19568351
A photometric redshift of z ∼9.4 for GRB 090429B
Gamma-ray bursts (GRBs) serve as powerful probes of the early universe, with their luminous afterglows revealing the locations and physical properties of star-forming galaxies at the highest redshifts, and potentially locating first-generation (Population III) stars. Since GRB afterglows have intrinsically very simple spectra, they allow robust redshifts from low signal-to-noise spectroscopy, or photometry. Here we present a photometric redshift of z ~ 9.4 for the Swift detected GRB 090429B based on deep observations with Gemini-North, the Very Large Telescope, and the GRB Optical and Near-infrared Detector. Assuming a Small Magellanic Cloud dust law (which has been found in a majority of GRB sight lines), the 90% likelihood range for the redshift is 9.06 7. The non-detection of the host galaxy to deep limits (Y(AB) ~ 28, which would correspond roughly to 0.001L* at z = 1) in our late-time optical and infrared observations with the Hubble Space Telescope strongly supports the extreme-redshift origin of GRB 090429B, since we would expect to have detected any low-z galaxy, even if it were highly dusty. Finally, the energetics of GRB 090429B are comparable to those of other GRBs and suggest that its progenitor is not greatly different from those of lower redshift bursts.
113407190
A THEORETICAL COLOR-VELOCITY CORRELATION FOR SUPERNOVAE ASSOCIATED WITH GAMMA-RAY BURSTS
We carry out the first multi-dimensional radiative transfer calculations to simultaneously compute synthetic spectra and light curves for models of supernovae driven by fast bipolar outflows. These allow us to make self-consistent predictions for the orientation dependence of both color evolution and spectral features. We compare models with different degrees of asphericity and metallicity and find significant observable consequences of both. In aspherical models, we find spectral and light curve features that vary systematically with observer orientation. In particular, we find that the early-phase light curves are brighter and bluer when viewed close to the polar axis but that the peak flux is highest for equatorial (off-axis) inclinations. Spectral line features also depend systematically on observer orientation, including the velocity of the Si II 6355 A line. Consequently, our models predict a correlation between line velocity and color that could assist the identification of supernovae associated with off-axis jet-driven explosions. The amplitude and range of this correlation depends on the degree of asphericity, the metallicity, and the epoch of observation but we find that it is always present and acts in the same direction.
5990408
The Science Case for PILOT I: Summary and Overview
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5-m optical/infrared telescope to be located at Dome C on the Antarctic plateau. Conditions at Dome C are known to be exceptional for astronomy. The seeing (above ∼30 m height), coherence time, and isoplanatic angle are all twice as good as at typical mid-latitude sites, while the water-vapour column, and the atmosphere and telescope thermal emission are all an order of magnitude better. These conditions enable a unique scientific capability for PILOT, which is addressed in this series of papers. The current paper presents an overview of the optical and instrumentation suite for PILOT and its expected performance, a summary of the key science goals and observational approach for the facility, a discussion of the synergies between the science goals for PILOT and other telescopes, and a discussion of the future of Antarctic astronomy. Paper II and Paper III present details of the science projects divided, respectively, between the distant Universe (i.e. studies of first light, and the assembly and evolution of structure) and the nearby Universe (i.e. studies of Local Group galaxies, the Milky Way, and the Solar System).
118556930
HATS-1b: The First Transiting Planet Discovered by the HATSouth Survey
We report the discovery of HATS-1b, a transiting extrasolar planet orbiting the moderately bright V = 12.05 G dwarf star GSC 6652-00186, and the first planet discovered by HATSouth, a global network of autonomous wide-field telescopes. HATS-1b has a period of P 3.4465 days, mass of Mp 1.86 M J, and radius of Rp 1.30 R J. The host star has a mass of 0.99 M ☉ and radius of 1.04 R ☉. The discovery light curve of HATS-1b has near-continuous coverage over several multi-day timespans, demonstrating the power of using a global network of telescopes to discover transiting planets.
3943345
First Searches for Optical Counterparts to Gravitational-wave Candidate Events
During the Laser Interferometer Gravitational-wave Observatory and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type.
13255925
The Mount Stromlo A bell Cluster Supernova Search
We have initiated a 3 year project to find supernovae in a well-defined sample of high-density southern Abell clusters with redshifts z ≤ 0.08. These observations will provide a volume-limited sample of Type Ia supernovae (SNe Ia) to more than a magnitude below their peak brightness and will enable us to (1) measure the luminosity function of SNe, (2) further explore the correlation of light-curve shape with the absolute luminosity of SNe Ia to better understand SNe Ia as distance indicators, (3) measure SN rates, (4) measure the bulk motion of the Local Group using SNe Ia, and (5) directly compare SN Ia distances with brightest cluster galaxy distances. We use the MACHO wide-field two-color imager on the 1.3 m telescope at Mount Stromlo to routinely monitor ~12 clusters per week. We describe our technique for target selection and scheduling search observations, and for finding and identifying SN candidates. We also describe the results from the first year of our program, including the detection of 19 SNe, several RR Lyrae variables, and hundreds of asteroids.
38972186
The trigger system of the NOMAD experiment
The NOMAD trigger system is described in the present paper. It is made up of a large area plastic scintillator veto system, two trigger scintillator planes inside a 0.4 T magnetic field and their associated trigger electronics. Special features of the system consist of the use of proximity mesh photomultipliers which allow the trigger scintillators to operate in the magnetic field, and the use of custom-built VME modules which perform the trigger logic decisions, the signal synchronisation and gate generation, event counting and livetime calculations. This paper also includes a description of each of the NOMAD triggers, with their calculated and measured rates, efficiencies and livetimes.
55436496
SINGLE-SHOT LONGITUDINAL DIAGNOSTICS WITH THz RADIATION
The longitudinal charge distribution in the electron bunches has a strong impact on the lasing process in a SASE FEL. For the 6 – 100 nm FEL FLASH at DESY, structures in the order of ten micrometers play a crucial role. The investigation of the longitudinal charge distribution in the electron bunches on a bunch-by-bunch basis is an important issue for optimizing the operation of the machine and improving its stability. This requires a single-shot device and is beyond the capability of existing spectroscopic diagnostic tools. This paper introduces a new diagnostics tool based on THz spectroscopy of coherent transition radiation (CTR). A novel spectrometer has been designed which permits to analyze the radiation of single electron bunches in a broad spectral range and with high resolution. Preliminary measurements with this spectrometer in both scanning mode and single-shot mode are presented and discussed.
96462303
INORGANIC SCINTILLATORS FOR PARTICLE BEAM PROFILE DIAGNOSTICS OF HIGHLY BRILLIANT AND HIGHLY ENERGETIC ELECTRON BEAMS
Scintillating screens are widely used for particle beam diagnostics, especially in transverse profile measurements at hadron machines and low energy electron machines where the intensity of optical transition radiation (OTR) is rather low. Their usage may serve as an alternative way to overcome limitations in OTR based beam diagnostics imposed by the influence of coherent emission. However, there is only little information about scintillator properties for applications with highly energetic electrons. Therefore, test experiments have been performed at the Mainz Microtron MAMI in order to study the screen applicability. The status of these experiments is presented and the results are discussed in view of scintillator material properties and observation geometry.
304037
RECENT RESULTS FROM THE NOMAD EXPERIMENT
NOMAD is a short baseline neutrino oscillation experiment searching for ! and ! e oscillations in the CERN SPS wide band neutrino beam. The experiment has been collecting data since July 1995 and the data taking will continue until at least the end of 1997. A preliminary analysis based on the 1995 data sample allows NOMAD to set 90% con dence limits of sin 2 < 3:4 10 3 for ! and sin 2 2 e < 2 10 3 for ! e oscillations at large m . c 1997 Burkhard Schmidt.
38942894
Stabilized Optical Fiber Links for the XFEL
The timing synchronization scheme for the European X-Ray free electron laser facility (XFEL) is based on the generation and distribution of sub-picosecond laser pulses with actively stabilized repetition rate which are used to synchronize local RF oscillators. An integral part of the scheme is the distribution of the optical pulse stream to parts of the facility via optical fiber links. The optical path length of the fiber has to be stabilized against short-term and long-term timing jitter due to environmental effects, such as temperature drifts and acoustic vibrations, to better than 10 fs for distances ranging from tens of meters to several kilometers. In this paper, we present first experimental results toward signal transmission through a 50 m-long fiber link with femtosecond stability.