Natalie M. Batalha

NASA, Вашингтон, West Virginia, United States

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Publications (103)713.5 Total impact

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    ABSTRACT: The Kepler mission discovered 2842 exoplanet candidates with 2 years of data. We provide updates to the Kepler planet candidate sample based upon 3 years (Q1-Q12) of data. Through a series of tests to exclude false-positives, primarily caused by eclipsing binary stars and instrumental systematics, 855 additional planetary candidates have been discovered, bringing the total number known to 3697. We provide revised transit parameters and accompanying posterior distributions based on a Markov Chain Monte Carlo algorithm for the cumulative catalogue of Kepler Objects of Interest. There are now 130 candidates in the cumulative catalogue that receive less than twice the flux the Earth receives and more than 1100 have a radius less than 1.5 Rearth. There are now a dozen candidates meeting both criteria, roughly doubling the number of candidate Earth analogs. A majority of planetary candidates have a high probability of being bonafide planets, however, there are populations of likely false-positives. We discuss and suggest additional cuts that can be easily applied to the catalogue to produce a set of planetary candidates with good fidelity. The full catalogue is publicly available at the NASA Exoplanet Archive.
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    ABSTRACT: We present an investigation of twelve candidate transiting planets from Kepler with orbital periods ranging from 34 to 207 days, selected from initial indications that they are small and potentially in the habitable zone (HZ) of their parent stars. Few of these objects are known. The expected Doppler signals are too small to confirm them by demonstrating that their masses are in the planetary regime. Here we verify their planetary nature by validating them statistically using the BLENDER technique, which simulates large numbers of false positives and compares the resulting light curves with the Kepler photometry. This analysis was supplemented with new follow-up observations (high-resolution optical and near-infrared spectroscopy, adaptive optics imaging, and speckle interferometry), as well as an analysis of the flux centroids. For eleven of them (KOI-0571.05, 1422.04, 1422.05, 2529.02, 3255.01, 3284.01, 4005.01, 4087.01, 4622.01, 4742.01, and 4745.01) we show that the likelihood they are true planets is far greater than that of a false positive, to a confidence level of 99.73% (3 sigma) or higher. For KOI-4427.01 the confidence level is about 99.2% (2.6 sigma). With our accurate characterization of the GKM host stars, the derived planetary radii range from 1.1 to 2.7 R_Earth. All twelve objects are confirmed to be in the HZ, and nine are small enough to be rocky. Excluding three of them that have been previously validated by others, our study doubles the number of known rocky planets in the HZ. KOI-3284.01 (Kepler-438b) and KOI-4742.01 (Kepler-442b) are the planets most similar to the Earth discovered to date when considering their size and incident flux jointly.
    The Astrophysical Journal 01/2015; 800(2). DOI:10.1088/0004-637X/800/2/99 · 6.28 Impact Factor
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    Natalie M Batalha
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    ABSTRACT: The Kepler Mission is exploring the diversity of planets and planetary systems. Its legacy will be a catalog of discoveries sufficient for computing planet occurrence rates as a function of size, orbital period, star type, and insolation flux. The mission has made significant progress toward achieving that goal. Over 3,500 transiting exoplanets have been identified from the analysis of the first 3 y of data, 100 planets of which are in the habitable zone. The catalog has a high reliability rate (85-90% averaged over the period/radius plane), which is improving as follow-up observations continue. Dynamical (e.g., velocimetry and transit timing) and statistical methods have confirmed and characterized hundreds of planets over a large range of sizes and compositions for both single- and multiple-star systems. Population studies suggest that planets abound in our galaxy and that small planets are particularly frequent. Here, I report on the progress Kepler has made measuring the prevalence of exoplanets orbiting within one astronomical unit of their host stars in support of the National Aeronautics and Space Administration's long-term goal of finding habitable environments beyond the solar system.
    Proceedings of the National Academy of Sciences 07/2014; 111(35). DOI:10.1073/pnas.1304196111 · 9.81 Impact Factor
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    ABSTRACT: We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurements, along with high-resolution imaging and spectroscopy, Doppler spectroscopy, and (for 11 stars) asteroseismology, we establish low false-positive probabilities for all of the transiting planets (41 of 42 have a false-positive probability under 1%), and we constrain their sizes and masses. Most of the transiting planets are smaller than 3X the size of Earth. For 16 planets, the Doppler signal was securely detected, providing a direct measurement of the planet's mass. For the other 26 planets we provide either marginal mass measurements or upper limits to their masses and densities; in many cases we can rule out a rocky composition. We identify 6 planets with densities above 5 g/cc, suggesting a mostly rocky interior for them. Indeed, the only planets that are compatible with a purely rocky composition are smaller than ~2 R_earth. Larger planets evidently contain a larger fraction of low-density material (H, He, and H2O).
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    ABSTRACT: Occultations and phase curves allow us to characterize atmopsheres of transiting exoplanets. We observe these signals in the light curves of several Kepler Objects of Interest (KOIs). Using sixteen quarters of data from the Kepler spacecraft, we determine the planetary effective temperature and geometric albedo for a sample of planetary candidates. We investigate the possibility of asymmetries (or lack therefor) in the phase curves which may provide information about atmospheric dynamics. We highlight the Kepler-10b and Kepler-41b light curves which both present statistically significant phase curve asymmetries.
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    ABSTRACT: The goal of detecting extrasolar planets has been part of human thought for many centuries and several plausible approaches for detecting them have been discussed for many decades. At this point in history the two most successful approaches have been the reflex radial velocity and transit approaches. These each have the additional merit of corroborating a discovery by the other approach, at least in some cases, thereby producing very convincing detections of objects that can't be seen. In the transit detection realm the key enabling technical factors were development of: - high quality large area electronic detectors - practical fast optics with wide fields of view - automated telescope systems - analysis algorithms to correct for inadequacies in the instrumentation - computing capability sufficient to cope with all of this This part of the equation is relatively straightforward. The more important part is subliminal, namely what went on in the minds of the proponents and detractors of the transit approach as events unfolded. Three major paradigm shifts had to happen. First, we had to come to understand that not all solar systems look like ours. The motivating effect of the hot Jupiter class of planet was profound. Second, the fact that CCD detectors can be much more stable than anybody imagined had to be understood. Finally, the ability of analysis methods to correct the data sufficiently well for the differential photometry task at hand had to be understood by proponents and detractors alike. The problem of capturing this changing mind-set in a collection of artifacts is a difficult one but is essential for a proper presentation of this bit of history.
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    ABSTRACT: Although data collection for the original Kepler mission is complete, a repurposed Kepler has the potential to discover many hundreds of new, small exoplanets around low-mass stars located in or near the ecliptic plane. This repurposing of the Kepler spacecraft, dubbed “K2,” seeks to maximize photometric performance using its two operational reaction wheels by observing in the ecliptic plane where solar torques can be carefully balanced to minimize boresight roll. The K2 mission shows great promise and, once approved, will observe many different fields during a sequence of two- to three-month campaigns over the next few years. Like the original Kepler mission, K2 has many challenges, but is anticipated to be well worth the climb scientifically. K2 can observe many thousands of new sources during each campaign and hundreds of thousands of new sources over its lifetime. In addition to its continued search for exoplanets, the K2 mission will provide access to a wide variety of scientifically interesting targets that include young and variable stars, open clusters of differing ages, star-forming regions, supernovae, white dwarfs, microlensing events, solar system objects, AGNs, normal galaxies, and the Galactic Center. Performance testing began in September, 2013, and has continued throughout the fall and early winter. The results of the first ecliptic-plane tests are described and used to predict photometric performance. A trade study reveals the likely number of targets, cadence durations, initial fields of view, and planned observing strategies. K2 is an exciting new mission that addresses a wide variety of scientific questions with expanded opportunities for community participation.
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    ABSTRACT: We provide updates to the Kepler planet candidate sample based upon nearly two years of high-precision photometry (i.e., Q1-Q8). From an initial list of nearly 13,400 Threshold Crossing Events (TCEs), 480 new host stars are identified from their flux time series as consistent with hosting transiting planets. Potential transit signals are subjected to further analysis using the pixel-level data, which allows background eclipsing binaries to be identified through small image position shifts during transit. We also re-evaluate Kepler Objects of Interest (KOI) 1-1609, which were identified early in the mission, using substantially more data to test for background false positives and to find additional multiple systems. Combining the new and previous KOI samples, we provide updated parameters for 2,738 Kepler planet candidates distributed across 2,017 host stars. From the combined Kepler planet candidates, 472 are new from the Q1-Q8 data examined in this study. The new Kepler planet candidates represent ~40% of the sample with Rp~1 Rearth and represent ~40% of the low equilibrium temperature (Teq<300 K) sample. We review the known biases in the current sample of Kepler planet candidates relevant to evaluating planet population statistics with the current Kepler planet candidate sample.
    The Astrophysical Journal Supplement Series 12/2013; 210(2). DOI:10.1088/0067-0049/210/2/19 · 14.14 Impact Factor
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    ABSTRACT: We present the detection of five planets-Kepler-62b, c, d, e, and f-of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets (Kepler-62e and -62f) are super-Earth-size (1.25 < planet radius ≤ 2.0 R⊕) planets in the habitable zone (HZ) of their host star, receiving 1.2 ± 0.2 and 0.41 ± 0.05 times the solar flux at Earth's orbit (S⊙). Theoretical models of Kepler-62e and -62f for a stellar age of ~7 Gyr suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.
    Science 04/2013; DOI:10.1126/science.1234702 · 31.48 Impact Factor
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    ABSTRACT: The Kepler Mission was launched on March 6, 2009 to perform a photometric survey of more than 100,000 dwarf stars to search for Earth-size planets with the transit technique. The reliability of the resulting planetary candidate list relies on the ability to identify and remove false positives. Major sources of astrophysical false positives are planetary transits and stellar eclipses on background stars. We describe several new techniques for the identification of background transit sources that are separated from their target stars, indicating an astrophysical false positive. These techniques use only Kepler photometric data. We describe the concepts and construction of these techniques in detail as well as their performance and relative merits.
    Publications of the Astronomical Society of the Pacific 02/2013; 125(930). DOI:10.1086/671767 · 3.23 Impact Factor
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    ABSTRACT: The Kepler Mission is uniquely suited to study the frequencies of extrasolar planets. This goal requires knowledge of the incidence of false positives such as eclipsing binaries in the background of the targets, or physically bound to them, which can mimic the photometric signal of a transiting planet. We perform numerical simulations to predict the occurrence of astrophysical false positives detectable by the Mission, and quantify the fraction of them that would pass the Kepler candidate vetting procedure. By comparing their distribution with that of the Kepler Objects of Interest detected during the first six quarters of operation of the spacecraft, we infer the false positive rate of Kepler and study its dependence on spectral type, candidate planet size, and orbital period. We find that the global false positive rate of Kepler is 9.4 %, peaking for giant planets (6-22 Earth radii) at 17.7 %, reaching a low of 6.7 % for small Neptunes (2-4 Earth radii), and increasing again for Earth-size planets (0.8-1.25 Earth radii) to 12.3 %. Most importantly, we also quantify and characterize the distribution and rate of occurrence of planets down to Earth size with no prior assumptions on their frequency, by subtracting from the population of actual Kepler candidates our simulated population of astrophysical false positives. We find that 16.5 +/- 3.6 % of main-sequence FGK stars have at least one planet between 0.8 and 1.25 Earth radii with orbital periods up to 85 days. There is no significant dependence of the rates of planet occurrence between 0.8 and 4 Earth radii with spectral type. In the process, we derive also a prescription for the signal recovery rate of Kepler that enables a good match to both the KOI size and orbital period distribution, as well as their signal-to-noise distribution.
    The Astrophysical Journal 01/2013; 766(2). DOI:10.1088/0004-637X/766/2/81 · 6.28 Impact Factor
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    ABSTRACT: Kepler-10b is a terrestrial planet orbiting its host star every 20 hours. At semi-major axis of 0.017 AU the planet receives a substantial amount of energy that heats the surface to approximately 2000 K. Data from the Kepler photometer with its wide band-pass provides a clear detection of thermal emission from the planet. Additionally, a secondary eclipse is clearly observed with a depth of 8 parts-per-million. We also also confirm the detection of a phase curve with a shape dominated by the day-night cycle of the planet. However, we also see a significant asymmetry in the phase curve. We put forth planetary surface thermal emission and reflection models which explain the asymmetry and present a surface brightness map of a rocky extrasolar planet.
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    ABSTRACT: In February 2011, the Kepler mission announced its discovery of 1,235 planet candidates, of which more than half have radii smaller than that of Neptune: RP<4R{earth}, where R{earth} plus is the Earth radius. We used reconnaissance spectra obtained by the Kepler Follow-up Observing Program (FOP) to derive metallicities for several hundred of the brighter planet candidates, and used the results to explore the relationship between planet size and host-star metallicity. (1 data file).
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    ABSTRACT: The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a 'fossil' record of the chemical composition of the initial protoplanetary disk. Metal-rich stars are much more likely to harbour gas giant planets, supporting the model that planets form by accumulation of dust and ice particles. Recent ground-based surveys suggest that this correlation is weakened for Neptunian-sized planets. However, how the relationship between size and metallicity extends into the regime of terrestrial-sized exoplanets is unknown. Here we report spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission, including objects that are comparable in size to the terrestrial planets in the Solar System. We find that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities. This observation suggests that terrestrial planets may be widespread in the disk of the Galaxy, with no special requirement of enhanced metallicity for their formation.
    Nature 06/2012; 486(7403):375-7. DOI:10.1038/nature11121 · 42.35 Impact Factor
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    ABSTRACT: We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.
    The Astrophysical Journal 05/2012; 750(2). DOI:10.1088/0004-637X/750/2/113 · 6.28 Impact Factor
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    ABSTRACT: The data acquisition period selected for this analysis spans the first three quarters (Q1-Q3) of science observation, spanning the interval from 2009 May 12 00:00:00 UTC to 2009 December 17 23:59:59 UTC, a total period of 218 days. (1 data file).
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    ABSTRACT: We present the results of a search for potential transit signals in the first three quarters of photometry data acquired by the Kepler mission. The targets of the search include 151,722 stars which were observed over the full interval and an additional 19,132 stars which were observed for only one or two quarters. From this set of targets we find a total of 5392 detections which meet the Kepler detection criteria: those criteria are periodicity of signal, an acceptable signal-to-noise ratio, and a composition test which rejects spurious detections which contain non-physical combinations of events. The detected signals are dominated by events with relatively low signal-to-noise ratio and by events with relatively short periods. The distribution of estimated transit depths appears to peak in the range between 40 and 100 parts per million, with a few detections down to fewer than 10 parts per million. The detections exhibit signal-to-noise ratios from 7.1σ, which is the lower cutoff for detections, to over 10,000σ, and periods ranging from 0.5 days, which is the lower cutoff used in the procedure, to 109 days, which is the upper limit of achievable periods given the length of the data set and the criteria used for detections. The detected signals are compared to a set of known transit events in the Kepler field of view which were derived by a different method using a longer data interval; the comparison shows that the current search correctly identified 88.1% of the known events. A tabulation of the detected transit signals, examples which illustrate the analysis and detection process, a discussion of future plans and open, potentially fruitful, areas of further research are included.
    The Astrophysical Journal Supplement Series 02/2012; 199(1):24. DOI:10.1088/0067-0049/199/1/24 · 14.14 Impact Factor
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    ABSTRACT: Having discovered 885 planet candidates in 361 multiple-planet systems, Kepler has made transits a powerful method for studying the statistics of planetary systems. The orbits of only two pairs of planets in these candidate systems are apparently unstable. This indicates that a high percentage of the candidate systems are truly planets orbiting the same star, motivating physical investigations of the population. Pairs of planets in this sample are typically not in orbital resonances. However, pairs with orbital period ratios within a few percent of a first-order resonance (e.g. 2:1, 3:2) prefer orbital spacings just wide of the resonance and avoid spacings just narrow of the resonance. Finally, we investigate mutual inclinations based on transit duration ratios. We infer that the inner planets of pairs tend to have a smaller impact parameter than their outer companions, suggesting these planetary systems are typically coplanar to within a few degrees.
    The Astrophysical Journal 02/2012; 790(2). DOI:10.1088/0004-637X/790/2/146 · 6.28 Impact Factor
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    ABSTRACT: We present new planet candidates identified in NASA Kepler quarter two public release data by volunteers engaged in the Planet Hunters citizen science project. The two candidates presented here survive checks for false-positives, including examination of the pixel offset to constrain the possibility of a background eclipsing binary. The orbital periods of the planet candidates are 97.46 days (KIC 4552729) and 284.03 (KIC 10005758) days and the modeled planet radii are 5.3 and 3.8 R_Earth. The latter star has an additional known planet candidate with a radius of 5.05 R_Earth and a period of 134.49 which was detected by the Kepler pipeline. The discovery of these candidates illustrates the value of massively distributed volunteer review of the Kepler database to recover candidates which were otherwise uncatalogued.
    The Astronomical Journal 02/2012; 145(6). DOI:10.1088/0004-6256/145/6/151 · 4.97 Impact Factor
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    ABSTRACT: New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1,091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multi-quarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and those at longer orbital periods (123% for candidates outside of 50-day orbits versus 85% for candidates inside of 50-day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1-- Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.
    The Astrophysical Journal Supplement Series 02/2012; DOI:10.1088/0067-0049/204/2/24 · 14.14 Impact Factor

Publication Stats

4k Citations
713.50 Total Impact Points

Institutions

  • 2014
    • NASA
      Вашингтон, West Virginia, United States
  • 2012
    • Yale University
      • Department of Astronomy
      New Haven, Connecticut, United States
    • San Diego State University
      • Department of Astronomy
      San Diego, CA, United States
  • 2008–2012
    • San Jose State University
      • Department of Physics and Astronomy
      San Jose, California, United States
  • 2011
    • Bay Area Environmental Research Institute
      Sonoma, California, United States
    • The University of Arizona
      Tucson, Arizona, United States
  • 2007
    • Las Cumbres Observatory Global Telescope Network
      Goleta, California, United States
  • 2006
    • SETI Institute
      Mountain View, California, United States