Showing papers by "Joseph L. Hora published in 1994"
TL;DR: In this article, high-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M2-9 and AFGL 2688, showing that the inner shell is dominated by emission from hydrogen recombination lines, and the outer shell is primarily emission from H2 lines in the 2-2.5 micron region.
Abstract: High-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M2-9 and AFGL 2688. The ability to spatially and spectrally resolve the various components of the nebulae has proved to be important in determining their physical structure and characteristics. In M2-9, the lobes are found to have a double-shell structure. The inner shell is dominated by emission from hydrogen recombination lines, and the outer shell is primarily emission from H2 lines in teh 2-2.5 micron region. Analysis of H2 line ratios indicates that the H2 emission is radiatively excited. A well-resolved photodissociation region is observed in the lobes. The spectrum of the central source is dominated by H recombination lines and a strong continuum rising toward longer wavelengths consistent with a T = 795 K blackbody. Also present are lines of He I and Fe II. In contrast, the N knot and E lobe of M2-9 show little continuum emission. The N knot spectrum consists of lines of (Fe II) and hydrogen recombination lines. In AGFL 2688, the emission from the bright lobes is mainly continuum reflected from the central star. Several molecular features from C2 and CN are present. In the extreme end of the N lobe and in the E equatorial region, the emission is dominated by lines of H2 in the 2-2.5 region. The observed H2 line ratios indicate that the emission is collisionally excited, with an excitation temperature T(sub ex) approixmately = 1600 +/- 100 K.
46 citations
TL;DR: In this paper, high-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M~2--9 and AFGL 2688, and it was found that the lobes have a double-shell structure.
Abstract: High-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M~2--9 and AFGL 2688. The ability to spatially and spectrally resolve the various components of the nebulae has proved to be important in determining their physical structure and characteristics. In M~2--9, the lobes are found to have a double-shell structure. Analysis of \h2\ line ratios indicates that the \h2\ emission is radiatively excited. A well-resolved photodissociation region is observed in the lobes. The spectrum of the central source is dominated by H recombination lines and a strong continuum rising towards longer wavelengths consistent with a $T = 795$ K blackbody. In AFGL 2688, the emission from the bright lobes is mainly continuum reflected from the central star. Several molecular features from C$_2$ and CN are present. In the extreme end of the N lobe and in the E equatorial region, the emission is dominated by lines of \h2 in the 2--2.5 \microns region. The observed \h2 line ratios indicate that the emission is collisionally excited, with an excitation temperature $T_{ex} \approx 1600\pm 100$ K.
45 citations
TL;DR: The K-band spectrograph (KSPEC) as discussed by the authors is a low-cost infrared spectrogram designed for spectroscopy in the 2.0-2.5 micrometer region.
Abstract: KSPEC (k-band spectrograph) is an infrared spectrograph designed primarily for spectroscopy in the 2.0-2.5 micrometer region. It offers two different optical configurations. The first is a cross-dispersed echelle mode designed to cover the atmospheric windows from 1-2.5 micrometer in one spectral frame of a 256x256 format on a Near Infrared Camera and Multi-Object Spectrometer-3 (NICMOS-3) HgCdTe detector array. This configuration of the spectrograph provides medium spectral resolution (lambda/delta-lambda approximately = 500) for spectral classification work, emission-line detection, and redshift measurements. Alternatively, KSPEC can be equipped with a different spectrograph camera, giving a long-slit, single-order spectrum from 2.05-2.35 micrometer. The instrument uses a second NICMOS-3 infrared detector array for slit viewing, to facilitate the acquisition of optically invisible objects, to document the slit position, and to monitor it during long spectroscopic integrations. KSPEC does not contain any moving components, making it a very reliable, relatively low-cost instrument that is easy to use.
26 citations
01 Jun 1994
TL;DR: The MegaCam as discussed by the authors is a two-color camera designed for use at the UH 2.2m telescope, which uses a Rockwell 1024 x 1024 HgCdTe detector array for 1-2.5 micrometers imaging and a 2048 x 4096 frame-store CCD (2048 x 2048 active area) for optical imaging.
Abstract: The MegaCam is a multi-purpose, wide-field, two-color camera being designed for use at the UH 2.2m telescope. The camera will utilize a Rockwell 1024 x 1024 HgCdTe detector array for 1-2.5 micrometers imaging, and a 2048 x 4096 frame-store CCD (2048 x 2048 active area) for optical imaging. The optics are based on a modified Offner relay design with additional lenses to give a 2:1 magnification in the infrared channel for a field of view of 5'.8 x 5'.8 (0.34 arcsec/pixel) using the f/10 telescope secondary, or a scale of 1'.9 x 1'.9 (0.15 arcsec/pixel) at f/31. This design provides a simple, high-throughput, and compact optical layout. A beamsplitter is placed in front of the IR optics at a low angle of incidence to form the optical image at 1:1 magnification on the CCD, for a field of view of 4'.7 x 4'.7 and 1'.5 x 1'.5 at f/10 and f/31, respectively. The optics and filters are to be housed in a LN2-cooled dewar. The CCD and IR arrays will be operated with modified SDSU-design controllers. The user interface will have several modes to make simultaneous optical/IR imaging simple to configure and perform at the telescope.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
12 citations
TL;DR: MIRAC as discussed by the authors is a mid-infrared camera built for ground-based astronomy by Steward Observatory at the University of Arizona, Harvard Smithsonian Center for Astrophysics, and the Center for Advanced Space Sensing at the Naval Research Laboratory.
10 citations
01 Jun 1994
3 citations
TL;DR: In this paper, results from MIRAC (mid-infra-red array camera) observations of the planets Mercury and Jupiter and Comet Swift-Tuttle are presented.
Abstract: Results from MIRAC (Mid-InfraRed Array Camera) observations of the planets Mercury and Jupiter and Comet Swift-Tuttle are presented. A complete description of MIRAC can be found in Hora (1991) and Hoffmann et al. (1993).
01 Jan 1994
TL;DR: In this article, the authors used KSPEC, a near-infrared spectrograph designed for the University of Hawaii 2.2 m telescope, along with broad-band near-IR imaging, to understand the nature of the emission from planetary nebulae.
Abstract: Medium-resolution 1–2.5 µm spectra of several planetary nebulae (PN) have been obtained using KSPEC, a near-infrared spectrograph designed for the University of Hawaii 2.2 m telescope. The data have been used, along with broad-band near-IR imaging, to understand the nature of the emission from these objects.