Constraining planet occurrence around ultracool dwarfs observed by K2

An undergrad mentee presented her research at the meeting. I am a co-author of the presentation. The abstract is available on ADS: https://ui.adsabs.harvard.edu/abs/2019AAS...23314019S/abstractThough we expect many planets around ultracool dwarfs, few have been detected. The K2 mission presents a unique opportunity to search for transiting planets around a large sample of ultracool dwarfs and place constraints on planet occurrence at the bottom of the main sequence. Planet detection using the transit method is dependent not only on geometric transit probability but also the effectiveness of transit-searching methods. In this work, we use K2 observations to measure transit detection efficiency in ultracool dwarfs and use our transit detection efficiency to calculate an upper limit on the planet occurrence rate. We measure our ability to recover various types of transits around dwarfs at the M/L transition. We inject synthetic planetary transits of radii from 0.1 to 3.5 Earth radii and of periods from 0.3 to 26 days into 382 K2 light curves of late-type M and L dwarfs. We attempt to recover them using Box-Least Squares and Levenberg-Marquardt optimization methods. We then calculate a detection efficiency, or fraction recovered, and a threshold of detectability relating to orbital period and radius for each dwarf. We present an upper limit on the planet occurrence rate, as well as constraints on the probability of seeing no planets around a given number of ultracool dwarfs.Published versio

Student learning outcomes with hybrid computer simulations and hands-on labs

Published versio

Upper limits on planet occurrence around ultracool dwarfs with K2

The occurrence of planets orbiting ultracool dwarfs is poorly constrained. We present results from a guest observer program on NASA's K2 spacecraft to search for transiting planets orbiting a sample of 827 ultracool dwarfs. Having found no transiting planets in our sample, we determined an upper limit on the occurrence of planets. We simulated planets orbiting our sample for a range of orbital periods and sizes. For the simulated planets that transit their host, we injected the transit light curve into the real K2 light curves, then attempted to recover the injected planets. For a given occurrence rate, we calculated the probability of seeing no planets, and use the results to place an upper limit on planet occurrence as a function of planet radius and orbital period. We find that short-period, mini-Neptune- and Jupiter-sized planets are rare around ultracool dwarfs, consistent with results for early- and mid-type M dwarf stars. We constrain the occurrence rate η for planets between 0.5 and 10 R_⊕ with orbital periods between 1 and 26.3 days.Accepted manuscrip

The Perkins INfrared Exosatellite Survey (PINES) I. survey overview, reduction pipeline, and early results

We describe the Perkins INfrared Exosatellite Survey (PINES), a near-infrared photometric search for short-period transiting planets and moons around a sample of 393 spectroscopically confirmed L- and T-type dwarfs. PINES is performed with Boston University’s 1.8 m Perkins Telescope Observatory, located on Anderson Mesa, Arizona. We discuss the observational strategy of the survey, which was designed to optimize the number of expected transit detections, and describe custom automated observing procedures for performing PINES observations. We detail the steps of the PINES Analysis Toolkit (PAT), software that is used to create light curves from PINES images. We assess the impact of second-order extinction due to changing precipitable water vapor on our observations and find that the magnitude of this effect is minimized in Mauna Kea Observatories J band. We demonstrate the validity of PAT through the recovery of a transit of WASP-2 b and known variable brown dwarfs, and use it to identify a new variable L/T transition object: the T2 dwarf WISE J045746.08-020719.2. We report on the measured photometric precision of the survey and use it to estimate our transit-detection sensitivity. We find that for our median brightness targets, assuming contributions from white noise only, we are sensitive to the detection of 2.5 R ⊕ planets and larger. PINES will test whether the increase in sub-Neptune-sized planet occurrence with decreasing host mass continues into the L- and T-dwarf regime.https://iopscience.iop.org/article/10.3847/1538-3881/ac64aa/pdfPublished versio

Calibration Data for Kinematic Stellar Age Models

<p>https://github.com/ssagear/KinematicAgePredictor</p&gt

Compressing deep neural networks on FPGAs to binary and ternary precision with HLS4ML

We present the implementation of binary and ternary neural networks in the hls4ml library, designed to automatically convert deep neural network models to digital circuits with FPGA firmware. Starting from benchmark models trained with floating point precision, we investigate different strategies to reduce the network's resource consumption by reducing the numerical precision of the network parameters to binary or ternary. We discuss the trade-off between model accuracy and resource consumption. In addition, we show how to balance between latency and accuracy by retaining full precision on a selected subset of network components. As an example, we consider two multiclass classification tasks: handwritten digit recognition with the MNIST data set and jet identification with simulated proton-proton collisions at the CERN Large Hadron Collider. The binary and ternary implementation has similar performance to the higher precision implementation while using drastically fewer FPGA resources