Engineering topics

Betz, A. L.

Publications and source records attributed to Betz, A. L..

At least 37 records · Page 2

NASA NTRS1990

Ionized carbon in side-illuminated molecular clouds

The C II fine-structure line has been observed in five sources for which the ionization front/molecular cloud interface is viewed approximately edge-on. The LSR velocity of the C II emission is generally in good agreement with that observed for molecular species such as CO. However, the observed linewidths of 3-14 km/s are typically wider than those of molecular lines and often show rapid spatial variations in the observed regions. The C II brightness temperature are typically equal to or slightly higher than the dust temperature at all locations observed. In the optically thin approximation, C II excitation temperatures are 100 K or more and column densities are 10 to the 18th/sq cm for all sources except M17, which has a more intense and complicated line profile with a larger spatial extent than any other source observed.

Boreiko, R. T.↗

NASA NTRS1989

Heterodyne spectroscopy of the J = 22-21 CO line in Orion

The J = 22-21 line of (C-12)O at 2528 GHz was observed in the IRc2 region of Orion. The spectra at 0.6 km/s resolution show both plateau emission with FWHM of about 35 km/s and a narrower component with FWHM of about 8 km/s. Comparison with heterodyne data of similar quality on the J = 17-16 line indicates that the broad and narrow components both originate in gas with an excitation temperature of about 600 K.

Boreiko, R. T.↗

NASA NTRS1989

Reversed far-infrared line emission from OH in Orion

The fundamental OH rotational transition at 2514 GHz has been observed in the Orion IRc2 region at a spectral resolution of 0.6 km/s. The emission is spatially compact and centered near IRc2. A comparison of the observed profile with spectra of other species known to exist in the region suggests that the entire blueshifted side of the OH profile has been self-absorbed, leaving only a redshifted emission component.

Betz, A. L.↗

NASA NTRS1989

Heterodyne spectroscopy of the J = 22-21 CO line in Orion

We have observed the J = 22-21 line of 12CO at 2528 GHz (118.8 micrometers) in the IRc2 region of Orion. The spectra at 0.6 km s-1 resolution show both plateau emission with FWHM approximately 35 km s-1 and a narrower component with FWHM approximately 8 km s-1. Comparison with heterodyne data of similar quality on the J = 17-16 line indicates that the broad and narrow components both originate in gas with an excitation temperature Tex approximately 600 K. The emission is consistent with the predictions of shock models in which the wide component arises from the heated outflow gas and postshock molecular material, while the narrow component comes from ambient material near the leading edge of the shock front where temperatures are high but significant acceleration has not yet occurred.

NASA Discipline Exobiology↗

NASA NTRS1989

Heterodyne spectroscopy of the J = 17-16 CO line in Orion

High-resolution spectra of the 153 micron J = 17-16 CO line in the BN-KL region of Orion using a laser heterodyne spectrometer are obtained. The line shows broad wings characteristic of the plateau emission as well as a narrower component probably associated with the quiescent gas in the molecular ridge. From an analysis of the plateau emission together with that observed in lower J CO transitions, an excitation temperature of 180 + or - 50 K and minimum column density of 1 x 10 to the 18th /sq cm are derived for CO in this component, which constitutes 80 percent of the total integrated intensity of the J = 17-16 line near BN. The peak intensity of the narrower component observed at 0.8 km/s resolution increases relative to that of the plateau component toward theta 1C and away from BN, while the width decreases from 10 to 4 km/s (FWHM).

Boreiko, R. T.↗

NASA NTRS1989

Heterodyne spectroscopy of the J = 17-16 CO line in Orion

We have obtained high-resolution spectra of the 153 micrometers J = 17-16 CO line in the BN-KL region of Orion using a laser heterodyne spectrometer. The line shows broad wings (30 km s-1 FWHM at BN) characteristic of the plateau emission as well as a narrower component probably associated with the quiescent gas in the molecular ridge. From an analysis of the plateau emission together with that observed in lower J CO transitions, we derive an excitation temperature of 180 +/- 50 K and minimum column density of 1 x 10(18) cm-2 for CO in this component, which constitutes 80% of the total integrated intensity of the J = 17-16 line near BN. The peak intensity of the narrower component observed at 0.8 km s-1 resolution increases relative to that of the plateau component toward theta 1C and away from BN, while the width decreases from 10 to 4 km s-1 (FWHM).

NASA Discipline Number 52-60↗

NASA NTRS1989

A corner-reflector mixer mount for far infrared wavelengths

A new type of corner-reflector mixer mount, which has the advantages of ease of fabrication and assembly as well as frequency versatility, has been designed and constructed. The predicted response patterns have been experimentally verified for various antenna lengths and operating frequencies between 800 and 2000 GHz. An important design feature is the incorporation of a microstrip matching network which eliminates IF impedance mismatch and provides mechanical isolation for the whisker antenna.

Zmuidzinas, J.↗

NASA NTRS1988

Neutral atomic carbon in dense molecular clouds

The 370 micron 3P2-3P1 fine-structure line of neutral carbon was detected in seven sources: OMC 1, NGC 2024, S140, W3, DR 21, M17, and W51. Simultaneous analysis of J = 2-1 data and available observations of the J = 1-0 line make it possible to deduce optical depths and excitation temperatures for these lines. These data indicate that both C I lines are likely to be optically thin, and that the ratio of C I to CO column densities in these clouds is typically about 0.1.

Zmuidzinas, J.↗

NASA NTRS1988

Heterodyne spectroscopy of the 158 micron C II line in M42

Velocity-resolved spectra of the C-12 II 157.8-micron 2P3/2-2P1/2 fine-structure line in the M42 region of Orion have been obtained. Observations at 0.8 km/s resolution with a laser heterodyne spectrometer show multiple velocity components in some locations, with typical linewidths of 3-5 km/s. Spectra of theta C and BN-KL also show weak emission from the F = 2-1 hyperfine component of the equivalent C-13 II line. From the observed C-12 II/C-13 II line intensity ratios, it is deduced that the C-12 II emission is optically thick with tau of about 5 at both positions.

Boreiko, R. T.↗

NASA NTRS1987

New lines of ethylene and a search for methylene in IRC + 10216

Seven new lines in the 10 micron nu7 band of C2H4 have been detected in the highly obscured carbon star IRC + 10216. The line intensities cannot be well described by a single rotational temperature, in contrast to the lines of CH4 and SiH4 previously observed in this source. There are at least three interpretations: the line intensities are variable on a time scale of months and years, C2H4 lines are formed over a region less homogeneous than that of CH4 and SiH4, or ethylene is somewhat nonthermally excited. Regardless, the line intensities indicate an average rotational temperature of 100 K and a column density of about 4 x 10 to the 15th/sq cm, which is approximately 2 x 10 to the -5th times the CO abundance. A search was also made for infrared transitions of CH2, the methylene radical. No lines were detected, but the observational limits are compared with the abundance and radial distribution for CH2 predicted by a model invoking the photodissociation of CH4.

Goldhaber, D. M.↗

NASA NTRS1986

Observations of neutral atomic carbon at 809 GHz

The 3P2-3P1 line at 809 GHz has been observed in four dense molecular clouds: M17, W51, W3, and DR 21(OH). The results indicate excitation temperatures of 30-60 K and optical depths of one or less. This implies that the roughly 10 to the 18th/sq cm lower limit to the C I abundance derived from 492-GHz observations is probably the actual abundance, which gives C I/CO of about 0.1 in dense molecular clouds.

Zmuidzinas, J.↗

NASA NTRS1985

Far-infrared heterodyne spectroscopy

A new far-infrared heterodyne spectrometer has been built for ground-based observations at the Cassegrain focus. The receiver, which features a Schottky-diode mixer and a laser local oscillator, was used in January 1984, to detect the 809 GHz fine-structure line of neutral carbon in OMCl. A second-generation version of the spectrometer is now being constructed for airborne observations between 600 and 1500 GHz.

Betz, A. L.↗

NASA NTRS1984

Silane in IRC +10216

Silane has been detected in the gas surrounding IRC +10216. Thirteen absorption lines in the nu-4 band around 917/cm were observed at 0.2 km/s resolution. A lower limit to the radial column density is 2 x 10 to the 15th/sq cm, and the relative strengths of the transitions indicate an average rotational temperature of 173 K.

Goldhaber, D. M.↗

NASA NTRS1981

Ethylene in IRC +10216

Ethylene has been detected in the circumstellar gas surrounding the supergiant star IRC +10216. Two lines of the nu sub 7 vibration-rotation band near 28 THz (949/cm) have been seen in absorption at an expansion velocity of 14 km/sec relative to the central star. The line intensities indicate a rotational temperature of T greater than 400 K and a radial C2H4 column density of 10 to the 16th to 10 to the 17th per sq cm.

Betz, A. L.↗

NASA NTRS1980

Infrared observations of circumstellar ammonia in OH/IR supergiants

Ammonia has been detected in the circumstellar envelopes of VY Canis Majoris, VX Sagittarii, and IRC +10420 by means of several absorption lines in the nu-2 vibration-rotation band near 950 kaysers. The line profiles are well resolved (0.2 km/sec resolution) and show the gas being accelerated to terminal expansion velocities near 30 km/sec. The observations reveal a method for determining the position of the central star on VLBI maps of OH maser emission to an accuracy of approximately 0.2 arcsec. A firm lower limit of 2 x 10 to the 15th/sq cm is obtained for the NH3 column density in VY Canis Majoris.

Mclaren, R. A.↗

NASA NTRS1980

Infrared heterodyne spectroscopy of circumstellar molecules

Ammonia has been detected in the circumstellar envelopes of IRC+10216, VY CMa, VX Sgr, and IRC+10420. A number of absorption lines of (N-14)H3 in the nu sub 2 vibration-rotation band around 28 THz (950 per cm) have been observed at a velocity resolution of 0.2 km/s. Typical linewidths are 1 to 4 km/s, and the details of the line profiles provide additional insights on the process of mass loss in these stars.

Betz, A. L.↗

NASA NTRS1979

The brightness distribution of IRC +10216 at 11 microns

The brightness distribution of IRC +10216 at a wavelength of 11 microns has been measured in detail by using spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 arcsec. The tapered shape of this component is consistent with a dust density dependence on the inverse square of radial distance. The compact component is unresolved (less than 0.2 arcsec in diameter) and represents emission from the central star seen through the circumstellar envelope.

Sutton, E. C.↗

NASA NTRS1979

NH3 in IRC +10216

Ammonia has been detected in the circumstellar envelope of IRC +10216 by means of three infrared absorption lines in the nu-2 band around 950 kaysers. The profiles are well resolved at a resolution of 0.22 km/s and show that most of the circumstellar gas is accelerated to expansion velocities around 14 km/s within a few stellar radii. The observed ammonia requires a rotational temperature between 400 and 700 K, an H2 density between 100 million and 10 billion per cu cm, and an NH3 column density of 10 to the 17th per sq cm. The H2 density indicates that the mass of the circumstellar envelope within a 1 arcsec radius is about 0.1 solar mass.

Betz, A. L.↗