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Transit Light Curves with Finite Integration Time: Fisher Information Analysis

Price, Ellen M. and Rogers, Leslie A. (2014) Transit Light Curves with Finite Integration Time: Fisher Information Analysis. Astrophysical Journal, 794 (1). Art. No. 92. ISSN 0004-637X.

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Kepler has revolutionized the study of transiting planets with its unprecedented photometric precision on more than 150,000 target stars. Most of the transiting planet candidates detected by Kepler have been observed as long-cadence targets with 30 minute integration times, and the upcoming Transiting Exoplanet Survey Satellite will record full frame images with a similar integration time. Integrations of 30 minutes affect the transit shape, particularly for small planets and in cases of low signal to noise. Using the Fisher information matrix technique, we derive analytic approximations for the variances and covariances on the transit parameters obtained from fitting light curve photometry collected with a finite integration time. We find that binning the light curve can significantly increase the uncertainties and covariances on the inferred parameters when comparing scenarios with constant total signal to noise (constant total integration time in the absence of read noise). Uncertainties on the transit ingress/egress time increase by a factor of 34 for Earth-size planets and 3.4 for Jupiter-size planets around Sun-like stars for integration times of 30 minutes compared to instantaneously sampled light curves. Similarly, uncertainties on the mid-transit time for Earth and Jupiter-size planets increase by factors of 3.9 and 1.4. Uncertainties on the transit depth are largely unaffected by finite integration times. While correlations among the transit depth, ingress duration, and transit duration all increase in magnitude with longer integration times, the mid-transit time remains uncorrelated with the other parameters. We provide code in Python and Mathematica for predicting the variances and covariances at

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URLURL TypeDescription Paper
Rogers, Leslie A.0000-0003-0638-3455
Additional Information:© The American Astronomical Society. Received 2014 January 8; accepted 2014 August 13; published 2014 September 25. We would like to thank John Johnson of the Harvard-Smithsonian Center for Astrophysics for his valuable input on this project and for establishing the Johnson Exolab as an environment where undergraduates and postdoctoral scholars can work together on projects like this one. We would also like to thank the referee for providing a very helpful and constructive review of this work. 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 contractNAS 5-26555. The LevelScheme (Caprio 2005) scientific figure preparation system for Mathematica was used in the preparation of this paper.
Funding AgencyGrant Number
Shirley and Carl LarsonUNSPECIFIED
NASA Hubble FellowshipHF-51313.01-A
Subject Keywords:methods: analytical; occultations; planetary systems; planets and satellites: general; techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20141106-132301532
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Official Citation:Transit Light Curves with Finite Integration Time: Fisher Information Analysis Ellen M. Price and Leslie A. Rogers 2014 ApJ 794 92
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51376
Deposited By: Jason Perez
Deposited On:07 Nov 2014 00:08
Last Modified:03 Oct 2019 07:32

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