PG 1351+489 is one of the 20 DBVs – pulsating helium-atmosphere white dwarf stars – known and has the simplest power spectrum for this class of star, making it a good candidate to study cooling rates. We report accurate period determinations for the main peak at 489.334 48 s and two other normal modes using data from the Whole Earth Telescope (WET) observations of 1995 and 2009. In 2009, we detected a new pulsation mode and the main pulsation mode exhibited substantial change in its amplitude compared to all previous observations. We were able to estimate the star’s rotation period, of 8.9 h, and discuss a possible determination of the rate of period change of (2.0 ± 0.9) × 10−13 s s −1, the first such estimate for a DBV.

The Large Synoptic Survey Telescope (LSST) will be a large, wide-field ground-based system designed to obtain, starting in 2015, multiple images of the sky that is visible from Cerro Pachon in Northern Chile. About 90% of the observing time will be devoted to a deep-wide-fast survey mode which will observe a 20,000 deg(2) region about 1000 times during the anticipated 10 years of operations (distributed over six bands, ugrizy). Each 30-second long visit will deliver 5 sigma depth for point sources of r similar to 24.5 on average. The co-added map will be about 3 magnitudes deeper, and will include 10 billion galaxies and a similar number of stars. We discuss various measurements that will be automatically performed for these 20 billion sources, and how they can be used for classification and determination of source physical and other properties. We provide a few classification examples based on SDSS data, such as color classification of stars, color-spatial proximity search for wide-angle binary stars, orbital-color classification of asteroid families, and the recognition of main Galaxy components based on the distribution of stars in the position-metallicity-kinematics space. Guided by these examples, we anticipate that two grand classification challenges for LSST will be 1) rapid and robust classification of sources detected in difference images, and 2) simultaneous treatment of diverse astrometric and photometric time series measurements for an unprecedentedly large number of objects.

In the history of astronomy, major advances in our understanding of the Universe have come from dramatic improvements in our ability to accurately measure astronomical quantities. Aided by rapid progress in information technology, current sky surveys are changing the way we view and study the Universe. Next- generation surveys will maintain this revolutionary progress. We focus here on the most ambitious survey currently planned in the visible band, the Large Synoptic Survey Telescope (LSST). LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: constraining dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. It will be a large, wide-field ground-based system designed to obtain multiple images covering the sky that is visible from Cerro Pachon in Northern Chile. The current baseline design, with an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2 field of view, and a 3,200 Megapixel camera, will allow about 10,000 square degrees of sky to be covered using pairs of 15-second exposures in two photometric bands every three nights on average. The system is designed to yield high image quality, as well as superb astrometric and photometric accuracy. The survey area will include 30,000 deg2 with ? < +34.5? , and will be imaged multiple times in six bands, ugrizy, covering the wavelength range 320-1050 nm. About 90% of the observing time will be devoted to a deep- wide-fast survey mode which will observe a 20,000 deg2 region about 1000 times in the six bands during the anticipated 10 years of operation. These data will result in databases including 10 billion galaxies and a similar number of stars, and will serve the majority of science programs. The remaining 10% of the observing time will be allocated to special programs such as Very Deep and Very Fast time domain surveys. We describe how the LSST science drivers led to these choices of system parameters.

mission. The proximity of the primary and tertiary surfaces enables fabrication of both mirrors from a single substrate. This unique design, referred to as the M1M3 monolith, offers significant advantages in the reduction of degrees of freedom during operational alignment and improved structural stiffness for the otherwise annular primary surface. The 3-mirror telescope feeds a 3 element refractive corrector to produce a 3.5-degree diameter field of view over a 64-cm flat focal surface in 6 spectral bands with excellent image quality. The most recent design optimization included null tests for each of the three camera lenses and resulted in significantly simpler test configurations and reduced asphericity on the secondary mirror. Detailed analysis of the optical effects of lens displacements, gravity distortions, glass quality, and fabrication errors have been carried out and show this system to be well within industry fabrications capabilities. Stray and scattered light analysis shows the LSST will achieve its signal to noise requirements. Further progress has been made on the development of mirror, antireflection, and filter coatings showing that the system throughput meets the depth requirements of the survey and the out of band filter rejection requirements. Performance and Analysis of the LSST Optical System C.F. Claver (NOAO), L. Seppala (LLNL), M. Liang (NOAO), K. Gilmore (SLAC), W. Gressler (NOAO), V. Krabbendam (NOAO), D. Niell (NOAO), S. Oliver (LLNL), J. Sebag (NOAO) and the LSST Collaboration

We investigate the use of a narrow-band DD051 filter for photometric identification of cool white dwarfs. We report photometric observations of 30 known cool white dwarfs with temperatures ranging from 10,000 K down to very cool temperatures (<= 3500 K). Follow-up spectroscopic observations of a sample of objects selected using this filter and our photometric observations show that DD051. filter photometry can help select cool white dwarf candidates for follow-up multi-object spectroscopy by rejecting 65 % of main sequence stars with the same broad-band colors as the cool white dwarfs. This technique is not selective enough to efficiently feed single-object spectrographs. I-Ale present the white dwarf cooling sequence using this filter. Our observations show that very cool white dwarfs form a sequence in the r - DDO vs. r - z color-color diagram and demonstrate that significant improvements are needed in white dwarf model atmospheres.

We investigate the use of a narrowband DDO51 filter for photometric identification of cool white dwarfs. We report photometric observations of 30 known cool white dwarfs with temperatures ranging from 10,000 K down to very cool temperatures (≤3500 K). Follow-up spectroscopic observations of a sample of objects selected using this filter and our photometric observations show that DDO51 filter photometry can help select cool white dwarf candidates for follow-up multiobject spectroscopy by rejecting 65% of main-sequence stars with the same broadband colors as the cool white dwarfs. This technique is not selective enough to efficiently feed single-object spectrographs. We present the white dwarf cooling sequence using this filter. Our observations show that very cool white dwarfs form a sequence in the r - DDO versus r - z color-color diagram and demonstrate that significant improvements are needed in white dwarf model atmospheres.

The 8.4m Large Synoptic Survey Telescope (LSST) is a wide-field telescope facility that will add a qualitatively new capability in astronomy. For the first time, the LSST will provide time-lapse digital imaging of faint astronomical objects across the entire sky. The LSST has been identified as a national scientific priority by diverse national panels, including multiple National Academy of Sciences committees. This judgment is based upon the LSST's ability to address some of the most pressing open questions in astronomy and fundamental physics, while driving advances in data-intensive science and computing. The LSST will provide unprecedented 3-dimensional maps of the mass distribution in the Universe, in addition to the traditional images of luminous stars and galaxies. These mass maps can be used to better understand the nature of the newly discovered and utterly mysterious Dark Energy that is driving the accelerating expansion of the Universe. The LSST will also provide a comprehensive census of our solar system, including potentially hazardous asteroids as small as 100 meters in size. The LSST facility consists of three major subsystems: 1) the telescope, 2) the camera and 3) the data processing system. The baseline design for the LSST telescope is a 8.4m 3-mirror design with a 3.5 degree field of view resulting in an A-Omega product (etendue) of 302deg(2)m(2). The camera consists of 3-element transmisive corrector producing a 64cm diameter flat focal plane. This focal plane will be populated with roughly 3 billion 10mum pixels. The data processing system will include pipelines to monitor and assess the data quality, detect and classify transient events, and establish a large searchable object database. We report on the status of the designs for these three major LSST subsystems along with the overall project structure and management.

We report on the analysis of multisite time-series photometry of the pulsating pre-white dwarf (GW Vir star) PG 1707+427, obtained by the Whole Earth Telescope collaboration. This is the last of the known GW Vir stars without surrounding nebulae to be resolved by multisite data. Successful resolution of the pulsation spectrum resulted from the combination of high signal-to-noise observations with a large telescope and wide coverage in longitude with smaller telescopes. We find a series of 8 pulsation frequencies (along with two nonlinear combination frequencies), and identify 7 of them as part of a sequence of l = 1 modes, with a common period spacing of 23.0 s. This spacing implies that the mass of PG 1707+427 is 0.57 M(circle dot). Preliminary model fits suggest that the mass determined via asteroseismology is consistent with the mass determined from spectroscopy combined with evolutionary tracks.

We report our search for the cool white dwarfs belonging to the Galactic disk by extending the NOAO Deep Wide-Field Survey. Narrow-band DDO51 photometry of the Deep Wide-Field Survey's northern field was obtained using the 4m-Mayall Telescope and the MOSAIC imager to separate cool white dwarfs from other stellar types of similar T_eff. Follow-up spectroscopy of four white dwarf candidates from our photometric search resulted in the discovery of two new cool white dwarfs as companions to M dwarfs.

We briefly report on the April 1995 XCov12 campaign on the DBV PG 1351+489.