or Number:2
Record Number:CaltechAUTHORS:20170620-080018077
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Official Citation:G. Á. Bakos et al 2015 ApJ 813 111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78357
Deposited By: Ruth Sustaita
Deposited On:20 Jun 2017 15:30
Last Modified:09 Mar 2020 13:18

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