Robert K. Pina

IRC +10420 - A cool hypergiant near the top of the H-R diagram

New data are reported for the OH/IR star IRC+10420, including optical/infrared imaging, spectroscopy, polarimetry, and photometry. We conclude the following: 1. The optical spectrum is that of a very luminous F supergiant (F Ia+) with a very strong O I blend at 7774 A. Hα is strongly in emission and shows a double-peaked profile similar to the emission seen in stars with rotating equatorial disks. 2. The optical image taken through polarizing filters is elongated, and shows that the star must be intrinsically polarized at a position angle near 90°. The 8.7 μm image is also elongated, but at a position angle near 150°

MID-INFRARED OBSERVATIONS OF THE NUCLEUS AND DUST OF COMET P/SWIFT-TUTTLE

NASA-CR-204995FINAL TECHNICAL REPORTNAGW 3127 Fund 23343AJune 1997 Barbara JonesMid-Infrared Observational and Theoretical Studies ofStar Formation and Early Solar SystemsThe first 2 years of this program were used to make mid-IR observations of regions of star for-mation in the Orion nebula with the UCSD mid-IR camera at the UCSDAJniversity of Minnesotatelescope at Mt. Lemmon. These observations attempted to make the first systematic study of anextended region, known to have newly forming stars, and expected to have complex mid-IR emis-sion. We discovered, to our surprise, that most of the thermal emission originated from extendedsources rather than from point sources. This interesting observation made the analysis of the datamuch more complex, since the chop/nod procedures used at these wavelengths produce a differ-ential measurement of the emission in one region compared to that in the adjacent region. Disen-tangling complex extended emission in such a situation is very difficult.In parallel with this work we were also observing comets in the thermal infrared, the othercomponent of the original proposal. Some spectacular data on the comet Swift-Tuttle wasacquired and published (Fomenkova, Jones et al., Astron. J., 1995, 110, 1866). This paperdescribes a changing jet structure observed over a 2 week period. The rotation period of the cometcan be measured at 66 hours. The size of the nucleus can also be estimated (at 30 km) from theobserved excess flux from the nucleus. These data have lead to the development of modelsdescribing the action of dust particles of differing sizes and composition leaving the nucleus. Thespatial distribution of the predicted IR emission has been compared to the observed jet structures,leading to estimates of both particles sizes, relative amounts of silicate vs organic grains, and theamounts of dust emitted in the jets vs isotopic emission. This work forms the basis for the PhDthesis of James Sarmecanic.

Skymapping with OSSE via the Mean Field Annealing Pixon Technique

We present progress toward using scanned OSSE observations for mapping and Sky Survey work. To this end, we have developed a technique for detecting pointlike sources of unknown number and location, given that they appear in a background that is relatively featureless or that can be modeled. The technique, based on the newly developed pixon concept and mean field annealing, is described, with sample reconstructions of data from the OSSE Virgo Survey. The results demonstrate the capability of reconstructing source information without any a priori information about the number and/or location of pointlike sources in the field of view.

PIXON-BASED IMAGE RECONSTRUCTION

This paper presents the theory of the pixon, the fundamental unit of picture information, and its application to Bayesian image reconstruction. This naturally leads to a discussion of picture information content and the degrees of freedom necessary to describe the underlying image (i.e. the noise-free, undistorted image) within the accuracy of the data. The implications of these concepts for the formulation of appropriate Goodness-of-Fit criteria (i.e. Maximum Likelihood) are discussed. Finally, examples of the applications of these methods to artificial and real data are presented. These examples demonstrate that pixon-based methods produce results superior to both pure Goodness-of-Fit methods and the best examples of Maximum Entropy methods.

Electronics imaging system overview and performance for the Keck long-wavelength spectrometer

This paper presents an overview of the electronic imaging system design and performance for the long wavelength spectrometer that is to be deployed on the Keck Telescope. Because the LWS employs 96 parallel read-out channels and 24 parallel processing channels, the LWS serves as a forerunner of next generation infrared astronomical instruments that are to use highly parallel output focal plane arrays like the Santa Barbara Research Center ALADDIN Near-IR 32 output FPA or any of the Rockwell Mid-IR 16 output arrays. Several principles regarding noise and grounding issues are discussed with the hope that they may help the developers of the next generation of infrared astronomical instruments. It is concluded that low noise performance is not something that can be added after-the-fact in the lab unless the necessary efforts have been made in the early phases of an instruments conceptual design. Low noise requirements will drive the highest level architectural issues of the electronics, and hence cannot be an afterthought.

10 and 20 micron imaging with arrays

We discuss imaging with arrays in the thermal IR. Aspects of the design and performance of the “Golden Gopher”, an infrared array camera are presented. This instrument operates in a high-background environment, for ground-based astronomical imaging from 5 to 27 μm. It is built around a 20×64 element Si:As Impurity Band Conduction (IBC) device manufactured by GenCorp Aerojet Electronic Systems Division, and has a noise-equivalent flux density (NEFD) of 23.5mJy min-1/2 arcsec-2 at λ=10μm, Δλ=1μm, on the Mt. Lemmon 1.5m telescope. We present and discuss a sample of the data. In addition we discuss the design and expected performance of the “Long Wavelength Spectrometer” which is now under construction for the Keck telescope.

University of California/San Diego's mid-IR astronomical array camera

We have implemented an infrared array camera for high-background, ground-based astronomical imaging in the mid-infrared spectral region from 5 to 27 microns. The camera is built around a 20 X 64 element Si:As Impurity Band Conduction (IBC) device manufactured by GenCorp Aerojet Electronic Systems Division. Observations with the camera on a 1.5 meter telescope (Mt. Lemmon Observing Facility, Tucson, Arizona) yield a noise- equivalent flux density (NEFD) of 23.5 mJy min-1/2 arcsec-2 at (lambda) equals 10 micrometers , (Delta) (lambda) equals 1 micrometers , and a readout frame rate of 366 Hz. We discuss the design and implementation of the camera and operational procedures for observation in a high-background environment (e.g. background subtraction and flat-fielding). We also present sample images obtained with our camera.