The effect of red noise on planetary transit detection

By F. Pont, S. Zucker, D. Queloz. 2006

459 citations recorded by the source corpus.

Since the discovery of short-period exoplanets a decade ago, photometric surveys have been recognized as a feasible method to detect transiting hot Jupiters. Many transit surveys are now underway, with instruments ranging from 10-cm cameras to the Hubble Space Telescope. However, the results of these surveys have been much below the expected capacity, estimated in the dozens of detections per year. One of the reasons is the presence of systematics (‘red noise’) in photometric time-series. In general, yield predictions assume uncorrelated noise (‘white noise’). In this paper, we show that the effect of red noise on the detection threshold and the expected yields cannot be neglected in typical ground-based surveys. We develop a simple method to determine the effect of red noise on photometric planetary transit detections. This method can be applied to determine detection thresholds for transit surveys. We show that the detection threshold in the presence of systematics can be much higher than that with the assumption of white noise, and obeys a different dependence on magnitude, orbital period and the parameters of the survey. Our method can also be used to estimate the significance level of a planetary transit candidate (to select promising candidates for spectroscopic follow-up). We apply our method to the OGLE planetary transit search, and show that it provides a reliable description of the actual detection threshold with real correlated noise. We point out in what way the presence of red noise could be at least partly responsible for the dearth of transiting planet detections from existing surveys, and examine some possible adaptations in survey planning and strategy. Finally, we estimate the photometric stability necessary to the detection of transiting ‘hot Neptunes’.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1ea711736e1179d3182c50e2fbd35075bb0b1e11

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In Astronomy and Astrophysics

1. Jon Fortney
2. D. Charbonneau
3. N. Madhusudhan
4. J. Southworth
5. J. Winn
6. Sara Seager
7. J. Johnson
8. A. Showman

In Instrumentation

1. Jon Fortney
2. J. Southworth
3. D. Charbonneau
4. J. Winn
5. N. Madhusudhan
6. Sara Seager
7. D. Sing
8. A. Showman

Citations in the corpus

• Hubble Space Telescope time-series photometry of the planetary transit of HD 189733: no moon, no rings, starspots (2007, methodology): “We therefore estimate the uncertainties on the transit parameters by allowing the data to move, as a whole, by a maximum of 10 − 4 in flux from the model, following the approach of Pont et al. (2006) to derive error intervals in the presence of correlated noise.”
• A Gaussian process framework for modelling instrumental systematics: application to transmission spectroscopy (2011, background): “The problem of correlated noise for observations of transiting exoplanets was first raised by Pont et al. (2006), who provided methods to estimate its effects on time series analysis, and take it into account when inferring physical properties of exoplanets from such data sets.”
• The SARS algorithm: detrending CoRoT light curves with Sysrem using simultaneous external parameters (2010, background): “The limiting factor for most planetary transit surveys is not the theoretical photon noise but rather the practicallyachieved red noise from non-astrophysical sources (Pont et al. 2006).”
• Homogeneous studies of transiting extrasolar planets – I. Light-curve analyses (2008, methodology): “A detailed investigation of how red noise affects the analysis of TEPs is given by Pont et al. (2006) To assess the effect of systematic errors on the uncertainties of the light curve parameter measurements, I have implemented into jktebop a residual-permutation (or “prayer bead”) algorithm…”
• THERMAL PHASE VARIATIONS OF WASP-12b: DEFYING PREDICTIONS (2011, unknown): “Pont et al. (2006) proposed a simple method to account for red noise by considering how the scatter in residuals decreases with bin size (bottom panels of Figures 3–5).”
• KEPLER-18b, c, AND d: A SYSTEM OF THREE PLANETS CONFIRMED BY TRANSIT TIMING VARIATIONS, LIGHT CURVE VALIDATION, WARM-SPITZER PHOTOMETRY, AND RADIAL VELOCITY MEASUREMENTS (2011, methodology): “To obtain an estimate of the correlated and systematic errors (Pont et al. 2006) in our measurements, we use the residual permutation bootstrap, or “Prayer Bead”, method as described in Désert et al. (2009).”
• A SUPER-EARTH TRANSITING A NAKED-EYE STAR (2011, background): “The factorβ is the ratio between the standard deviation of residuals binned to 15 min, and the standard deviation one would expect based on the unbinned data assuming white noise (see, e.g., Pont et al. 2006, Carter & Winn 2009).”
• Detection of atmospheric haze on an extrasolar planet: the 0.55–1.05 μm transmission spectrum of HD 189733b with the Hubble Space Telescope (2007, methodology): “The computed uncertainties take residual systematics noise into account following the prescriptions of Pont et al. (2006).”
• Misaligned spin-orbit in the XO-3 planetary system?† (2008, background): “According to Pont et al. (2006), correlated noise usually dominates the total parameter error budget for ground-based transit light curves.”
• THE FALSE POSITIVE RATE OF KEPLER AND THE OCCURRENCE OF PLANETS (2013, background): “Pont et al. (2006) have shown that time-correlated noise features in photometric time-series can produce spurious detections well over this threshold, and that this has significant implications for the yield of transit surveys.”
• SEARCH FOR CARBON MONOXIDE IN THE ATMOSPHERE OF THE TRANSITING EXOPLANET HD 189733b (2009, background): “The possible presence of correlated noise in the light curve has to be considered (Pont et al. 2006).”
• Global Climate and Atmospheric Composition of the Ultra-hot Jupiter WASP-103b from HST and Spitzer Phase Curve Observations (2018, methodology): “To account for red noise in the Spitzer 3.6µm light curve, we use the approach of Pont et al. (2006) to determine the red noise contribution on the timescale of the eclipse.”
• Hubble Space Telescope hot Jupiter transmission spectral survey: a detection of Na and strong optical absorption in HAT-P-1b (2013, methodology): “To investigate the noise in our light curves, we applied the time-averaging procedure (Pont et al. 2006; Winn et al. 2009) and binned light curve residuals in time by n data points.”
• Transits and Occultations (2010, background): “gnoring the correlations leads to false precision in the derived parameters, but accounting for correlations is not straightforward and can be computationally intensive. Some suggestions are given by Pont et al. (2006) and Carter & Winn (2009a). The treatment of stellar limb darkening presents a”
• TRANSIT DETECTION IN THE MEarth SURVEY OF NEARBY M DWARFS: BRIDGING THE CLEAN-FIRST, SEARCH-LATER DIVIDE (2012, methodology): “If left unmodelled, such red noise could substantially bias a transit’s detection significance (Pont et al. 2006); we discuss a correction for red noise in §4.2.6.”