Optical colors of 56 near-Earth objects: trends with size and orbit

We present the results of BVRIZ photometry of 56 near-Earth objects (NEOs) obtained with the 1-m Jacobus Kapteyn telescope on La Palma during 2000 and 2001. Our sample includes many NEOs with particularly deep 1 - mum pyroxene/olivine absorption bands, similar to Q-type asteroids. We also classify three NEOs with particularly blue colors. No D-type asteroids were found, placing an upper limit of similar to2% on the fraction of the NEO population originating in the outer main belt or the Trojan clouds. The ratio of dark to bright objects in our sample was found to be 0.40, significantly higher than current theoretical predictions. As well as classifying the NEOs, we have investigated color trends with size and orbit. We see a general trend for larger silicate objects to have shallower absorption bands but find no significant difference in the distribution of taxonomic classes at small and large sizes. Our data clearly show that different taxonomic classes tend to occupy different regions of (a, e) space. By comparing our data with current model predictions for NEO dynamical evolution we see that Q- R-, and V-type NEOs tend to have orbits associated with "fast track" delivery from the main belt, whereas S-type NEOs tend to have orbits associated with "slow track" delivery. This outcome would be expected if space weathering occurs on time scales of >10(6) years. (C) 2003 Elsevier Science (USA). All rights reserved.

Near-field distribution of optical transmission of periodic subwavelength holes in a metal film

Optical transmission of a two-dimensional array of subwavelength holes in a metal film has been numerically studied using a differential method. Transmission spectra have been calculated showing a significant increase of the transmission in certain spectral ranges corresponding to the excitation of the surface polariton Bloch waves on a metal surface with a periodic hole structure. Under the enhanced transmission conditions, the near-field distribution of the transmitted light reveals an intensity enhancement greater than 2 orders of magnitude in localized (similar to 40 nm) spots resulting from the interference of the surface polaritons Bragg scattered by the holes in an array.

Extensive optical and near-infrared observations of the nearby, narrow-lined type Ic SN 2007gr: days 5 to 415

We present photometric and spectroscopic observations at optical and near-infrared wavelengths of the nearby type Ic supernova 2007gr. These represent the most extensive data-set to date of any supernova of this sub-type, with frequent coverage from shortly after discovery to more than one year post-explosion. We deduce a rise time to B-band maximum of 11.5 +/- 2.7 d. We find a peak B-band magnitude of M-B = -16.8, and light curves which are remarkably similar to the so-called "hypernova" SN 2002ap. In contrast, the spectra of SNe 2007gr and 2002ap show marked differences, not least in their respective expansion velocities. We attribute these differences primarily to the density profiles of their progenitor stars at the time of explosion i.e. a more compact star for SN 2007gr compared to SN 2002ap. From the quasi-bolometric light curve of SN 2007gr, we estimate that 0.076 +/- 0.010 M-circle dot of Ni-56 was produced in the explosion. Our near-infrared (IR) spectra clearly show the onset and disappearance of the first overtone of carbon monoxide (CO) between similar to 70 to 175 d relative to B-band maximum. The detection of the CO molecule implies that ionised He was not microscopically mixed within the carbon/oxygen layers. From the optical spectra, near-IR light curves, and colour evolution, we find no evidence for dust condensation in the ejecta out to about +400 d. Given the combination of unprecedented temporal coverage, and high signal-to-noise data, we suggest that SN 2007gr could be used as a template object for supernovae of this sub-class.

Optical Nonlocalities and Additional Waves in Epsilon-Near-Zero Metamaterials

We analyze the optical properties of plasmonic nanorod metamaterials in the epsilon-near-zero regime and show, both theoretically and experimentally, that the performance of these composites is strongly affected by nonlocal response of the effective permittivity tensor. We provide the evidence of interference between main and additional waves propagating in the room-temperature nanorod metamaterials and develop an analytical description of this phenomenon. Additional waves are present in the majority of low-loss epsilon-near-zero structures and should be explicitly considered when designing applications of epsilon-near-zero composites, as they represent a separate communication channel.

Optical and near-infrared coverage of SN 2004et: physical parameters and comparison with other Type IIP supernovae

We present new optical and near-infrared (NIR) photometry and spectroscopy of the Type IIP supernova (SN), SN 2004et. In combination with already published data, this provides one of the most complete studies of optical and NIR data for any Type IIP SN from just after explosion to +500 d. The contribution of the NIR flux to the bolometric light curve is estimated to increase from 15 per cent at explosion to around 50 per cent at the end of the plateau and then declines to 40 per cent at 300 d. SN 2004et is one of the most luminous IIP SNe which has been well studied and characterized, and with a luminosity of log L = 42.3 erg s-1 and a 56Ni mass of 0.06 +/- 0.04 M-circle dot, it is two times brighter than SN 1999em. We provide parametrized bolometric corrections as a function of time since explosion for SN 2004et and three other IIP SNe that have extensive optical and NIR data. These can be used as templates for future events in optical and NIR surveys without full wavelength coverage. We compare the physical parameters of SN 2004et with those of other well-studied IIP SNe and find that the kinetic energies span a range of 1050-1051 erg. We compare the ejected masses calculated from hydrodynamic models with the progenitor masses and limits derived from pre-discovery images. Some of the ejected mass estimates are significantly higher than the progenitor mass estimates, with SN 2004et showing perhaps the most serious mass discrepancy. With the current models, it appears difficult to reconcile 100 d plateau lengths and high expansion velocities with the low ejected masses of 5-6 M-circle dot implied from 7-8 M-circle dot progenitors. The nebular phase is studied using very late-time Hubble Space Telescope photometry, along with optical and NIR spectroscopy. The light curve shows a clear flattening at 600 d in the optical and the NIR, which is likely due to the ejecta impacting on circumstellar material. We further show that the [O i] 6300, 6364 A line strengths in the nebular spectra of four Type IIP SNe imply ejected oxygen masses of 0.5-1.5 M-circle dot.

SN 2005cs in M51-II. Complete evolution in the optical and the near-infrared

We present the results of the one-year long observational campaign of the type 11 plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the Whirlpool galaxy). This extensive data set makes SN 2005cs the best observed low-luminosity, Ni-56-poor type II plateau event so far and one of the best core-collapse supernovae ever. The optical and near-infrared spectra show narrow P-Cygni lines characteristic of this SN family, which are indicative of a very low expansion velocity (about 1000 km s(-1)) of the ejected material. The optical light curves cover both the plateau phase and the late-time radioactive tail, until about 380 d after core-collapse. Numerous unfiltered observations obtained by amateur astronomers give us the rare opportunity to monitor the fast rise to maximum light, lasting about 2 cl. In addition to optical observations, we also present near-infrared light curves that (together with already published ultraviolet observations) allow us to construct for the first time a reliable bolometric light Curve for an object of this class. Finally. comparing the observed data withthose derived front it semi-analytic model, we infer for SN 2005cs a Ni-56 mass of about 3 x 10(-3) M-circle dot a total ejected mass of 8-13 M-circle dot and an explosion energy of about 3 x 10(50) erg.

Magneto-optical trapping and background-free imaging for atoms near nanostructured surfaces

We demonstrate a combined magneto-optical trap and imaging system that is suitable for the investigation of cold atoms near surfaces. In particular, we are able to trap atoms close to optically scattering surfaces and to image them with an excellent signal-to-noise ratio. We also demonstrate a simple magneto-optical atom cloud launching method. We anticipate that this system will be useful for a range of experimental studies of novel atom-surface interactions and atom trap miniaturization.

Fluorescence enhancement and energy transfer in apertureless scanning near-field optical microscopy

We investigate the mechanisms for fluorescence enhancement and energy transfer near a gold tip in apertureless scanning near-field optical microscopy. Using a simple quasi-static model, we show that the observed enhancement of fluorescence results from competition between enhancement and quenching, and is dependent on a range of experimental parameters. We find good qualitative agreement with the results of measurements of the effect of both sharp and blunt tips on quantum dot fluorescence, and provide a demonstration of tip-enhanced fluorescence imaging with 60 nm resolution.

Effect of the surface water layer on the optical signal in apertureless scanning near field optical microscopy

Optical signals measured in apertureless scanning near field optical microscopy (ASNOM) under ambient conditions are found to be affected significantly by the thin water layer absorbed on the surface under investigation, the presence of which is detected through measurements of the shear force experienced by the tip. This water layer also results in a large hysteresis between optical signals measured during approach and withdrawal of the tip to the sample surface. The role of this effect in ASNOM is anticipated to be significant, with the possibility of resultant topographically induced artefacts for ASNOM involving intermittent contact of tip and sample, but also providing a potential mechanism for nanoscale optical resolution.

Optical and near-infrared observations of SN 2011dh - The first 100 days

We present optical and near-infrared (NIR) photometry and spectroscopy of the Type IIb supernova (SN) 2011dh for the first 100 days. We complement our extensive dataset with Swift ultra-violet (UV) and Spitzer mid-infrared (MIR) data to build a UV to MIR bolometric lightcurve using both photometric and spectroscopic data. Hydrodynamical modelling of the SN based on this bolometric lightcurve have been presented in Bersten et al. (2012, ApJ, 757, 31). We find that the absorption minimum for the hydrogen lines is never seen below ~11 000 km s-1 but approaches this value as the lines get weaker. This suggests that the interface between the helium core and hydrogen rich envelope is located near this velocity in agreement with the Bersten et al. (2012) He4R270 ejecta model. Spectral modelling of the hydrogen lines using this ejecta model supports the conclusion and we find a hydrogen mass of 0.01-0.04 M⊙ to be consistent with the observed spectral evolution. We estimate that the photosphere reaches the helium core at 5-7 days whereas the helium lines appear between ~10 and ~15 days, close to the photosphere and then move outward in velocity until ~40 days. This suggests that increasing non-thermal excitation due to decreasing optical depth for the γ-rays is driving the early evolution of these lines. The Spitzer 4.5 μm band shows a significant flux excess, which we attribute to CO fundamental band emission or a thermal dust echo although further work using late time data is needed. Thedistance and in particular the extinction, where we use spectral modelling to put further constraints, is discussed in some detail as well as the sensitivity of the hydrodynamical modelling to errors in these quantities. We also provide and discuss pre- and post-explosion observations of the SN site which shows a reduction by ~75 percent in flux at the position of the yellow supergiant coincident with SN 2011dh. The B, V and r band decline rates of 0.0073, 0.0090 and 0.0053 mag day-1 respectively are consistent with the remaining flux being emitted by the SN. Hence we find that the star was indeed the progenitor of SN 2011dh as previously suggested by Maund et al. (2011, ApJ, 739, L37) and which is also consistent with the results from the hydrodynamical modelling. Figures 2, 3, Tables 3-10, and Appendices are available in electronic form at http://www.aanda.orgThe photometric tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A17

The near-edge structure in energy-loss spectroscopy: many-electron and magnetic effects in transition metal nitrides and carbides

We investigate the ability of the local density approximation (LDA) in density functional theory to predict the near-edge structure in electron energy-loss spectroscopy in the dipole approximation. We include screening of the core hole within the LDA using Slater's transition state theory. We find that anion K-edge threshold energies are systematically overestimated by 4.22 +/- 0.44 eV in twelve transition metal carbides and nitrides in the rock-salt (B1) structure. When we apply this 'universal' many-electron correction to energy-loss spectra calculated within the transition state approximation to LDA, we find quantitative agreement with experiment to within one or two eV for TiC, TiN and VN. We compare our calculations to a simpler approach using a projected Mulliken density which honours the dipole selection rule, in place of the dipole matrix element itself. We find remarkably close agreement between these two approaches. Finally, we show an anomaly in the near-edge structure in CrN to be due to magnetic structure. In particular, we find that the N K edge in fact probes the magnetic moments and alignments of ther sublattice.

Optical spectroscopy of the M 15 intermediate velocity cloud

We present echelle spectrograph observations in the Na D lines, at resolutions of 6.2-8.5 km s(-1), for 11 stars located in the line-of-sight to the M15 intermediate velocity cloud (IVC), which has a radial velocity of similar to +70 km s(-1) in the Local Standard of Rest. This cloud is a part of IVC Complex gp. The targets range in magnitude from m(V) = 13.3-14.8. Seven of the observed stars are in the M15 globular cluster, the remaining four being field stars. Three of the observed cluster stars are located near a peak in intensity of the IVC Hi column density as observed at a resolution of similar to 1 arcmin. Intermediate velocity gas is detected in absorption towards 7 stars, with equivalent widths in NaD2 ranging from similar to0.09-0.20 Angstrom, corresponding to log(10)(N-Na cm(-2)) similar to 11.8-12.5, and Na I/H I column density ratios (neglecting the HII component) ranging from similar to(1-3) x 10(-8). Over scales ranging from 30 arcsec to 1 arcmin, the Na i column density and the Na i/H i ratio varies by upto 70 per cent and a factor of similar to 2, respectively. Combining the current sightlines with previously obtained Nai data from Kennedy et al. (1998b), the Na i/H i column density ratio over cluster sightlines varies by upto a factor of similar to 25, when using Hi data of resolution similar to 2 x 1 arcmin. One cluster star, M15 ZNG-1, was also observed in the Ca i (lambda(air) = 4226.728 Angstrom) and Ca ii (lambda(air) = 3933.663 Angstrom) lines. A column density ratio N(Ca i)/N(Ca ii) <0.03 was found, typical of values seen in the warm ionised interstellar medium. Towards this sightline, the IVC has a Nai/Ca ii column density ratio of &SIM; 0.25, similar to that observed in the local interstellar medium. Finally, we detect tentative evidence for IV absorption in Ki (?(air) = 7698:974 &ANGS) towards 3 cluster stars, which have N(K i)/N(H i) ratios of &SIM;0.5-3 x 10(-9).