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At least 379 records · Page 21
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NASA NTRS2023

TOI-5344 b: A Saturn-like Planet Orbiting a Super-solar Metallicity M0 Dwarf

We confirm the planetary nature of TOI-5344 b as a transiting giant exoplanet around an M0-dwarf star. TOI-5344 b was discovered with the Transiting Exoplanet Survey Satellite photometry and confirmed with ground-based photometry (the Red Buttes Observatory 0.6 m telescope), radial velocity (the Habitable-zone Planet Finder), and speckle imaging (the NN-Explore Exoplanet Stellar Speckle Imager). TOI-5344 b is a Saturn-like giant planet (ρ = 0.80 +0.17 −0.15 g cm −3 ) with a planetary radius of 9.7 ± 0.5 R⊕ (0.87 ± 0.04 R Jup ) and a planetary mass of 135 +17 −18 M⊕ (0.42 +0.05 −0.06 M Jup ). It has an orbital period of 3.792622 +0.000010 −0.000010 days and an orbital eccentricity of 0.06 +0.07 −0.04 . We measure a high metallicity for TOI-5344 of [Fe/H] = 0.48 ± 0.12, where the high metallicity is consistent with expectations from formation through core accretion. We compare the metallicity of the M-dwarf hosts of giant exoplanets to that of M-dwarf hosts of nongiants (≲8 R⊕). While the two populations appear to show different metallicity distributions, quantitative tests are prohibited by various sample caveats.

Te Han↗
NASA NTRS2020

TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period–radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, r(p)=1.738(+0.087,-0.076)R(ꚛ)), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R(s) = 0.630 ± 0.015 R(ꙩ), M(s) = 0.640 ± 0.016 M(ꙩ)). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of 6.91(+0.75,-0.85) M(ꚛ), which implies an iron core mass fraction of 20(+15,-12)% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin (P=21.8(+0.9,-0.8) days, m(p) sin i= 13.0(+3.8,-5.3)M(ꚛ)) that cannot be firmly ruled out by our data.

Ryan Cloutier↗
NASA NTRS2020

TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period–radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, r(p)=1.738 (+0.087, -0.076) Rꚛ), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (R(s) = 0.630 ± 0.015 Rꙩ, M(s) = 0.640 ± 0.016 Mꙩ}$). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of 6.91 (+0.75, -0.85) Mꚛ, which implies an iron core mass fraction of 20 (+15,-12)% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin P= 21.8(+0.9, _0.8) days, m(p)sin i= 13.0 (+3.8,-5.3) Mꚛ) that cannot be firmly ruled out by our data.

Ryan Cloutier↗
NASA NTRS1973

A study of B 6 stars.

Because detailed information about the spectra of normal late B type stars is deficient, a study of the spectrum of zeta-Draconis, beta-Sextantis, and alpha-Leonis was undertaken to fill this lack and to provide data for comparison with observations of Bp stars, many of which are of late B spectral type. The study was made from high dispersion spectrograms which cover the spectral region 3100 to 6700 A, and from OAO-II spectral scans covering the spectral region 1100 to 3600 A. Profiles, equivalent widths, and central intensities of many lines in the spectrum of zeta-Draconis and of the major lines of beta-Sextantis are presented. The star alpha-Leonis rotates too rapidly for these measurements to be made from high resolution spectrograms. The star beta-Sextantis is the most massive and hottest of the three stars studied.

Underhill, A. B.↗
NASA NTRS1975

The ultraviolet spectrum of B-type supergiants

OAO-2 spectral scans of several early-type main-sequence stars and the shell star zeta Tau are analyzed to derive a representative UV spectrum for B-type supergiants. The absorption lines in the spectra of the B-type supergiants are shown to be stronger than those in main-sequence stars and to have a broad pointed feature at 1720 A that is constant in all such stars. The UV resonance lines of C IV, N V, Si III, and Si IV are found to be displaced toward the shorter wavelengths by velocities of up to 1800 km/s, indicating an escaping atmosphere. For B5 stars, the atmosphere is estimated to be expanding at about 120 km/s. The spectrum of eta CMa (B5Ia) is found to be well represented by the LTE theory of line formation, the presence of a stationary circumstellar shell, and a slowly expanding model atmosphere.

Underhill, A. B.↗
NASA NTRS1977

A flight investigation of the wake turbulence alleviation resulting from a flap configuration change on a B-747 aircraft

A flight test investigation was conducted to evaluate the effects of a flap configuration change on the vortex wake characteristics of a Boeing 747 (B-747) aircraft as measured by differences in upset response resulting from deliberate vortex encounters by a following Learjet aircraft and by direct measurement of the velocities in the wake. The flaps of the B-747 have a predominant effect on the wake. The normal landing flap configuration produces a strong vortex that is attenuated when the outboard flap segments are raised; however, extension of the landing gear at that point increases the vortex induced upsets. These effects are in general agreement with existing wind tunnel and flight data for the modified flap configuration.

Jacobsen, R. A.↗
NASA NTRS1978

Gas Control System for HEAO-B

The HEAO-B Gas Control System consists of a high pressure gas storage supply together with distribution and regulation assemblies and their associated electronics for management of gas required for HEAO-B X-ray counter experiments. The Gas Control System replenishes a gas mixture (82 percent argon, 12.3 percent carbon dioxide, 5.7 percent xenon) in the counter volumes which is lost by: diffusion through controlled leakage plugs, diffusion through counter windows, and consumption resulting from periodic purges. The gas density in each counter volume is maintained constant to within 0.25 percent by comparison with a sealed reference volume. The system is fully redundant, capable of operating at atmospheric pressure as well as in a vacuum, contains interlocks which shut down gas flow in the event of either leakage or excessive pressure, and is able to shut down counter high voltage if counter pressure is abnormally low. The system is electronically controlled by ground command and self-sustaining in orbit for a period of at least one year.

Taylor, B.↗
NASA NTRS1982

Converting Time Signals From BCD to IRIG-B

Coded representation of time signals--day, hour, minute, second--is changed from binary-coded decimal (BCD) to IRIG standard time-code format B by circuit that uses nine integrated circuits. Input to code-converter circuit is parallel BCD pulses on bus output is serial pulses of IRIG-B on single line.

Houston, J. B.↗
NASA NTRS1984

Monitoring of the tidal dynamics of the Dutch Waddensea by SIR-B

The potential of LANDSAT data, covering the entire tidal flats at a certain, known, tidal situation, was assessed. It was discovered that the data cannot be used for systematic survey because of the long interval between subsequent passes, weather conditions often interfere with recording, and of the lack of correlation between passes and the tidal situation. The objective is to overcome the problems by using: (1) the synoptic view obtained by SIR-B, which has the potential of surveying large areas of the flats simultaneously; (2) the all-weather capability of the microwave system; (3) the recording during consecutive days, which results in a straightforeward correlation with the tidal cycle and the picturing of different tidal stages; and (4) the multiangle incidence of SIR-B to analyze the bottom configuration of submerged parts of the flats. The use of a weather independent monitoring device, such as radar, an improvement in the monitoring technique of tidal coastal areas.

Koopmans, B. N.↗
NASA NTRS1985

The final COS-B database now publicly available

The data obtained by the gamma ray satellite COS-B was processed, condensed and integrated together with the relevant mission and experiment parameters into the Final COS-B Database. The database contents and the access programs available with the database are outlined. The final sky coverage and a presentation of the large scale distribution of the observed Milky Way emission are given. The database is announced to be available through the European Space Agency.

Mayer-Hasselwander, H. A.↗
NASA NTRS1984

1300 + 361 A,B is not a gravitational lens

Spectroscopic observations toward 1300 + 361 B obtained at 320-940 nm using a double spectrograph with CCD detectors on the 5-m Hale telescope (resolution about 7 A at 470-940 nm and 10-12 A at 320-470 nm on April 4-5, 1984, are reported. Two objects with magnitude 20 and spectral characteristics resembling those of an interacting pair of metal-poor H II regions at redshift 0.107 are observed, separated by about 10.6 arcsec and with a velocity difference of less than 80 km/s. It is considered unlikely that these objects form a gravitational-lens system. The ratio of the dereddened flux of the 5007-A forbidden line of O III to that of H-beta is found to be 5.03 for 1300 + 361 A and 3.67 for 1300 + 361 B; the difference is attributed to the presence of star-forming regions in the interacting system.

Halpern, J. P.↗
NASA NTRS1983

Developments with multispectral thermal-IR and active microwave systems - TIMS, SIR-A, SIR-B, and radarsat

An update of current and future systems for spectral scanning of geological features in the thermal-IR, and active microwave bands is presented. The design characteristics of four individual systems are described, including the NASA Thermal Infrared Multispectral Scanner (TIMS); the Shuttle Imaging Radars A and B (SIRA-A and SIRA-B); and the Canadian RADARSAT satellite for geological mapping and ice monitoring. The applications of spectral data from the Side Looking Airborne Radar (SLAR), the GEMS 100 mapping system, and the Landsat RBV instrument to the mapping of large geological structures are also described.

Harrison, P. G.↗
NASA NTRS1986

IUE observations of interstellar hydrogen and deuterium toward Alpha Centauri B

A high dispersion profile is presented of the Lyman-alpha emission toward Alpha Cen B as recorded in two images taken with the IUE spacecraft. The spectra were examined with a three-parameter Gaussian or five-parameter solar-type profile to derive the intrinsic background stellar emission. Voight absorption profiles were calculated for the intervening H I and D I gas. A uniform, thermally broadened medium was assumed, with the calculations being based on the free stellar parameters of density, velocity dispersion and the bulk velocity of H I, and the density of D I. The use of a small aperture is shown to have been effective in eliminating geocoronal and interplanetary diffuse Ly-alpha contamination. The H I absorption profile toward Alpha Cen B is found to be equivalent to that toward Alpha Cen A, indicating that the H I profiles derived are essentially independent of stellar emission. Less success, however, was attained in obtaining any definitive D I profile, although an asymmetry in the blue and red wings of the Lyman-alpha emissions did show the presence of absorption by interstellar deuterium and allow setting a lower limit of 0.00001 for the D I/H I ratio.

Landsman, W. B.↗
NASA NTRS1986

SIR-B observations of dominant ocean waves near hurricane Josephine

Radar images of ocean surface waves near hurricane Josephine were acquired with the Shuttle imaging radar B (SIR-B) system on October 12, 1984. Fast Fourier transform analyses of the images have been performed along most of the 600-km image track. These data reveal the presence of at least two dominant wave systems which undergo significant spatial variations in wavelength and direction.

Holt, B.↗
NASA NTRS1986

Sondrestrom radar observations of the effect of the IMF B(y) component on polar cap convection

Sondrestrom incoherent-scatter radar measurements of plasma drift in the auroral oval and the polar cap are used to examine the effect of the IMF B(y) component in the dusk, midnight, and dawn sectors. The individual radar observations are briefly reviewed, and the average convection patterns obtained by binning the drift data for the two orientations of the IMF B(y) component are shown. These patterns are compared to the various models of convection that have been proposed. None of the models seem to reproduce the observed convections well, although some features of the models are seen in the radar data.

De La Beaujardiere, O.↗
NASA NTRS1989

Closed loop navigation and guidance for gravity probe B orbit insertion

This paper addresses the problem of guiding the Gravity Probe B (GP-B) spacecraft from its location after initial insertion to a very precise low earth orbit. Specifically, the satellite orbit is required to be circular to within 0.001 eccentricity, polar to within 0.001 deg inclination, and aligned with the direction of the star Rigel to within 0.001 deg. Navigation data supplied by an on-board GPS receiver is used as feedback to a control algorithm designed to minimize the time to achieve the desired orbit. Translational control is provided by the proportional helium thrusters, which are used for drag-free and attitude control during the remainder of the science mission. Simulations of the guidance system are presented which give an indication of performance characteristics for several types of orbit injection errors. This research is the first reported effort to use GPS as a sensor for a closed loop space guidance system.

Axelrad, P.↗
NASA NTRS1989

The Gravity-Probe-B relativity gyroscope experiment - Development of the prototype flight instrument

The Gravity-Probe-B relativity gyroscope experiment (GP-B) will measure the geodetic and frame-dragging precession rates of gyroscopes in a 650 km high polar orbit about the earth. The goal is to measure these two effects, which are predicted by Einstein's General Theory of Relativity, to 0.01 percent (geodetic) and 1 percent (frame-dragging). This paper presents the development progress for full-size prototype flight hardware including the gyroscopes, gyro readout and magnetic shielding system, and an integrated ground test instrument.

Turneaure, J. P.↗
NASA NTRS1991

High-resolution CO observations of luminous infrared galaxies with large L(ir)/L(B) ratios - IRAS 10173 + 0828, Zw 049.057, IRAS 17208 - 0014

The Owens Valley mm-wave interferometer has been used for high-resolution (about 3-7 arcsec) mapping of CO emission in three luminous IRAS galaxies: IRAS 17208 - 0014, 15107 + 0724, and IRAS 10173 + 0828. These galaxies are among the most extreme, in terms of their L(ir)/L(B) ratio, for objects in the IRAS Bright Galaxy Surveys. The CO emission detected in the three galaxies originates from a single region centered on the IRAS emission peak. These observations have shown that these galaxies have similar values for the global L(ir)/M(H2) ratio, for the surface density of molecular gas in their central regions and for the extinction toward the nucleus (above 300 mag). A high L(ir)/L(B) ratio seems to be a good predictor for both a high global L(ir)/M(H2) ratio and very large central H2 surface densities.

Planesas, P.↗