119201613
PAndromeda—First results from the high-cadence monitoring of M31 with Pan-STARRS 1
The Pan-STARRS 1 (PS1) survey of M31 (PAndromeda) is designed to identify gravitational microlensing events, caused by bulge and disk stars (self-lensing) and by compact matter in the halos of M31 and the Milky Way (halo lensing or lensing by massive compact halo objects). With the 7 deg{sup 2} field of view (FOV) of PS1, the entire disk of M31 can be imaged with one single pointing. Our aim is to monitor M31 with this wide FOV with daily sampling (20 minutes day{sup -1}). In the 2010 season, we acquired in total 91 nights toward M31, with 90 nights in the r{sub P1} and 66 nights in the i{sub P1}. The total integration time in r{sub P1} and i{sub P1} are 70,740 s and 36,180 s, respectively. As a preliminary analysis, we study a 40' Multiplication-Sign 40' sub-field in the central region of M31, a 20' Multiplication-Sign 20' sub-field in the disk of M31, and a 20' Multiplication-Sign 20' sub-field for the investigation of astrometric precision. We demonstrate that the point-spread function is good enough to detect microlensing events. We present light curves for six candidate microlensing events. This is a competitive rate compared with previous M31 microlensing surveys. Finally,more » we also present one example light curve for Cepheids, novae, and eclipsing binaries in these sub-fields.« less
119266289
THE Pan-STARRS1 PHOTOMETRIC SYSTEM
The Pan-STARRS1 survey is collecting multi-epoch, multi-color observations of the sky north of declination –30° to unprecedented depths. These data are being photometrically and astrometrically calibrated and will serve as a reference for many other purposes. In this paper, we present our determination of the Pan-STARRS1 photometric system: g P1, r P1, i P1, z P1, y P1, and w P1. The Pan-STARRS1 photometric system is fundamentally based on the Hubble Space Telescope Calspec spectrophotometric observations, which in turn are fundamentally based on models of white dwarf atmospheres. We define the Pan-STARRS1 magnitude system and describe in detail our measurement of the system passbands, including both the instrumental sensitivity and atmospheric transmission functions. By-products, including transformations to other photometric systems, Galactic extinction, and stellar locus, are also provided. We close with a discussion of remaining systematic errors.
119252361
First Results from Pan-STARRS1: Faint, High Proper Motion White Dwarfs in the Medium-Deep Fields
The Pan-STARRS1 survey has obtained multi-epoch imaging in five bands (Pan-STARRS1 g P1, r P1, i P1, z P1, and y P1) on 12 "Medium-Deep fields," each of which spans a 33 circle. For the period between 2009 April and 2011 April these fields were observed 50-200 times. Using a reduced proper motion diagram, we have extracted a list of 47 white dwarf (WD) candidates whose Pan-STARRS1 astrometry indicates a non-zero proper motion at the 6σ level, with a typical 1σ proper motion uncertainty of 10 mas yr–1. We also used astrometry from the Sloan Digital Sky Survey (when available) and USNO-B to assess our proper motion fits. None of the WD candidates exhibits evidence of statistically significant parallaxes, with a typical 1σ uncertainty of 8 mas. Twelve of these candidates are known WDs, including the high proper motion (17 yr–1) WD LHS 291. We confirm seven more objects as WDs through optical spectroscopy. Based on the Pan-STARRS1 colors, ten of the stars are likely to be cool WDs with 4170 K <T eff < 5000 K and cooling ages ≈ 8 Gyr. Based on their kinematics, these objects are likely thick disk WDs, but a subset may belong to the halo. Our current sample represents only a small fraction of the Pan-STARRS1 data. With continued coverage from the Medium-Deep Field Survey and the 3π survey, Pan-STARRS1 should find many more high proper motion WDs that are part of the old thick disk and halo.
41180894
PHOTOMETRIC CALIBRATION OF THE FIRST 1.5 YEARS OF THE PAN-STARRS1 SURVEY
We present a precise photometric calibration of the first 1.5 years of science imaging from the PanSTARRS1 survey (PS1), an ongoing optical survey of the entire sky north of declination −30 ◦ in five bands. Building on the techniques employed by Padmanabhan et al. (2008) in the Sloan Digital Sky Survey (SDSS), we use repeat PS1 observations of stars to perform the relative calibration of PS1 in each of its five bands, solving simultaneously for the system throughput, the atmospheric transparency, and the large-scale detector flat field. Both internal consistency tests and comparison against the SDSS indicate that we achieve relative precision of < 10 mmag in g, r, and iP1, and ∼ 10 mmag in z and yP1. The spatial structure of the differences with the SDSS indicates that errors in both the PS1 and SDSS photometric calibration contribute similarly to the differences. The analysis suggests that both the PS1 system and the Haleakala site will enable < 1% photometry over much of the sky. Subject headings: Surveys: Pan-STARRS1
119209508
HIP 38939B: A NEW BENCHMARK T DWARF IN THE GALACTIC PLANE DISCOVERED WITH Pan-STARRS1
We report the discovery of a wide brown dwarf companion to the mildly metal-poor ([Fe/H] = –0.24), low Galactic latitude (b = 188) K4V star HIP 38939. The companion was discovered by its common proper motion with the primary and its red optical (Pan-STARRS1) and blue infrared (Two Micron All Sky Survey) colors. It has a projected separation of 1630 AU and a near-infrared spectral type of T4.5. As such it is one of only three known companions to a main-sequence star which have early/mid T spectral types of (the others being HN Peg B and e Indi B). Using chromospheric activity we estimate an age for the primary of 900±1900 600 Myr. This value is also in agreement with the age derived from the star's weak ROSAT detection. Comparison with evolutionary models for this age range indicates that HIP 38939B falls in the mass range 38 ± 20 M Jup with an effective temperature range of 1090 ± 60 K. Fitting our spectrum with atmospheric models gives a best-fitting temperature of 1100 K. We include our object in an analysis of the population of benchmark T dwarfs and find that while older atmospheric models appeared to overpredict the temperature of the coolest objects compared to evolutionary models, more recent atmospheric models provide better agreement.
9863216
OBSERVATIONAL AND DYNAMICAL CHARACTERIZATION OF MAIN-BELT COMET P/2010 R2 (La Sagra)
We present observations of the recently discovered comet-like main-belt object P/2010 R2 (La Sagra) obtained by Pan-STARRS1 and the Faulkes Telescope-North on Haleakala in Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on Mauna Kea, the Danish 1.54 m telescope (operated by the MiNDSTEp consortium) at La Silla, and the Isaac Newton Telescope on La Palma. An antisolar dust tail is observed to be present from 2010 August through 2011 February, while a dust trail aligned with the object's orbit plane is also observed from 2010 December through 2011 August. Assuming typical phase darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag between 2010 August and December, suggesting that dust production is ongoing over this period. These results strongly suggest that the observed activity is cometary in nature (i.e., driven by the sublimation of volatile material), and that P/La Sagra is therefore the most recent main-belt comet to be discovered. We find an approximate absolute magnitude for the nucleus of HR = 17.9 ± 0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an albedo of p = 0.05. Comparing the observed scattering surface areas of the dust coma to that of the nucleus when P/La Sagra was active, we find dust-to-nucleus area ratios of Ad /AN = 30-60, comparable to those computed for fellow main-belt comets 238P/Read and P/2008 R1 (Garradd), and one to two orders of magnitude larger than for two other main-belt comets (133P/Elst-Pizarro and 176P/LINEAR). Using optical spectroscopy to search for CN emission, we do not detect any conclusive evidence of sublimation products (i.e., gas emission), finding an upper limit CN production rate of Q CN 100 Myr, suggesting that it is likely native to its current location and that its composition is likely representative of other objects in the same region of the main belt, though the relatively close proximity of the 13:6 mean-motion resonance with Jupiter and the (3,–2,–1) three-body mean-motion resonance with Jupiter and Saturn mean that dynamical instability on larger timescales cannot be ruled out.
138804061
GAS EVOLUTION FROM EPOXY RESINS BY HIGH ENERGY RADIATION.
107773393
Proposed Magnet Alignment Changes for AP-1
AP-1 was built to connect the Antiproton Source with the Main Ring accelerator. The beamline was designed to support modes of operation at both 8 GeV and 120 GeV kinetic energy. During the days of Main Ring operation, 120 GeV beam was extracted through the field region of a Lambertson at F-17 and transported approximately 174 meters to the production target. This 'pbar production' mode required a lattice that would focus the proton beam to a small spot size on the target to maximize antiproton yield. The AP-1 line would also be reconfigured to operate at 8 GeV to support antiproton transfers and tuning cycles with protons. The AP-1 line is also connected to the Accumulator via AP-3, so the lattices of these beamlines needed to be compatible. After the Main Injector was built to replace the Main Ring, a beamline was required to connect it with the Antiproton Source. Designers chose to combine beam transfers of 150 GeV protons to the Tevatron, 120 GeV protons to AP-1, 120 GeV protons to Switchyard and 8 GeV proton tune-up or antiproton transfers via AP-1 into the P1 and P2 lines. The P2 line resides in the Main Ring tunnel enclosure betweenmore » F-0 and F-17 and utilizes original Main Ring magnets. The lattice was designed to duplicate the Twiss parameters of the old Main Ring at F-17, including the large horizontal beta and dispersion functions. The addition of the P1 and P2 lines add almost an additional 1,000 meters and an extra Lambertson magnet (at F0) to beam transfers to and from the Main Injector versus the Main Ring. Although Lambertson magnets are still used to extract beam from the Main Injector, the Lambertson at F-17 was no longer required. Unfortunately, the limited aperture C-magnets at F-17 remained, necessitated by the P3 line which is intended to provide beam to Switchyard for future 'Meson 120' operation. The C-magnets are one of the limiting horizontal apertures in the AP-1 line due to the combination of small physical aperture and the large horizontal beta and dispersion functions. Most of the AP-1 magnets were originally used in Switchyard. Apertures of these magnets are adequate for high energy operation, but have apertures that are smaller than magnets traditionally used in other 8 GeV transfer lines. This makes the AP-1 line unusually sensitive to alignment and steering errors. In addition, the lattice constraints imposed by the beamlines attached to AP-1 does not allow much freedom in suppressing the lattice functions at key locations to reduce the beam size.« less
95194327
Stress relaxation of natural rubber during irradiation
Abstract The site of chain scission and crosslinking in vulcanized natural rubber irradiated with 4 MeV electrons has been determined by analysis of stress relaxation data. Sulfur and peroxide vulcanizates of different crosslink densities were prepared and the crosslink densities determined from stress—strain measurements. Stress relaxation was measured during irradiation using modified commercial relaxometers. The specimens were maintained in an atmosphere of nitrogen to minimize oxidative side effects. Scission is deduced to take place in the vicinity of crosslinks, since the rate of continuous stress relaxation is independent of crosslink density. Scission may be associated both with crosslinks initially present and with those subsequently introduced by irradiation. Crosslinking by radiation is largely a random process. However, there is a crosslinking reaction dependent to a slight extent on crosslink density as well as a small contribution from random scission reactions. G values for the random react...
54530109
8 GEV BEAM LINE OPTICS OPTIMIZATION FOR THE RAPID ANTIPROTON TRANSFERS AT FERMILAB
Tevatron Run-II upgrade requires a significant increase of the efficiency and speed of the antiproton transfers from the Accumulator to the Recycler. The goal for the total transfer time is challenging a reduction from 1 hour down to a few minutes. Here we discuss the beam line optics aspects of this project. Results of lattice measurements and optimization are analyzed in terms of transport efficiency and stability.
14422873
Neutrino Propulsion for Interstellar Spacecraft
An exotic spacecraft propulsion technology is described which exploits parity violation in weak interactions. Anisotropic neutrino emission from a polarized assembly of weakly interacting particles converts rest mass directly to spacecraft impulse.