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Briotta, D. A., Jr.

Publications and source records attributed to Briotta, D. A., Jr..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Abundances in galactic H II regions. III - G25.4-0.2, G45.5+0.06, M8, S159, and DR 22

Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeI (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.

Pipher, J. L.↗
NASA NTRS1984

Abundances in galactic H2 regions, 3: G25.4-0.2, G45.5+0.06, M8, S159 and DR22

Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeII (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.

Pipher, J. L.↗
NASA NTRS1983

Determinations of S III, O IV, and Ne V abundances in planetary nebulae from infrared lines

Twelve planetary nebulae have been subjected to airborne observations of the S III (18.71 microns), Ne V (24.28 microns) and O IV (25.87 microns) IR forbidden lines, of which one or more lines were detected in seven of the nebulae. These results are insensitive to nebula temperatures, in contrast to optical or UV lines, although density estimates from the latter were required to obtain abundances. The Ne V electron temperature of 11,200 + 2000 or - 1100 K temperature obtained overlaps O III temperature measurements. Since the ionization potential of Ne IV is much greater than that of O II, the electron temperature of Ne V should be much greater than that of O III. This discrepancy may indicate inaccuracies in currently available atomic parameters for Ne V.

Shure, M. A.↗
NASA NTRS1983

Detection of sulfur in the galactic center

A strong detection at the S III forbidden 18.71 micron line is reported for the galactic center region, Sgr A West. A line flux of 1.7 + or - 0.2 x 10 to the -17th W/sq cm is found for a 20 inch beam size measurement centered on IRS 1. A preliminary analysis indicates that the S III abundance relative to hydrogen is consistent with the cosmic abundance of sulfur, 0.000016, if a filling factor of unity within the known clumps is assumed. However, the sulfur abundance in the galactic center may be as much as a factor of 3 overabundant if a filling factor of 0.03 is adopted, a value found to hold for some galactic H II regions.

Herter, T.↗
NASA NTRS1983

Detection of sulphur in the galactic center

A strong detection at the (SIII) 18.71 micron line is reported for the Galactic Center region, Sgr A West. A line flux of 1.7 + or - 0.2x10 to the -17th power W cm(-2) is found for a 20-arc second beam-size measurement centered on IRS 1. A preliminary analysis indicates that the SIII abundance relative to hydrogen is consistent with the cosmic abundance of sulfur, 1.6x10 to the -5th power, if a filling factor of unity within the known clumps is assumed. However, the sulfur abundance in the Galactic Center may be as much as a factor of 3 overabundant if a filling factor of 0.03 is adopted, a value found to hold for some galactic HII regions.

Herter, T.↗
NASA NTRS1983

Determinations of SIII, OIV and NeV abundances in planetary nebulae from IR lines

Airborne observations of the infrared forbidden lines (SIII) 18.71 microns, (NeV) 24.28 microns and (OIV) 25.87 microns were made for twelve planetary nebulae. One or more of the lines was detected in seven of these nebulae and ionic abundances were calculated. These results are insensitive to nebula temperatures, in contrast to the case for optical or UV lines. However, density estimates from optical and UV forbidden lines were required to obtain abundances. The NeV infrared line flux from NGC 7662 was combined with the 3426A flux to obtain a NeV electron temperature of 11,200 (+2000, - 1100) K, which overlaps OIII temperature measurements. Since the ionization potential of NeIV is much greater than that of OII, T sub e (NeV) would be expected to be much greater than T sub e (OIII). In fact, numerical models predict T sub e (NeV) (16-20) x 1000 K. This discrepancy may indicate inaccuracies in currently available atomic parameters for NeV.

Shure, M. A.↗
NASA NTRS1982

Abundances in five nearby galactic H II regions from infrared forbidden lines

Airborne measurements of the Ar II (6.99 micron) and S II (18.7) micron lines for five compact H II regions in the solar neighborhood are presented, as well as 2-4 micron and 8-13 micron spectroscopy where available. From these data and radio data, lower limits to the elemental abundances of Ar, Ne, and S are deduced. Some of these H II regions suffer substantial nebular extinction, and some are extended. After correcting for beam size effects an extinction, it is found that four of the objects are consistent with standard abundances, within the uncertainties of correcting for unobserved ionization states. A Perseus arm object, S156, is apparently overabundant in sulfur.

Herter, T.↗
NASA NTRS1982

Observations of the infrared fine-structure lines of S III at 18.71 and 33.47 microns in four H II regions

Infrared fine-structure lines provide a particularly useful probe of ionized nebulae. The present investigation is concerned with measurements of the forbidden S III lines at 18.71 and 33.47 micrometers for four H II regions, S158A, S158G, G75.84+0.4, and W3 IRS 1. These lines are used to estimate densities, and comparisons are made with rms densities determined from radio observations to evaluate the importance of clumping. For the case of the optical H II region S158A, comparisons are made with both optical and forbidden O III line determinations of the density. The reported observations were made using a dual-grating, liquid-helium-cooled spectrometer containing a three-element Si:Sb detector array and a three-element Ge:Ga detector array. It is found that clumping is important in the cases of G75.84+0.4, W3 IRS 1, and M42. These three H II regions have filling factors of 0.024, 0.09, and 0.03, respectively.

Herter, T.↗
NASA NTRS1982

Observations of the 30 micron feature in IRC + 10216

Infrared observations from 30 to 37 microns of IRC+10216 extend the wavelength coverage of the 30-micron feature found in four carbon stars and two planetary nebulae by Forrest, Houck, and McCarthy (1981). The present data confirm the existence of this newly observed feature and determine its shape beyond 30 microns. The determination of the long-wavelength end of the spectral excess depends critically on the assumed underlying continuum. A combined spectrum of the excess is presented and shows the feature to extend to at least 37 microns.

Herter, T.↗
NASA NTRS1982

The suppression of charged-particle-induced noise in infrared detectors

A d.c.-coupled transimpedance amplifier/pulse suppression circuit designed to remove charged-particle-induced noise from infrared detectors is described. Noise spikes produced by single particle events are large and have short rise times, and can degrade the performance of an infrared detector in moderate radiation environments. The use of the suppression circuit improves the signal-to-noise ratio by a factor of 1.6:1, which corresponds to a reduction in required observing time by a factor of about 2.6.

Houck, J. R.↗
NASA NTRS1980

The galactic center - 16-30 micron observations and the 18 micron extinction

Within the galactic center, ionized gas, stars, and heated dust are in close proximity to each other. Observations of the galactic center were made during two flight series on NASA aircraft flying at altitudes of more than 12 km. In both series the instrument used was a 10-channel liquid helium cooled grating spectrometer. Three 16-30 micrometers continuum spectra are presented along with two-color scans of the galactic center. No 18.71 micrometers line emission has been detected from Sgr A West. This is consistent with large dust extinction and normal S III/H II abundances. All three 16-30 micrometers continuum spectra show a broad depression centered at about 18 micrometers. This observation is attributed to absorption by cold silicate dust grains. The characteristics of a silicate model are discussed.

Mccarthy, J. F.↗
NASA NTRS1979

Ge:Ga testing at Cornell

The spiking and memory behavior of a number of Ge:Ga detectors was studied. The detectors were manufactured at a number of locations using several different contacting techniques. Two detectors manufactured for the IRAS program by Rockwell International were studied more extensively than the others. These detectors IRD 1981 and IRD 1982 were 'witness sample' detectors for the IRAS bands 4 and 3, respectively. During the testing period both the apparatus and the test procedures were changed numerous times. At each change consistency checks were made. The data are believed to be internally consistent from end to end.

Briotta, D. A., Jr.↗
NASA NTRS1977

High resolution 10 mu spectrometry at different planetary latitudes. A practical Hadamard transform spectrometer for astronomical application

Infrared observations at different latitudes were studied in order to obtain spectra in the 10 micrometers region to understand differences in chemical composition or physical structure of the optical features. In order to receive such spectra of a rotating planet, simultaneous observations at different latitudes were made. A Hadamard transform spectrometer with 15 entrance slits was used to obtain 15 simultaneous spectra, at a resolution of 0.01 micrometers. The spectral band covered contained 255 spectral elements.

Tai, M. H.↗
NASA NTRS1975

Practical multi-spectrum Hadamard transform spectrometer

Specifications of a new Hadamard transform spectrometer for infrared astronomical applications are presented. The instrument has 15 entrance slits and 255 exit slits. Data can be gathered at the rate of up to five readings per second so that the entire spectral run lasts some thirteen minutes. The data is processed in real time by a minicomputer. At the end of the thirteen minute run the spectrum is available for immediate viewing on a CRT display. The spectra can be punched and stored on paper tape for later processing.

Tai, M. H.↗
NASA NTRS1975

A practical multi-spectrum Hadamard Transform Spectrometer

A Hadamard Transform Spectrometer (HTS) which simultaneously obtains fifteen infrared spectra, each having 255 spectral elements was constructed. Spectra are obtained essentially in real time through use of a minicomputer with 8K words of memory and a CRT display. This permits operation of the instrument in the field.

Tai, M. H.↗
NASA NTRS1973

Hadamard transform spectrometry of the atmospheres of Earth and Jupiter

A Hadamard-transform spectrometer was used to obtain a spectrum of Jupiter from 880-770/cm. Three ammonia absorption features stood out at 870, 851, and 833/cm. The general shape of the spectrum implied an atmosphere with a monotonically decreasing temperature profile up to the 125 K level. Transmission profiles of the earth's atmosphere were taken between 16 microns and 25 for five consecutive nights under varying amounts of atmospheric water and air mass. There are many saturated lines, but nightly variations were fairly constant and agreed well with a theoretical profile. These results show that the Hadamard-transform technique is a useful method for obtaining astronomical spectra.

Phillips, P. G.↗