Diameter Field Of View Research Articles

H 2O + Production Rates of Comets Austin 1990 V and P/Halley 1986 III

We obtained high-spectral-resolution scans of H 2O + emissions from Comet Austin 1990 V using the Wisconsin dual-etalon Fabry-Perot spectrometer at the McMath-Pierce solar telescope on Kitt Peak. The 10.5 diameter field of view on the sky was centered on the comet head. From the Doppler shifts of the emissions, we determined the outflow velocities of the cometary plasma. Adopting a simple model of the ion distribution within the field of view, we determine a lower limit φ H 2O + to the flux of H 2O + ions away from the nucleus for each night of observations. We apply a similar analysis to our previous observations of H 2O + emissions from Comet P/Halley 1986 III. Comparing φ H 2O + with the water production rate Q H 2O , we find that the average ratio φ H 2O + / Q H 2O is 1.2 × 10 -3 for Comet Halley (solar minimum) and 2.6 × 10 -3 for Comet Austin (solar maximum); these values are significantly smaller than theoretical values of the relative H 2O + production rate Q H 2O+ / Q H 2O .

The O(1D) Distribution of Comet Austin 1989c1 = 1990 V

We obtained images of [OI]6300 emission from Comet Austin 1990 V using the Wisconsin dual-etalon Fabry-Perot/CCD imaging spectrometer at the McMath solar telescope on Kitt Peak. The field of view diameter on the sky was approximately 10.5. The spectral resolution of 0.21 Å was sufficient to image cometary [OI]6300 emission uncontaminated by nearby NH2 and telluric [OI]6300 emissions. Using a Haser model for the photodissociation of H2O and OH as sources of O(1D), we find that the OH mean lifetime τOH at 1 AU is (1.1 ± 0.3) × 105 sec.

Comet Austin (1989c1) O( 1D) and H 2O production rates

Groundbased observations of Comet Austin (1989c1) were carried out using the Wisconsin dual-etalon Fabry-Perot spectrometer at the McMath solar telescope on Kitt Peak. The field of view diameter on the sky was approximately 10′.5. Spectral scans were acquired at a resolution of 0.21 Å, which was sufficient to resolve cometary [OI]6300 emission from nearby NH 2 and telluric [OI]6300 emissions. From these measurements, we obtained the O( 1D) production rate Q( O( 1 D)) , which is nearly model independent. By taking into account photodissociation of H 2O and OH as sources of O( 1D), we determine Q(H 2O) from our Q( O( 1 D)) results.

Comet Halley O( 1D) and H 2O production rates

Ground-based observations of Comet Halley [OI]6300 were carried out using the Wisconsin dual-etalon Fabry-Perot spectrometer at the McMath solar telescope on Kitt Peak. The field of view diameter on the sky was approximately 7′ preperihelion and 10′ postperihelion. Spectral scans were acquired at a resolution of 0.2 Å, which was sufficient to resolve cometary [OI]6300 emission from nearby cometary NH 2 and telluric [OI]6300 emissions. From these measurements, we determined the production rate Q( O( 1 D)) . By taking into account photodissociation of H 2O and OH as sources of O( 1D), we find that the ratio Q( H 2 O) Q( O( 1 D)) is 6 and obtain Q(H 2O) from our Q( O( 1 D)) measurements We compare our Q(H 2O) results with measurements by other groups.

Investigation of a Technique for Providing a Pseudo-Continuous Detector Ring for Positron Tomography

The use of small bismuth germanate (BGO) detectors (2.5-4.5 mm wide) and a simple coding technique for identification of the crystal of interaction with the impinging gamma-ray was investigated in terms of a technique for providing a positron tomography system of the highest possible intrinsic resolution with the additional capability of providing an artifact free image in a stationary system. The technique employs one photomultiplier per two BGO crystals in a scheme of alternating single PMT/crystal and shared PMT/crystal combinations to form a pseudo-continuous ring. Problems of crosstalk between detectors, nonuniform sensitivities and variable resolution are shown to be minimized once discriminator thresholds are clearly above the energy of the bismuth x-rays induced in the BGO crystals by the 511 keV gammas from the positron annihilations. A stationary circular system employing 4.5 mm wide BGO detectors can provide transverse sampling equal to 1/2 the center to center crystal distance or 2.5 mm sampling. The measured intrinsic resolution of a bench top version of this system is 5 to 6 mm FWHH for a 30cm diameter field of view for a 100 cm system diameter. The 2.5 mm sampling with reconstruction filter of appropriate frequency response should provide a high resolution image on the order of 7 to 8 mm FWHM with good signal to noise characteristics which is free of significant aliasing artifacts.

Detection of the [Fe XIV] Coronal Line at 5303 Å in the Cygnus Loop

view Abstract Citations (56) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of the [Fe XIV] Coronal Line at 5303 Å in the Cygnus Loop Woodgate, B. E. ; Stockman, H. S., Jr. ; Angel, J. R. P. ; Kirshner, R. P. Abstract Emission in the [Fe xlvi coronal line at 5303 A has been detected in strong X-ray emitting regions of the Cygnus Loop. For the strongest region the flux measured was (7.1 + 1.2) x t(r12 ergs (cm2 s) 1, giving an average brightness of (3.1 + 0.5) X t(r8 ergs (cm2 s sr) 1 in the 1?0 diameter field of view used, a result different from zero by 6 standard deviations. These fluxes agree well with calculations based on a thermal model for X-ray emission with normal iron abundance. Upper limits to fluxes in the llne.were obtained for the center of the Cygnus Loop and for Puppis A and IC 443. Subject headings: nebulae - supernova remnants - X-ray sources Publication: The Astrophysical Journal Pub Date: March 1974 DOI: 10.1086/181438 Bibcode: 1974ApJ...188L..79W full text sources ADS | data products SIMBAD (2)