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How Low can You go? The Photoeccentric Effect for Planets of Various Sizes

Price, Ellen M. and Rogers, Leslie A. and Johnson, John Asher and Dawson, Rebekah I. (2015) How Low can You go? The Photoeccentric Effect for Planets of Various Sizes. Astrophysical Journal, 799 (1). Art. No. 17. ISSN 0004-637X.

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It is well-known that the light curve of a transiting planet contains information about the planet's orbital period and size relative to the host star. More recently, it has been demonstrated that a tight constraint on an individual planet's eccentricity can sometimes be derived from the light curve via the "photoeccentric effect," the effect of a planet's eccentricity on the shape and duration of its light curve. This has only been studied for large planets and high signal-to-noise scenarios, raising the question of how well it can be measured for smaller planets or low signal-to-noise cases. We explore the limits of the photoeccentric effect over a wide range of planet parameters. The method hinges upon measuring g directly from the light curve, where g is the ratio of the planet's speed (projected on the plane of the sky) during transit to the speed expected for a circular orbit. We find that when the signal-to-noise in the measurement of g is <10, the ability to measure eccentricity with the photoeccentric effect decreases. We develop a "rule of thumb" that for per-point relative photometric uncertainties σ = {10^(–3), 10^(–4), 10^(–5)}, the critical values of the planet-star radius ratio are R_p /R_★ ≈ {0.1, 0.05, 0.03} for Kepler-like 30 minute integration times. We demonstrate how to predict the best-case uncertainty in eccentricity that can be found with the photoeccentric effect for any light curve. This clears the path to study eccentricities of individual planets of various sizes in the Kepler sample and future transit surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Rogers, Leslie A.0000-0003-0638-3455
Johnson, John Asher0000-0001-9808-7172
Dawson, Rebekah I.0000-0001-9677-1296
Additional Information:© 2015 American Astronomical Society. Received 2014 July 10; accepted 2014 December 1; published 2015 January 12. We thank A. Pál and H. Knutson for use of their photometry data. E.M.P. acknowledges funding provided by Shirley and Carl Larson for her 2013 Carolyn Ash SURF Fellowship. L.A.R. acknowledges support provided by NASA through Hubble Fellowship grant HF-51313.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. J.A.J. is grateful for the generous grant support provided by the Alfred P. Sloan and David & Lucile Packard foundations. R.I.D. gratefully acknowledges support by the Miller Institute for Basic Research in Science at University of California, Berkeley.
Funding AgencyGrant Number
Carolyn Ash SURF FellowshipUNSPECIFIED
NASA Hubble FellowshipHF-51313.01-A
NASANAS 5-26555
Alfred P. Sloan FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
University of California Berkeley Miller Institute for Basic Research in ScienceUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords: planetary systems; techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20150227-140952698
Persistent URL:
Official Citation:How Low can You go? The Photoeccentric Effect for Planets of Various Sizes Ellen M. Price et al. 2015 ApJ 799 17
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55341
Deposited By: Ruth Sustaita
Deposited On:02 Mar 2015 16:36
Last Modified:09 Mar 2020 13:18

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