In response to the failure of the SDF to properly output science data at 277/19:10 the NSSC-1 ATP was inhibited and SDF input enabled via Ops Request 18933. This will facilitate the recovery of the remaining science data in the SIs and interception of the reprocessed SMS.
FUV Detector Dark Monitor
Monitor the FUV detector dark rate by taking long science exposures without illuminating the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.
The Frequency and Chemical Composition of Planetary Debris Discs around Young White Dwarfs
Throughout the past few years, it has become increasingly clear that the most plausible scenario to explain the metal-pollution observed in ~20% of all cool white dwarfs is accretion from rocky debris material - suggesting that these white dwarfs may have had, or may still have terrestial planets as well. This hypothesis is corroborated through the infrared detection of circumstellar dust around the most heavily polluted white dwarfs. Traditionally, the detection of metal pollution is done in the optical using the Ca H/K lines, leading to a strong bias against hot/young white dwarfs. Hence, most of our knowledge about the late evolution of planetary systems is based on white dwarfs with cooling ages >0.5Gyr. We propose an HST/COS ultraviolet spectroscopic snapshot survey to carry out the first systematic investigation of the fraction of metal-pollution among young (20-100Myr) white dwarfs, probing the correlation with white dwarf (and hence progenitor) mass, and determining the Si/H, C/H, and potentially N/H and O/H abundance ratios of their circumstellar debris material.
What are the Locations and Kinematics of Mass Outflows in AGN?
Mass outflows of ionized gas in AGN, first revealed through blueshifted UV and X-ray absorption lines, are likely important feedback mechanisms for the enrichment of the IGM, self-regulation of black-hole growth, and formation of structure in the early Universe. To understand the origin, dynamics, and impact of the outflowing absorbers on their surroundings, we need to know their locations (radial positions and polar angles with respect to the AGN rotation axes) and kinematics (radial and transverse velocities). We will use COS high-resolution spectra of 11 Seyfert 1 galaxies to derive velocity-dependent covering factors, ionic column densities, number densities (via metastable lines or variability), and ionization parameters (via photoionization models) of the UV absorbers, and thereby determine their radial locations as we have done for NGC 4151. We will use absorption variability over time scales of up to ~20 years, to determine transverse velocities and detect changes in radial velocities. We will use STIS G430M long-slit spectra and WFC3 [OIII] images to resolve the kinematics of the narrow-line region (NLR) and determine the inclinations of the AGN, to investigate the connection between nuclear absorption and NLR emission outflows and their dependence on polar angle.
The Temperature Profiles of Quasar Accretion Disks
We can now routinely measure the size of quasar accretion disks using gravitational microlensing of lensed quasars. At optical wavelengths we observe a size and scaling with black hole mass roughly consistent with thin disk theory but the sizes are larger than expected from the observed optical fluxes. One solution would be to use a flatter temperature profile, which we can study by measuring the wavelength dependence of the disk size over the largest possible wavelength baseline. Thus, to understand the size discrepancy and to probe closer to the inner edge of the disk we need to extend our measurements to UV wavelengths, and this can only be done with HST. For example, in the UV we should see significant changes in the optical/UV size ratio with black hole mass. We propose monitoring 5 lenses spanning a broad range of black hole masses with well-sampled ground based light curves, optical disk size measurements and known GALEX UV fluxes during Cycles 17 and 18 to expand from our current sample of two lenses. We would obtain 5 observations of each target in each Cycle, similar to our successful strategy for the first two targets.