10981233
Milli-arcsecond images of the Herbig Ae star HD 163296
Context. The very close environments of young stars are the hosts of fundamental physical processes, such as planet formation, stardisk interactions, mass accretion, and ejection. The complex morphological structure of these environments has been confirmed by the now quite rich data sets obtained for a few objects by near-infrared long-baseline interferometry. Aims. We gathered numerous interferometric measurements for the young star HD 163296 with various interferometers (VLTI, IOTA, KeckI and CHARA), allowing for the first time an image independent of any a priori model to be reconstructed. Methods. Using the Multi-aperture image Reconstruction Algorithm (MiRA), we reconstruct images of HD 163296 in the H and K bands. We compare these images with reconstructed images obtained from simulated data using a physical model of the environment of HD 163296. Results. We obtain model-independent H and K-band images of the surroundings of HD 163296. The images present several significant features that we can relate to an inclined asymmetric flared disk around HD 163296 with the strongest intensity at about 4-5 mas. Because of the incomplete spatial frequency coverage, we cannot state whether each of them individually is peculiar in any way. Conclusions. For the first time, milli-arcsecond images of the environment of a young star are produced. These images confirm that the morphology of the close environment of young stars is more complex than the simple models used in the literature so far.
18853087
The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer
Aims. We undertook an H band interferometric examination of Arcturus, a star frequently used as a spatial and spectral calibrator. 
Methods. Using the IOTA 3 telescope interferometer, we performed spectro-interferometric observations (R ≈ 35) of Arcturus. 
Atmospheric models and prescriptions were fitted to the data to derive the brightness distribution of the photosphere. Image reconstruction 
was performed using two software algorithms: Wisard and Mira. 
Results. An achromatic power law proved to be a good model of the brightness distribution, with a limb darkening compatible with 
the one derived from atmospheric model simulations using our marcs model. A Rosseland diameter of 21.05 ± 0.21 was derived, 
corresponding to an effective temperature of Teff = 4295 ± 26 K. No companion was detected from the closure phases, with an upper 
limit on the brightness ratio of 8 × 10^−4 at 1 AU. The dynamic range at such distance from the photosphere was established as 
1.5 × 10^−4 (1σrms). An upper limit of 1.7×10^−3 was also derived for the level of brightness asymmetries present in the photosphere.
118331555
Characterization of integrated optics components for the second generation of VLTI instruments
Two of the three instruments proposed to ESO for the second generation instrumentation of the VLTI would use integrated optics for beam combination. Several design are studied, including co-axial and multi-axial recombination. An extensive quantity of combiners are therefore under test in our laboratories. We will present the various components, and the method used to validate and compare the different combiners. Finally, we will discuss the performances and their implication for both VSI and Gravity VLTI instruments.
14528716
FU Orionis Resolved by Infrared Long-Baseline Interferometry at a 2 AU Scale
We present the first infrared interferometric observations of a young stellar object with a spatial projected resolution better than 2 AU. The observations were obtained with the Palomar Testbed Interferometer (PTI). FU Orionis exhibits a visibility of V2=0.72 ± 0.07 for a 103 ± 5 m-projected baseline at λ=2.2 μm. On the spatial scale probed by the PTI, the data are consistent with both a binary system scenario (a maximum magnitude difference of 2.7 ± 0.5 mag and the smallest separation of 0.35 ± 0.05 AU) and a standard luminous accretion disk model ( ~6 × 10−5 M☉ yr-1), where the thermal emission dominates the stellar scattering, and are inconsistent with a single stellar photosphere.
119296696
GRAVITY: getting to the event horizon of Sgr A*
We present the second-generation VLTI instrument GRAVITY, which currently is in the preliminary design phase. GRAVITY is specifically designed to observe highly relativistic motions of matter close to the event horizon of Sgr A*, the massive black hole at center of the Milky Way. We have identified the key design features needed to achieve this goal and present the resulting instrument concept. It includes an integrated optics, 4-telescope, dual feed beam combiner operated in a cryogenic vessel; near infrared wavefront sensing adaptive optics; fringe tracking on secondary sources within the field of view of the VLTI and a novel metrology concept. Simulations show that the planned design matches the scientific needs; in particular that 10µas astrometry is feasible for a source with a magnitude of K=15 like Sgr A*, given the availability of suitable phase reference sources.
118593802
Imaging the spotty surface of Betelgeuse in the H band
Aims. This paper reports on H-band interferometric observations of Betelgeuse made at the three-telescope interferometer IOTA. We image Betelgeuse and its asymmetries to understand the spatial variation of the photosphere, including its diameter, limb darkening, effective temperature, surrounding brightness, and bright (or dark) star spots. Methods. We used different theoretical simulations of the photosphere and dusty environment to model the visibility data. We made images with parametric modeling and two image reconstruction algorithms: MIRA and WISARD. Results. We measure an average limb-darkened diameter of 44.28 ± 0.15 mas with linear and quadratic models and a Rosseland diameter of 45.03 ± 0.12 mas with a MARCS model. These measurements lead us to derive an updated effective temperature of 3600 ± 66 K. We detect a fully-resolved environment to which the silicate dust shell is likely to contribute. By using two imaging reconstruction algorithms, we unveiled two bright spots on the surface of Betelgeuse. One spot has a diameter of about 11 mas and accounts for about 8.5% of the total flux. The second one is unresolved (diameter < 9 mas) with 4.5% of the total flux. Conclusions. Resolved images of Betelgeuse in the H band are asymmetric at the level of a few percent. The MOLsphere is not detected in this wavelength range. The amount of measured limb-darkening is in good agreement with model predictions. The two spots imaged at the surface of the star are potential signatures of convective cells.
125088636
Performance of Jets and Missing Transverse Energy in CMS
A summary of the measurements of jet energy calibration and missing transverse energy calibration and resolution is presented. The jet energy calibration is performed with data samples collected in proton-proton collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 1.6 fb−1. The final jet energy calibration is based on dijet, γ+jet and Z+jet events. The results are presented for the “Particle Flow” approach, which attempts to reconstruct all stable particles in the event individually, prior to the jet clustering, based on information from all relevant subdetectors. We discuss the effect of pile-up interactions and the state of the art mitigation techniques used in CMS. Furthermore, we describe the main uncertainty sources for the jet energy calibration. Finally, the results of comprehensive studies of the missing transverse energy are presented, performed with 0.7 fb−1 of Z(→ μμ)+jets events collected at 8 TeV.
122779026
NONLINEAR EVOLUTION AT SMALL x WITH IMPACT PARAMETER DEPENDENCE
Nonlinear evolution at small x was evaluated numerically with full dependence on impact parameter using the BK equation. several distinct behaviors were found and are presented for the leading logarithmic kernel in the BK evolution equation with both fixed and running coupling. The value of the saturation scale at various dipole sizes was found to agree with analytic expectations. Calculation of the F2 structure function from the numerical solution of the evolution with running coupling were then compared to the HERA data and qualitative agreement found. The agreement is improved with inclusion of soft contributions and these are discussed.