The Swinburne intermediate-latitude pulsar survey

We have conducted a survey of intermediate Galactic latitudes using the 13-beam 21-cm multibeam receiver of the Parkes 64-m radio telescope. The survey covered the region enclosed by 5°<| b |<15° and −100°< l <50° with 4702 processed pointings of 265 s each, for a total of 14.5 d of integration time. 13 2×96‐channel filterbanks provided 288 MHz of bandwidth at a centre frequency of 1374 MHz, one-bit sampled every 125 μs and incurring ∼ DM/13.4 cm⁻³ pc samples of dispersion smearing. The system was sensitive to slow and most millisecond pulsars in the region with flux densities greater than approximately 0.3–1.1 mJy . Offline analysis on the 64-node Swinburne workstation cluster resulted in the detection of 170 pulsars of which 69 were new discoveries. Eight of the new pulsars, by virtue of their small spin periods and period derivatives, may be recycled and have been reported elsewhere. The slow pulsars discovered are typical of those already known in the volume searched, being of intermediate to old age. Several pulsars experience pulse nulling and two display very regular drifting subpulses. We discuss the new discoveries and provide timing parameters for the 48 slow pulsars for which we have a phase-connected solution.     

VOEvent authentication via XML digital signature

A trivial modification to the XML schema of VOEvent v1.1 allows the inclusion of W3C digital signatures. Signatures enable identification, identification enables trust, and trust enables authorization. Such changes would inhibit abuse of the VOEvent networks. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Integrating VOEvent into the ground‐based O/IR system: A case study at NOAO

In this article we describe a case study of how NOAO is considering improving its management of Target‐of‐Opportunity (ToO) observations by integrating VOEvent into the flow of activities. We believe that using VOEvent to help document and track the use of ToO time will improve the user experience of ToOs at NOAO. It will also greatly aid in the management of the process and of the resulting data, allowing us to better track the ownership and provenance of the data and any resulting data products. Finally, it will provide an important method of archival access to the data and data “collections,” which might include not only processed data from a single VOEvent triggered observation but could also include multiple observations traceable to a single (or set of related) VOEvents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New observing modes of a future HTN‐based distributed detection network for high time resolution and quantum optical astrophysics experiments

This contribution aims to introduce the idea that a well‐evolved HTN of the far future, with the anticipated addition of very large apertures, could also be made to incorporate the ability to carry out photonic astronomy observations, particularly Optical VLBI in a revived Hanbury‐Brown and Twiss Intensity Interferometry (HBTII) configuration. Such an HTN could exploit its inherent rapid reconfigurational ability to become a multi‐aperture distributed photon‐counting network able to study higher‐order spatiotemporal photon correlations and provide a unique tool for direct diagnostics of astrophysical emission processes. We very briefly review various considerations associated with the switching of the HTN to a special mode in which single‐photon detection events are continuously captured for a posteriori intercorrelation. In this context, photon arrival times should be determined to the highest time resolution possible and extremely demanding absolute time keeping and absolute time distribution schemes should be devised and implemented in the HTN nodes involved. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Towards a real‐time transient classification engine

Temporal sampling does more than add another axis to the vector of observables. Instead, under the recognition that how objects change (and move) in time speaks directly to the physics underlying astronomical phenomena, next‐generation wide‐field synoptic surveys are poised to revolutionize our understanding of just about anything that goes bump in the night (which is just about everything at some level). Still, even the most ambitious surveys will require targeted spectroscopic follow‐up to fill in the physical details of newly discovered transients. We are now building a new system intended to ingest and classify transient phenomena in near real‐time from high‐throughput imaging data streams. Described herein, the Transient Classification Project at Berkeley will be making use of classification techniques operating on “features” extracted from time series and contextual (static) information. We also highlight the need for a community adoption of a standard representation of astronomical time series data (ie. “VOTimeseries”). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Parkes Southern Pulsar Survey — III. Timing of long-period pulsars

The Parkes survey of the entire southern sky for millisecond and other low-luminosity pulsars has now been completed. The survey system and initial results were described by Manchester et al. and the final results and population studies are described by Lyne et al. A total of 298 pulsars were detected, including 101 new discoveries of which 17 were millisecond pulsars. Here we report on timing observations at Parkes and Jodrell Bank of the 84 long-period (non-millisecond) pulsars discovered in the survey, including timing solutions for 78 of them. Pulse profiles and arrival times were obtained at several different frequencies over intervals of more than a year, yielding a position, period, period derivative and dispersion measure for each pulsar. Pulse profiles at frequencies near 400 MHz and 600 or 1400 MHz are presented for most of the observed pulsars. Significant timing noise was detected for five pulsars and a glitch was observed in the period of PSR J1123–6259.     

The Gaia spectrophotometric standard stars survey: II. Instrumental effects of six ground‐based observing campaigns

The Gaia SpectroPhotometric Standard Stars (SPSS) survey started in 2006, was awarded almost 450 observing nights and accumulated almost 100000 raw data frames with both photometric and spectroscopic observations. Such large observational effort requires careful, homogeneous, and automatic data reduction and quality control procedures. In this paper, we quantitatively evaluate instrumental effects that might have a significant (i.e., ≥1 %) impact on the Gaia SPSS flux calibration. The measurements involve six different instruments, monitored over the eight years of observations dedicated to the Gaia flux standards campaigns: DOLORES@TNG in La Palma, EFOSC2@NTT and ROSS@REM in La Silla, CAFOS@2.2m in Calar Alto, BFOSC@Cassini in Loiano, and LaRuca@1.5m in San Pedro Mártir. We examine and quantitatively evaluate the following effects: CCD linearity and shutter times, calibration frames stability, lamp flexures, second order contamination, light polarization, and fringing. We present methods to correct for the relevant effects which can be applied to a wide range of observational projects at similar instruments. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rapid mapping of the sky at 240 MHz using the antennas of the Giant Metrewave Radio Telescope

In this paper we describe a method for measuring the effective receiver temperature T _erc and its variation for the entire receiver chain of a radio telescope, and use it to make a radio-continuum map of the sky at 240 MHz using the Giant Metrewave Radio Telescope (GMRT). We also show that in the case of GMRT, T _erc varies mainly with elevation and ambient temperature. The calibration techniques evolved here are applicable to similar interferometers with a large number of antennas, several frequency bands and a number of receiver systems at room temperature (where conventional methods are time-consuming). This method ideally requires just one complete day of observations in a frequency band.     

The WARPS survey – IV. The X-ray luminosity–temperature relation of high-redshift galaxy clusters

We present a measurement of the cluster X-ray luminosity–temperature ( L – T ) relation out to high redshift ( z ∼0.8). Combined ROSAT PSPC spectra of 91 galaxy clusters detected in the Wide Angle ROSAT Pointed Survey (WARPS) are simultaneously fitted in redshift and luminosity bins. The resulting temperature and luminosity measurements of these bins, which occupy a region of the high-redshift L – T relation not previously sampled, are compared with existing measurements at low redshift in order to constrain the evolution of the L – T relation. We find the best fit to low-redshift ( z <0.2) cluster data, at T >1 keV, to be L ∝ T ^3.15±0.06. Our data are consistent with no evolution in the normalization of the L – T relation up to z ∼0.8. Combining our results with ASCA measurements taken from the literature, we find η =0.19±0.38 (for Ω₀=1, with 1 σ errors) where L _Bol∝(1+ z ) ^η T ^3.15, or η =0.60±0.38 for Ω₀=0.3. This lack of evolution is considered in terms of the entropy-driven evolution of clusters. Further implications for cosmological constraints are also discussed.     

Quasar candidates selection in the Virtual Observatory era

We present a method for the photometric selection of candidate quasars in multiband surveys. The method makes use of a priori knowledge derived from a subsample of spectroscopic confirmed quasi-stellar objects (QSOs) to map the parameter space. The disentanglement of QSOs candidates and stars is performed in the colour space through the combined use of two algorithms, the probabilistic principal surfaces and the negative entropy clustering, which are for the first time used in an astronomical context. Both methods have been implemented in the voneural package on the Astrogrid Virtual Observatory platform. Even though they belong to the class of the unsupervised clustering tools, the performances of the method are optimized by using the available sample of confirmed quasars and it is therefore possible to learn from any improvement in the available 'base of knowledge'. The method has been applied and tested on both optical and optical plus near-infrared data extracted from the visible Sloan Digital Sky Survey (SDSS) and infrared United Kingdom Infrared Deep Sky Survey-Large Area Survey public data bases. In all cases, the experiments lead to high values of both efficiency and completeness, comparable if not better than the methods already known in the literature. A catalogue of optical candidate QSOs extracted from the SDSS Data Release 7 Legacy photometric data set has been produced and is publicly available at the URL http://voneural.na.infn.it/qso.html .     

The X‐shooter pipeline

The X‐shooter data reduction pipeline is an integral part of the X‐shooter project, it allows the production of reduced data in physical quantities from the raw data produced by the instrument. The pipeline is based on the data reduction library developed by the X‐shooter consortium with contributions from France, The Netherlands and ESO and it uses the Common Pipeline Library (CPL) developed at ESO. The pipeline has been developed for two main functions. The first function is to monitor the operation of the instrument through the reduction of the acquired data, both at Paranal, for a quick‐look control, and in Garching, for a more thorough evaluation. The second function is to allow an optimized data reduction for a scientific user. In the following I will first outline the main steps of data reduction with the pipeline then I will briefly show two examples of optimization of the results for science reduction (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The effect of the detector response time on bolometric cosmic microwave background anisotropy experiments

We analyse the effects of the detector response time on bolometric measurements of the anisotropy of the cosmic microwave background (CMB). We quantify the effect in terms of a single dimensionless parameter L defined as the ratio between the time the beam sweeps its own size and the bolometer response time. As L decreases below ∼ 2.5, the point-source response of the experiment becomes elongated. We introduce a window function matrix based on the timestream data to assess the effects of the elongated beam. We find that the values of the window function matrix elements decrease slowly as a function of L . Our analysis and results apply to other cases of beam asymmetry. For the High Frequency Instrument on board the Planck Surveyor satellite we show that, for a broad range of L , the ability of the experiment to extract the cosmological parameters is not degraded. Our analysis enhances the flexibility in tuning the design parameters of CMB anisotropy experiments.     

Thread safe astronomy

Observational astronomy is the beneficiary of an ancient chain of apprenticeship. Kepler's laws required Tycho's data. As the pace of discoveries has increased over the centuries, so has the cadence of tutelage (literally, “watching over”). Naked eye astronomy is thousands of years old, the telescope hundreds, digital imaging a few decades, but today's undergraduates will use instrumentation yet unbuilt – and thus, unfamiliar to their professors – to complete their doctoral dissertations. Not only has the quickening cadence of astronomical data‐taking overrun the apprehension of the science within, but the contingent pace of experimental design threatens our capacity to learn new techniques and apply them productively. Virtual technologies are necessary to accelerate our human processes of perception and comprehension to keep up with astronomical instrumentation and pipelined dataflows. Necessary, but not sufficient. Computers can confuse us as efficiently as they illuminate. Rather, as with neural pathways evolved to meet competitive ecological challenges, astronomical software and data must become organized into ever more coherent ‘threads’ of execution. These are the same threaded constructs as understood by computer science. No datum is an island. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)