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.

title: Discovery of GRB 020405 and its Underlying Supernova

title: The Science Case for PILOT I: Summary and Overview
abstract: 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.

title: On the significance of the excess number of strong Mg II absorbers observed toward gamma-ray bursts
abstract: The number of strong (equivalent width >1 A) Mg II absorbers observed toward gamma-ray bursts (GRBs) has been found to be statistically larger than the number of strong absorbers toward quasi-stellar objects (QSOs). We formalize this "Mg II problem" and present a detailed explanation of the statistical tools required to assess the significance of the discrepancy. We find that the problem exists at the 4σ level for GRBs with high-resolution spectra. It has been suggested that the discrepancy can be resolved by the combination of a dust obscuration bias toward QSOs, and a strong gravitational lensing bias toward GRBs. We investigate one of the two most probable lensed GRBs that we presented in our previous work (GRB020405) and find that it is not strongly gravitationally lensed, constraining the percentage of lensed GRBs to be <35% (2σ). Dust obscuration of QSOs has been estimated to be a significant effect with dusty Mg II systems removing ~20% of absorbed objects from flux-limited QSO samples. We find that if ~30% of the strong Mg II systems toward QSOs are missing from the observed samples, then GRBs and QSOs would have comparable numbers of absorbers per unit redshift. Thus, strong gravitational lensing bias is likely to make only a modest contribution to solving the Mg II problem. However, if the dust obscuration bias has been slightly underestimated, the Mg II problem would no longer persist.

title: A RECONNAISSANCE OF THE POSSIBLE DONOR STARS TO THE KEPLER SUPERNOVA
abstract: The identity of Type Ia supernova progenitors remains a mystery, with various lines of evidence pointing toward either accretion from a nondegenerate companion or the rapid merger of two degenerate stars leading to the thermonuclear destruction of a white dwarf. In this paper, we spectroscopically scrutinize 24 of the brightest stars residing in the central 38'' × 38'' of the SN 1604 (Kepler) supernova remnant to search for a possible surviving companion star. We can rule out, with high certainty, a red giant companion star—a progenitor indicated by some models of the supernova remnant. Furthermore, we find no star that exhibits properties uniquely consistent with those expected of a donor star down to L > 10 L {sub ☉}. While the distribution of star properties toward the remnant are consistent with unrelated stars, we identify the most promising candidates for further astrometric and spectroscopic follow up. Such a program would either discover the donor star or place strong limits on progenitor systems to luminosities with L << L {sub ☉}.

title: A THEORETICAL COLOR-VELOCITY CORRELATION FOR SUPERNOVAE ASSOCIATED WITH GAMMA-RAY BURSTS
abstract: 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.

title: A search for low-mass WIMPs with EDELWEISS-II heat-and-ionization detectors
abstract: We report on a search for low-energy (E < 20 keV) WIMP-induced nuclear recoils using data collected in 2009 - 2010 by EDELWEISS from four germanium detectors equipped with thermal sensors and an electrode design (ID) which allows to efficiently reject several sources of background. Using an exposure of 113 kg.d, we find no evidence for an exponential distribution of low-energy nuclear recoils that could be attributed to WIMP elastic scattering. For WIMPs of mass 10 GeV, the observation of one event in the WIMP search region results in a 90% CL limit of 1.0 \times 10^-5 pb on the spin-independent WIMP-nucleon scattering cross-section, which constrains the parameter space associated with the findings reported by the CoGeNT, DAMA and CRESST experiments.

title: Precision measurement of D meson mass differences
abstract: A bstractUsing three- and four-body decays of D mesons produced in semileptonic b-hadron decays, precision measurements of D meson mass differences are made together with a measurement of the D0 mass. The measurements are based on a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected in pp collisions at 7 TeV. Using the decay D0 → K+K−K−π+, the D0 mass is measured to be
$ M\left( } \right)={{{1864.75\pm 0.15\left( {\mathrm{stat}} \right)\pm 0.11\left( {\mathrm{syst}} \right)\mathrm{MeV}}} \left/ {{{c^2}}} \right.}. $
 The mass differences
 $ \begin{array}{*{20}{c}} {{{{M\left( } \right)-M\left( } \right)=4.76\pm 0.12\left( {\mathrm{stat}} \right)\pm 0.07\left( {\mathrm{syst}} \right)\mathrm{MeV}}} \left/ {{{c^2}}} \right.},} \hfill \\ {{{{M\left( } \right)-M\left( } \right)=98.68\pm 0.03\left( {\mathrm{stat}} \right)\pm 0.04\left( {\mathrm{syst}} \right)\mathrm{MeV}}} \left/ {{{c^2}}} \right.}} \hfill \\ \end{array} $
 are measured using the D0 → K+K−π+π− and $ D_{(s)}^{+}\to {K^{+}}{K^{-}}{\pi^{+}} $ modes.

title: A SUB 100 FS ELECTRON BUNCH ARRIVAL-TIME MONITOR SYSTEM FOR FLASH
abstract: The stability of free-electron lasers and experiments carried out in pump-probe configurations depends sensitively on precise synchronization between the photoinjector laser, low-level RF-systems, probe lasers, and other components in the FEL. A precise measurement of the arrival-time of the electron bunch with respect to the clock signal of a master oscillator is, therefore, of special importance. For this task, we propose an arrival-time monitor based on a beam pick-up with several GHz bandwidth which permits measurements in the sub 100 fs regime. The RF-signal from the beam pick-up is sampled by an ultrashort laser pulse using a broadband electro-optical modulator. The modulator converts the deviation of the electron bunch arrival-timefrom a referenceinto an amplitudemodulation of the laser pulse. This modulation is detected by a photo detector and sampled by a fast ADC. By directly using the laser pulses from the future master laser oscillator of the machine, any additional timing jitter is avoided. In this paper we present the layout of the system and first experimental results.

title: BROADBAND SINGLE SHOT SPECTROMETER
abstract: This paper summarizes the ongoing activities at DESY for the longitudinal phase space studies on ultra short bunches of VUV-FEL using infrared spectroscopy.

title: LAYOUT OF THE OPTICAL SYNCHRONIZATION SYSTEM FOR FLASH
abstract: At FLASH, we observe an electron bunch arrival time jitter ∼ 200 fs on a timescale of several minutes and drifts of picoseconds over the course of a day.. The short term jitter of 200 fs is mainly due to the amplitude stability of the first acceleration module. The long-term drifts however, are predominantly caused by the RF distribution and various front ends of the synchronization system. We propose a new type of synchronization system based on optical techniques. The optical synchronization system will satisfy 2 goals: Firstly to provide a high-stability local oscillator for low-level RF regulation, secondly to synchronize experimental lasers for the FEL users and for beam diagnostics which might also utilize the timing laser pulse train directly.