A Caltech Library Service

KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a Mid-F Star

Siverd, Robert J. and Crepp, Justin R. and Fulton, Benjamin J. (2012) KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a Mid-F Star. Astrophysical Journal, 761 (2). Art. No. 123. ISSN 0004-637X.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) transit survey. A joint analysis of the spectroscopic, radial velocity, and photometric data indicates that the V = 10.7 primary is a mildly evolved mid-F star with T eff = 6516 ± 49 K, log g = 4.228^(+0.014)_(–0.021), and [Fe/H] = 0.052 ± 0.079, with an inferred mass M_* = 1.335 ± 0.063 M_☉ and radius R_* = 1.471^(+0.045)_(–0.035) R_☉. The companion is a low-mass brown dwarf or a super-massive planet with mass M_P = 27.38 ± 0.93 M_(Jup) and radius R_P = 1.116^(+0.038)_(–0.029) R_(Jup). The companion is on a very short (~29 hr) period circular orbit, with an ephemeris T_c (BJD_(TDB)) = 2455909.29280 ± 0.00023 and P = 1.217501 ± 0.000018 days. KELT-1b receives a large amount of stellar insolation, resulting in an estimated equilibrium temperature assuming zero albedo and perfect redistribution of T_(eq) = 2423^(+34)_(–27) K. Comparison with standard evolutionary models suggests that the radius of KELT-1b is likely to be significantly inflated. Adaptive optics imaging reveals a candidate stellar companion to KELT-1 with a separation of 588 ± 1 mas, which is consistent with an M dwarf if it is at the same distance as the primary. Rossiter-McLaughlin measurements during transit imply a projected spin-orbit alignment angle λ = 2 ± 16 deg, consistent with a zero obliquity for KELT-1. Finally, the v sin I_* = 56 ± 2 km ^(s–1) of the primary is consistent at ~2σ with tidal synchronization. Given the extreme parameters of the KELT-1 system, we expect it to provide an important testbed for theories of the emplacement and evolution of short-period companions, as well as theories of tidal dissipation and irradiated brown dwarf atmospheres.

Item Type:Article
Related URLs:
URLURL TypeDescription
Siverd, Robert J.0000-0001-5016-3359
Crepp, Justin R.0000-0003-0800-0593
Fulton, Benjamin J.0000-0003-3504-5316
Additional Information:© 2012 American Astronomical Society. Received 2012 June 6; accepted 2012 October 26; published 2012 December 4. We particularly thank Bruce Gary for acquiring and reducing the data from HAO, Saurav Dhital for estimating the chance probability of a close companion, and Bence Beky and the HATNet team for giving up one night on the FLWO 1.2 m on short notice. We thank Subo Dong, Jonathan Fortney, Fred Rasio, and Aristotle Socrates for useful discussions. We thank the referee, John Southworth, for a prompt and helpful report. Earlywork on KELT-North was supported by NASA Grant NNG04GO70G. Work by B.S.G., J.D.E., and T.G.B. was partially supported by NSF CAREER Grant AST-1056524. E.L.N.J. thanks Chris Capron and Peng Zhao for help with these observations, and gratefully acknowledges the support of the National Science Foundation’s PREST program, which helped to establish the Peter van de Kamp Observatory through grant AST-0721386. K.A.C. was supported by a NASA Kentucky Space Grant Consortium Graduate Fellowship. J.A.P. and K.G.S. acknowledge support from the Vanderbilt Office of the Provost through the Vanderbilt Initiative in Data-intensive Astrophysics. K.G.S. and L.H. acknowledge the support of the National Science Foundation through PAARE grant AST-0849736 and AAG grant AST-1009810. The TRES and KeplerCam observations were obtained with partial support from the Kepler Mission through NASA Cooperative Agreement NNX11AB99A with the Smithsonian Astrophysical Observatory, PI: D.W.L. This work has made use of NASA’s Astrophysics Data System, the Exoplanet Orbit Database at, and the Extrasolar Planet Encyclopedia at (Schneider et al. 2011).
Funding AgencyGrant Number
Kentucky Space Grant ConsortiumUNSPECIFIED
Vanderbilt Initiative in Data-Intensive Astrophysics (VIDA)UNSPECIFIED
Subject Keywords:planetary systems; stars: individual: KELT-1, TYC 2785-2130-1; techniques: photometric; techniques: spectroscopic
Issue or Number:2
Record Number:CaltechAUTHORS:20130111-100335969
Persistent URL:
Official Citation:KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a Mid-F Star Robert J. Siverd et al. 2012 ApJ 761 123
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36316
Deposited By: Ruth Sustaita
Deposited On:11 Jan 2013 18:39
Last Modified:09 Mar 2020 13:19

Repository Staff Only: item control page