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HAT-P-26b: A Low-density Neptune-mass Planet Transiting a K Star

Hartman, J. D. and Bakos, G. Á. and Kipping, D. M. and Torres, G. and Kovács, G. and Noyes, R. W. and Latham, D. W. and Howard, A. W. and Fischer, D. A. and Johnson, J. A. and Marcy, G. W. and Isaacson, H. and Quinn, S. N. and Buchhave, L. A. and Béky, B. and Sasselov, D. D. and Stefanik, R. P. and Esquerdo, G. A. and Everett, M. and Perumpilly, G. and Lázár, J. and Papp, I. and Sári, P. (2011) HAT-P-26b: A Low-density Neptune-mass Planet Transiting a K Star. Astrophysical Journal, 728 (2). Art. No. 138. ISSN 0004-637X.

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We report the discovery of HAT-P-26b, a transiting extrasolar planet orbiting the moderately bright V = 11.744 K1 dwarf star GSC 0320–01027, with a period P = 4.234516 ± 0.000015 days, transit epoch T_c = 2455304.65122 ± 0.00035 (BJD; Barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time (UTC)), and transit duration 0.1023 ± 0.0010 days. The host star has a mass of 0.82 ± 0.03 M_⊙ , radius of 0.79^(+0.10)_(–0.04) R_⊙ , effective temperature 5079 ± 88 K, and metallicity [Fe/H] = -0.04 ± 0.08. The planetary companion has a mass of 0.059 ± 0.007 M_J, and radius of 0.565^(+0.072)_(–0.032) R_J yielding a mean density of 0.40 ± 0.10 g cm^(-3). HAT-P-26b is the fourth Neptune-mass transiting planet discovered to date. It has a mass that is comparable to those of Neptune and Uranus, and slightly smaller than those of the other transiting Super-Neptunes, but a radius that is ~65% larger than those of Neptune and Uranus, and also larger than those of the other transiting Super-Neptunes. HAT-P-26b is consistent with theoretical models of an irradiated Neptune-mass planet with a 10 M_⊕ heavy element core that comprises ≳50% of its mass with the remainder contained in a significant hydrogen-helium envelope, though the exact composition is uncertain as there are significant differences between various theoretical models at the Neptune-mass regime. The equatorial declination of the star makes it easily accessible to both Northern and Southern ground-based facilities for follow-up observations.

Item Type:Article
Related URLs:
URLURL TypeDescription
Hartman, J. D.0000-0001-8732-6166
Bakos, G. Á.0000-0001-7204-6727
Torres, G.0000-0002-5286-0251
Latham, D. W.0000-0001-9911-7388
Howard, A. W.0000-0001-8638-0320
Fischer, D. A.0000-0003-2221-0861
Johnson, J. A.0000-0001-9808-7172
Marcy, G. W.0000-0002-2909-0113
Isaacson, H.0000-0002-0531-1073
Quinn, S. N.0000-0002-8964-8377
Buchhave, L. A.0000-0003-1605-5666
Sasselov, D. D.0000-0001-7014-1771
Esquerdo, G. A.0000-0002-9789-5474
Everett, M.0000-0002-0885-7215
Additional Information:© 2011 American Astronomical Society. Received 2010 October 4; accepted 2010 December 14; published 2011 January 31. Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NASA (N018Hr and N167Hr). HATNet operations have been funded by NASA grants NNG04GN74G, NNX08AF23G, and SAO IR&D. Work of G. Á .B. and J.A.J. were supported by the Postdoctoral Fellowship of the NSF Astronomy and Astrophysics Program (AST-0702843 and AST-0702821, respectively). G.T. acknowledges partial support from NASA grant NNX09AF59G. We acknowledge partial support also from the Kepler Mission under NASA Cooperative Agreement NCC2-1390 (PI: D.W.L.). G.K. thanks the Hungarian Scientific Research Foundation (OTKA) for support through grant K-81373. This research has made use of Keck telescope time granted through NASA (N018Hr and N167Hr).
Funding AgencyGrant Number
NSF Astronomy and Astrophysics FellowshipAST-0702843
NSF Astronomy and Astrophysics FellowshipAST-0702821
Hungarian Scientific Research Fund (OTKA)K-81373
Subject Keywords:planetary systems; stars: individual (HAT-P-26, GSC 0320-01027); techniques: photometric; techniques: spectroscopic
Issue or Number:2
Classification Code:PACS: 97.82.-j; 95.85.Kr; 97.20.Jg; 95.10.Gi
Record Number:CaltechAUTHORS:20110322-091236708
Persistent URL:
Official Citation:HAT-P-26b: A Low-density Neptune-mass Planet Transiting a K Star J. D. Hartman , G. Á. Bakos , D. M. Kipping , G. Torres , G. Kovács , R. W. Noyes , D. W. Latham , A. W. Howard , D. A. Fischer , J. A. Johnson , G. W. Marcy , H. Isaacson , S. N. Quinn , L. A. Buchhave , B. Béky , D. D. Sasselov , R. P. Stefanik , G. A. Esquerdo , M. Everett , G. Perumpilly , J. Lázár , I. Papp and P. Sári 2011 ApJ 728 138 doi: 10.1088/0004-637X/728/2/138
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23033
Deposited By: Ruth Sustaita
Deposited On:23 Mar 2011 15:07
Last Modified:09 Mar 2020 13:19

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