• ASASSN-15no: the Supernova that plays hide-and-seek

      Benetti, S; Zampieri, L; Pastorello, A; Cappellaro, E; Pumo, M L; Elias-Rosa, N; Ochner, P; Terreran, G; Tomasella, L; Taubenberger, S; Turatto, M; Morales-Garoffolo, A; Harutyunyan, A; Tartaglia, L; Univ Arizona, Dept Astron, 933 N Cherry Ave, Tucson, AZ 85719 USA; Univ Arizona, Steward Observ, 933 N Cherry Ave, Tucson, AZ 85719 USA (OXFORD UNIV PRESS, 2018-05)
      We report the results of our follow-up campaign of the peculiar supernova ASASSN-15no, based on optical data covering similar to 300 d of its evolution. Initially the spectra show a pure black-body continuum. After few days, the HeI lambda lambda 5876 transition appears with a P-Cygni profile and an expansion velocity of about 8700 km s(-1). Fifty days after maximum, the spectrum shows signs typically seen in interacting supernovae. A broad (FWHM similar to 8000 km s(-1)) H alpha becomes more prominent with time until similar to 150 d after maximum and quickly declines later on. At these phases Hastarts to show an intermediate component, which together with the blue pseudo-continuum are clues that the ejecta begin to interact with the circumstellar medium (CSM). The spectra at the latest phases look very similar to the nebular spectra of stripped-envelope SNe. The early part (the first 40 d after maximum) of the bolometric curve, which peaks at a luminosity intermediate between normal and superluminous supernovae, is well reproduced by a model in which the energy budget is essentially coming from ejecta recombination and Ni-56 decay. From the model, we infer a mass of the ejecta M-ej = 2.6M(circle dot); an initial radius of the photosphere R-0 = 2.1 x 10(14) cm; and an explosion energy E-expl = 0.8 x 10(51) erg. A possible scenario involves a massive and extended H-poor shell lost by the progenitor star a few years before explosion. The shell is hit, heated, and accelerated by the supernova ejecta. The accelerated shell+ejecta rapidly dilutes, unveiling the unperturbed supernova spectrum below. The outer ejecta start to interact with a H-poor external CSM lost by the progenitor system about 9-90 yr before the explosion.
    • Quantifying the Sensitivity of Sea Level Change in Coastal Localities to the Geometry of Polar Ice Mass Flux

      Mitrovica, Jerry X.; Hay, Carling C.; Kopp, Robert E.; Harig, Christopher; Latychev, Konstantin; Univ Arizona, Dept Geosci, Tucson, AZ 85721 USA (AMER METEOROLOGICAL SOC, 2018-05)
      It has been known for over a century that the melting of individual ice sheets and glaciers drives distinct geographic patterns, or fingerprints, of sea level change, and recent studies have highlighted the implications of this variability for hazard assessment and inferences of meltwater sources. These studies have computed fingerprints using simplified melt geometries; however, a more generalized treatment would be advantageous when assessing or projecting sea level hazards in the face of quickly evolving patterns of ice mass flux. In this paper the usual fingerprint approach is inverted to compute site-specific sensitivity kernels for a global database of coastal localities. These kernels provide a mapping between geographically variable mass flux across each ice sheet and glacier and the associated static sea level change at a given site. Kernels are highlighted for a subset of sites associated with melting from Greenland, Antarctica, and the Alaska-Yukon-British Columbia glacier system. The latter, for example, reveals an underappreciated sensitivity of ongoing and future sea level change along the U.S. West Coast to the geometry of ice mass flux in the region. Finally, the practical utility of these kernels is illustrated by computing sea level predictions at a suite of sites associated with annual variability in Greenland ice mass since 2003 constrained by satellite gravity measurements.
    • Do L chondrites come from the Gefion family?

      McGraw, Allison M; Reddy, Vishnu; Sanchez, Juan A; Univ Arizona, Lunar & Planetary Lab, 1629 E Univ Blvd, Tucson, AZ 85721 USA (OXFORD UNIV PRESS, 2018-05)
      Ordinary chondrites (H, L, and LL chondrites) are the most common type of meteorites comprising 80 per cent of the meteorites that fall on Earth. The source region of these meteorites in the main asteroid belt has been a basis of considerable debate in the small bodies community. L chondrites have been proposed to come from the Gefion asteroid family, based on dynamical models. We present results from our observational campaign to verify a link between the Gefion asteroid family and L chondrite meteorites. Near-infrared spectra of Gefion family asteroids (1839) Ragazza, (2373) Immo, (2386) Nikonov, (2521) Heidi, and (3860) Plovdiv were obtained at the NASA Infrared Telescope Facility (IRTF). Spectral band parameters including band centres and the band area ratio were measured from each spectrum and used to constrain the composition of these asteroids. Based on our results, we found that some members of the Gefion family have surface composition similar to that of H chondrites, primitive achondrites, and basaltic achondrites. No evidence was found for L chondrites among the Gefion family members in our small sample study. The diversity of compositional types observed in the Gefion asteroid family suggests that the original parent body might be partially differentiated or that the three asteroids with non-ordinary chondrite compositions might be interlopers.
    • Full-Duplex or Half-Duplex: A Bayesian Game for Wireless Networks with Heterogeneous Self-Interference Cancellation Capabilities

      Afifi, Wessam; Abdel-Rahman, Mohammad J.; Krunz, Marwan; MacKenzie, Allen B.; Univ Arizona, Dept Elect & Comp Engn (IEEE COMPUTER SOC, 2018-05)
      Recently, tremendous progress has been made in self-interference cancellation (SIC) techniques that enable a wireless device to transmit and receive data simultaneously on the same frequency channel, a.k.a. in-band full-duplex (FD). Although operating in FD mode significantly improves the throughput of a single wireless link, it doubles the number of concurrent transmissions, which limits the potential for coexistence between multiple FD-enabled links. In this paper, we consider the coexistence problem of concurrent transmissions between multiple FD-enabled links with different SIC capabilities; each link can operate in either FD or half-duplex mode. First, we consider two links and formulate the interactions between them as a Bayesian game. In this game, each link tries to maximize its throughput while minimizing the transmission power cost. We derive a closed-form expression for the Bayesian Nash equilibrium and determine the conditions under which no outage occurs at either link. Then, we study the coexistence problem between more than two links, assuming that each link is only affected by its dominant interfering link. We show that under this assumption, no more than two links will be involved in a single game. Finally, we corroborate our analytical findings via extensive simulations and numerical results.
    • A joint chance-constrained programming approach for the single-item capacitated lot-sizing problem with stochastic demand

      Gicquel, Céline; Cheng, Jianqiang; Univ Arizona, Dept Syst & Ind Engn (SPRINGER, 2018-05)
      We study the single-item single-resource capacitated lot-sizing problem with stochastic demand. We propose to formulate this stochastic optimization problem as a joint chance-constrained program in which the probability that an inventory shortage occurs during the planning horizon is limited to a maximum acceptable risk level. We investigate the development of a new approximate solution method which can be seen as an extension of the previously published sample approximation approach. The proposed method relies on a Monte Carlo sampling of the random variables representing the demand in all planning periods except the first one. Provided there is no dependence between the demand in the first period and the demand in the later periods, this partial sampling results in the formulation of a chance-constrained program featuring a series of joint chance constraints. Each of these constraints involves a single random variable and defines a feasible set for which a conservative convex approximation can be quite easily built. Contrary to the sample approximation approach, the partial sample approximation leads to the formulation of a deterministic mixed-integer linear problem having the same number of binary variables as the original stochastic problem. Our computational results show that the proposed method is more efficient at finding feasible solutions of the original stochastic problem than the sample approximation method and that these solutions are less costly than the ones provided by the Bonferroni conservative approximation. Moreover, the computation time is significantly shorter than the one needed for the sample approximation method.
    • Abstraction, Concrescence, and Identity in Descriptive Metadata

      Radio, Erik; University of Arizona (Taylor & Francis, 2018-04-27)
      Descriptive metadata is affected by the challenge of using language that is resilient to semantic transformation over time. Yet part of this is directly related to a bibliographic rift between between abstract and concrete elements. By exploring the materiality of information objects and how descriptive values are subsequently derived, ideological formations and their impact become apparent. An examination into the origins of abstract elements demonstrates their identitarian tendencies and the effect on conceptual organization. Alternatives offered by negative dialectics and critical realism are explored towards a different model of information organization and retrieval.
    • Emergency transportation interventions for reducing adverse pregnancy outcomes in low- and middle-income countries: a systematic review protocol

      Ehiri, John; Alaofè, Halimatou; Asaolu, Ibitola; Chebet, Joy; Esu, Ekpereonne; Meremikwu, Martin; Department of Health Promotion Sciences, Mel and Enid Zuckerman College of Public Health, University of Arizona (BioMed Central, 2018-04-25)
      Transportation interventions seek to decrease delay in reaching a health facility for emergency obstetric care and are, thus, believed to contribute to reductions in such adverse pregnancy and childbirth outcomes as maternal deaths, stillbirths, and neonatal mortality in low- and middle-income countries (LMICs). However, there is limited empirical evidence to support this hypothesis. The objective of the proposed review is to summarize and critically appraise evidence regarding the effect of emergency transportation interventions on outcomes of labor and delivery in LMICs. The following databases will be searched from inception to March 31, 2018: MEDLINE/PubMed, EMBASE, Web of Science, EBSCO (PsycINFO and CINAHL), the Cochrane Pregnancy and Child Birth Group's Specialized Register, and the Cochrane Central Register of Controlled Trials. We will search for studies in the grey literature through Google and Google Scholar. We will solicit unpublished reports from such relevant agencies as United Nations Fund for Population Activities (UNFPA), the World Health Organization (WHO), the United Nations Children's Fund (UNICEF), the United States Agency for International Development (USAID), and the United Kingdom Department for International Development (DfID) among others. Data generated from the search will be managed using Endnote Version 7. We will perform quantitative data synthesis if studies are homogenous in characteristics and provide adequate outcome data for meta-analysis. Otherwise, data will be synthesized, using the narrative synthesis approach. Among the many barriers that women in LMICs face in accessing life-saving interventions during labor and delivery, lack of access to emergency transportation is particularly important. This review will provide a critical summary of evidence regarding the impact of transportation interventions on outcomes of pregnancy and childbirth in LMICs. PROSPERO CRD42017080092.
    • Spatial clustering of dark matter haloes: secondary bias, neighbour bias, and the influence of massive neighbours on halo properties

      Salcedo, Andrés N; Maller, Ariyeh H; Berlind, Andreas A; Sinha, Manodeep; McBride, Cameron K; Behroozi, Peter S; Wechsler, Risa H; Weinberg, David H; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2018-04-21)
      We explore the phenomenon commonly known as halo assembly bias, whereby dark matter haloes of the same mass are found to be more or less clustered when a second halo property is considered, for haloes in the mass range 3.7 x 10(11)-5.0 x 10(13) h(-1)M(circle dot). Using the Large Suite of Dark Matter Simulations (LasDamas) we consider nine commonly used halo properties and find that a clustering bias exists if haloes are binned by mass or by any other halo property. This secondary bias implies that no single halo property encompasses all the spatial clustering information of the halo population. The mean values of some halo properties depend on their halo's distance to a more massive neighbour. Halo samples selected by having high values of one of these properties therefore inherit a neighbour bias such that they are much more likely to be close to a much more massive neighbour. This neighbour bias largely accounts for the secondary bias seen in haloes binned by mass and split by concentration or age. However, haloes binned by other mass-like properties still show a secondary bias even when the neighbour bias is removed. The secondary bias of haloes selected by their spin behaves differently than that for other halo properties, suggesting that the origin of the spin bias is different than of other secondary biases.
    • Event Horizon Telescope observations as probes for quantum structure of astrophysical black holes

      Giddings, Steven B.; Psaltis, Dimitrios; Univ Arizona, Dept Astron, Tucson, AZ 85721 USA; Univ Arizona, Dept Phys, Tucson, AZ 85721 USA (AMER PHYSICAL SOC, 2018-04-19)
      The need for a consistent quantum evolution for black holes has led to proposals that their semiclassical description is modified not just near the singularity, but at horizon or larger scales. If such modifications extend beyond the horizon, they influence regions accessible to distant observation. Natural candidates for these modifications behave like metric fluctuations, with characteristic length scales and timescales set by the horizon radius. We investigate the possibility of using the Event Horizon Telescope to observe these effects, if they have a strength sufficient to make quantum evolution consistent with unitarity, without introducing new scales. We find that such quantum fluctuations can introduce a strong time dependence for the shape and size of the shadow that a black hole casts on its surrounding emission. For the black hole in the center of the Milky Way, detecting the rapid time variability of its shadow will require nonimaging timing techniques. However, for the much larger black hole in the center of the M87 galaxy, a variable black-hole shadow, if present with these parameters, would be readily observable in the individual snapshots that will be obtained by the Event Horizon Telescope.
    • Gut Microbiota Contributes to Resistance Against Pneumococcal Pneumonia in Immunodeficient Rag(-/-) Mice

      Felix, Krysta M.; Jaimez, Ivan A.; Nguyen, Thuy-Vi V.; Ma, Heqing; Raslan, Walid A.; Klinger, Christina N.; Doyle, Kristian P.; Wu, Hsin-Jung J.; Univ Arizona, Dept Immunobiol, Tucson, AZ 85721 USA; Univ Arizona, Coll Med, Dept Neurol, Tucson, AZ USA; Univ Arizona, Coll Med, Arizona Arthrit Ctr, Tucson, AZ 85721 USA (FRONTIERS MEDIA SA, 2018-04-18)
      Streptococcus pneumoniae causes infection-related mortality worldwide. lmmunocompromised individuals, including young children, the elderly, and those with immunodeficiency, are especially vulnerable, yet little is known regarding S. pneumoniae-related pathogenesis and protection in immunocompromised hosts. Recently, strong interest has emerged in the gut microbiota's impact on lung diseases, or the "gut-lung axis." However, the mechanisms of gut microbiota protection against gut-distal lung diseases like pneumonia remain unclear. We investigated the role of the gut commensal, segmented filamentous bacteria (SFB), against pneumococcal pneumonia in immunocompetent and immunocompromised mouse models. For the latter, we chose the Rag(-/-) model, with adaptive immune deficiency. lmmunocompetent adaptive protection against S. pneumoniae infection is based on antibodies against pneumococcal capsular polysaccharides, prototypical T cell independent-II (TI-II) antigens. Although SFB colonization enhanced TI-II antibodies in C57BL/6 mice, our data suggest that SFB did not further protect these immunocompetent animals. Indeed, basal B cell activity in hosts without SFB is sufficient for essential protection against S. pneumoniae. However, in immunocompromised Rag(-/-) mice, we demonstrate a gut-lung axis of communication, as SFB influenced lung protection by regulating innate immunity. Neutrophil resolution is crucial to recovery, since an unchecked neutrophil response causes severe tissue damage. We found no early neutrophil recruitment differences between hosts with or without SFB; however, we observed a significant drop in lung neutrophils in the resolution phase of S. pneumoniae infection, which corresponded with lower CD47 expression, a molecule that inhibits phagocytosis of apoptotic cells, in SFB-colonized Rag(-/-) mice. SFB promoted a shift in lung neutrophil phenotype from inflammatory neutrophils expressing high levels of CD18 and low levels of CD62L, to pro-resolution neutrophils with low CD18 and high CD62L. Blocking CD47 in SFB(-) mice increased pro-resolution neutrophils, suggesting CD47 down-regulation may be one neutrophil-modulating mechanism SFB utilizes. The SFB-induced lung neutrophil phenotype remained similar with heat-inactivated S. pneumoniae treatment, indicating these SFB-induced changes in neutrophil phenotype during the resolution phase are not simply secondary to better bacterial clearance in SFB(+) than SFB(-) mice. Together, these data demonstrate that the gut commensal SFB may provide much-needed protection in immunocompromised hosts in part by promoting neutrophil resolution post lung infection.
    • Strong-Isospin-Breaking Correction to the Muon Anomalous Magnetic Moment from Lattice QCD at the Physical Point

      Chakraborty, B.; Davies, C. T. H.; DeTar, C.; El-Khadra, A. X.; Gámiz, E.; Gottlieb, Steven; Hatton, D.; Koponen, J.; Kronfeld, A. S.; Laiho, J.; Lepage, G. P.; Liu, Yuzhi; Mackenzie, P. B.; McNeile, C.; Neil, E. T.; Simone, J. N.; Sugar, R.; Toussaint, D.; Van de Water, R. S.; Vaquero, A.; Univ Arizona, Dept Phys, Tucson, AZ 85721 USA (AMER PHYSICAL SOC, 2018-04-12)
      All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to a(mu)(HVP) for the first time with physical values of m(u) and m(d) and dynamical u, d, s, and c quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of delta a(mu)(HVP,) (mu not equal md) = +1.5(7)%, in agreement with estimates from phenomenology.
    • A Hubble Space Telescope imaging study of four FeLoBAL quasar host galaxies

      Lawther, D; Vestergaard, M; Fan, X; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2018-04-11)
      We study the host galaxies of four Iron Low-Ionization Broad Absorption-line Quasars (FeLoBALs), using Hubble Space Telescope imaging data, investigating the possibility that they represent a transition between an obscured active galactic nucleus (AGN) and an ordinary optical quasar. In this scenario, the FeLoBALs represent the early stage of merger-triggered accretion, in which case their host galaxies are expected to show signs of an ongoing or recent merger. Using PSF subtraction techniques, we decompose the images into host galaxy and AGN components at rest-frame ultraviolet and optical wavelengths. The ultraviolet is sensitive to young stars, while the optical probes stellar mass. In the ultraviolet we image at the BAL absorption trough wavelengths so as to decrease the contrast between the quasar and host galaxy emission. We securely detect an extended source for two of the four FeLoBALs in the rest-frame optical; a third host galaxy is marginally detected. In the rest-frame UV we detect no host emission; this constrains the level of unobscured star formation. Thus, the host galaxies have observed properties that are consistent with those of non-BAL quasars with the same nuclear luminosity, i.e. quiescent or moderately star-forming elliptical galaxies. However, we cannot exclude starbursting hosts that have the stellar UV emission obscured by modest amounts of dust reddening. Thus, our findings also allow the merger-induced young quasar scenario. For three objects, we identify possible close companion galaxies that may be gravitationally interacting with the quasar hosts.
    • Rotational Failure of Rubble-pile Bodies: Influences of Shear and Cohesive Strengths

      Zhang, Yun; Richardson, Derek C.; Barnouin, Olivier S.; Michel, Patrick; Schwartz, Stephen R.; Ballouz, Ronald-Louis; Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA (IOP PUBLISHING LTD, 2018-04-10)
      The shear and cohesive strengths of a rubble-pile asteroid could influence the critical spin at which the body fails and its subsequent evolution. We present results using a soft-sphere discrete element method to explore the mechanical properties and dynamical behaviors of self-gravitating rubble piles experiencing increasing rotational centrifugal forces. A comprehensive contact model incorporating translational and rotational friction and van der Waals cohesive interactions is developed to simulate rubble-pile asteroids. It is observed that the critical spin depends strongly on both the frictional and cohesive forces between particles in contact; however, the failure behaviors only show dependence on the cohesive force. As cohesion increases, the deformation of the simulated body prior to disruption is diminished, the disruption process is more abrupt, and the component size of the fissioned material is increased. When the cohesive strength is high enough, the body can disaggregate into similar-size fragments, which could be a plausible mechanism to form asteroid pairs or active asteroids. The size distribution and velocity dispersion of the fragments in high-cohesion simulations show similarities to the disintegrating asteroid P/2013 R3, indicating that this asteroid may possess comparable cohesion in its structure and experience rotational fission in a similar manner. Additionally, we propose a method for estimating a rubble pile's friction angle and bulk cohesion from spin-up numerical experiments, which provides the opportunity for making quantitative comparisons with continuum theory. The results show that the present technique has great potential for predicting the behaviors and estimating the material strengths of cohesive rubble-pile asteroids.
    • Multiple Gaps in the Disk of the Class I Protostar GY 91

      Sheehan, Patrick D.; Eisner, Josh A.; Univ Arizona, Steward Observ, 933 North Cherry Ave, Tucson, AZ 85721 USA (IOP PUBLISHING LTD, 2018-04-10)
      We present the highest spatial resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations to date of the Class I protostar GY 91 in the rho Ophiuchus L1688 molecular cloud complex. Our 870 mu m and 3 mm dust continuum maps show that the GY 91 disk has a radius of similar to 80 au, and an inclination of similar to 40 degrees, but most interestingly that the disk has three dark lanes located at 10, 40, and 70 au. We model these features assuming they are gaps in the disk surface density profile and find that their widths are 7, 30, and 10 au. These gaps bear a striking resemblance to the gaps seen in the HL Tau disk, suggesting that there may be Saturn-mass planets hiding in the disk. To constrain the relative ages of GY 91 and HL Tau, we also model the disk and envelope of HL Tau and find that they are of similar ages, although GY 91. may be younger. Although snow lines and magnetic dead zones can also produce dark lanes, if planets are indeed carving these gaps then Saturn-mass planets must form within the first similar to 0.5 Myr of the lifetime of protoplanetary disks.
    • Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67

      Souto, Diogo; Cunha, Katia; Smith, Verne V.; Prieto, C. Allende; García-Hernández, D. A.; Pinsonneault, Marc; Holzer, Parker; Frinchaboy, Peter; Holtzman, Jon; Johnson, J. A.; Jönsson, Henrik; Majewski, Steven R.; Shetrone, Matthew; Sobeck, Jennifer; Stringfellow, Guy; Teske, Johanna; Zamora, Olga; Zasowski, Gail; Carrera, Ricardo; Stassun, Keivan; Fernandez-Trincado, J. G.; Villanova, Sandro; Minniti, Dante; Santana, Felipe; Univ Arizona, Steward Observ, 933 North Cherry Ave, Tucson, AZ 85721 USA (IOP PUBLISHING LTD, 2018-04-10)
      Detailed chemical abundance distributions for 14 elements are derived for eight high-probability stellar members of the solar metallicity old open cluster M67 with an age of similar to 4 Gyr. The eight stars consist of four pairs, with each pair occupying a distinct phase of stellar evolution: two G dwarfs, two turnoff stars, two G subgiants, and two red clump (RC) K giants. The abundance analysis uses near-IR high-resolution spectra (lambda 1.5-1.7 mu m) from the Apache Point Observatory Galactic Evolution Experiment survey and derives abundances for C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe. Our derived stellar parameters and metallicity for 2M08510076+1153115 suggest that this star is a solar twin, exhibiting abundance differences relative to the Sun of <= 0.04 dex for all elements. Chemical homogeneity is found within each class of stars (similar to 0.02 dex), while significant abundance variations (similar to 0.05-0.20 dex) are found across the different evolutionary phases; the turnoff stars typically have the lowest abundances, while the RCs tend to have the largest. Non-LTE corrections to the LTE-derived abundances are unlikely to explain the differences. A detailed comparison of the derived Fe, Mg, Si, and Ca abundances with recently published surface abundances from stellar models that include chemical diffusion provides a good match between the observed and predicted abundances as a function of stellar mass. Such agreement would indicate the detection of chemical diffusion processes in the stellar members of M67.
    • Dark Matter under the Microscope: Constraining Compact Dark Matter with Caustic Crossing Events

      Diego, Jose M.; Kaiser, Nick; Broadhurst, Tom; Kelly, Patrick L.; Rodney, Steve; Morishita, Takahiro; Oguri, Masamune; Ross, Timothy W.; Zitrin, Adi; Jauzac, Mathilde; Richard, Johan; Williams, Liliya; Vega-Ferrero, Jesus; Frye, Brenda; Filippenko, Alexei V.; Univ Arizona, Steward Observ, Dept Astron, 933 North Cherry Ave, Tucson, AZ 85721 USA (IOP PUBLISHING LTD, 2018-04-10)
      A galaxy cluster acts as a cosmic telescope over background galaxies but also as a cosmic microscope magnifying the imperfections of the lens. The diverging magnification of lensing caustics enhances the microlensing effect of substructure present within the lensing mass. Fine-scale structure can be accessed as a moving background source brightens and disappears when crossing these caustics. The recent discovery of a distant lensed star near the Einstein radius of the galaxy cluster MACSJ1149.5+ 2223 allows a rare opportunity to reach subsolar-mass microlensing through a supercritical column of cluster matter. Here we compare these observations with high-resolution ray-tracing simulations that include stellar microlensing set by the observed intracluster starlight and also primordial black holes that may be responsible for the recently observed LIGO events. We explore different scenarios with microlenses from the intracluster medium and black holes, including primordial ones, and examine strategies to exploit these unique alignments. We find that the best constraints on the fraction of compact dark matter (DM) in the small-mass regime can be obtained in regions of the cluster where the intracluster medium plays a negligible role. This new lensing phenomenon should be widespread and can be detected within modest-redshift lensed galaxies so that the luminosity distance is not prohibitive for detecting individual magnified stars. High-cadence Hubble Space Telescope monitoring of several such optimal arcs will be rewarded by an unprecedented mass spectrum of compact objects that can contribute to uncovering the nature of DM.
    • Inside-out Planet Formation. IV. Pebble Evolution and Planet Formation Timescales

      Hu, Xiao; Tan, Jonathan C.; Zhu, Zhaohuan; Chatterjee, Sourav; Birnstiel, Tilman; Youdin, Andrew N.; Mohanty, Subhanjoy; Univ Arizona, Dept Astron, 933 North Cherry Ave, Tucson, AZ 85721 USA; Univ Arizona, Steward Observ, 933 North Cherry Ave, Tucson, AZ 85721 USA (IOP PUBLISHING LTD, 2018-04-10)
      Systems with tightly packed inner planets (STIPs) are very common. Chatterjee & Tan proposed Inside-out Planet Formation (IOPF), an in situ formation theory, to explain these planets. IOPF involves sequential planet formation from pebble-rich rings that are fed from the outer disk and trapped at the pressure maximum associated with the dead zone inner boundary (DZIB). Planet masses are set by their ability to open a gap and cause the DZIB to retreat outwards. We present models for the disk density and temperature structures that are relevant to the conditions of IOPF. For a wide range of DZIB conditions, we evaluate the gap-opening masses of planets in these disks that are expected to lead to the truncation of pebble accretion onto the forming planet. We then consider the evolution of dust and pebbles in the disk, estimating that pebbles typically grow to sizes of a few centimeters during their radial drift from several tens of astronomical units to the inner, less than or similar to 1 au scale disk. A large fraction of the accretion flux of solids is expected to be in such pebbles. This allows us to estimate the timescales for individual planet formation and the entire planetary system formation in the IOPF scenario. We find that to produce realistic STIPs within reasonable timescales similar to disk lifetimes requires disk accretion rates of similar to 10(-9) M-circle dot yr(-1) and relatively low viscosity conditions in the DZIB region, i.e., a Shakura-Sunyaev parameter of alpha similar to 10(-4).
    • A Decade of MWC 758 Disk Images: Where Are the Spiral-arm-driving Planets?

      Ren, Bin; Dong, Ruobing; Esposito, Thomas M.; Pueyo, Laurent; Debes, John H.; Poteet, Charles A.; Choquet, Élodie; Benisty, Myriam; Chiang, Eugene; Grady, Carol A.; Hines, Dean C.; Schneider, Glenn; Soummer, Rémi; Univ Arizona, Steward Observ, Tucson, AZ 85719 USA; Univ Arizona, Steward Observ, Tucson, AZ 85721 USA (IOP PUBLISHING LTD, 2018-04-10)
      Large-scale spiral arms have been revealed in scattered light images of a few protoplanetary disks. Theoretical models suggest that such arms may be driven by and corotate with giant planets, which has called for remarkable observational efforts to look for them. By examining the rotation of the spiral arms for the MWC 758 system over a 10 year timescale, we are able to provide dynamical constraints on the locations of their perturbers. We present reprocessed Hubble Space Telescope (HST )/NICMOS F110W observations of the target in 2005, and the new Keck/NIRC2 L′-band observations in 2017. MWC 758ʼs two well-known spiral arms are revealed in the NICMOS archive at the earliest observational epoch. With additional Very Large Telescope (VLT )/SPHERE data, our joint analysis leads to a pattern speed of 0.6 degrees(+3.3 degrees)(-0.6 degrees) yr(-1) at 3σ for the two major spiral arms. If the two arms are induced by a perturber on a near-circular orbit, its best-fit orbit is at 89 au (0 59), with a 3σ lower limit of 30 au (0 20). This finding is consistent with the simulation prediction of the location of an arm-driving planet for the two major arms in the system.
    • Quantum key distribution using basis encoding of Gaussian-modulated coherent states

      Huang, Peng; Huang, Jingzheng; Zhang, Zheshen; Zeng, Guihua; Univ Arizona, Dept Mat Sci & Engn, Coll Opt Sci, Tucson, AZ 85721 USA (AMER PHYSICAL SOC, 2018-04-09)
      The continuous-variable quantum key distribution (CVQKD) has been demonstrated to be available in practical secure quantum cryptography. However, its performance is restricted strongly by the channel excess noise and the reconciliation efficiency. In this paper, we present a quantum key distribution (QKD) protocol by encoding the secret keys on the random choices of two measurement bases: the conjugate quadratures X and P. The employed encoding method can dramatically weaken the effects of channel excess noise and reconciliation efficiency on the performance of the QKD protocol. Subsequently, the proposed scheme exhibits the capability to tolerate much higher excess noise and enables us to reach a much longer secure transmission distance even at lower reconciliation efficiency. The proposal can work alternatively to strengthen significantly the performance of the known Gaussian-modulated CVQKD protocol and serve as a multiplier for practical secure quantum cryptography with continuous variables.
    • Climate change and the global pattern of moraine-dammed glacial lake outburst floods

      Harrison, Stephan; Kargel, Jeffrey S.; Huggel, Christian; Reynolds, John; Shugar, Dan H.; Betts, Richard A.; Emmer, Adam; Glasser, Neil; Haritashya, Umesh K.; Klimes, Jan; Reinhardt, Liam; Schaub, Yvonne; Wiltshire, Andy; Regmi, Dhananjay; Vilimek, Vit; Univ Arizona, Dept Hydrol & Atmospher Sci, Tucson, AZ 85742 USA (COPERNICUS GESELLSCHAFT MBH, 2018-04-09)
      Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.