Samson A. Johnson
A5008101712- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Technology Assessment and Management
- Adaptive optics and wavefront sensing
- Historical Astronomy and Related Studies
- Scientific Computing and Data Management
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Computational Physics and Python Applications
- Space Exploration and Technology
- Particle Accelerators and Free-Electron Lasers
- Space Satellite Systems and Control
- History and Developments in Astronomy
- Scientific Research and Discoveries
- High-pressure geophysics and materials
- Geological Modeling and Analysis
- Robotics and Automated Systems
- Magnetic confinement fusion research
- Geographic Information Systems Studies
- Astrophysics and Cosmic Phenomena
- Spacecraft Design and Technology
Jet Propulsion Laboratory
2024
The Ohio State University
2017-2023
The Wide Field Infrared Survey Telescope (WFIRST) is a 2.4m space telescope with 0.281 deg^2 field of view for near-IR imaging and slitless spectroscopy coronagraph designed > 10^8 starlight suppresion. As background information Astro2020 white papers, this article summarizes the current design anticipated performance WFIRST. While WFIRST does not have UV imaging/spectroscopic capabilities Hubble Space Telescope, wide surveys hundreds times more efficient. Some most ambitious multi-cycle...
The Nancy Grace Roman Space Telescope (Roman) will perform a Galactic Exoplanet Survey (RGES) to discover bound exoplanets with semi-major axes greater than 1 au using gravitational microlensing. even be sensitive planetary mass objects that are not gravitationally any host star. Such free-floating (FFPs) detected as isolated microlensing events timescales shorter few days. A measurement of the abundance and function FFPs is powerful diagnostic formation evolution systems, well physics via...
Abstract In order to exhume the buried signatures of “missing planetary caustics” in Korea Microlensing Telescope Network (KMTNet) data, we conducted a systematic anomaly search residuals from point-source point-lens fits, based on modified version KMTNet EventFinder algorithm. This revealed lowest-mass-ratio caustic date microlensing event OGLE-2019-BLG-1053, for which signal had not been noticed before. The system has planet–host mass ratio q = (1.25 ± 0.13) × 10 −5 . A Bayesian analysis...
Abstract We report the analysis of OGLE-2019-BLG-0960, which contains smallest mass-ratio microlensing planet found to date ( q = 1.2–1.6 × 10 −5 at 1 σ ). Although there is substantial uncertainty in satellite parallax measured by Spitzer, measurement annual effect combined with finite source allows us determine mass host star M L 0.3–0.6 ⊙ ), its m p 1.4–3.1 ⊕ projected separation between and a ⊥ 1.2–2.3 au), distance lens system D 0.6–1.2 kpc). The plausibly blend, could be checked...
ABSTRACT We present the discovery and characterization of six short-period, transiting giant planets from NASA’s Transiting Exoplanet Survey Satellite (TESS) -- TOI-1811 (TIC 376524552), TOI-2025 394050135), TOI-2145 88992642), TOI-2152 395393265), TOI-2154 428787891), TOI-2497 97568467). All orbit bright host stars (8.9 <G < 11.8, 7.7 <K 10.1). Using a combination time-series photometric spectroscopic follow-up observations TESS Follow-up Observing Program Working...
We present Large Binocular Telescope difference imaging data for the final years of four Type II-P/L supernovae progenitors. For all four, we find no significant evidence stochastic or steady variability in U, B, V, R-bands. Our limits constrain to more than roughly 5-10% expected R-band luminosities These are comparable observed red supergiants Magellanic Clouds. Based on these events, probability a progenitor having an extended outburst after Oxygen ignition is <37% at 90% confidence....
Abstract We report the discovery of KELT-20b, a hot Jupiter transiting <?CDATA $V\sim 7.6$?> early A star, HD 185603, with an orbital period $P\simeq 3.47$?> days. Archival and follow-up photometry, Gaia parallax, radial velocities, Doppler tomography, AO imaging were used to confirm planetary nature KELT-20b characterize system. From global modeling we infer that KELT-20 is rapidly rotating ( $v\sin {I}_{* }\simeq 120\,\mathrm{km}\ {{\rm{s}}}^{-1}$?> ) A2V star effective temperature...
The Minerva-Australis telescope array is a facility dedicated to the follow-up, confirmation, characterization, and mass measurement of planets orbiting bright stars discovered by Transiting Exoplanet Survey Satellite (TESS)—a category in which it almost unique Southern Hemisphere. It located at University Queensland's Mount Kent Observatory near Toowoomba, Australia. Its flexible design enables multiple 0.7 m robotic telescopes be used both combination, independently, for high-resolution...
Abstract We present the discovery of two extended ∼0.12 mag dimming events weak-lined T Tauri star V1334. The start first event was missed but came to an end in late 2003, and second began 2009 February, continues as 2016 November. Since egress current has not yet been observed, it suggests a period >13 years if this is periodic. Spectroscopic observations suggest presence small inner disk, although spectral energy distribution shows no infrared excess. explore possibility that are caused...
We present the discovery of giant planet KELT-19Ab, which transits moderately bright $(\mathrm{V} \sim 9.9)$ A8V star TYC 764-1494-1 with an orbital period 4.61 days. confirm planetary nature companion via a combination radial velocities, limit mass to $< 4.1\,\mathrm{M_J}$ $(3\sigma)$, and clear Doppler tomography signal, indicates retrograde projected spin-orbit misalignment $\lambda = -179.7^{+3.7}_{-3.8}$ degrees. Global modeling that $\rm{T_{eff}} =7500 \pm 110\,\mathrm{K}$ host has...
Little is observationally known about the progenitors of Type Ibc supernovae (SNe) or typical activity SNe in their final years. Here, we analyse deep Large Binocular Telescope imaging data spanning 4 yr before and after SN 2012fh using difference imaging. We place 1σ upper limits on detection progenitor star at MU > −3.8, MB −3.1, MV −3.8 MR −4.0 mag. These are tightest placed a to date they largely rule out single evolutionary models favour binary channel as origin this SN. also constrain...
We present the discovery of KELT-22Ab, a hot Jupiter from KELT-South survey. KELT-22Ab transits moderately bright ($V\sim 11.1$) Sun-like G2V star TYC 7518-468-1. The planet has an orbital period $P = 1.3866529 \pm 0.0000027 $ days, radius $R_{P} 1.285_{-0.071}^{+0.12}~R_{J}$, and relatively large mass $M_{P} 3.47_{-0.14}^{+0.15}~ M_{J}$. $R_{\star} 1.099_{-0.046}^{+0.079}~ R_{\odot}$, $M_{\star} 1.092_{-0.041}^{+0.045}~ M_{\odot}$, ${T_{\rm eff}\,} 5767_{-49}^{+50}~$ K, ${\log{g_\star}}...
The MINiature Exoplanet Radial Velocity Array (MINERVA) is a dedicated observatory of four 0.7 m robotic telescopes fiber-fed to KiwiSpec spectrograph. MINERVA mission discover super-Earths in the habitable zones nearby stars. This can be accomplished with MINERVA's unique combination high precision and cadence over long time periods. In this work, we detail changes facility that have occurred since our previous paper. We then describe control software, process by which perform 1D spectral...
The Wide Field Infrared Survey Telescope (WFIRST) will monitor $\sim 2$ deg$^2$ toward the Galactic bulge in a wide ($\sim 1-2~μ$m) W149 filter at 15-minute cadence with exposure times of $\sim$50s for 6 seasons 72 days each, total $\sim$41,000 exposures taken over $\sim$432 days, spread 5-year prime mission. This be one deepest sky ever taken, reaching photon-noise photometric precision 0.01 mag per and collecting 10^9$ photons course survey W149$_{\rm AB}\sim 21$ star. Of order $4 \times...
We present a computationally tractable implementation of spectro-perfectionism, method which minimizes error imparted by spectral extraction. develop our in conjunction with full raw reduction pipeline for the MINiature Exoplanet Radial Velocity Array (MINERVA), capable performing both optimal extraction and spectro-perfectionism. Although spectro-perfectionism remains expensive, can extract MINERVA exposure approximately $30\,\text{min}$. describe localized procedure approach to point...
The \textit{Nancy Grace Roman Space Telescope} (\textit{ Roman}) will provide an enormous number of microlensing light curves with much better photometric precisions than ongoing ground-based observations. Such enable us to observe high-order effects which have been previously difficult detect. In this paper, we investigate \textit{Roman}'s potential detect and characterize short-period planets brown dwarfs (BDs) in source systems using the orbital motion stars, so-called xallarap effect. We...
Abstract For microlenses with sufficiently low mass, the angular radius of source star can be much larger than Einstein ring lens. such extreme finite effect (EFSE) events, effects dominate throughout duration event. Here, we demonstrate and explore a continuous degeneracy between multiple parameters EFSE events. The first component in arises from fact that directly observable peak change flux depends on both ratio to fraction baseline is attributable lensed star. second because event impact...
Free-floating planets are the remnants of violent dynamical rearrangements planetary systems. It is possible that even our own solar system ejected a large planet early in its evolution. WFIRST will have ability to detect free-floating over wide range masses, but it not be able directly measure their masses. Microlensing parallax observations can used masses isolated objects, including planets, by observing microlensing events from two locations. The intra-L2 separation between and Euclid...
Abstract We present a new analysis of the KELT-24 system, comprising well-aligned hot Jupiter, b, and bright ( V = 8.3), nearby d 96.9 pc) F-type host star. b was independently discovered by two groups in 2019, with each reporting best-fit stellar parameters that were notably inconsistent. Here, we three independent analyses incorporating broad range photometric spectroscopic data, including eight sectors Transiting Exoplanet Survey Satellite (TESS) photometry more than 200 radial velocities...
We present SynthPop, a new open source, modular population synthesis Galactic modeling software to simulate catalogs of Milky Way stars along any sightline outward from the Sun. Motivated by lack flexibility in existing models, SynthPop is coded entirely python, can be run standalone or as an imported module, and configured json files that allow different model components switched out desired. describe code structure, how generation process runs, use code. also validation testing known...
We present a new analysis of the KELT-24 system, comprising well-aligned hot Jupiter, KELT-24~b, and bright ($V=8.3$), nearby ($d=96.9~\mathrm{pc}$) F-type host star. KELT-24~b was independently discovered by two groups in 2019, with each reporting best-fit stellar parameters that were notably inconsistent. Here, we three independent analyses incorporating broad range photometric spectroscopic data, including eight sectors TESS photometry more than 200 radial velocities (RVs) from MINERVA....