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Upgraded photometric system on the 85-cm telescope at Xinglong station
摘要： The 85-cm telescope at Xinglong station is a prime focus system that operates well with high science outputs. The telescope has been upgraded since 2014 with a new corrector, and new filters and camera, which are provided by Beijing Normal University. The filter set is the Johnson-Cousins UBVRI system. We report the test results of the new system including bias, dark current, linearity, gain and readout noise of the CCD camera. Then we derive accurate instrumental calibration coefficients in UBVRI bands with Landolt standard stars during photometric nights. Finally, we give the limiting magnitudes with various exposure times and signal-to-noise ratios for observers as references.
关键词： CCD photometry,instrumentation,telescope
更新于2025-09-23 15:23:52
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Results of Photometric and Spectroscopic Observations of the Young Variable Star V730 Cep
摘要： We present the results of our photometric (V RI) and spectroscopic observations of the young variable star V730 Cep (MisV1147) classified by Uemura et al. (2004) as a Herbig Be star. Our photometry confirms the conclusion of the above authors that this star has a complex pattern of variability including periodic or quasi-periodic brightness variations with a period of about 14 days and deep Algol-like minima typical for UX Ori stars. Our spectroscopy shows that the classification of V730 Cep as a Herbig Be star is wrong. Actually, this star has a much lower temperature and belongs to the family of T Tauri stars. This allows us to explain the nature of the unusual photometric activity of V730 Cep based on a combination of two well-known models of variable circumstellar extinction applied to young stars: AA Tau- and UX Ori-type variability. It follows from our observations that the color tracks on the V ?(V ?I) color–magnitude diagram for these models slightly differ: the AA Tau-type variability of circumstellar extinction is caused by larger grains than the UX Ori-type variability. Such a difference can be due to an increase in the characteristic sizes of circumstellar dust as the star is approached and has a simple explanation: small dust grains evaporate faster than large ones.
关键词： optical photometry and spectroscopy,T Tauri and Herbig Be stars,activity mechanisms
更新于2025-09-23 15:22:29
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Reliability of Heterochromatic Flicker Photometry in Measuring Macular Pigment Optical Density among Preadolescent Children
摘要： Macular pigment optical density (MPOD)—assessed using customized heterochromatic flicker photometry (cHFP)—is related to better cognition and brain lutein among adults. However, the reliability of MPOD assessed by cHFP has not been investigated in children. We assessed inter-session reliability of MPOD using modified cHFP. 7–10-year-olds (n = 66) underwent cHFP over 2 visits using 11 examiners. Reliability was also assessed in a subsample (n = 46) with only 2 examiners. Among all participants, there was no significant difference between the two sessions (p = 0.59—session 1: 0.61 ± 0.28; session 2: 0.62 ± 0.27). There was no significant difference in the MPOD of boys vs. girls (p = 0.56). There was a significant correlation between sessions (Y = 0.52x + 0.31; R2 = 0.29, p ≤ 0.005), with a reliability of 0.70 (Cronbach’s α). Among the subsample with 2 examiners, there was a significant correlation between sessions (Y = 0.54x + 0.31; R2 = 0.32, p < 0.005), with a reliability of 0.72 (Cronbach’s α). In conclusion, there is moderate reliability for modified cHFP to measure MPOD in preadolescents. These findings provide support for future studies aiming to conduct noninvasive assessments of retinal xanthophylls and study their association with cognition during childhood.
关键词： retinal lutein,heterochromatic flicker photometry,macular pigment optical density
更新于2025-09-23 15:22:29
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Deep <i>R</i> -band counts of <i>z</i> ≈ 3 Lyman-break galaxy candidates with the LBT
摘要： Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different fields, Q0933, Q1623, and COSMOS, for a total area of ～1500 arcmin2. The data were obtained with the Large Binocular Camera on the Large Binocular Telescope. Methods. To select our Lyman-break galaxy (LBG) candidates, we adopted the well established and widely used color-selection criterion (U ? G vs. G ? R). One of the main advantages of our survey is that it has a wider dynamic color range for U-dropout selection than in previous studies. This allows us to fully exploit the depth of our R-band images, obtaining a robust sample with few interlopers. In addition, for 2 of our fields we have spectroscopic redshift information that is needed to better estimate the completeness of our sample and interloper fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band (5σ) and 28.6(AB) in the U band (1σ). This dataset was used to derive LBG candidates at z ≈ 3. We obtained a catalog with a total of 12 264 sources down to the 50% completeness magnitude limit in the R band for each field. We find a surface density of ～3 LBG candidates arcmin?2 down to R = 25.5, where completeness is ≥95% for all 3 fields. This number is higher than the original studies, but consistent with more recent samples.
关键词： surveys,ultraviolet: galaxies,galaxies: high-redshift,galaxies: photometry,catalogs
更新于2025-09-23 15:22:29
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Enzymatic method of urea determination in LTCC microfluidic system based on absorption photometry
摘要： In this paper a novel microanalytical system based on absorption photometry for urea determination in small-volume biological samples is described. The developed microsystem with built-in microreactor with urease immobilised on its surface was fabricated using low temperature co-fired ceramics (LTCC) technology. For detection of the ammonium ions – product of urea hydrolysis, the modified Berthelot’s reaction was applied and conditions of this reaction were optimised in a way to be suitable for analysis in microsystems and for particular application, with special regards to very small alternation of urea concentration in culture medium. The best results were obtained for reagent R1 composed of: 180 mM sodium salicylate, 15 mM sodium nitroprusside, 2 mM EDTA in phosphate buffer solution of pH 7 and reagent R2 containing 16.9 mM sodium hypochlorite in phosphate buffer solution of pH 12. Linear concentration range of urea detection with the use of the developed LTCC microfluidic system for the selected flow rate of 4 μl/min, was in the range up to 1 mM, and the calculated lower limit of detection – 0.002 mM. The developed microsystem enables urea determination in samples of post-culture medium and of cells lysates of minimised volume c.a. 1 μl. Preliminary studies related to determination of urea in real samples, performed using hepatic cells lysates and post-culture medium were successful. As reference methods, commercially available tests were applied. The determined urea concentration measured by means of the QuantiChrom? and BioMaxima test and by the developed method based on the LTCC microanalytical system differs by c.a. 9% and 2% respectively. To the best of our knowledge, this is the first urea analysis microsystem for use in cells culture studies characterised by: the smallest volume of sample – 1 μl, long lifetime with stable response - reduced by 14%, through experimental time span of 30 days as well as suitability for quasi-monitoring of cells in vitro with sampling rate - 6 samples per hour.
关键词： LTCC technology,enzymatic microreactor,microfluidic systems,lab-on-a-chip,enzymatic urea determination,absorption photometry
更新于2025-09-23 15:22:29
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The space photometry revolution and our understanding of RR Lyrae stars
摘要： The study of RR Lyrae stars has recently been invigorated thanks to the long, uninterrupted, ultra-precise time series data provided by the Kepler and CoRoT space telescopes. We give a brief overview of the new observational ?ndings concentrating on the connection between period doubling and the Blazhko modulation, and the omnipresence of additional periodicities in all RR Lyrae subtypes, except for non-modulated RRab stars. Recent theoretical results demonstrate that if more than two modes are present in a nonlinear dynamical system such as a high-amplitude RR Lyrae star, the outcome is often an extremely intricate dynamical state. Thus, based on these discoveries, an underlying picture of complex dynamical interactions between modes is emerging which sheds new light on the century-old Blazhko-phenomenon, as well. New directions of theoretical e?orts, like multidimensional hydrodynamical simulations, future space photometric missions and detailed spectroscopic investigations will pave the way towards a more complete understanding of the atmospheric and pulsation dynamics of these enigmatic touchstone objects.
关键词： RR Lyrae stars,space photometry,period doubling,additional periodicities,Blazhko modulation
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Colorimetric Characterization of Modern Mobile Displays
摘要： Due to the development of display technology higher and higher resolution devices are getting on the market. To characterize those high resolution display devices special measurement techniques are needed partly because most of them are handheld devices. Based on the recommendation of the International Committee for Display Metrology we have characterized some modern mobile displays and investigated how to choose the right application area of those devices. We have also tested if those devices would be proper to use them as diagnostic medical devices used by medical doctors.
关键词： AMOLED,colorimetry,mobile display,LED,photometry
更新于2025-09-23 15:21:21
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Estimating the relative contribution of streetlights, vehicles, and residential lighting to the urban night sky brightness
摘要： Under stable atmospheric conditions the brightness of the urban sky varies throughout the night following the time course of the anthropogenic emissions of light. Different types of artificial light sources (e.g. streetlights, residential, and vehicle lights) have specific time signatures, and this feature makes it possible to estimate the amount of brightness contributed by each of them. Our approach is based on transforming the time representation of the zenithal night sky brightness into a modal expansion in terms of time signatures of the different sources of light. The modal coefficients, and hence the absolute and relative contributions of each type of source, can be estimated by means of a linear least squares fit. A practical method for determining the time signatures of different contributing sources is also described, based on wide-field time-lapse photometry of the urban nightscape. Our preliminary results suggest that, besides the dominant streetlight contribution, artificial light leaking out of the windows of residential buildings may account for a significant share of the time-varying part of the zenithal night sky brightness at the measurement locations, whilst the contribution of the vehicle lights seems to be significantly smaller.
关键词： streetlights,urban night sky brightness,vehicles,light pollution,time-lapse photometry,residential lighting
更新于2025-09-23 15:21:01
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DustPedia: Multiwavelength photometry and imagery of 875 nearby galaxies in 42 ultraviolet-microwave bands
摘要： Aims. The DustPedia project is capitalising on the legacy of the Herschel Space Observatory, using cutting-edge modelling techniques to study dust in the 875 DustPedia galaxies – representing the vast majority of extended galaxies within 3000 km s?1 that were observed by Herschel. This work requires a database of multiwavelength imagery and photometry that greatly exceeds the scope (in terms of wavelength coverage and number of galaxies) of any previous local-Universe survey. Methods. We constructed a database containing our own custom Herschel reductions, along with standardised archival observations from GALEX, SDSS, DSS, 2MASS, WISE, Spitzer, and Planck. Using these data, we performed consistent aperture-matched photometry, which we combined with external supplementary photometry from IRAS and Planck. Results. We present our multiwavelength imagery and photometry across 42 UV-microwave bands for the 875 DustPedia galaxies. Our aperture-matched photometry, combined with the external supplementary photometry, represents a total of 21 857 photometric measurements. A typical DustPedia galaxy has multiwavelength photometry spanning 25 bands. We also present the Comprehensive & Adaptable Aperture Photometry Routine (CAAPR), the pipeline we developed to carry out our aperture-matched photometry. CAAPR is designed to produce consistent photometry for the enormous range of galaxy and observation types in our data. In particular, CAAPR is able to determine robust cross-compatible uncertainties, thanks to a novel method for reliably extrapolating the aperture noise for observations that cover a very limited amount of background. Our rich database of imagery and photometry is being made available to the community.
关键词： surveys,dust,catalogs,extinction,galaxies: photometry,galaxies: general,techniques: photometric
更新于2025-09-23 15:21:01
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Handbook of Exoplanets || HR8799: Imaging a System of Exoplanets
摘要： The HR 8799 planetary system is the most intriguing and spectacular system yet discovered by direct imaging. With four gas giant planets (5–7 MJ up) orbiting at wide separations (15–70 AU) from an unusual, young A star, HR 8799 serves as a Rosetta Stone for atmospheric and planet formation physics. With direct access to the light from the planets themselves, extensive photometric and spectroscopic studies of the system have been undertaken, painting a fascinating picture of cloud formation, nonequilibrium chemistry, and potential elemental abundance measurements that can constrain formation pathways. The dynamical structure of the system is complex, with the four massive planets likely stabilized through participation in mean-motion resonances. Two belts of debris flank the planets, with a warm belt analogous to the solar system asteroid belt and a wide, cold ring comparable to the Kuiper belt. HR 8799 will continue to be studied extensively from the ground and space in the coming years, with the exciting possibility that additional planets remain to be discovered in the system.
关键词： spectroscopy,exoplanets,dynamics,system architecture,planetary system,HR 8799,photometry,direct imaging,debris disk,atmospheric properties
更新于2025-09-23 15:21:01