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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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At least 379 records · Page 21
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NASA NTRS1983

Photoelectric photometry of selected SAO stars. III

Photometric observations of 131 SAO stars for use in calibrating data obtained from the Near Infrared Photographic Sky Survey (NIPSS) are reported. The serial numbers of the primary NIPSS program fields in which the photometry was done are shown along with the approximate position of each field and the number of stars observed in each field. The observations are listed, showing the SAO numbers of the program stars, their 1950 equatorial coordinates, the V magnitudes, and the (V-R) and (V-I) color indices. The mean errors in magnitudes and color indices obtained by averaging deviations from the mean for each star are on the order of 0.02 mag.

Scharlach, W. W. G.↗
NASA NTRS1983

Ultraviolet observations of M1-2 (= VV 8)

First IUE spectrograms of the peculiar emission-line object M1-2 (= VV 8) are presented. In the wavelength region 1150-3200 A this object is characterized by emission lines superposed on a moderately strong continuum. Some ultraviolet and optical properties of M1-2 are discussed in the context of symbiotic stars and protoplanetary and planetary nebulae. An E(B-V) extinction of 0.37 mag is obtained from the ratio of the He II flux at 1640 and 4686 A and is compared with values derived from other parameters. The ultraviolet observations suggest that M1-2 is a young, high-density planetary nebula of excitation class 5 or 6 with characteristics similar to IC 4997.

Feibelman, W. A.↗
NASA NTRS1984

PG 1012-029 - A high-excitation eclipsing cataclysmic variable

The paper presents a photometric and spectrophotometric analysis of a new eclipsing cataclysmic variable, PG 1012-029, with an orbital period of 3 hr 14 minutes 18.7 s. The eclipse depth reaches 1.9 mag, is rounded at minimum, and shows a prolonged egress 'shoulder', as found for UX UMa and some other eclipsing systems. The spectrum shows strong high-excitation lines at optical and UV wavelengths. A large fraction of the He II flux disappears during the eclipse, when the hydrogen spectrum fits a cooler temperature, and the continuum reddens. This behavior is attributed to eclipse of the hotter inner disk region.

Penning, W. R.↗
NASA NTRS1984

Optical identification of 2S 1417-62

The 17 s X-ray pulsar 2S 1417-62 has been identified with a V of approximately 16.9 mag OB star on the basis of an X-ray position obtained with the Einstein X-Ray Observatory and spectrophotometry with the 4-m telescope at Cerro Tololo Inter-American Observatory. Strong H-alpha emission is observed as well as significant changes in X-ray luminosity. The optical counterpart may be either a Be or a B I star, but the H-alpha emission strength and galactic position suggest that a Be star is more likely. A Be star identification also further supports the limit of approximately 15 days or more on the system binary period obtained by Kelley et al. (1981) from pulse timing studies.

Grindlay, J. E.↗
NASA NTRS1984

A reevaluation of the 20-micron magnitude system

The 20-micron infrared magnitude system is reexamined by observing primary infrared standards and seven A V stars. The purpose is to determine whether Alpha Lyr has colors consistent with the average of A0 stars and to determine the relative magnitude of the primary standards to that of Alpha Lyr. The data presented are consistent with the interpretation that the spectrum of Alpha Lyr is a blackbody and that it is a viable flux standard at 10 and 20 microns. The absolute flux density scale, the physical quantity of interest, is found to be consistent with an extrapolation of the Alpha Lyr spectrum from the near infrared on the basis of the comparison of stars to Mars and asteroids. Adoption of a 0.0 magnitude for Alpha Lyr requires that the magnitudes given by Morrison and Simon (1973) and by Simon et al. (1972) be revised downward by 0.14 mag.

Tokunaga, A. T.↗
NASA NTRS1984

Discovery of the first carbon star in NGC 6822

A new photometric technique has been developed for detecting carbon and M stars in distant stellar systems, leading to isolation of carbon-star candidates in a number of Local-Group galaxies. One of the brighter candidates in NGC 6822 has been confirmed spectroscopically; at a distance of approximately 0.5 Mpc, it is the first truly extragalactic carbon star to be positively identified. The star has M(I) = about -5.7 mag, placing it near the upper-luminosity end of known carbon stars in the Magellanic Clouds.

Aaronson, M.↗
NASA NTRS1984

IRAS observations of the diffuse infrared background

IRAS data reveal bright emission from interplanetary dust which dominates the celestial background at 12, 25, and 60 microns except near the galactic plane. At 100 microns, interplanetary dust emission is prominent only near the ecliptic plane; diffuse galactic emission is found over the rest of the sky. At the galactic poles, the observed brightness implies that A(v) is likely to be of order 0.1 mag. The angular variation of the zodiacal emission in the ecliptic plane and in the plane at elongation 90 deg, and an annual modulation of the ecliptic pole brightness, are generally consistent with previously determined interplanetary dust distributions.

Hauser, M. G.↗
NASA NTRS1984

IRAS observations of Shapley-Ames galaxies

A preliminary discussion of the infrared properties of a representative subsample of galaxies in the Revised Shapley-Ames Catalog (B less than about 13 mag) is presented. Of the 165 galaxies in the sample, 108 predominantly spiral galaxies, are detected in the infrared by IRAS. None of the elliptical galaxies and only about 25 percent of the lenticular galaxies scanned were detected. The range of infrared-to-blue luminosity ratios, a measure of the infrared excess of galaxies, is large, varying from roughly 0.1 to roughly 5. The data suggest that weakly infrared emitting galaxies are cool (100-60 micron color temperatures of about 25 K), while the more infrared luminous ones tend to be warmer (about 50 K). The rate of star formation in barred spiral galaxies is apparently higher than in normal spirals. About 1 solar mass/year of interstellar matter is converted into massive stars in the typical spiral galaxy.

De Jong, T.↗
NASA NTRS1984

Infrared galaxies in the IRAS minisurvey

A total of 86 galaxies have been detected at 60 microns in the high galactic latitude portion of the IRAS minisurvey. The surface density of detected galaxies with flux densities greater than 0.5 Jy is 0.25 sq deg. Virtually all the galaxies detected are spiral galaxies and have an infrared to blue luminosity ratio ranging from 50 to 0.5. For the infrared-selected sample, no obvious correlation exists between infrared excess and color temperature. The infrared flux from 10 to 100 microns contributes approximately 5 percent of the blue luminosity for galaxies in the magnitude range 14 less than m(pg) less than 18 mag. The fraction of interacting galaxies is between one-eighth and one-fourth of the sample.

Soifer, B. T.↗
NASA NTRS1984

Notes on the system TV Geminorum

Low-resolution SWP spectra and high-resolution LWR spectra of the SRc variable star TV Gem have been studied. The available ultraviolet spectrophotometry and UBV photometry of the system can be interpreted in terms of the blended light from a B3.5 IV star and an M1 Iab star. The separation of the two stars is less than about 3 arc sec. Since the magnitude difference is a minimum in the B filter, being about 1.6 mag there, direct observation of TV Gem in a passband at 4400 A under conditions of good seeing might reveal the blue companion. No evidence was found for absorption lines of Mg II formed in the part of the wind of the M star which is projected against the disk of the B star.

Underhill, A. B.↗
NASA NTRS1982

A worldwide photographic network for wide-field observations of Halley's Comet in 1985-1986

A global network of ground-based observatories for the study of Halley's Comet in 1985/1986 is discussed. Recommendations are made with respect to improving coordination between reporting observatories, in order to ensure detailed imaging of such fast-generating cometary phenomena as plasma-tail knots, helices, disconnected tails, rays and condensations. A method for calibrating telescopes is considered by which well-studied objects will be photographed to provide references for images of Halley's Comet. This procedure is expected to reduce errors to approximately 0.05 mag. A coordinated study of Halley's Comet will provide important data on the physical properties of the Comet. Examples of the topics of study related to the plasma physics of the Comet's tail include: magnetic reconnection, rippling and tearing modes, kink instability, Kelvin-Helmholtz instability, and the flute instability.

Niedner, M. B., Jr.↗
NASA NTRS1984

The elusive variability of BD + 10.2179 deg

High-speed photometry of the hydrogen-deficient star BD + 10.2179 deg has been obtained in order to ascertain if it is presently pulsationally unstable with the previously published period of 0.162 to 0.164 d. During an observing run of 0.21 d no pulsations were observed above the noise limit of 0.002 mag. Either the previously published period is not real or the star is no longer pulsating.

Drilling, J. S.↗
NASA NTRS1984

An unprecedented UV/optical flare in TV Columbae

A surprising, 2 mag, short time scale (hr) outburst of TV Col (2A 0526-328) was observed simultaneously at IUE and optical wavelengths in 1982 November. During this 'flare', the IUE emission lines of N v 1240, C IV 1550, and He II 1640, intensified by more than an order of magnitude and developed P Cygni profiles, indicating mass loss. Continuum fits with a power-law plus a blackbody from the UV through the optical showed a steepening of the UV power-law component and an increase in the temperature and size of the blackbody component during the flare activity. This unusual behavior is discussed in terms of an accretion disk instability.

Szkody, P.↗
NASA NTRS1984

The S201 far-ultraviolet imaging survey - A summary of results and implications for future surveys

The results from all-sky surveys with the S201 FUV camera/spectrograph from the moon during the Apollo 16 mission are summarized with respect to implications for future UV all-sky surveys. The scans provided imagery of 10 fields, each 20 deg in diameter, in the wavelength ranges 1050-1600 A and 1250-1600 A. Best detection thresholds were obtained with 10 and 30 min exposures at 1400 A. Only 7 percent sky coverage was recorded, and then only down to 11th mag. A Mark II camera may be flown on the Shuttle on the Spartan 3 mission, as may be an all-reflector Schmidt telescope. An additional 20 percent of the sky will be mapped and microchannel intensification will increase the diffuse source sensitivity by two orders of magnitude. Several objects sighted with the S201 will be reviewed with the Mark II.

Carruthers, G. R.↗
NASA NTRS1984

Time Series Photometry with a CCD Camera

Time series observations of a field in the cluster NGC 4755 with a CCD camera are used to show that differential photometry between stars on the CCD frame is limited in accuracy mostly by photon statistics, over a 5 magnitude range. Scintillation noise appears to be almost entirely suppressed. The maximum accuracy possible is limited by the storage capacity of the CCD to about 0.001 mag.

Walker, A. R.↗
NASA NTRS1984

The Use of Self-scanned Silicon Photodiode Arrays for Astronomical Spectrophotometry

The use of a Reticon self scanned silicon photodiode array for precision spectrophotometry is discussed. It is shown that internal errors are + or - 0.003 mag. Observations obtained with a photodiode array are compared with observations obtained with other types of detectors with agreement, from 3500 A to 10500 A, of 1%. The photometric properties of self scanned photodiode arrays are discussed. Potential pitfalls are given.

Cochran, A. L.↗
NASA NTRS1985

The Feinheit method: A phase-independent formulation of the period-luminosity relation for Cephids

The tight correlation between color and luminosity during the cyclical variation of a Cepheid is calibrated and shown to be a direct means by which most of the phase-dependent temperature-induced amplitude of the variable can be transformed away. The resulting Feinheit function, F = V - alpha (B-V) gives rise to a random-phase period-luminosity relation with an rms scatter of less than 0.20 mag. A comparison shows that the blue Feinheit method for distance determinations method from single-phase observations is as accurate as near-infrared photometry but has the added advantage of being able to use panoramic detectors for the data acquisition. The Feinheit function is identified as the surface area variation of the Cepheid during its cycle.

Madore, B. F.↗
NASA NTRS1984

The FK Comae candidate UX Librae

New optical spectroscopic and photometric data are presented for the active chromosphere FK Com candidate UZ Lib. The star is shown to have an extremely large photometric amplitude in V of 0.35 mag, and its rotation period is established as 4.75 + or - 0.01 days. The optical spectrum is that of an early K giant, broadened by a rotation velocity of approximately 65 km/s. H-alpha is visible as a very broad emission feature, with a profile resembling that seen in FK Com. The emission intensity and profile are variable over the rotation period, with the strongest emission present at photometric minimum, in accord with dark starspot models. The photospheric absorption line profiles show variable asymmetries and distortions which are interpreted as due to the effects of the dark starspot rotating across the line of sight. New radial velocity measures are combined with published data to demonstrate the UZ Lib is a member of a binary system in synchronous rotation with a secondary of mass approximately 0.5 solar masses. This information is considered in light of the conflicting models for the origin of the optical and spectral variability of the FK Com stars, as well as their uncertain evolutionary status.

Bopp, B. W.↗