Olivia L. Lupie

Hubble Space Telescope Observations of the Gravitationally Lensed Cloverleaf Broad Absorption Line QSO H1413+1143: Imaging

An analysis of Hubble Space Telescope (HST) Wide Field Planetary Camera (WFPC) and Wide Field Planetary Camera 2 (WFPC2) images of the gravitationally lensed Cloverleaf broad absorption line quasi-stellar object (QSO) H1413+1143 is presented. Astrometric and photometric measurements are derived for the four components of the lensed QSO for five different epochs over a baseline of 2.76 yr. Because of the replacement of WFPC with WFPC2 and the change in the purpose of the observation at the various epochs, the data were not always taken with the same filter. With the exception of the declination of component D, the relative positions of the four components are measured to within ≈ 3 mas; these results are consistent with but considerably more accurate than earlier measurements. The relative photometric measurements at any one epoch are typically accurate to ≈ 0.02-0.03 mag (1 σ). The initial HST WFPC images cover a baseline of 1.26 yr (1992.21-1993.47 [1992 March 16-1993 June 22]), and over this time interval there is little evidence for brightness variations of any of the components relative to one another at levels >0.06 mag (>2 σ). Photometric measurements of the more accurate WFPC2 data obtained with different filters extends this baseline an additional 1.50 yr (to 1994.97 [1994 December 22]). The WFPC2 data also fail to reveal significant brightness variations among the components. In addition, the WFPC2 data include both UV (F336W) and near-infrared (F814W) images. These color data indicate the presence of sight-line-dependent extinction, causing the F336W-F814W color index of component B (the most reddened component) to be 0.56 ± 0.04 mag redder than that of component C (the least reddened component). The lack of evidence for significant component brightness variations at all HST observation epochs suggests that the data could be reliably extinction-corrected to derive the relative amplifications of the four image components. This is done for several reasonable dust-extinction models. Thus, the derived astrometry along with the photometric analysis set clear constraints on models for the Cloverleaf. Since component D shows some evidence for microlensing, the results on its relative amplification should be used with caution. While existing models can successfully reproduce the relative positions, the relative amplifications have not yet been successfully modeled. The WFPC2 imaging data has also permitted a sensitive search for component structure and the gravitational lens itself. There is marginal evidence for elongated structure between components A and C that may be part of an Einstein ring. However, no significant evidence for the lensing object is found. The various measurements are quantified in ways useful for setting model constraints. Limits on the mass-to-light ratio and detectability of the lensing galaxy are also discussed.

The First Ultraviolet and Optical Spectropolarimetry of the B[e] Star HD 50138

We report the first ultraviolet spectropolarimetry of the B[e] star HD 50138, obtained with the Wisconsin Ultraviolet Photo-Polarimeter Experiment aboard the Astro-2 Space Shuttle mission in 1995 March. The data cover the spectral range 1500-3200 A. Spectropolarimetry obtained contemporaneously in the range of 3800-10,000 A in the visual-to-near-IR region are presented as well. The presence of intrinsic polarization is detected from the UV to the near-IR. Strong evidence of a thin gaseous disk around the star is found. An almost flat wavelength dependence of the intrinsic polarization in the optical spectral region indicates that electron scattering, rather than dust scattering, is the dominant polarizing mechanism, although a small contribution due to dust scattering cannot be completely ruled out. A small inclination of the disk away from edge-on with respect to the line of sight is suggested. Comparison with similar polarimetric observations obtained for different objects that have the same circumstellar geometry shows that the envelope of HD 50138 probably has a rather large density contrast between the equatorial and polar regions that does not produce a position angle flip like that observed in other objects, notably HD 45677.

Hubble Space Telescope* Imaging Polarimetry of η Carinae

Linear polarization measurements have been a key to our understanding of the massive star system ? Carinae and its surrounding Homunculus nebula. We here present the results of (linear) polarimetric imaging of ? Carinae in the V band (F555W) with the Hubble Space Telescopes Wide Field Planetary Camera 2 (HST/WFPC2). The data agree well with previous ground-based measurements of the large-scale polarization across the Homunculus, allowing us to confirm that it is primarily a reflection nebula. The HST observations add information on the variation of the polarization across the lobes on small spatial scales. We provide measurements of the polarization in a variety of structures such as the jet, the skirt, the paddle, the southern ridge, and the spot, and discuss the properties of the polarization of the Homunculus on large and small spatial scales. Using a simple Mie-scattering model, we argue that of three previously proposed geometries for the three-dimensional structure of the Homunculus only the double-flask geometry represents a dust distribution which is consistent with our polarization map.

Characterization of infrared filters for the wide-field camera 3 of Hubble Space Telescope

The Wide Field Camera 3 (WFC3) is a panchromatic imager that will be deployed in the Hubble Space Telescope (HST) in 2004. The mission of the WFC3 is to enhance HSTs imaging capability in the ultraviolet, visible and near-infrared spectral regions. Together with a wavelength coverage spanning 2000A to 1.7 microns, the WFC3 high sensitivity, high spatial resolution, and large field-of-view provide the astronomer with an unprecedented set of tools for exploring all types of exciting astrophysical terrain and for addressing many key questions is astronomy today. The filter compliment, which includes broad, medium, and narrow band filters, naturally reflects the diversity of astronomical programs to be targeted with WFC3. The WFC3 holds 61 UVIS filters elements, 14 IR filters, and 3 dispersive elements. Accurate and comprehensive knowledge of the optical performance of these components including its pass-band and out-of-band rejection behavior are necessary to verify that the instrument will meet its scientific objectives. The measured throughput curves are essential components in instrument performance models used to plan observations, and in calibration algorithms for removing the instrument signature from in-flight data. We will report on the normal incidence in-band and out-of-band transmittance of the IR filters measured near the operating temperature of -30 degree(s)C and additional tests used to characterizes the filters performance. Details of the characterization apparatus, that include an optical cryostat, and a grating spectrometer are discussed.

Line-of-sight jitter of the Hubble Space Telescope

We report on the results of a dedicated on-orbit test which we have performed to measure the line-of-sight jitter of the Hubble Space Telescope. The test, which made use of one of the science instruments on board the spacecraft, had a very high sensitivity (a fraction of a milliarcsecond) and covered all frequencies up to 500 Hz. As was previously known from gyroscope data analysis, the bulk of the line-of-sight jitter occurs at frequencies lower than 5 Hz and is caused by motion of the spacecraft body reacting against the oscillation of its appendages. However, the test indicates that there are also minor contributions by various modes of the telescope structure in the 15 - 30 Hz range and the vibration of the primary mirror at 61 Hz when it is excited by thermally induced shocks or the running of the tape recorder. There are also traces of a component around 300 Hz induced by the tape recorder.

Fine guidance sensors aboard the Hubble Space Telescope: the scientific capabilities of these interferometers

The fine guidance sensors (FGS) aboard the Hubble Space Telescope (HST) are optical white light shearing interferometers that offer a unique capability to astronomers. The FGSs photometric dynamic range, fringe visibility, and fringe tracking ability allow the instrument to exploit the benefits of performing interferometry form a space-based platform. The FGSs routinely provide HST with 2 milli-seconds of arc pointing stability. The FGS designated as the Astronomer, FGS3, has also been used to (1) perform 2 mas relative astrometry over the central 4 arc minutes of its field of view, (2) determine the true relative orbits of close faint binary systems, (3) measure the angular diameter of a giant star, (4) search for extra-solar planets, (5) observe occultations of stars by solar system objects, as well as (6) photometrically monitor stellar flares on a low mas M dwarf. In this paper we discuss this unique instrument, its design, performance, and the areas of science for which it is the only device able to successfully observe objects of interest.

Widefield camera 3 for the Hubble Space Telescope

In June 1997, NASA made the decision to extend the end of the Hubble Space Telescope (HST) mission from 2005 until 2010. As a result, the age of the instruments on board the HST became a consideration. After careful study, NASA decided to ensure the imaging capabilities of the HST by replacing the Wide Field Planetary Camera 2 with a low-cost facility instrument, the Wide Field Camera 3. This paper provides an overview of the scientific goals and capabilities of the instrument.

The fine guidance sensors aboard the Hubble Space Telescope: The scientific capabilities of these interferometers

The fine guidance sensors (FGS) aboard the Hubble Space Telescope (HST) are optical white light shearing interferometers that offer a unique capability to astronomers. The FGSs photometric dynamic range, fringe visibility, and fringe tracking ability allow the instrument to exploit the benefits of performing interferometry form a space-based platform. The FGSs routinely provide HST with 2 milli-seconds of arc pointing stability. The FGS designated as the Astronomer, FGS3, has also been used to (1) perform 2 mas relative astrometry over the central 4 arc minutes of its field of view, (2) determine the true relative orbits of close faint binary systems, (3) measure the angular diameter of a giant star, (4) search for extra-solar planets, (5) observe occultations of stars by solar system objects, as well as (6) photometrically monitor stellar flares on a low mas M dwarf. In this paper we discuss this unique instrument, its design, performance, and the areas of science for which it is the only device able to successfully observe objects of interest.

The fine guidance sensors aboard the Hubble Space Telescope

The fine guidance sensors (FGS) aboard the Hubble Space Telescope (HST) are optical white light shearing interferometers that offer a unique capability to astronomers. The FGSs photometric dynamic range, fringe visibility, and fringe tracking ability allow the instrument to exploit the benefits of performing interferometry form a space-based platform. The FGSs routinely provide HST with 2 milli-seconds of arc pointing stability. The FGS designated as the Astronomer, FGS3, has also been used to (1) perform 2 mas relative astrometry over the central 4 arc minutes of its field of view, (2) determine the true relative orbits of close faint binary systems, (3) measure the angular diameter of a giant star, (4) search for extra-solar planets, (5) observe occultations of stars by solar system objects, as well as (6) photometrically monitor stellar flares on a low mas M dwarf. In this paper we discuss this unique instrument, its design, performance, and the areas of science for which it is the only device able to successfully observe objects of interest.