2326076
Detection of new optical counterpart candidates to PSR B1951+32 with HST/WFPC2
There remain several definitive-ray pulsars that are as yet undetected in the optical regime. A classic case is the pulsar PSR B1951+32, associated with the complex CTB 80 SNR. Previous ground based high speed 2-d optical studies have ruled out candidates to mV 24. Hester (2000a) has reported an analysis of archival HST/WFPC2 observations of the CTB 80 complex which suggest a compact synchrotron nebula coincident with the pulsar's radio position. Performing a similar analysis, we have identified a possible optical counterpart within this synchrotron nebula at mV 25:5 26, and another optical counterpart candidate nearby at mV 24:5. We assess the reality of these counterpart candidates in the context of existing models of pulsar emission.
117023123
A new survey of variability in the core of M15 with TRIFFID-2
A two-week campaign of high-resolution imaging of the centre of M15 using the tip/tilt correcting TRIFFID-2 camera, followed by analysis with ISIS (image matching & subtraction software), has produced the most sensitive survey to date of variable stars in the central ~1x1 arcmin^2 - a total of 48 were detected -, and constrains the size of the dwarf nova population.
16393661
A Photometric Method for estimating CNO Abundances in Globular Clusters
Stromgren indices v and b are combined with broad-band index I, and a new index p, the short wavelength half of the v band, to estimate CN 4215A molecular absorption in a sample of stars in M22. The results have been used to estimate carbon and nitrogen abundances and suggest groups of stars within this cluster, each with a characteristic nitrogen abundance, but with a range of carbon abundances. The results suggest the possibility of stars consisting of material which has undergone CNO recycling two or three times. The method can be subsequently used for other globular clusters.
15947685
Parallel Astronomical Data Processing with Python: Recipes for multicore machines
Abstract High performance computing has been used in various fields of astrophysical research. But most of it is implemented on massively parallel systems (supercomputers) or graphical processing unit clusters. With the advent of multicore processors in the last decade, many serial software codes have been re-implemented in parallel mode to utilize the full potential of these processors. In this paper, we propose parallel processing recipes for multicore machines for astronomical data processing. The target audience is astronomers who use Python as their preferred scripting language and who may be using PyRAF/IRAF for data processing. Three problems of varied complexity were benchmarked on three different types of multicore processors to demonstrate the benefits, in terms of execution time, of parallelizing data processing tasks. The native multiprocessing module available in Python makes it a relatively trivial task to implement the parallel code. We have also compared the three multiprocessing approaches—Pool/Map, Process/Queue and Parallel Python. Our test codes are freely available and can be downloaded from our website.
122473897
OTTER Experiments Pertinent to CADE-10
This Argonne report serves as a companion to our CADE-10 paper. To fulfill promises made in that paper, we include here detailed proofs in clause notation, input files compatible with OTTER, and explanations for our choice of approach. We also include certain of the original and unpublished proofs (of Winker) that answered four open questions, two in equivalent calculus and two in the R-calculus. The organization parallels that of our CADE-10 paper. 34 refs.
118330157
Advanced simulation techniques for straylight prediction of high performance mm-wave reflecting telescope
The prediction of the antenna radiation pattern can be extremely complex for antenna system composed of several reflector surfaces. Typically, at mm-wavelengths, telescopes are composed of mirrors and shields, and an accurate prediction of the whole system response is therefore complicated. This is the case for the optical system of the ESA Planck mission. Planck represents the third generation of mm-wave instruments designed for space observations of CMB anisotropies over the whole sky, and has unprecedented sensitivity and angular resolution. The Low Frequency Instrument (LFI) is one of the two instruments onboard the satellite. LFI consists of an array of 46 cooled HEMT-based receivers coupled to the 1.5 meter off-axis dual reflector telescope by an array of 23 dual profiled corrugated feed horns working at four frequencies between 30 and 100 GHz. Owing to the small level of CMB anisotropies, the control of the systematic effects is mandatory, and this is assured by means of a dedicated instrument design and by an accurate knowledge of instrument characteristics. The telescope is a source of systematic errors both in the main beam region (aberrations) and in the sidelobes region (straylight contamination) and efficient and accurate radiation pattern simulations of the telescope-feed system are needed. We report on the simulations of the full pattern applied to the Planck/LFI-Telescope system. These simulations, based on advanced GTD methods, are used to evaluate the straylight rejection of the entire optical system, by applying a new approach for evaluating the sidelobes in a rigorous way, even at very low levels.
110174503
Cryogenic environment and performance for testing the Planck radiometers
The Planck LFI Radiometer Chain Assemblies (RCAs) have been calibrated in two dedicated cryogenic facilities. In this paper the facilities and the related instrumentation are described. The main satellite thermal interfaces for the single chains have to be reproduced and stability requirements have to be satisfied. Setup design, problems occurred and improving solutions implemented are discussed. Performance of the cryogenic setup are reported.
118514274
Thermal susceptibility of the Planck-LFI receivers
This paper describes the impact of the Planck Low Frequency Instrument front end physical temperature fluctuations on the output signal. The origin of thermal instabilities in the instrument are discussed, and an analytical model of their propagation and impact on the receivers signal is described. The experimental test setup dedicated to evaluate these effects during the instrument ground calibration is reported together with data analysis methods. Finally, main results obtained are discussed and compared to the requirements.
23277998
Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
This paper presents an overview of the polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse maps of dust polarization fraction and polarization angle at 1° resolution, taking into account noise bias and possible systematic effects. The sensitivity of the Planck HFI polarization measurements allows for the first time a mapping of Galactic dust polarized emission on large scales, including low column density regions. We find that the maximum observed dust polarization fraction is high (p_(max) = 19.8%), in particular in some regions of moderate hydrogen column density (N_H < 2 × 10^(21) cm^(-2)). The polarization fraction displays a large scatter at N_H below a few 10^(21) cm^(-2). There is a general decrease in the dust polarization fraction with increasing column density above N_H ≃ 1 × 10^(21) cm-2 and in particular a sharp drop above N_H ≃ 1.5 × 10^(22) cm^(-2). We characterize the spatial structure of the polarization angle using the angle dispersion function. We find that the polarization angle is ordered over extended areas of several square degrees, separated by filamentary structures of high angle dispersion function. These appear as interfaces where the sky projection of the magnetic field changes abruptly without variations in the column density. The polarization fraction is found to be anti-correlated with the dispersion of polarization angles. These results suggest that, at the resolution of 1°, depolarization is due mainly to fluctuations in the magnetic field orientation along the line of sight, rather than to the loss of grain alignment in shielded regions. We also compare the polarization of thermal dust emission with that of synchrotron measured with Planck, low-frequency radio data, and Faraday rotation measurements toward extragalactic sources. These components bear resemblance along the Galactic plane and in some regions such as the Fan and North Polar Spur regions. The poor match observed in other regions shows, however, that dust, cosmic-ray electrons, and thermal electrons generally sample different parts of the line of sight.