The Calibration and Data Products of the Galaxy Evolution Explorer

We describe the calibration status and data products pertaining to the GR2 and GR3 data releases of the Galaxy Evolution Explorer (GALEX). These releases have identical pipeline calibrations that are significantly improved over the GR1 data release. GALEX continues to survey the sky in the Far Ultraviolet (FUV, ~154 nm) and Near Ultraviolet (NUV, ~232 nm) bands, providing simultaneous imaging with a pair of photon counting, microchannel plate, delay line readout detectors. These 1.25 degree field-of-view detectors are well-suited to ultraviolet observations because of their excellent red rejection and negligible background. A dithered mode of observing and photon list output pose complex requirements on the data processing pipeline, entangling detector calibrations and aspect reconstruction algorithms. Recent improvements have achieved photometric repeatability of 0.05 and 0.03 mAB in the FUV and NUV, respectively. We have detected a long term drift of order 1% FUV and 6% NUV over the mission. Astrometric precision is of order 0.5" RMS in both bands. In this paper we provide the GALEX user with a broad overview of the calibration issues likely to be confronted in the current release. Improvements are likely as the GALEX mission continues into an extended phase with a healthy instrument, no consumables, and increased opportunities for guest investigations.Comment: Accepted to the ApJS (a special GALEX issue

CalFUSE v3: A Data-Reduction Pipeline for the Far Ultraviolet Spectroscopic Explorer

Since its launch in 1999, the Far Ultraviolet Spectroscopic Explorer (FUSE) has made over 4600 observations of some 2500 individual targets. The data are reduced by the Principal Investigator team at the Johns Hopkins University and archived at the Multimission Archive at Space Telescope (MAST). The data-reduction software package, called CalFUSE, has evolved considerably over the lifetime of the mission. The entire FUSE data set has recently been reprocessed with CalFUSE v3.2, the latest version of this software. This paper describes CalFUSE v3.2, the instrument calibrations upon which it is based, and the format of the resulting calibrated data files.Comment: To appear in PASP; 29 pages, 13 figures, uses aastex, emulateap

GRB 110709A, 111117A and 120107A: Faint high-energy gamma-ray photon emission from Fermi/LAT observations and demographic implications

Launched on June 11, 2008, the LAT instrument onboard the $Fermi$ Gamma-ray Space Telescope has provided a rare opportunity to study high energy photon emission from gamma-ray bursts. Although the majority of such events (27) have been iden tified by the Fermi LAT Collaboration, four were uncovered by using more sensiti ve statistical techniques (Akerlof et al 2010, Akerlof et al 2011, Zheng et al 2 012). In this paper, we continue our earlier work by finding three more GRBs ass ociated with high energy photon emission, GRB 110709A, 111117A and 120107A. To s ystematize our matched filter approach, a pipeline has been developed to identif y these objects in near real time. GRB 120107A is the first product of this anal ysis procedure. Despite the reduced threshold for identification, the number of GRB events has not increased significantly. This relative dearth of events with low photon number prompted a study of the apparent photon number distribution. W e find an extremely good fit to a simple power-law with an exponent of -1.8 $\pm$ 0.3 for the differential distribution. As might be expected, there is a substa ntial correlation between the number of lower energy photons detected by the GBM and the number observed by the LAT. Thus, high energy photon emission is associ ated with some but not all of the brighter GBM events. Deeper studies of the pro perties of the small population of high energy emitting bursts may eventually yi eld a better understanding of these entire phenomena.Comment: accepted to Ap

Reconstructing the calibrated strain signal in the Advanced LIGO detectors

Advanced LIGO's raw detector output needs to be calibrated to compute dimensionless strain h(t). Calibrated strain data is produced in the time domain using both a low-latency, online procedure and a high-latency, offline procedure. The low-latency h(t) data stream is produced in two stages, the first of which is performed on the same computers that operate the detector's feedback control system. This stage, referred to as the front-end calibration, uses infinite impulse response (IIR) filtering and performs all operations at a 16384 Hz digital sampling rate. Due to several limitations, this procedure currently introduces certain systematic errors in the calibrated strain data, motivating the second stage of the low-latency procedure, known as the low-latency gstlal calibration pipeline. The gstlal calibration pipeline uses finite impulse response (FIR) filtering to apply corrections to the output of the front-end calibration. It applies time-dependent correction factors to the sensing and actuation components of the calibrated strain to reduce systematic errors. The gstlal calibration pipeline is also used in high latency to recalibrate the data, which is necessary due mainly to online dropouts in the calibrated data and identified improvements to the calibration models or filters.Comment: 20 pages including appendices and bibliography. 11 Figures. 3 Table

Simulating a dual beam combiner at SUSI for narrow-angle astrometry

The Sydney University Stellar Interferometer (SUSI) has two beam combiners, i.e. the Precision Astronomical Visible Observations (PAVO) and the Microarcsecond University of Sydney Companion Astrometry (MUSCA). The primary beam combiner, PAVO, can be operated independently and is typically used to measure properties of binary stars of less than 50 milliarc- sec (mas) separation and the angular diameters of single stars. On the other hand, MUSCA was recently installed and must be used in tandem with the for- mer. It is dedicated for microarcsecond precision narrow-angle astrometry of close binary stars. The performance evaluation and development of the data reduction pipeline for the new setup was assisted by an in-house computer simulation tool developed for this and related purposes. This paper describes the framework of the simulation tool, simulations carried out to evaluate the performance of each beam combiner and the expected astrometric precision of the dual beam combiner setup, both at SUSI and possible future sites.Comment: 28 pages, 23 figures, accepted for publication in Experimental Astronomy. The final publication is available at http://link.springer.co

Pipeline model of a Fermi-sea electron pump

The use of a band offset between the two leads of an electron pump driven by a local oscillating voltage is shown to increase the pump current dramatically. The structure of the electron transmission suggests the existence of dominant inelastic channels which we call pipelines. This permits the formulation of a simple model that gives a physical account of the numerical results for a realistic device. A spectral analysis reveals the pump current to be carried by scattering states with initial energy deep within the Fermi sea and not at its surface, thereby rendering the effect insensitive to temperature. We show this is compatible with the current flowing near the Fermi surface in the leads.Comment: 6 pages in RevTex4 (beta4), 4 figures; status: accepted for publication reason for replacement: A more detailed discussion of the differences to Ref. [5] has been provided & new reference adde