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Open accessProceedings ArticleDOI: 10.1117/12.2562997

The Nancy Grace Roman Space Telescope Coronagraph Instrument (CGI) Technology Demonstration.

Abstract: The Coronagraph Instrument (CGI) on the Nancy Grace Roman Space Telescope will demonstrate the high-contrast technology necessary for visible-light exoplanet imaging and spectroscopy from space via direct imaging of Jupiter-size planets and debris disks. This in-space experience is a critical step toward future, larger missions targeted at direct imaging of Earth-like planets in the habitable zones of nearby stars. This paper presents an overview of the current instrument design and requirements, highlighting the critical hardware, algorithms, and operations being demonstrated. We also describe several exoplanet and circumstellar disk science cases enabled by these capabilities. A competitively selected Community Participation Program team will be an integral part of the technology demonstration and could perform additional CGI observations beyond the initial tech demo if the instrument performance warrants it.

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Topics: Coronagraph (56%), Exoplanet (53%)

6 results found

Open accessJournal ArticleDOI: 10.3847/1538-4357/AC1789
Abstract: Exoplanets that receive stellar irradiance of approximately Earth's or less have been discovered and many are suitable for spectral characterization. Here we focus on the temperate planets that have massive H2-dominated atmospheres, and trace the chemical reactions and transport following the photodissociation of H2O, CH4, NH3, and H2S, with K2-18 b, PH2 b, and Kepler-167 e representing temperate/cold planets around M and G/K stars. We find that NH3 is likely depleted by photodissociation to the cloud deck on planets around G/K stars but remains intact in the middle atmosphere of planets around M stars. A common phenomenon on temperate planets is that the photodissociation of NH3 in presence of CH4 results in HCN as the main photochemical product. The photodissociation of CH4 together with H2O leads to CO and CO2, and the synthesis of hydrocarbon is suppressed. Temperate planets with super-solar atmospheric metallicity and appreciable internal heat may have additional CO and CO2 from the interior and less NH3 and thus less HCN. Our models of K2-18 b can explain the transmission spectrum measured by Hubble, and indicate that future observations in 0.5-5.0 um would provide the sensitivity to detect the equilibrium gases CH4, H2O, and NH3, the photochemical gas HCN, as well as CO2 in some cases. Temperate and H2-rich exoplanets are thus laboratories of atmospheric chemistry that operate in regimes not found in the Solar System, and spectral characterization of these planets in transit or reflected starlight promises to greatly expand the types of molecules detected in exoplanet atmospheres.

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Topics: Exoplanet (59%), Planet (57%), Solar System (54%) ... show more

1 Citations

Open accessJournal ArticleDOI: 10.3847/1538-3881/AC27AB
Yiting Li1, Timothy D. Brandt1, G. Mirek Brandt1, Trent J. Dupuy2  +5 moreInstitutions (7)
Abstract: Radial velocity (RV) surveys have discovered hundreds of exoplanetary systems but suffer from a fundamental degeneracy between planet mass $M_p$ and orbital inclination $i$. In this paper we break this degeneracy by combining RVs with complementary absolute astrometry taken from the \Gaia EDR3 version of the cross-calibrated \Hipparcos-\Gaia Catalog of Accelerations (HGCA). We use the Markov Chain Monte Carlo orbit code $\orvara$ to simultaneously fit literature RVs and absolute astrometry from the HGCA. We constrain the orbits, masses, and inclinations of nine single and massive RV companions orbiting nearby G and K stars. We confirm the planetary nature of six companions: HD 29021 b ($4.47_{-0.65}^{+0.67}\Mjup$), HD 81041 b ($7.24_{-0.37}^{+1.0}\Mjup$), HD 87883 b ($6.31_{-0.32}^{+0.31}\Mjup$), HD 98649 b ($9.7_{-1.9}^{+2.3}\Mjup$), HD 106252 b ($10.00_{-0.73}^{+0.78}\Mjup$), and HD 171238 b ($8.8_{-1.3}^{+3.6}\Mjup$). We place one companion, HD 196067 b ($12.5_{-1.8}^{+2.5}\Mjup$) on the planet-brown dwarf boundary, and two companions in the low mass brown dwarf regime: HD 106515 Ab ($18.9_{-1.4}^{+1.5}\Mjup$), and HD 221420 b (${20.6}_{-1.6}^{+2.0}\Mjup$). The brown dwarf HD 221420 b, with a semi-major axis of ${9.99}_{-0.70}^{+0.74}$ AU, a period of ${27.7}_{-2.5}^{+3.0}$ years, and an eccentricity of $0.162_{-0.030}^{+0.035}$ represents a promising target for high-contrast imaging. The RV orbits of HD 87883 b, HD 98649 b, HD 171238 b, and HD 196067 b are not fully constrained yet because of insufficient RV data. We find two possible inclinations for each of these orbits due to difficulty in separating prograde from retrograde orbits, but we expect this will change decisively with future Gaia data releases.

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Open accessJournal ArticleDOI: 10.1093/MNRAS/STAB3023
Abstract: As gravitational-wave (GW) interferometers become more sensitive and probe ever more distant reaches, the number of detected binary neutron star mergers will increase. However, detecting more events farther away with GWs does not guarantee corresponding increase in the number of electromagnetic counterparts of these events. Current and upcoming wide-field surveys that participate in GW follow-up operations will have to contend with distinguishing the kilonova from the ever increasing number of transients they detect, many of which will be consistent with the GW sky-localization. We have developed a novel tool based on a temporal convolutional neural network architecture, trained on sparse early-time photometry and contextual information for Electromagnetic Counterpart Identification (El-CID). The overarching goal for El-CID is to slice through list of new transient candidates that are consistent with the GW sky localization, and determine which sources are consistent with kilonovae, allowing limited target-of-opportunity resources to be used judiciously. In addition to verifying the performance of our algorithm on an extensive testing sample, we validate it on AT2017gfo - the only EM counterpart of a binary neutron star merger discovered to date - and AT2019npv - a supernova that was initially suspected as a counterpart of the gravitational-wave event, GW190814, but was later ruled out after further analysis.

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Topics: Kilonova (55%)

Open accessJournal ArticleDOI: 10.3847/1538-3881/AC1B31
Abstract: Giant stars as known exoplanet hosts are relatively rare due to the potential challenges in acquiring precision radial velocities and the small predicted transit depths. However, these giant host stars are also some of the brightest in the sky and so enable high signal-to-noise follow-up measurements. Here we report on new observations of the bright (V ~ 3.3) giant star $\iota$ Draconis ($\iota$ Dra), known to host a planet in a highly eccentric ~511 day period orbit. TESS observations of the star over 137 days reveal asteroseismic signatures, allowing us to constrain the stellar radius, mass, and age to ~2%, ~6%, and ~28%, respectively. We present the results of continued radial velocity monitoring of the star using the Automated Planet Finder over several orbits of the planet. We provide more precise planet parameters of the known planet and, through the combination of our radial velocity measurements with Hipparcos and Gaia astrometry, we discover an additional long-period companion with an orbital period of ~$68^{+60}_{-36}$ years. Mass predictions from our analysis place this sub-stellar companion on the border of the planet and brown dwarf regimes. The bright nature of the star combined with the revised orbital architecture of the system provides an opportunity to study planetary orbital dynamics that evolve as the star moves into the giant phase of its evolution.

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Topics: Exoplanet (62%), Planet (60%), Radial velocity (58%) ... show more


29 results found

Open accessJournal ArticleDOI: 10.1051/AAS:2000332
Abstract: SIMBAD is the astronomical data base produced and maintained by the Centre de Donnees astronomiques de Strasbourg (CDS), at the Observatoire de Strasbourg, France.

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Topics: SIMBAD (72%)

1,337 Citations

Open accessPosted Content
B. Scott Gaudi1, Sara Seager2, Bertrand Mennesson3, Alina Kiessling3  +182 moreInstitutions (20)
Abstract: The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.

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Topics: Exoplanet (57%), Observatory (56%), Coronagraph (53%) ... show more

104 Citations

Open accessJournal ArticleDOI: 10.1117/1.JATIS.2.1.011013
Abstract: The prospect of extreme high-contrast astronomical imaging from space has inspired developments of new coronagraph methods for exoplanet imaging and spectroscopy. However, the requisite imaging contrast, at levels of 1 billion to one or better for the direct imaging of cool mature exoplanets in reflected visible starlight, leads to challenging new requirements on the stability and control of the optical wavefront, at levels currently beyond the reach of ground-based telescopes. We review the design, performance, and science prospects for the hybrid Lyot coronagraph (HLC) on the WFIRST-AFTA telescope. Together with a pair of deformable mirrors for active wavefront control, the HLC creates a full 360-deg high-contrast dark field of view at 10−9 contrast levels or better, extending to within angular separations of 3 λ0/D from the central star, over spectral bandwidths of 10% or more.

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Topics: Coronagraph (64%), Deformable mirror (53%), Telescope (51%)

94 Citations

Open accessJournal ArticleDOI: 10.1117/1.JATIS.2.1.011012
Abstract: Coronagraphs of the apodized pupil and shaped pupil varieties use the Fraunhofer diffraction properties of amplitude masks to create regions of high contrast in the vicinity of a target star. Here we present a hybrid coronagraph architecture in which a binary, hard-edged shaped pupil mask replaces the gray, smooth apodizer of the apodized pupil Lyot coronagraph (APLC). For any contrast and bandwidth goal in this configuration, as long as the prescribed region of contrast is restricted to a finite area in the image, a shaped pupil is the apodizer with the highest transmission. We relate the starlight cancellation mechanism to that of the conventional APLC. We introduce a new class of solutions in which the amplitude profile of the Lyot stop, instead of being fixed as a padded replica of the telescope aperture, is jointly optimized with the apodizer. Finally, we describe shaped pupil Lyot coronagraph (SPLC) designs for the baseline architecture of the Wide-Field Infrared Survey Telescope–Astrophysics Focused Telescope Assets (WFIRST-AFTA) coronagraph. These SPLCs help to enable two scientific objectives of the WFIRST-AFTA mission: (1) broadband spectroscopy to characterize exoplanet atmospheres in reflected starlight and (2) debris disk imaging.

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Topics: Lyot stop (61%), Coronagraph (59%), Aperture (50%)

84 Citations

Open accessPosted Content
Abstract: The Large UV/Optical/Infrared Surveyor (LUVOIR) mission is one of four Decadal Survey Mission Concepts studied by NASA in preparation for the US National Academies' Astro2020 Decadal Survey. This observatory has the major goal of characterizing a wide range of exoplanets, including those that might be habitable -- or even inhabited. It would simultaneously enable a great leap forward in a broad range of astrophysics -- from the epoch of reionization, through galaxy formation and evolution, to star and planet formation. Powerful remote sensing observations of Solar System bodies will also be possible. This Final Report on the LUVOIR study presents the scientific motivations and goals of the mission concept, the engineering design, and technology development information. Please refer to the LUVOIR Final Report Appendices (separate document) for additional information.

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74 Citations

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