TRANSIT DETECTION IN THE MEarth SURVEY OF NEARBY M DWARFS: BRIDGING THE CLEAN-FIRST, SEARCH-LATER DIVIDE

By Z. K. Berta, J. Irwin, D. Charbonneau, C. Burke, Emilio E. Falco. 2012

137 citations recorded by the source corpus.

In the effort to characterize the masses, radii, and atmospheres of potentially habitable exoplanets, there is an urgent need to find examples of such planets transiting nearby M dwarfs. The MEarth Project is an ongoing effort to do so, as a ground-based photometric survey designed to detect exoplanets as small as 2 R⊕ transiting mid-to-late M dwarfs within 33 pc of the Sun. Unfortunately, identifying transits of such planets in photometric monitoring is complicated both by the intrinsic stellar variability that is common among these stars and by the nocturnal cadence, atmospheric variations, and instrumental systematics that often plague Earth-bound observatories. Here, we summarize the properties of MEarth data gathered so far, emphasizing the challenges they present for transit detection. We address these challenges with a new framework to detect shallow exoplanet transits in wiggly and irregularly spaced light curves. In contrast to previous methods that clean trends from light curves before searching for transits, this framework assesses the significance of individual transits simultaneously while modeling variability, systematics, and the photometric quality of individual nights. Our Method for Including Starspots and Systematics in the Marginalized Probability of a Lone Eclipse (MISS MarPLE) uses a computationally efficient semi-Bayesian approach to explore the vast probability space spanned by the many parameters of this model, naturally incorporating the uncertainties in these parameters into its evaluation of candidate events. We show how to combine individual transits processed by MISS MarPLE into periodic transiting planet candidates and compare our results to the popular box-fitting least-squares method with simulations. By applying MISS MarPLE to observations from the MEarth Project, we demonstrate the utility of this framework for robustly assessing the false alarm probability of transit signals in real data.

Subfields: Astronomy and Astrophysics, Computational Mechanics, Instrumentation

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In Astronomy and Astrophysics

1. Jon Fortney
2. D. Charbonneau
3. N. Madhusudhan
4. E. Gaidos
5. Sara Seager
6. D. Deming
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In Computational Mechanics

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In Instrumentation

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8. J. Winn

Citations in the corpus

• AN EMPIRICAL CALIBRATION TO ESTIMATE COOL DWARF FUNDAMENTAL PARAMETERS FROM H-BAND SPECTRA (2014, background): “MEarth M dwarfs Newton et al. (2014) obtained spectra of447 mid to late M dwarfs in the solar neighborhood that are targets of the MEarth transiting planet survey (Berta et al. 2012; Irwin etal.”
• THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS (2013, background): “…a habitable planet and has motivated numerous planet surveys to target M dwarfs (Delfosse et al. 1999; Endl et al. 2003; Nutzman & Charbonneau 2008; Zechmeister et al. 2009; Apps et al. 2010; Barnes et al. 2012; Berta et al. 2012; Bowler et al. 2012; Giacobbe et al. 2012; Law et al. 2012).”
• THE OCCURRENCE OF POTENTIALLY HABITABLE PLANETS ORBITING M DWARFS ESTIMATED FROM THE FULL KEPLER DATASET AND AN EMPIRICAL MEASUREMENT OF THE DETECTION SENSITIVITY (2015, unknown): “…et al. 2010), CHEOPS (Broeg et al. 2013), ExoplanetSat (Smith et al. 2010), ExTrA9, HPF (Mahadevan et al. 2010), MEarth (Nutzman & Charbonneau 2008; Berta et al. 2012), PLATO (Rauer et al. 2014), K2 (Howell et al. 2014), SPECULOOS (Gillon et al. 2013), SPIRou (Thibault et al. 2012), and TESS…”
• Optimized transit detection algorithm to search for periodic transits of small planets (2019, background): “Some years ago, BLS performance was noted as “10 minutes run time on a desktop workstation” for Article number, page 8 of 14 a MEarth star with 1000 data points (Berta et al. 2012).”
• NEAR-INFRARED METALLICITIES, RADIAL VELOCITIES, AND SPECTRAL TYPES FOR 447 NEARBY M DWARFS (2013, background): “…radius of an M dwarf is also favorable for follow-up studies of an orbiting planet’s atmosphere with transmission or occultation techniques and nearby mid M dwarfs are bright enough in the NIR for precise spec- troscopic studies (e.g. Bean et al. 2011; Crossfield et al. 2011; Berta et al. 2012).”
• Observations of Transiting Exoplanets with the James Webb Space Telescope (JWST) (2014, methodology): “MEarth (Nutzman & Charbonneau 2008; Berta et al. 2012a) began monitoring the northern sky with eight 40-cm telescopes in 2008 and recently expanded to the southern sky with an additional eight telescopes.”
• The CARMENES search for exoplanets around M dwarfs (2018, methodology): “We analyzed photometric time series for GJ 3779 from The MEarth Project (Charbonneau et al. 2008; Berta et al. 2012) from January 2009 to July 2010 in the RG715 filter.”
• A FRAMEWORK FOR CHARACTERIZING THE ATMOSPHERES OF LOW-MASS LOW-DENSITY TRANSITING PLANETS (2013, methodology): “With the rise of specialized ground-based transit survey for M dwarfs (Nutzman & Charbonneau 2008; Berta et al. 2012b; Giacobbe et al. 2012; Sozzetti et al. 2013) and the Transiting Exoplanet Survey Satellite (Ricker et al. 2010), the prospects are extremely good.”
• THE Hα EMISSION OF NEARBY M DWARFS AND ITS RELATION TO STELLAR ROTATION (2016, methodology): “The MEarth Project is a transiting planet survey looking for super Earths around 3000 mid-to-late M dwarfs within 33pc (Berta et al. 2012; Irwin et al. 2015).”
• Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, background): “A few of the largest planets might even be detectable by ground-based surveys such as MEarth (Berta et al. 2012).”
• Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, background): “A large fraction of them are fast rotators with high flare frequencies, which can inhibit the detection of small planets (see e.g. Berta et al. 2012; Kipping et al. 2017).”