Richard R. Joyce

Infrared Spectroscopy of Symbiotic Stars. I. Orbits for Well-Known S-Type Systems

First results are reported for a program of monitoring symbiotic-star velocities in the 1.6 μm region with infrared-array technology. Infrared radial velocities have been used to determine single-lined spectroscopic orbits for six well-known symbiotic stars, EG And, T CrB, CI Cyg, BX Mon, RS Oph, and AG Peg. The new orbits are in general agreement with previous orbits derived from optical velocities. From the combined optical and infrared velocities improved orbital elements for the six systems have been determined. Each of the orbital periods has been determined solely from the radial-velocity data. With the addition of our new velocities, the orbital period of BX Mon has been revised to 1259 days, a 10% decrease from the previously reported result.

Johnson Noise Limited Operation of Photovoltaic InSb Detectors

Photovoltaic indium antimonide detectors have been operated at temperatures </=77 K with sufficiently low background radiation levels that Johnson noise limited performance is realized. Under such conditions the noise equivalent power (NEP) is completely determined by the detector operating temperature, resistance, and quantum efficiency. Optimization of these parameters in the manufacture of commercially available detectors has led to 5-mum NEPs as low as 10(-15) W. The particular preamplifier is critical to the achievement of Johnson noise limited operation and is described in detail.

Infrared Spectroscopy of Symbiotic Stars. II. Orbits for Five S-Type Systems with Two-Year Periods

Infrared radial velocities have been used to determine orbital elements for the cool giants of five well-known symbiotic systems, Z And, AG Dra, V443 Her, AX Per, and FG Ser, all of which have orbital periods near the two-year mean period for S-type symbiotics. The new orbits are in general agreement with previous orbits derived from optical velocities. From the combined optical and infrared velocities, improved orbital elements for the five systems have been determined. Each of the orbital periods has been determined solely from the radial-velocity data. The orbits are circular and have quite small mass functions of 0.001–0.03 M⊙. The infrared velocities of AG Dra do not show the large orbital velocity residuals found for its optical radial velocities.

Infrared Spectroscopy of Symbiotic Stars. III. First Orbits for Three S-Type Systems

Infrared radial velocities have been used to derive the first well-determined orbital elements for the cool giants of three symbiotic systems, BF Cyg, V1329 Cyg, and V343 Ser=AS 289. Periods found for BF Cyg and V1329 Cyg from the radial velocity data are in good agreement with periods previously determined for their light variations, and the orbits are circular. Masses for the components of BF Cyg and V1329 Cyg were determined by combining our orbital elements for the cool giants with elements for their hot stars. BF Cyg and V1329 Cyg are shown to be detached binary systems. The third system, V343 Ser, has an orbital period of 450.5 days, a value that is typical for symbiotic binaries. However, the system is atypical because of its somewhat eccentric orbit, with e = 0.135 and the possibility that it is a semidetached system. An orbital inclination of 18° is estimated, indicating that V343 Ser does not eclipse.

Infrared photometry of V1057 Cygni (1971-87)

Infrared photometry of V1057 Cyg at wavelengths between 1 and 20 microns is presented, and the IR light curve of this star for the 17-year period following its optical outburst in 1970 is described. From 1971 to 1984 the near-IR flux decreased exponentially with e-folding times ranging from 12 yr at a wavelength of 1.25 micron to 67 yr at 4.8 microns. Since 1984 the brightness near 1 micron has leveled off, or perhaps risen slightly, while the emission at 5 microns has started to fall much more rapidly than before. Between 1971 and 1987 the broadband photometric fluxes at 10 and 20 microns declined in proportion to the fourth-root and square root, respectively, of the time that has elapsed since the outburst. The IR spectral energy distributions deduced from the photometry are compared with the predictions of accretion disk models.

Evaluation of a PtSi Schottky infrared CCD for astronomy

This paper presents the results of a preliminary evaluation of a platinum silicide (PtSi) Schottky CCD as an imaging array for astronomical applications. The work was done in the near-infrared (1.2 μm < λ < 2.5 μm) spectral regime, where there is presently a lack of commercially available panoramic arrays with acceptable performance. During an initial test run, the array detected a star of magnitude 3.5 using an integration time of 128 msec. Proper optimization of the readout electronics, cryostat configuration, and matching of the telescope image scale to the pixel size could allow detection of a source ~100 times fainter in a 1-sec integration time. This paper will discuss the array architecture, measurement and signal processing techniques, and the observatory and laboratory evaluation tests.

Indium Antimonide Detectors For Ground-Based Astronomy

Many of the recent advances in infrared astronomy in the 1 - 5 μm region have been the result of efforts to utilize and optimize indium antimonide (InSb) detectors for this application. This paper will briefly review the progress which has been made in obtaining 2 μm NEP values as low as 10-16w-Hz-1/2 with photovoltaic InSb. More recent efforts have concentrated on other types of InSb operation, such as CIDs and CCDs, which are more suited to array formats for spectroscopic and imaging applications. Advances in the fabrication of InSb photodiodes makes possible the integration of photocurrent on the detector capacitance, with the potential of measuring infrared fluxes of a few photon/s during integration times > 1000 s.