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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2021

A nearby transiting rocky exoplanet that is suitable for atmospheric investigation

Spectroscopy of transiting exoplanets can be used to investigate their atmospheric properties and habitability. Combining radial velocity (RV) and transit data provides additional information on exoplanet physical properties. We detect a transiting rocky planet with an orbital period of 1.467 days around the nearby red dwarf star Gliese 486. The planet Gliese 486 b is 2.81 Earth masses and 1.31 Earth radii, with uncertainties of 5%, as determined from RV data and photometric light curves. The host star is at a distance of ~8.1 parsecs, has a J-band magnitude of ~7.2, and is observable from both hemispheres of Earth. On the basis of these properties and the planet’s short orbital period and high equilibrium temperature, we show that this terrestrial planet is suitable for emission and transit spectroscopy.

T. Trifonov↗
NASA NTRS2022

TESS in the Extended Mission: A Powerful Tool for Time-Domain Exoplanet Science

Since its launch in 2018, the Transiting Exoplanet Survey Satellite (TESS) has embarked on an ambitious mission to image almost the entire sky in search of nearby transiting exoplanet systems. Upon completion of its Primary Mission in July 2020, TESS transitioned to its first Extended Mission, during which it has returned to both the southern and northern ecliptic hemispheres and revisited most of the targets it observed during the first two years of operation. With future Extended Missions likely, the end-to-end time baseline provided by TESS will significantly exceed that of Kepler, enabling a plethora of scientific investigations into time-domain exoplanet science. TESS has already established itself as an extremely productive tool for studying visible-wavelength exoplanet phase curves. During the Primary Mission, we carried out a systematic phase-curve analysis of more than 30 transiting exoplanet systems. These datasets constrained the dayside hemisphere brightness temperatures, day-night brightness contrasts, and optical geometric albedos of a wide range of gas giant planets, revealing some tantalizing trends that warrant further study. In particular, we uncovered a tentative positive correlation between geometric albedo and equilibrium temperature for gas giants with 1500 < Teq < 3000 K. The new light curves from the Extended Mission have refined the measured astrophysical parameters of the previously studied systems and yielded statistically significant secondary eclipse and phase-curve detections for dozens of more systems. By comparing the phase-curve properties obtained from TESS observations separated by months or years, we have also probed for possible atmospheric variability, as well as transit-timing variations due to orbital decay or additional companions. In this presentation, I will provide an overview of the main results from our ongoing multiyear study of TESS light curves and discuss potentially fruitful avenues for further research as TESS continues its all-sky survey into the future.

Ian Wong↗
NASA NTRS2010

A Point Spread Function for the EPOXI Mission

The Extrasolar Planet Observation Characterization and the Deep Impact Extended Investigation missions (EPOXI) are currently observing the transits of exoplanets, two comet nuclei at short range, and the Earth and Mars using the High Resolution Instrument (HRI) - a 0.3 m f/35 telescope on the Deep Impact probe. The HRI is in a permanently defocused state with the instrument pOint of focus about 0.6 cm before the focal plane due to the use of a reference flat mirror that took a power during ground thermal-vacuum testing. Consequently, the point spread function (PSF) covers approximately nine pixels FWHM and is characterized by a patch with three-fold symmetry due to the three-point support structures of the primary and secondary mirrors. The PSF is also strongly color dependent varying in shape and size with change in filtration and target color. While defocus is highly desirable for exoplanet transit observations to limit sensitivity to intra-pixel variation, it is suboptimal for observations of spatially resolved targets. Consequently, all images used in our analysis of such objects were deconvolved with an instrument PSF. The instrument PSF is also being used to optimize transit analysis. We discuss development and usage of an instrument PSF for these observations.

Barry, Richard K.↗
NASA NTRS2019

TESS Data Release Notes: Sectors 1 & 2, Multi-Sector 1-2, DR3

This release note discusses the planetary transit search data products produced by the Science Processing Operations Center at Ames Research Center from Sectors 1-2 observations made with the TESS (Transiting Exoplanet Survey Satellite) spacecraft and cameras as a means to document instrument performance and data characteristics.

TESS Mission↗
NASA NTRS2021

TESS Delivers Five New Hot Giant Planets Orbiting Bright Stars from the Full-frame Images

We present the discovery and characterization of five hot and warm Jupiters—TOI-628 b(TIC 281408474; HD288842), TOI-640 b(TIC 147977348), TOI-1333 b (TIC 395171208, BD+47 3521A), TOI-1478 b (TIC409794137), and TOI-1601 b (TIC 139375960)—based on data from NASA’s Transiting Exoplanet Survey Satellite(TESS). The five planets were identified from the full-frame images and were confirmed through a series of photometric and spectroscopic follow-up observations by the TESS Follow-up Observing Program Working Group. The planets are all Jovian size (RP=1.01–1.77RJ) and have masses that range from 0.85 to 6.33MJ. The host stars of these systems have F and G spectral types (5595Teff 6460 K)and are all relatively bright (9.5 1.7RJ, possibly a result of its host star’s evolution) and resides on an orbit with a period longer than 5 days. TOI-628 b is the most massive, hot Jupiter discovered to date by TESS with a measured mass of-+6.310.300.28MJ and a statistically significant, nonzero orbital eccentricity of e=-+0.0740.0220.021. This planet would not have had enough time to circularize through tidal forces from our analysis, suggesting that it might be remnant eccentricity from its migration. The longest-period planet in this sample, TOI-1478 b (P=10.18 days), is a warm Jupiter in a circular orbit around a near-solar analog. NASA’s TESS mission is continuing to increase the sample of well-characterized hot and warm Jupiters, complementing its primary mission goals.

Exoplanet astronomy↗
NASA NTRS2018

Photochemical Haze Formation in the Atmospheres of Super-Earths and Mini-Neptunes

UV (ultraviolet) radiation can induce photochemical processes in the atmospheres of exoplanet and produce haze particles. Recent transmission spectra of super-Earths and mini-Neptunes have demonstrated the possibility that exoplanets have haze/cloud layers at high altitudes in their atmospheres. Haze particles play an important role in planetary atmospheres because they affect the chemistry, dynamics, and radiation flux in planetary atmospheres, and may provide a source of organic material to the surface which may impact the origin or evolution of life. However, very little information is known about photochemical processes in cool, high-metallicity exoplanetary atmospheres. We present here photochemical haze formation in laboratory simulation experiments with UV radiation; we explored temperatures ranging from 300 to 600 degrees Kelvin and a range of atmospheric metallicities (100 times, 1000 times, and 10000 times solar metallicity). We find that photochemical hazes are generated in all simulated atmospheres, but the haze production rates appear to be temperature dependent: the particles produced in each metallicity group decrease as the temperature increases. The images taken with an atomic force microscope (AFM) show that the particle size (15 nanometers to 190 nanometers) varies with temperature and metallicity. Our results provide useful laboratory data on the photochemical haze formation and particle properties, which can serve as critical inputs for exoplanet atmosphere modeling, and guide future observations of exoplanets with the Transiting Exoplanet Survey Satellite (TESS), the James Webb Space Telescope (JWST), and the Wide-Field Infrared Survey Telescope (WFIRST).

He, Chao↗
NASA NTRS2021

Identifying Planetary Transit Candidates in TESS Full-frame Image Light Curves via Convolutional Neural Networks

The Transiting Exoplanet Survey Satellite(TESS)mission measured light from stars in∼75% of the sky throughout its 2 yr primary mission, resulting in millions of TESS 30-minute-cadence light curves to analyze in the search for transiting exoplanets. To search this vast data trove for transit signals, we aim to provide an approach that both is computationally efficient and produces highly performant predictions. This approach minimizes the required human search effort. We present a convolutional neural network, which we train to identify planetary transit signals and dismiss false positives. To make a prediction for a given light curve, our network requires no prior transit parameters identified using other methods. Our network performs inference on a TESS 30-minute-cadence light curve in∼5 ms on a single GPU, enabling large-scale archival searches. We present 181 new planet candidates identified by our network, which pass subsequent human vetting designed to rule out false positives.Our neural network model is additionally provided as open-source code for public use and extension

Gregory Olmschenk↗
NASA NTRS2019

Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc

We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of {1.38}_{-0.12}^{+0.13} {R}_{\oplus }, an orbital period of {5.35882}_{-0.00031}^{+0.00030} days, and an equilibrium temperature of {433}_{-27}^{+28} K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 {M}_{\oplus } on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.

Binaries↗
NASA NTRSDate not supplied

Primary Mission Threshold Crossing Events in the TESS SPOC Transit Search

We present an overview of the single- and multiple-sector results of the Science Processing Operations Center (SPOC) transit search in the primary Transiting Exoplanet Survey Satellite (TESS) mission. TESS was designed to survey bright stars in the greater Solar neighborhood in search of transiting exoplanets. Data were acquired at a 2-minute cadence for 16,000-20,000 pre-selected target stars in each 28-day observation sector and processed in the SPOC pipeline at NASA Ames Research Center. The photometry pipeline produced a systematic error corrected light curve for each target star. Light curves were searched for transiting planet signatures by sector for all target stars, and separately for target stars observed in multiple sectors. Potential transit signals for which the transiting planet detection threshold was exceeded and a series of transit consistency tests were passed are referred to as Threshold Crossing Events (TCEs). We highlight the full TCE population and the population of SPOC TCEs that were later identified as TESS Objects of Interest (TOIs). Characteristics of the TCE populations implied by limb-darkened transiting planet model fits are also presented. SPOC pipeline data products are delivered to the Mikulski Archive for Space Telescopes (MAST)(http://archive.stsci.edu/missions-and-data/tess) for access by the community. Funding for the TESS Mission has been provided by the NASA Science Mission Directorate.

TESS↗
NASA NTRS2020

Securing the Legacy of TESS through the Care and Maintenance of TESS Planet Ephemerides

Much of the science from the exoplanets detected by the Transiting Exoplanet Survey Satellite (TESS) mission relies on precisely predicted transit times that are needed for many follow-up characterization studies. We investigate ephemeris deterioration for simulated TESS planets and find that the ephemerides of 81% of those will have expired (i.e., 1σ mid-transit time uncertainties greater than 30 minutes) 1 yr after their TESS observations. We verify these results using a sample of TESS planet candidates as well. In particular, of the simulated planets that would be recommended as James Webb Space Telescope (JWST) targets by Kempton et al., ∼80% will have midtransit time uncertainties >30 minutes by the earliest time JWST would observe them. This rapid deterioration is driven primarily by the relatively short time baseline of TESS observations. We describe strategies for maintaining TESS ephemerides fresh through follow-up transit observations. We find that the longer the baseline between the TESS and the follow-up observations, the longer the ephemerides stay fresh, and that 51% of simulated primary mission TESS planets will require space-based observations. The recently approved extension to the TESS mission will rescue the ephemerides of most (though not all) primary mission planets, but the benefits of these new observations can only be reaped 2 yr after the primary mission observations. Moreover, the ephemerides of most primary mission TESS planets (as well as those newly discovered during the extended mission) will again have expired by the time future facilities such as the ELTs, Ariel, and the possible LUVOIR/Origins Space Telescope missions come online, unless maintenance follow-up observations are obtained.

Diana Dragomir↗
NASA NTRS2024

Short–Period Variables in TESS Full–Frame Image Light Curves Identified via Convolutional Neural Networks

The Transiting Exoplanet Survey Satellite (TESS) mission measured light from stars in ∼85% of the sky throughout its 2 yr primary mission, resulting in millions of TESS 30-minute-cadence light curves to analyze in the search for transiting exoplanets. To search this vast data set, we aim to provide an approach that is computationally efficient, produces accurate predictions, and minimizes the required human search effort. We present a convolutional neural network that we train to identify short-period variables. To make a prediction for a given light curve, our network requires no prior target parameters identified using other methods. Our network performs inference on a TESS 30-minute-cadence light curve in ∼5 ms on a single GPU, enabling large-scale archival searches. We present a collection of 14,156 short-period variables identified by our network. The majority of our identified variables fall into two prominent populations, one of close-orbit main-sequence binaries and another of δ Scuti stars. Our neural network model and related code are additionally provided as open-source code for public use and extension.

Convolutional neural networks↗
NASA NTRS2020

LHS 1815b: The First Thick-disk Planet Detected by TESS

We report the first discovery of a thick-disk planet, LHS 1815b (TOI-704b, TIC 260004324), detected in the Transiting Exoplanet Survey Satellite (TESS) survey. LHS 1815b transits a bright (V = 12.19 mag, K = 7.99 mag) and quiet M dwarf located 29.87 ± 0.02 pc away with a mass of 0.502 ± 0.015 M⊙ and a radius of 0.501 ± 0.030 R⊙. We validate the planet by combining space- and ground-based photometry, spectroscopy, and imaging. The planet has a radius of 1.088 ± 0.064 R⊕ with a 3σ mass upper limit of 8.7 M⊕. We analyze the galactic kinematics and orbit of the host star LHS 1815 and find that it has a large probability (Pthick/Pthin = 6482) to be in the thick disk with a much higher expected maximal height (Zmax = 1.8 kpc) above the Galactic plane compared with other TESS planet host stars. Future studies of the interior structure and atmospheric properties of planets in such systems using, for example, the upcoming James Webb Space Telescope, can investigate the differences in formation efficiency and evolution for planetary systems between different Galactic components (thick disks, thin disks, and halo).

LHS 1815b↗
NASA NTRS2021

Follow-up and Validation of K2 and TESS Planetary Systems with Keck NIRC2 Adaptive Optics Imaging

High resolution imaging (HRI) is a critical part of the transiting exoplanet follow-up and validation process. HRI allows previously unresolved stellar companions and background blends to be resolved, vetting false positive signals and improving the radii measurements of true planets. Through a multi-semester Keck NIRC2 adaptive optics imaging program, we have pursued HRI of K2 and TESS candidate planet host systems to provide the transiting exoplanet community with necessary data for system validation and characterization. Here we present a summary of our ongoing program that includes an up to date list of targets observed, a description of the observations and data reduction, and a discussion of planetary systems validated by the community using these data. This observing program has been key in NASA’s K2 and TESS missions reaching their goals of identifying new exoplanets ideal for continued follow-up observations to measure their masses and investigate their atmospheres. All observations presented here are available as calibrated images and resulting contrast curves through the Exoplanet Follow-up Observing Program (ExoFOP) website. We encourage members of the exoplanet community to use these data products in their ongoing planetary system validation and characterization efforts.

Adaptive optics↗
NASA NTRS2018

On-Orbit Results and Lessons Learned from the ASTERIA Space Telescope Mission

The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) was deployed from the International Space Station (ISS) on 20 November 2017, beginning a technology demonstration and opportunistic science mission to advance the state of the art in nanosatellite performance for astrophysical observations. The goal of ASTERIA is to achieve arcsecond-level line-of-sight pointing error and highly stable focal plane temperature control. These capabilities enable precision photometry—i.e. the careful measurement of stellar brightness over time—which in turn allows investigation of astrophysical phenomena such as transiting exoplanets. By the end of the 90-day prime mission, ASTERIA had achieved line-of-sight pointing stability of approximately 0.5 arcseconds root mean square (RMS) over 20-minute observations, pointing repeatability of 1 milliarcsecond RMS from one observation to the next, and focal plane temperature stability better than ±0.01 K over 20-minute observations. This paper presents an overview of the ASTERIA flight and ground system, summarizes the pre-delivery test campaign, and discusses the on-orbit performance obtained by the pointing and thermal control subsystems. We also describe the process for planning opportunistic science observations and present lessons learned from development and operations. Having successfully operated for over 200 days as of this writing, ASTERIA is currently in an extended mission to observe nearby bright stars for transiting exoplanets.

Seager, Sara↗