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Abbasi, R. U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Chae, M. J.,Cheon, B. G.,Chiba, J.,Chikawa, M.,Cho, W. R.,Fujii, IOP Publishing 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.790 No.2
<P>We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 yr period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20 degrees radius circles. The hotspot has a Li-Ma statistical significance of 5.1 sigma, and is centered at R. A. = 146 degrees 7, decl. = 43 degrees 2. The position of the hotspot is about 19 degrees off of the supergalactic plane. The probability of a cluster of events of 5.1 sigma significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7 x 10(-4) (3.4 sigma).</P>
Spectroscopic needs for imaging dark energy experiments
Newman, J.A.,Abate, A.,Abdalla, F.B.,Allam, S.,Allen, S.W.,Ansari, R.,Bailey, S.,Barkhouse, W.A.,Beers, T.C.,Blanton, M.R.,Brodwin, M.,Brownstein, J.R.,Brunner, R.J.,Carrasco Kind, M.,Cervantes-Cota, North-Holland 2015 Astroparticle physics Vol.63 No.-
Ongoing and near-future imaging-based dark energy experiments are critically dependent upon photometric redshifts (a.k.a. photo-z's): i.e., estimates of the redshifts of objects based only on flux information obtained through broad filters. Higher-quality, lower-scatter photo-z's will result in smaller random errors on cosmological parameters; while systematic errors in photometric redshift estimates, if not constrained, may dominate all other uncertainties from these experiments. The desired optimization and calibration is dependent upon spectroscopic measurements for secure redshift information; this is the key application of galaxy spectroscopy for imaging-based dark energy experiments. Hence, to achieve their full potential, imaging-based experiments will require large sets of objects with spectroscopically-determined redshifts, for two purposes:*Training: Objects with known redshift are needed to map out the relationship between object color and z (or, equivalently, to determine empirically-calibrated templates describing the rest-frame spectra of the full range of galaxies, which may be used to predict the color-z relation). The ultimate goal of training is to minimize each moment of the distribution of differences between photometric redshift estimates and the true redshifts of objects, making the relationship between them as tight as possible. The larger and more complete our ''training set'' of spectroscopic redshifts is, the smaller the RMS photo-z errors should be, increasing the constraining power of imaging experiments. Requirements: Spectroscopic redshift measurements for ~30,000 objects over >~15 widely-separated regions, each at least ~20arcmin in diameter, and reaching the faintest objects used in a given experiment, will likely be necessary if photometric redshifts are to be trained and calibrated with conventional techniques. Larger, more complete samples (i.e., with longer exposure times) can improve photo-z algorithms and reduce scatter further, enhancing the science return from planned experiments greatly (increasing the Dark Energy Task Force figure of merit by up to ~50%). Options: This spectroscopy will most efficiently be done by covering as much of the optical and near-infrared spectrum as possible at modestly high spectral resolution (λ/Δλ>~3000), while maximizing the telescope collecting area, field of view on the sky, and multiplexing of simultaneous spectra. The most efficient instrument for this would likely be either the proposed GMACS/MANIFEST spectrograph for the Giant Magellan Telescope or the OPTIMOS spectrograph for the European Extremely Large Telescope, depending on actual properties when built. The PFS spectrograph at Subaru would be next best and available considerably earlier, c. 2018; the proposed ngCFHT and SSST telescopes would have similar capabilities but start later. Other key options, in order of increasing total time required, are the WFOS spectrograph at TMT, MOONS at the VLT, and DESI at the Mayall 4m telescope (or the similar 4MOST and WEAVE projects); of these, only DESI, MOONS, and PFS are expected to be available before 2020. Table 2-3 of this white paper summarizes the observation time required at each facility for strawman training samples. To attain secure redshift measurements for a high fraction of targeted objects and cover the full redshift span of future experiments, additional near-infrared spectroscopy will also be required; this is best done from space, particularly with WFIRST-2.4 and JWST. Calibration: The first several moments of redshift distributions (the mean, RMS redshift dispersion, etc.), must be known to high accuracy for cosmological constraints not to be systematics-dominated (equivalently, the moments of the distribution of differences between photometric and true redshifts could be determined instead). The ultimate goal of calibration is to characterize these moments for every subsample used in analyses - i.e., to minimi
Mass composition of ultrahigh-energy cosmic rays with the Telescope Array Surface Detector data
Abbasi, R. U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Cheon, B. G.,Chiba, J.,Chikawa, M.,di Matteo, A.,Fujii, T.,Fujita, K.,Fukushim American Physical Society 2019 Physical review. D Vol.99 No.2
Choi, J.-Y.,Shin, I.-G.,Park, S.-Y.,Han, C.,Gould, A.,Sumi, T.,Udalski, A.,Beaulieu, J.-P.,Street, R.,Dominik, M.,Allen, W.,Almeida, L. A.,Bos, M.,Christie, G. W.,Depoy, D. L.,Dong, S.,Drummond, J.,Ga IOP Publishing 2012 The Astrophysical journal Vol.751 No.1
<P>We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of theta(E) similar to 0.08 mas combined with the short timescale of t(E) similar to 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of similar to 0.84M(circle dot) is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio.</P>
Characterization of the LIGO detectors during their sixth science run
Aasi, J,Abadie, J,Abbott, B P,Abbott, R,Abbott, T,Abernathy, M R,Accadia, T,Acernese, F,Adams, C,Adams, T,Adhikari, R X,Affeldt, C,Agathos, M,Aggarwal, N,Aguiar, O D,Ajith, P,Allen, B,Allocca, A,Ceron IOP Publishing 2015 Classical and quantum gravity Vol.32 No.11
<P>In 2009-2010, the Laser Interferometer Gravitational-Wave Observatory (LIGO) operated together with international partners Virgo and GEO600 as a network to search for gravitational waves (GWs) of astrophysical origin. The sensitivity of these detectors was limited by a combination of noise sources inherent to the instrumental design and its environment, often localized in time or frequency, that couple into the GW readout. Here we review the performance of the LIGO instruments during this epoch, the work done to characterize the detectors and their data, and the effect that transient and continuous noise artefacts have on the sensitivity of LIGO to a variety of astrophysical sources.</P>
Abbasi, R. U.,Abe, M.,Zayyad, T. Abu-,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Chae, M. J.,Cheon, B. G.,Chiba, J.,Chikawa, M.,Cho, W. R.,Fujii, IOP Publishing 2015 The Astrophysical journal Vol.804 No.2
<P>We report on the search for steady point-like sources of neutral particles around 10(18) eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km(-2) yr(-1) for E > 1 EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km(-2) yr(-1) for E > 0.5 EeV. This is an order of magnitude lower than previous flux measurements.</P>
The characterization of Virgo data and its impact on gravitational-wave searches
Aasi, J,Abadie, J,Abbott, B P,Abbott, R,Abbott, T D,Abernathy, M,Accadia, T,Acernese, F,Adams, C,Adams, T,Addesso, P,Adhikari, R,Affeldt, C,Agathos, M,Agatsuma, K,Ajith, P,Allen, B,Allocca, A,Ceron, E IOP Publishing 2012 Classical and quantum gravity Vol.29 No.15
Enhanced sensitivity of the LIGO gravitational wave detector by using squeezed states of light
Aasi, J.,Abadie, J.,Abbott, B. P.,Abbott, R.,Abbott, T. D.,Abernathy, M. R.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Affeldt, C.,Aguiar, O. D.,Ajith, P.,Allen, B.,Amador Ceron, E.,Amariutei, D. Springer Science and Business Media LLC 2013 Nature photonics Vol.7 No.8
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Chae, M.J.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fuku Elsevier 2015 Astroparticle physics Vol.64 No.-
<P><B>Abstract</B></P> <P>Previous measurements of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s Eye (HiRes) and Pierre Auger Observatory (PAO) are seemingly contradictory, but utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array (TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of <SUB> X max </SUB> are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.</P>
Search for EeV protons of galactic origin
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Fujii, T.,Fukushima, M.,Goto, T.,Hanlon, W.,Haya North-Holland 2017 Astroparticle physics Vol.86 No.-
<P>Cosmic rays in the energy range 10(18.0)-10(18.5) eV are thought to have a light, probably protonic, composition. To study their origin one can search for anisotropy in their arrival directions. Extragalactic cosmic rays should be isotropic, but galactic cosmic rays of this type should be seen mostly along the galactic plane, and there should be a shortage of events coming from directions near the galactic anticenter. This is due to the fact that, under the influence of the galactic magnetic field, the transition from ballistic to diffusive behavior is well advanced, and this qualitative picture persists over the whole energy range. Guided by models of the galactic magnetic field that indicate that the enhancement along the galactic plane should have a standard deviation of about 20 degrees in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50 degrees in galactic longitude, we use the data of the Telescope Array surface detector in 10(18.0) to 10(18.5) eV energy range to search for these effects. The data are isotropic. Neither an enhancement along the galactic plane nor a deficit in the galactic anticenter direction is found. Using these data we place an upper limit on the fraction of EeV cosmic rays of galactic origin at 1.3% at 95% confidence level. Published by Elsevier B.V.</P>