Whole Earth Telescope observations of the helium interacting binary PG 1346+082 (CR bootis)

We present our analysis of 240 hr of white-light, high-speed photometry of the dwarf nova-like helium variable PG 1346+082 (CR Boo). We identify two frequencies in the low-state power spectrum, at 679.670±0.004 μHz and 669.887±0.008 μHz. The 679.670 μHz variation is coherent over at least a 2 week time span, the first demonstration of a phase-coherent photometric variation in any dwarf nova-like interacting binary white dwarf system. The high-state power spectrum contains a complex fundamental with a frequency similar, but not identical, to the low-state spectrum, and a series of harmonics not detected in low state. We also uncover an unexpected dependence of the high-frequency powerÏs amplitude and frequency structure on overall system magnitude. We discuss these Ðndings in light of the general AM CVn system model, particularly the implications of the high-order harmonics on future studies of disk structure, mass transfer, and disk viscosity

Rubin Observatory primary tertiary mirror cell assembly: Optical testing of the fully assembled mirror support

The Vera C. Rubin Observatory Primary Tertiary Mirror (M1M3), together with the fully-assembled mirror support system, underwent two optical testing campaigns at the University of Arizona Richard F. Caris Mirror Lab. The objectives of the testing campaigns were: (1) optimizing the M1M3 surfaces with support forces, and (2) characterizing how the surfaces respond to actuator forces, including measuring the bending modes and single actuator influence functions. Both objectives were successfully achieved. The differences between the measured bending modes and the Finite Element Analysis (FEA) predicted modes were shown to be less than a few percent. The surface optimizations routinely resulted in Root-Mean-Square (RMS) surface errors below 30 nm for M1 and M3, simultaneously. The entire system was shown to be robust and repeatable. In this paper, we present the results of the optical testing and the analyses performed using the data acquired. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Large Synoptic Survey Telescope: From science drivers to reference design

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 δ < +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

Whole Earth Telescope observations of the helium interacting binary PG 1346+082 (CR bootis)

We present our analysis of 240 hr of white-light, high-speed photometry of the dwarf nova-like helium variable PG 1346+082 (CR Boo). We identify two frequencies in the low-state power spectrum, at 679.670±0.004 μHz and 669.887±0.008 μHz. The 679.670 μHz variation is coherent over at least a 2 week time span, the first demonstration of a phase-coherent photometric variation in any dwarf nova-like interacting binary white dwarf system. The high-state power spectrum contains a complex fundamental with a frequency similar, but not identical, to the low-state spectrum, and a series of harmonics not detected in low state. We also uncover an unexpected dependence of the high-frequency powerÏs amplitude and frequency structure on overall system magnitude. We discuss these Ðndings in light of the general AM CVn system model, particularly the implications of the high-order harmonics on future studies of disk structure, mass transfer, and disk viscosity

Understanding the cool DA white dwarf pulsator G29-38

The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post-main-sequence evolution, along with their cooling rates, which will allow us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DA variables (DAVs), which have not been explored previously through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning 10 yr, we explore the pulsation spectrum of the cool DAV, G29-38 and find an underlying structure of 19 (not including multiplet components) normal-mode, probably l=1 pulsations amidst an abundance of time variability and linear combination modes. Modeling results are incomplete, but we suggest possible starting directions and discuss probable values for the stellar mass and hydrogen layer size. For the first time, we have made sense out of the complicated power spectra of a large-amplitude DA pulsator. We have shown that its seemingly erratic set of observed frequencies can be understood in terms of a recurring set of normal-mode pulsations and their linear combinations. With this result, we have opened the interior secrets of the DAVs to future asteroseismological modeling, thereby joining the rest of the known white dwarf pulsators

High-speed photometric observations of the pulsating da white dwarf gd 165

New high-speed photometric observations ofthe pulsating DA white dwarfGD 165 are presented. The Fourier spectrum ofthe light curve ofGD 165 exhibits two main regions ofpower at 120 and 193 s. The presence of a high-amplitude long period mode near ~1800 s reported by Bergeron and McGraw is not confirmed by these new observations. Light curves obtained with the Canada-France-Hawaii Telescope reveal previously undetected low-amplitude harmonic oscillations. Observations with the Whole Earth Telescope are used to resolve the two principal regions of power. The 120 and 193 s peaks are shown to be multiplets composed of at least three, and possibly tive frequency components. The most likely explanation is that these two peaks correspond to nonradial gravity modes with different values of the radial order k and with I= 1 or 2 split into 21+1 components by slow rotation. The frequency differences observed between the three dominant components of each peak are consistent with equal spacing, but a slight asymmetry in spacing cannot be totally ruled out at this stage. They suggest a rotation time scale of the order of 4.2 days. Within a peak, power is not distributed evenly or symmetrically among the three frequency components, particularly for the 193 s mode. Consequently, a simple interpretation in terms of geometric effects (inclination of the pulsation axis with respect to the line of sight) cannot be invoked here. The tentative identification of modes with l=1 or 2 is used to constrain the hydrogen layer mass in GD 165. In particular, the 120 s pulsation mode has a period sufficiently short that useful limits can be derived on this quantity. Using recent adiabatic pulsation calculations and new determinations of the atmospheric parameters of GD 165, it is found that ..(H)/*~>10-3.7 or~>10-6.4 if the 120 s pulsation is a mode with l=1 or 2, respectively

High-speed photometric observations of the pulsating da white dwarf gd 165

New high-speed photometric observations ofthe pulsating DA white dwarfGD 165 are presented. The Fourier spectrum ofthe light curve ofGD 165 exhibits two main regions ofpower at 120 and 193 s. The presence of a high-amplitude long period mode near ~1800 s reported by Bergeron and McGraw is not confirmed by these new observations. Light curves obtained with the Canada-France-Hawaii Telescope reveal previously undetected low-amplitude harmonic oscillations. Observations with the Whole Earth Telescope are used to resolve the two principal regions of power. The 120 and 193 s peaks are shown to be multiplets composed of at least three, and possibly tive frequency components. The most likely explanation is that these two peaks correspond to nonradial gravity modes with different values of the radial order k and with I= 1 or 2 split into 21+1 components by slow rotation. The frequency differences observed between the three dominant components of each peak are consistent with equal spacing, but a slight asymmetry in spacing cannot be totally ruled out at this stage. They suggest a rotation time scale of the order of 4.2 days. Within a peak, power is not distributed evenly or symmetrically among the three frequency components, particularly for the 193 s mode. Consequently, a simple interpretation in terms of geometric effects (inclination of the pulsation axis with respect to the line of sight) cannot be invoked here. The tentative identification of modes with l=1 or 2 is used to constrain the hydrogen layer mass in GD 165. In particular, the 120 s pulsation mode has a period sufficiently short that useful limits can be derived on this quantity. Using recent adiabatic pulsation calculations and new determinations of the atmospheric parameters of GD 165, it is found that ..(H)/*~>10-3.7 or~>10-6.4 if the 120 s pulsation is a mode with l=1 or 2, respectively

Nonradial pulsation of the unevolved hot (gamma) scuti star cd-24 7599 discovered with the whole earth telescope

We report a frequency analysis of the δ Scuti star CD-24°7599 and the discovery that it pulsates nonradially with at least 7 frequencies between 27.01 and 38.11 cycles per day (312 to 441 μHz). These results are based on 116.7 hours of photometric data obtained with the Whole Earth Telescope network. New uvbyβ photometry implies that the star is unevolved and located near the observed hot border of the classical instability strip. We give arguments for interpreting the pulsation periods in terms of low-order low-degree nonradial p-modes. Rotational m-mode splitting is likely. Few radial modes could also be present. The rich modal content and unevolved state of CD-24°7599 emphasize its importance for δ Scuti star asteroseismology. We detect linear combination frequencies of the pulsation modes with the highest photometric amplitudes and suggest they are not normal modes excited by resonance

Nonradial pulsation of the unevolved hot (gamma) scuti star cd-24 7599 discovered with the whole earth telescope

We report a frequency analysis of the δ Scuti star CD-24°7599 and the discovery that it pulsates nonradially with at least 7 frequencies between 27.01 and 38.11 cycles per day (312 to 441 μHz). These results are based on 116.7 hours of photometric data obtained with the Whole Earth Telescope network. New uvbyβ photometry implies that the star is unevolved and located near the observed hot border of the classical instability strip. We give arguments for interpreting the pulsation periods in terms of low-order low-degree nonradial p-modes. Rotational m-mode splitting is likely. Few radial modes could also be present. The rich modal content and unevolved state of CD-24°7599 emphasize its importance for δ Scuti star asteroseismology. We detect linear combination frequencies of the pulsation modes with the highest photometric amplitudes and suggest they are not normal modes excited by resonance