124077973
Nobel Lecture: Accelerating expansion of the Universe through observations of distant supernovae
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.
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.
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.
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.
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).
18491403
Study of beauty hadron decays into pairs of charm hadrons
First observations of the decays Λb 0 → Λc +D(s) - are reported using data corresponding to an integrated luminosity of 3fb-1 collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction B(Bs 0→D+Ds -) is made and a search is performed for the decays B(s) 0→Λc +Λc -. The results obtained are B(Λb 0→Λc +D-)/ B(Λb 0→Λc +D s -)=0.042±0.003(stat)±0.003(syst), [B(Λb 0→Λc +D s -)/B(B0→D+D s -)]/[B(Λb 0→Λ c +π-)/B(B0→D +π-)]=0.96±0.02(stat)±0.06(syst),B(B s 0→D+Ds -)/ B(B0→D+Ds -)=0. 038±0.004(stat)±0.003(syst),B(B0→Λ c +Λc -)/B(B 0→D+Ds -)<0.0022[95%C.L.], B(Bs 0→Λc +Λ c -)/B(Bs 0→D+D s -)<0.30[95%C.L.]. Measurement of the mass of the Λb 0 baryon relative to the B0 meson gives M(Λb 0)-M(B0)=339. 72±0.24(stat)±0.18(syst)MeV/c2. This result provides the most precise measurement of the mass of the Λb 0 baryon to date.
117847087
Measurement of the gluon structure function from direct photon data at the CERN p collider
Abstract A measurement of the gluon structure fusion using direct photon events observed with the UA2 detector in p p collisions at √ s =630 GeV is presented. The x -range covered by this analysis is between 0.049 and 0.207 and the Q 2 range is between 280 GeV 2 and 3670 GeV 2 . The data sample corresponds to an integrated luminosity of 7.14 pb −1 . The results are found to be in good agreement with the gluon distributions measured in deep inelastic scattering experiments extrapolated to the UA2 Q 2 values.
124862478
BUNCH COMPRESSION MONITOR
The longitudinal charge distribution in the electron bunches has a strong impact on the lasing process in a Free-Electron Laser based on the principle of Self Amplified Spontaneous Emission of radiation. For the ultraviolet and soft X ray FEL FLASH at DESY, structures in the range of ten to hundred 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 bunch compression and improving the performance of the machine. This paper introduces a new tool for longitudinal diagnostics based on THz spectroscopy of coherent radiation. 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 are presented. A strong variation of the CTR intensity in the 40 μm regime is observed when the off-crest phase in the accelerating cavities preceding the first magnetic bunch compressor is changed in small steps. This variation in the CTR intensity is found to be correlated with a similar variation in the pulse energy of the FEL light. Hence the THz spectrometer appears to be a very sensitive device for controlling the parameters of the bunch compression scheme.
118504484
Final results of the EDELWEISS-II WIMP search using a 4-kg array of cryogenic germanium detectors with interleaved electrodes
Abstract The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ -induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4 × 10 − 8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.
1728923
Performance of the LHCb muon system
The performance of the LHCb Muon system and its stability across the full 2010 data taking with LHC running at root s = 7 TeV energy is studied. The optimization of the detector setting and the time calibration performed with the first collisions delivered by LHC is described. Particle rates, measured for the wide range of luminosities and beam operation conditions experienced during the run, are compared with the values expected from simulation. The space and time alignment of the detectors, chamber efficiency, time resolution and cluster size are evaluated. The detector performance is found to be as expected from specifications or better. Notably the overall efficiency is well above the design requirements.