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  • 1
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    A comprehensive study of the open cluster NGC 6866 (2015)
    Oxford University Press
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    Publication Date: 2015-08-25
    Description: We present CCD UBVRI photometry of the field of the open cluster NGC 6866. Structural parameters of the cluster are determined utilizing the stellar density profile of the stars in the field. We calculate the probabilities of the stars being physical members of the cluster, using their astrometric data, and perform further analyses using only the most probable members. The reddening and metallicity of the cluster were determined by independent methods. The LAMOST spectra and the ultraviolet excess of the F- and G-type main-sequence stars in the cluster indicate that the metallicity of the cluster is about the solar value. We estimated the reddening E ( B – V ) = 0.074 ± 0.050 mag using the U – B versus B – V two-colour diagram. The distance modula, the distance and the age of NGC 6866 were derived as μ = 10.60 ± 0.10 mag, d  = 1189 ± 75 pc and t  = 813 ± 50 Myr, respectively, by fitting colour–magnitude diagrams of the cluster with the PARSEC isochrones. The Galactic orbit of NGC 6866 indicates that the cluster is orbiting in a slightly eccentric orbit with e  = 0.12. The mass function slope x  = 1.35 ± 0.08 was derived by using the most probable members of the cluster.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Phytophthora manipulates a plant RNA helicase [Plant Biology] (2015)
    National Academy of Sciences
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    Publication Date: 2015-05-06
    Description: A broad range of parasites rely on the functions of effector proteins to subvert host immune response and facilitate disease development. The notorious Phytophthora pathogens evolved effectors with RNA silencing suppression activity to promote infection in plant hosts. Here we report that the Phytophthora Suppressor of RNA Silencing 1 (PSR1)...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    An independent test of the photometric selection of white dwarf candidates using LAMOST DR3 (2015)
    Oxford University Press
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    Publication Date: 2015-07-10
    Description: In previous work by Gentile Fusillo et al., we developed a selection method for white dwarf candidates which makes use of photometry, colours and proper motions to calculate a probability of being a white dwarf ( P WD ). The application of our method to the Sloan Digital Sky Survey (SDSS) data release 10 resulted in ~=66 000 photometrically selected objects with a derived P WD , approximately ~=21 000 of which are high-confidence white dwarf candidates. Here, we present an independent test of our selection method based on a sample of spectroscopically confirmed white dwarfs from the Large Sky Area Multi-Fiber Spectroscopic Telescope (LAMOST) survey. We do this by cross-matching all our ~=66 000 SDSS photometric white dwarf candidates with the over 4 million spectra available in the third data release of LAMOST. This results in 1673 white dwarf candidates with no previous SDSS spectroscopy, but with available LAMOST spectra. Among these objects, we identify 309 genuine white dwarfs. We find that our P WD can efficiently discriminate between confirmed LAMOST white dwarfs and contaminants. Our white dwarf candidate selection method can be applied to any multiband photometric survey and in this work we conclusively confirm its reliability in selecting white dwarfs without recourse to spectroscopy. We also discuss the spectroscopic completeness of white dwarfs in LAMOST, as well as deriving effective temperatures, surface gravities and masses for the hydrogen-rich atmosphere white dwarfs in the newly identified LAMOST sample.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    White dwarfs identified in LAMOST DR 2 (2015)
    Oxford University Press
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    Publication Date: 2015-10-16
    Description: Here we present a catalogue of 1056 spectroscopically identified hydrogen-dominated white dwarfs (DAWDs), 34 helium-dominated white dwarfs (DBWDs) and 276 white dwarf main sequence (WDMS) binaries from the Large sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey data release 2 (DR2). 383 DAWDs, 4 DBWDs and 138 WDMSs are new identifications after cross-match with literature. There are ~4100 k spectra in total from DR 2. The low ratio of white dwarfs found in LAMOST is attributed to biased selection of LAMOST input catalogue and much brighter targets relative to stars observed in Sloan Digital Sky Survey. In this paper, a new DAWD selection method is adopted as a new attempt and supplement to the traditional methods. The effective temperature, surface gravity, mass, cooling age and distance of high signal-to-noise DAWDs are estimated. The peak of the mass distribution is found to be ~0.6 M , which is consistent with previous work. The parameters of WDMS binaries are also provided in this paper. As the foundation of our future work, which is to identify more WDs with debris disc, WDs found in LAMOST showed a lot of potential. Interesting infrared-excess WDs will be reported in our forthcoming paper.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Quantum teleportation from light beams to vibrational states of a macroscopic diamond (2016)
    Springer Nature
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    Publication Date: 2016-06-02
    Description: Article Quantum teleportation has found important applications in quantum technologies, but pushing it to macroscopic objects is challenging because of the fragility of quantum states. Here, the authors demonstrate teleportation of states from light beams to the vibrational states of a macroscopic diamond sample. Nature Communications doi: 10.1038/ncomms11736 Authors: P.-Y. Hou, Y.-Y. Huang, X.-X. Yuan, X.-Y. Chang, C. Zu, L. He, L.-M. Duan
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 6
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    The LAMOST stellar parameter pipeline at Peking University - LSP3 (2015)
    Oxford University Press
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    Publication Date: 2015-02-12
    Description: We introduce the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) stellar parameter pipeline at Peking University – lsp3 , developed and implemented for the determinations of radial velocity V r and stellar atmospheric parameters (effective temperature T eff , surface gravity log  g , metallicity [Fe/H]) for the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC). We describe the algorithms of lsp3 and examine the accuracy of parameters yielded by it. The precision and accuracy of parameters yielded are investigated by comparing results of multi-epoch observations and of candidate members of open and globular clusters, with photometric calibration, as well as with independent determinations available from a number of external data bases, including the PASTEL archive, the APOGEE, SDSS and RAVE surveys, as well as those released in the LAMOST DR1. The uncertainties of lsp3 parameters are characterized and quantified as a function of the spectral signal-to-noise ratio (SNR) and stellar atmospheric parameters. We conclude that the current implementation of lsp3 has achieved an accuracy of 5.0 km s –1 , 150 K, 0.25 dex, 0.15 dex for the radial velocity, effective temperature, surface gravity and metallicity, respectively, for LSS-GAC spectra of FGK stars of SNRs per pixel higher than 10. The lsp3 has been applied to over a million LSS-GAC spectra collected hitherto. Stellar parameters yielded by the lsp3 will be released to the general public following the data policy of LAMOST, together with estimates of the interstellar extinction E ( B – V ) and stellar distances, deduced by combining spectroscopic and multiband photometric measurements using a variety of techniques.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Relative flux calibration for the LAMOST Spectroscopic Survey of the Galactic anticentre (2015)
    Oxford University Press
    Details
    Publication Date: 2015-02-05
    Description: We have developed and implemented an iterative algorithm of flux calibration for the LAMOST Spectroscopic Survey of the Galactic anticentre (LSS-GAC). For a given LSS-GAC plate, the spectra are first processed with a set of nominal spectral response curves (SRCs) and used to derive initial stellar atmospheric parameters (effective temperature T eff , surface gravity log  g and metallicity [Fe/H]) as well as dust reddening E ( B  –  V ) of all targeted stars. For each of the 16 spectrographs, several F-type stars with good signal-to-noise ratios are selected as flux standard stars for further, iterative spectral flux calibration. Comparison of spectrophotometric colours, deduced from the flux-calibrated spectra, with the photometric measurements yield average differences of 0.02 ± 0.07 and –0.04 ± 0.09 mag for ( g  –  r ) and ( g  –  i ), respectively. The relatively large negative offset in ( g  –  i ) is because we have opted not to correct for the telluric bands, most notably the atmospheric A band in the wavelength range of the i band. Comparison of LSS-GAC multi-epoch observations of duplicate targets indicates that the algorithm has achieved an accuracy of about 10 per cent in relative flux calibration for the wavelength range 4000–9000 Å. The shapes of SRCs deduced for individual LAMOST spectrographs vary by up to 30 per cent for a given night, and larger for different nights, indicating that the derivation of SRCs for the individual plates is essential to achieve accurate flux calibration for the LAMOST spectra.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Enhanced polarization of (11–22) semi-polar InGaN nanorod array structure (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-10-09
    Description: By means of a cost effective nanosphere lithography technique, an InGaN/GaN multiple quantum well structure grown on (11–22) semipolar GaN has been fabricated into two dimensional nanorod arrays which form a photonic crystal (PhC) structure. Such a PhC structure demonstrates not only significantly increased emission intensity, but also an enhanced polarization ratio of the emission. This is due to an effective inhibition of the emission in slab modes and then redistribution to the vertical direction, thus minimizing the light scattering processes that lead to randomizing of the optical polarization. The PhC structure is designed based on a standard finite-difference-time-domain simulation, and then optically confirmed by detailed time-resolved photoluminescence measurements. The results presented pave the way for the fabrication of semipolar InGaN/GaN based emitters with both high efficiency and highly polarized emission.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 9
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    Measure the distance and extinction for stars in LAMOST survey with Bayesian method (2015)
    Oxford University Press
    Details
    Publication Date: 2015-12-19
    Description: Using a Bayesian technique, which combines both photometric and spectral information, as well as prior knowledge on the Milky Way, we measured the distance and extinction for about one million stars in the first data release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey. Simulations have been performed based on the observed distributions for both the sky position and the magnitude, which show that the parallaxes have been underestimated by 10 per cent for dwarfs, while for giants the parallaxes have been overestimated by 15 per cent. The true fractional errors for dwarfs (giants) increase systematically with the fractional uncertainties in the output when the fractional uncertainties greater than ~0.4(0.5). A comparison with Hipparcos parallaxes and related clusters distance shows good agreement with our measurements. We also compared the distances with those of the empirical photometric parallax for main-sequence thin-disc stars, which reveal that the distances have been systematically underestimated due to uncertainties in the stellar parameters for cold dwarfs with T eff 〈 4500 K. The kinematic corrections introduced by Schönrich et al. from two proper motion catalogues, Position and Proper Motion Extended-L (PPMXL) and Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4), are calculated to detect and correct any systematic errors, which confirm the systematically underestimated distance for cold dwarfs, and the corrections from PPMXL are consistent with those from UCAC4 when the errors of proper motion are well accounted for. We also compared our extinction results with those of Berry et al., and the Rayleigh–Jeans Color Excess method. The extinction is well recovered over 4 mag.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    HST and LAMOST discover a dual active galactic nucleus in J0038+4128 (2014)
    Oxford University Press
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    Publication Date: 2014-03-21
    Description: We report the discovery of a kiloparsec-scale dual active galactic nucleus (AGN) in J0038+4128. From the Hubble Space Telescope ( HST ) Wide Field Planetary Camera 2 (WFPC2) images, we find two optical nuclei with a projection separation of 4.7 kpc (3.44 arcsec). The southern component (J0038+4128S) is spectroscopically observed with the HST Goddard High Resolution Spectrograph in the UV range and is found to be a Seyfert 1 galaxy with a broad Lyα emission line. The northern component (J0038+4128N) is spectroscopically observed during the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (also named the Guoshoujing Telescope) pilot survey in the optical range. The observed line ratios as well as the consistency of redshift of the nucleus emission lines and the host galaxy's absorption lines indicate that J0038+4128N is a Seyfert 2 galaxy with narrow lines only. These results thus confirm that J0038+4128 is a Seyfert 1–Seyfert 2 AGN pair. The HST WFPC2 F 336 W / U -band image of J0038+4128 also reveals for the first time for a dual AGN system two pairs of bi-symmetric arms, as are expected from the numerical simulations of such system. Being one of a few confirmed kiloparsec-scale dual AGNs exhibiting a clear morphological structure of the host galaxies, J0038+4128 provides a unique opportunity to study the co-evolution of the host galaxies and their central supermassive black holes undergoing a merging process.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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