Showing papers by "Edward L. Wright published in 2021"
TL;DR: In this article, the authors presented the final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs and provided polynomial fits to the bulk trends.
Abstract: We present final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs. We combine these with prior studies to build a list of 525 known L, T, and Y dwarfs within 20 pc of the Sun, 38 of which are presented here for the first time. Using published photometry and spectroscopy as well as our own follow-up, we present an array of color-magnitude and color-color diagrams to further characterize census members, and we provide polynomial fits to the bulk trends. Using these characterizations, we assign each object a $T_{\rm eff}$ value and judge sample completeness over bins of $T_{\rm eff}$ and spectral type. Except for types $\ge$ T8 and $T_{\rm eff} <$ 600K, our census is statistically complete to the 20-pc limit. We compare our measured space densities to simulated density distributions and find that the best fit is a power law ($dN/dM \propto M^{-\alpha}$) with $\alpha = 0.6{\pm}0.1$. We find that the evolutionary models of Saumon & Marley correctly predict the observed magnitude of the space density spike seen at 1200K $< T_{\rm eff} <$ 1350K, believed to be caused by an increase in the cooling timescale across the L/T transition. Defining the low-mass terminus using this sample requires a more statistically robust and complete sample of dwarfs $\ge$Y0.5 and with $T_{\rm eff} <$ 400K. We conclude that such frigid objects must exist in substantial numbers, despite the fact that few have so far been identified, and we discuss possible reasons why they have largely eluded detection.
74 citations
TL;DR: The CatWISE2020 catalog as mentioned in this paper consists of 1,890,715,640 sources over the entire sky selected from Wide-Field Infrared Survey Explorer (WISE) and NEOWISE survey data at 3.4 and 4.6 μm (W1 and W2) collected from 2010 January 7 to 2018 December 13.
Abstract: Author(s): Marocco, F; Eisenhardt, PRM; Fowler, JW; Kirkpatrick, JD; Meisner, AM; Schlafly, EF; Stanford, SA; Garcia, N; Caselden, D; Cushing, MC; Cutri, RM; Faherty, JK; Gelino, CR; Gonzalez, AH; Jarrett, TH; Koontz, R; Mainzer, A; Marchese, EJ; Mobasher, B; Schlegel, DJ; Stern, D; Teplitz, HI; Wright, EL | Abstract: The CatWISE2020 Catalog consists of 1,890,715,640 sources over the entire sky selected from Wide-field Infrared Survey Explorer (WISE) and NEOWISE survey data at 3.4 and 4.6 μm (W1 and W2) collected from 2010 January 7 to 2018 December 13. This data set adds two years to that used for the CatWISE Preliminary Catalog, bringing the total to six times as many exposures spanning over 16 times as large a time baseline as the AllWISE catalog. The other major change from the CatWISE Preliminary Catalog is that the detection list for the CatWISE2020 Catalog was generated using crowdsource from Schlafly et al., while the CatWISE Preliminary Catalog used the detection software used for AllWISE. These two factors result in roughly twice as many sources in the CatWISE2020 Catalog. The scatter with respect to Spitzer photometry at faint magnitudes in the COSMOS field, which is out of the Galactic Plane and at low ecliptic latitude (corresponding to lower WISE coverage depth) is similar to that for the CatWISE Preliminary Catalog. The 90% completeness depth for the CatWISE2020 Catalog is at W1 = 17.7 mag and W2 = 17.5 mag, 1.7 mag deeper than in the CatWISE Preliminary Catalog. In comparison to Gaia, CatWISE2020 motions are accurate at the 20 mas yr-1 level for W1∼15 mag sources and at the ∼100 mas yr-1 level for W1∼17 mag sources. This level of accuracy represents a 12 improvement over AllWISE. The CatWISE catalogs are available in the WISE/NEOWISE Enhanced and Contributed Products area of the NASA/IPAC Infrared Science Archive.
68 citations
TL;DR: In this paper, a traveling-wave tube (TWT) power amplifier operating in the ${W}$ -band (75-110 GHz) frequency range is presented, which is based on a serpentine waveguide (SWG) amplification circuit, a slow wave circuit type capable of high power and broad instantaneous bandwidth.
Abstract: We present the experimental demonstration of a traveling-wave tube (TWT) power amplifier operating in the ${W}$ -band (75–110 GHz) frequency range. The device is based on a serpentine waveguide (SWG) amplification circuit, a slow wave circuit type capable of high power and broad instantaneous bandwidth in the upper millimeter-wave range. A 20 kV, 140-mA round solenoid-focused electron beam powers the device. At 20 kV, we measure 215 ± 2 W peak RF output power at 93 GHz with 20.1 ± 0.15 dB saturated gain, pulsed at 0.1% duty. We observe 10-GHz instantaneous amplification bandwidth at 100-W minimum output power, covering the range 88–98 GHz. Operating at 20.8 kV, the TWT produces 285 ± 3 W at 91 GHz with 22.4 ± 0.15 dB gain, and 7 GHz, 3-dB bandwidth. The peak electronic efficiency measured is approximately 10%.
18 citations
01 Feb 2021
TL;DR: In this paper, an analysis of the accuracy of geometric albedos determined for asteroids through the modeling of observed thermal infrared radiation is presented, and it is shown that albedo uncertainty is dominated by the uncertainty on the measured $H_V$ absolute magnitude.
Abstract: We present an analysis of the accuracy of geometric albedos determined for asteroids through the modeling of observed thermal infrared radiation. We show that albedo uncertainty is dominated by the uncertainty on the measured $H_V$ absolute magnitude, and that any analysis using albedos in a statistical application will also be dominated by this source of uncertainty. For all but the small fraction of asteroids with a large amount of characterization data, improved knowledge of the $H_V$ magnitude will be fundamentally limited by incomplete phase curve coverage, incomplete light curve knowledge, and the necessary conversion from the observed band to the $V$ band. Switching the absolute magnitude standard to a different band such a $r'$ would mitigate the uncertainty due to band conversion for many surveys, but this only represents a small component of the total uncertainty. Therefore, techniques making use of these albedos must ensure that their uncertainties are being properly accounted for.
13 citations
Goddard Space Flight Center1, Grumman Aircraft Corporation2, University of Connecticut3, University of Maryland, College Park4, Lockheed Martin Space Systems5, NASA Headquarters6, University of Michigan7, Jet Propulsion Laboratory8, University of California, Irvine9, The Institute of Optics10, Chalmers University of Technology11, Cornell University12, University of California, Santa Cruz13, Northrop Grumman Corporation14, University of Nottingham15, Netherlands Institute for Space Research16, Space Telescope Science Institute17, Harvard University18, University of Florida19, University of Massachusetts Amherst20, University of Tokyo21, University of California, San Diego22, University of British Columbia23, Johns Hopkins University24, University of Arizona25, University of Illinois at Urbana–Champaign26, University of California, Los Angeles27, California Institute of Technology28
TL;DR: The Origins Space Telescope as mentioned in this paper was designed to trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life, and it was the first telescope to operate at mid-and far-infrared (IR) wavelengths.
Abstract: The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20 μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588 μm, making wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural background-limited sensitivity.
11 citations
Posted Content•
TL;DR: In this paper, diameters and albedos for the near-Earth and Main Belt asteroids observed by the NEOWISE spacecraft during the sixth and seventh years of its Reactivation mission were calculated from fitting thermal models to NEOWIS observations of $199$ and $5851$ MBAs detected during the 6th and 7th years of the survey.
Abstract: We present diameters and albedos computed for the near-Earth and Main Belt asteroids observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of $199$ NEOs and $5851$ MBAs detected during the sixth year of the survey, and $175$ NEOs and $5861$ MBAs from the seventh year. Comparisons of the near-Earth object diameters derived from Reactivation data with those derived from the WISE cryogenic mission data show a $\sim30\%$ relative uncertainty. This larger uncertainty compared to data from the cryogenic mission is due to the need to assume a beaming parameter for the fits to the shorter wavelength data that the Reactivation mission is limited to. We also present an analysis of the orbital parameters of the Main Belt asteroids that have been discovered by NEOWISE during Reactivation, finding that these objects tend to be on orbits that result in their perihelia being far from the ecliptic, and thus missed by other surveys. To date, the NEOWISE Reactivation survey has provided thermal fits of $1415$ unique NEOs. Including the mission phases before spacecraft hibernation increases the count of unique NEOs characterized to $1845$ from WISE's launch to the present.
7 citations
TL;DR: In this article, Meisner et al. studied the properties of the WISEA J153429.3 and concluded that it is most likely an old, metal-poor brown dwarf and possibly the first Y subdwarf.
Abstract: Continued follow-up of WISEA J153429.75−104303.3, announced in Meisner et al., has proven it to have an unusual set of properties. New imaging data from Keck/MOSFIRE and HST/WFC3 shows that this object is one of the few faint proper motion sources known with J − ch2 >8 mag, indicating a very cold temperature consistent with the latest known Y dwarfs. Despite this, it has W1−W2 and ch1−ch2 colors ~1.6 mag bluer than a typical Y dwarf. A new trigonometric parallax measurement from a combination of WISE, Spitzer, and HST astrometry confirms a nearby distance of ${16.3}_{-1.2}^{+1.4}$ pc and a large transverse velocity of 207.4 ± 15.9 km s−1. The absolute J, W2, and ch2 magnitudes are in line with the coldest known Y dwarfs, despite the highly discrepant W1−W2 and ch1−ch2 colors. We explore possible reasons for the unique traits of this object and conclude that it is most likely an old, metal-poor brown dwarf and possibly the first Y subdwarf. Given that the object has an HST F110W magnitude of 24.7 mag, broadband spectroscopy and photometry from JWST are the best options for testing this hypothesis.
5 citations
University of Arizona1, Johnson State College2, Goddard Space Flight Center3, Jet Propulsion Laboratory4, Southwest Research Institute5, Search for extraterrestrial intelligence6, California Institute of Technology7, University of Washington8, Finnish Geodetic Institute9, Georgia Institute of Technology10, University of Rochester11, Centre national de la recherche scientifique12, Johns Hopkins University13, University of California, Santa Cruz14, Northern Arizona University15, University of California, Los Angeles16
TL;DR: In this article, Bannister et al. proposed a method to solve the problem of how to find the minimum number of observations required for a given set of observations to be collected.
Abstract: Coauthors/Endorsers: P. Abell (JSC), Michele T. Bannister, School of Physical and Chemical Sciences | Te Kura Matū, U. Canterbury, B. Barbee (GSFC), J. Barnes (U. Arizona), J.F. Bell III (ASU), L. Benner (JPL), B. Betts (Planetary Society), Maitrayee Bose (ASU), W. Bottke (SwRI), D. Britt (U. Central Florida), M. Brozović (JPL), M. Bruckner (U. Arizona), Michael W. Busch (SETI), S. Carey (IPAC/Caltech), J. Castillo-Rogez (JPL), J. Chesley (JPL), E. Christensen (U. Arizona), P. Chodas (JPL), D. Cotto-Figueroa (U. Puerto Rico at Humacao), M. Delbó (Observatoire de la Côte d'Azur), R. T. Daly (JHU/APL), J. Dotson (NASA-Ames), P. Eisenhardt (JPL), Y. R. Fernandez (U. Central Florida), Ronald A. Fevig (U. North Dakota), T. Grav (U. Arizona), S. Greenstreet (U. Washington), M. Gritsevich (Finnish Geospatial Research Institute), Heidi B. Hammel (AURA), A. Harris (DLR), W. Harris (U. Arizona), D. Hickson (U. Central Florida), Kynan Hughson (Georgia Institute of Technology), Željko Ivezić (U. Washington), Devanshu Jha (MVJCE, India), Lynne Jones (U. Washington), Mario Jurić (U. Washington), B. Kacar (U. Arizona), D. Lauretta (U. Arizona), Joseph Lazio (JPL), Rosaly M.C. Lopes (JPL), F. Marchis (SETI Institute), Sean E. Marshall (Arecibo/U. Central Florida), J. Masiero (JPL), D. Mathias (NASA-Ames), R. S. McMillan (U. Arizona), C. McMurtry (U. Rochester), P. Michel (U Côte d’Azur, Obs. Côte d’Azur, CNRS), S. Naidu (JPL), M. C. Nolan (U. Arizona), T. Okada (ISAS/JAXA), J. L. Pipher (U. Rochester), Carol Raymond (JPL), E. Rivera-Valentín (LPI/URSA), A. Rivkin (APL/Johns Hopkins University) C. A. Schambeau (U. Central Florida), D. Scheeres (U. Colorado), Jennifer Scully (JPL), S. Sonnett (PSI), T. Spahr (NEO Sciences), A. Stern (SwRI), T. Swindle (U. Arizona), P. Taylor (LPI/USRA), D. Takir (JSC), M. Telus (UC Santa Cruz), C. Thomas (NAU), F. C. F. Venditti (Arecibo/U. Central Florida), Anne K. Virkki (Arecibo/U. Central Florida), A. Wong (U. Arizona), E. L. Wright (UCLA)
5 citations
Goddard Space Flight Center1, Grumman Aircraft Corporation2, California Institute of Technology3, University of Connecticut4, University of Maryland, College Park5, Lockheed Martin Space Systems6, NASA Headquarters7, University of Michigan8, Jet Propulsion Laboratory9, University of California, Irvine10, The Aerospace Corporation11, Coherent, Inc.12, University of California, Santa Cruz13, Universities Space Research Association14, Harvard University15, University of Rochester16, University of Florida17, Space Telescope Science Institute18, University of Massachusetts Amherst19, Raytheon20, University of Arizona21, University of Tokyo22, University of California, San Diego23, Johns Hopkins University24, University of Illinois at Urbana–Champaign25, University of California, Los Angeles26
TL;DR: The Origins Space Telescope as mentioned in this paper traces the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life and is designed to answer the alluring questions of how galaxies evolve from the earliest galactic systems to those found in the universe today.
Abstract: The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? We describe how Origins was designed to answer these alluring questions. We discuss the key decisions taken by the Origins mission concept study team, the rationale for those choices, and how they led through an exploratory design process to the Origins baseline mission concept. To understand the concept solution space, we studied two distinct mission concepts and descoped the second concept, aiming to maximize science per dollar and hit a self-imposed cost target. We report on the study approach and describe the concept evolution. The resulting baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. The chosen architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch. The cryo-thermal system design leverages James Webb Space Telescope technology and experience.
4 citations
Space Telescope Science Institute1, Johns Hopkins University2, University of California, Irvine3, Goddard Space Flight Center4, California Institute of Technology5, University of Connecticut6, University of Maryland, College Park7, NASA Headquarters8, University of Michigan9, Jet Propulsion Laboratory10, Chalmers University of Technology11, University of California, Santa Cruz12, University of Paris13, Centre national de la recherche scientifique14, Netherlands Institute for Space Research15, Harvard University16, University of Florida17, University of Massachusetts Amherst18, University of Tokyo19, University of California, San Diego20, University of British Columbia21, University of Arizona22, University of Illinois at Urbana–Champaign23, University of California, Los Angeles24
TL;DR: The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispersal of elements essential to life, the formation of planetary systems, and the transport of water to habitable worlds and the atmospheres of exoplanets around nearby K- and M-dwarfs to identify potentially habitable and even inhabited worlds.
Abstract: The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispersal of elements essential to life, the formation of planetary systems, and the transport of water to habitable worlds and the atmospheres of exoplanets around nearby K- and M-dwarfs to identify potentially habitable—and even inhabited—worlds. These science priorities are aligned with NASA’s three major astrophysics science goals: How does the Universe work? How did we get here? and Are we alone? We briefly describe the science case that arose from the astronomical community and the science traceability matrix for Origins. The science traceability matrix prescribes the design of Origins and demonstrates that it will address the key science questions motivated by the science case.
3 citations
TL;DR: In this article, the authors present a near infrared spectrum of the Y dwarf WISEP 182831.8, which covers the 0.9-1.7 um wavelength range at a resolving power of lambda/Delta lambda ~180 and is a significant improvement over the previously published spectrum.
Abstract: We present a Hubble Space Telescope/Wide-Field Camera 3 near infrared spectrum of the archetype Y dwarf WISEP 182831.08+265037.8. The spectrum covers the 0.9-1.7 um wavelength range at a resolving power of lambda/Delta lambda ~180 and is a significant improvement over the previously published spectrum because it covers a broader wavelength range and is uncontaminated by light from a background star. The spectrum is unique for a cool brown dwarf in that the flux peaks in the Y, J, and H band are of near equal intensity in units of f_lambda. We fail to detect any absorption bands of NH_3 in the spectrum, in contrast to the predictions of chemical equilibrium models, but tentatively identify CH_4 as the carrier of an unknown absorption feature centered at 1.015 um. Using previously published ground- and spaced-based photometry, and using a Rayleigh Jeans tail to account for flux emerging longward of 4.5 um, we compute a bolometric luminosity of log (L_bol/L_sun)=-6.50+-0.02 which is significantly lower than previously published results. Finally, we compare the spectrum and photometry to two sets of atmospheric models and find that best overall match to the observed properties of WISEP 182831.08+265037.8 is a ~1 Gyr old binary composed of two T_eff~325 K, ~5 M_Jup brown dwarfs with subsolar [C/O] ratios.
TL;DR: In this article, an experimental characterization of a 20kV, 130-mA thermionic electron gun, which is a component of a traveling-wave tube (TWT) power amplifier, is presented.
Abstract: We present experimental characterization of a 20-kV, 130-mA thermionic electron gun, which is a component of a ${W}$ -band traveling-wave tube (TWT) power amplifier. The electron beam is strongly focused by a 6.6-kG permanent magnet solenoid, producing a peak current density up to 800 A/cm2. The cathode temperature, focus electrode voltage, and modulating anode voltage are varied to characterize the emitted cathode current and beam transport through the beam tunnel of the TWT RF circuit. We observe the variation of the cathode current from 107 to 155 mA and peak beam transmission of 95% measured at the collector. Experimental results are compared to 2-D simulations with the electron gun and collector design code MICHELLE.
TL;DR: In this paper, the authors explore possible reasons for the unique traits of this object and conclude that it is most likely an old, metal-poor brown dwarf and possibly the first Y subdwarf.
Abstract: Continued follow-up of WISEA J153429.75-104303.3, announced in Meisner et al (2020), has proven it to have an unusual set of properties. New imaging data from Keck/MOSFIRE and HST/WFC3 show that this object is one of the few faint proper motion sources known with J-ch2 > 8 mag, indicating a very cold temperature consistent with the latest known Y dwarfs. Despite this, it has W1-W2 and ch1-ch2 colors ~1.6 mag bluer than a typical Y dwarf. A new trigonometric parallax measurement from a combination of WISE, Spitzer, and HST astrometry confirms a nearby distance of $16.3^{+1.4}_{-1.2}$ pc and a large transverse velocity of $207.4{\pm}15.9$ km/s. The absolute J, W2, and ch2 magnitudes are in line with the coldest known Y dwarfs, despite the highly discrepant W1-W2 and ch1-ch2 colors. We explore possible reasons for the unique traits of this object and conclude that it is most likely an old, metal-poor brown dwarf and possibly the first Y subdwarf. Given that the object has an HST F110W magnitude of 24.7 mag, broad-band spectroscopy and photometry from JWST are the best options for testing this hypothesis.
TL;DR: In this paper, the authors present a near infrared spectrum of the Y dwarf WISEP 182831.8, which covers the 0.9-1.7 um wavelength range at a resolving power of lambda/Delta lambda ~180 and is a significant improvement over the previously published spectrum.
Abstract: We present a Hubble Space Telescope/Wide-Field Camera 3 near infrared spectrum of the archetype Y dwarf WISEP 182831.08+265037.8. The spectrum covers the 0.9-1.7 um wavelength range at a resolving power of lambda/Delta lambda ~180 and is a significant improvement over the previously published spectrum because it covers a broader wavelength range and is uncontaminated by light from a background star. The spectrum is unique for a cool brown dwarf in that the flux peaks in the Y, J, and H band are of near equal intensity in units of f_lambda. We fail to detect any absorption bands of NH_3 in the spectrum, in contrast to the predictions of chemical equilibrium models, but tentatively identify CH_4 as the carrier of an unknown absorption feature centered at 1.015 um. Using previously published ground- and spaced-based photometry, and using a Rayleigh Jeans tail to account for flux emerging longward of 4.5 um, we compute a bolometric luminosity of log (L_bol/L_sun)=-6.50+-0.02 which is significantly lower than previously published results. Finally, we compare the spectrum and photometry to two sets of atmospheric models and find that best overall match to the observed properties of WISEP 182831.08+265037.8 is a ~1 Gyr old binary composed of two T_eff~325 K, ~5 M_Jup brown dwarfs with subsolar [C/O] ratios.
Posted Content•
TL;DR: In this article, an analysis of the accuracy of geometric albedos determined for asteroids through the modeling of observed thermal infrared radiation is presented, and it is shown that albedo uncertainty is dominated by the uncertainty on the measured $H_V$ absolute magnitude.
Abstract: We present an analysis of the accuracy of geometric albedos determined for asteroids through the modeling of observed thermal infrared radiation. We show that albedo uncertainty is dominated by the uncertainty on the measured $H_V$ absolute magnitude, and that any analysis using albedos in a statistical application will also be dominated by this source of uncertainty. For all but the small fraction of asteroids with a large amount of characterization data, improved knowledge of the $H_V$ magnitude will be fundamentally limited by incomplete phase curve coverage, incomplete light curve knowledge, and the necessary conversion from the observed band to the $V$ band. Switching the absolute magnitude standard to a different band such a $r'$ would mitigate the uncertainty due to band conversion for many surveys, but this only represents a small component of the total uncertainty. Therefore, techniques making use of these albedos must ensure that their uncertainties are being properly accounted for.