HATS-7b: A HOT SUPER NEPTUNE TRANSITING A QUIET K DWARF STAR

Journal Article · Tue Nov 10 04:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/813/2/111· OSTI ID:22862870

Bakos, G. Á.; Penev, K.; Hartman, J. D.; Zhou, G.; Val-Borro, M. de; Bhatti, W.; Csubry, Z. ^[1]; Bayliss, D.; Schmidt, B. ^[2]; Brahm, R.; Jordán, A.; Rabus, M.; Espinoza, N. ^[3]; Mancini, L.; Ciceri, S.; Henning, T. ^[4]; Howard, A. W.; Fulton, B. J. ^[5]; Buchhave, L. A. ^[6]; Isaacson, H. ^[7] ; others, and

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1. Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States)
2. Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)
3. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile)
4. Max Planck Institute for Astronomy, Heidelberg (Germany)
5. Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI (United States)
6. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
7. Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120 ± 0.012 M{sub J}, a radius of 0.563{sub −0.034}{sup +0.046} R{sub J}, and an orbital period of 3.1853 days. The host star is a moderately bright (V=13.340 ± 0.010 mag, K{sub S}=10.976 ± 0.026 mag) K dwarf star with a mass of 0.849 ± 0.027 M{sub ⊙}, a radius of 0.815{sub −0.035}{sup +0.049} R{sub ⊙}, 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{sub 2}–He envelope), or 9 ± 4% (ice core and H{sub 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{sub 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{sub J}

• OSTI ID: 22862870
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 813; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPUTERIZED SIMULATION
DISTRIBUTION
DWARF STARS
HELIUM
HYDROGEN
METALLICITY
RADIAL VELOCITY
SOUTHERN HEMISPHERE
SPECTRA
STELLAR ATMOSPHERES