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4,097 results on '"Equivalent width"'

1. Local Scour Around Non-uniform Bridge Piers: Vortex Power Concept

Author

Veerappadevaru, G., Nagesh, M. A., Devasharma, H., di Prisco, Marco, Series Editor, Chen, Sheng-Hong, Series Editor, Vayas, Ioannis, Series Editor, Kumar Shukla, Sanjay, Series Editor, Sharma, Anuj, Series Editor, Kumar, Nagesh, Series Editor, Wang, Chien Ming, Series Editor, Nandagiri, Lakshman, editor, Narasimhan, M. C., editor, and Marathe, Shriram, editor

Published
2023
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2. Study on equivalent width of section coal pillar in rock burst coal seam under water-rich conditions

Author

ZHU Guang’an, SHI Zhixian, JIANG Qipeng, SU Boru

Subjects
rock burst, soaked coal pillar, equivalent width, bearing capacity, stress distribution, Mining engineering. Metallurgy, TN1-997
Abstract

Affected by the soaking of goaf water, the reduced bearing capacity of section coal pillar is not conducive to disaster prevention and control. In order to study the equivalent width of section coal pillar in rock burst coal seam under water-rich conditions, taking the 4-2 302 working face of a coal mine as an example, stress distribution characteristics and evolution laws of section coal pillars under immersion and natural water content conditions were analyzed by theoretical calculation, numerical simulation and engineering practice. The theoretical calculation results indicate that compared to immersion conditions, the width of the naturally water-bearing coal pillar decreased by 5.66 m, the width of the plastic zone decreased by 2.69 m, and the width of the elastic core zone decreased by 3.53 m. Furthermore, through numerical simulation and comparative analysis of stress peaks and ranges of 36 m immersed coal pillar and 26 m, 28 m, 30 m, 32 m with non-immersed coal pillar, it was found that the stress distribution curves of 30 m non-immersed coal pillar was similar to that of 36 m immersed coal pillar.

Published
2023
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5. Stellar Spectra

Author

Karttunen, Hannu, Kröger, Pekka, Oja, Heikki, Poutanen, Markku, Donner, Karl Johan, Karttunen, Hannu, editor, Kröger, Pekka, editor, Oja, Heikki, editor, Poutanen, Markku, editor, and Donner, Karl Johan, editor

Published
2017
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10. Diffusion in Magnetic Fields

Author

Michaud, Georges, Alecian, Georges, Richer, Jacques, Börner, Gerhard, Series editor, Burkert, Andreas, Series editor, Burton, W.B., Series editor, Coustenis, Athena, Series editor, Dopita, Michael A., Series editor, Leibundgut, Bruno, Series editor, Meynet, Georges, Series editor, Schneider, Peter, Series editor, Trimble, Virginia, Series editor, Ward-Thompson, Derek, Series editor, Robson, E. Ian, Series editor, Michaud, Georges, Alecian, Georges, and Richer, Jacques

Published
2015
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12. Sources of Astronomical Data

Author

Chattopadhyay, Asis Kumar, Chattopadhyay, Tanuka, Hilbe, Joseph M., Series editor, Babu, Jogesh, Series editor, Lauritzen, Steffen, Series editor, Chattopadhyay, Asis Kumar, and Chattopadhyay, Tanuka

Published
2014
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13. Thermal Shield

Author

Lei, Mingzhun, Song, Yuntao, Liu, Sumei, Du, Shijun, Ling, Frederick F., Editor-in-chief, Winer, Ward O., Series editor, Bergles, Arthur E., Series editor, Klutke, Georgia A., Series editor, Wang, Kuo K., Series editor, Finnie, Iain, Series editor, Welty, J. R., Series editor, Bryant, Michael D., Series editor, Yang, Henry T., Series editor, Mow, Van C., Series editor, Leckie, Frederick A., Series editor, Gross, Dietmar, Series editor, Song, Yuntao, Wu, Weiyue, and Du, Shijun

Published
2014
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14. Radial Velocity Variations of the Na I D Lines for the High-Latitude Supergiant Star 89 Her.

Author

Khalilov, A. M., Hasanova, A. R., and Hajiyeva, G. M.

Subjects
*VELOCITY, *STELLAR atmospheres, *SUPERGIANT stars, *SODIUM compounds, *SPECTROGRAMS
Abstract

The variations in the spectral parameters of the sodium doublet Na I D line of the high-latitude supergiant 89 Her were investigated on the basis of the spectrograms obtained at the 2-m telescope of Shamakhy Astrophysical Observatory for 1975–2017. The research has shown that, in addition to shorter periodic changes, which were found earlier by various authors, there are also long-period changes in the atmosphere of this star. It has been found that the sodium doublet Na I D line's radial velocity of the absorption component varies with a period of 5000 days. The orbital elements of the binary system were determined for the first time within the spectral-binary system model. [ABSTRACT FROM AUTHOR]

Published
2019
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15. The 6.7 keV thermal emission lines in the stellar flare spectra of two chromospherically active Binaries: Algol and GT Mus

Author

Ambrose Chukwudi Eze, Chikwem Obinna Goodwill, Sudum Esaenwi, and Fidelis Okey Madu

Subjects
Physics, Atmospheric Science, Astrophysics::High Energy Astrophysical Phenomena, Galactic ridge, Starspot, Aerospace Engineering, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Galactic plane, Galaxy, law.invention, Luminosity, Geophysics, Space and Planetary Science, law, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, General Earth and Planetary Sciences, Emission spectrum, Equivalent width, Astrophysics::Galaxy Astrophysics, Flare
Abstract

Chromospherically active binaries’ (CABs) are late-type evolved stars with strong chromosphere/coronae and high flare activity levels. Starspot evolution in these CABs and binaries reveals strong stellar and chromospheric activities. In binaries, the tidal interaction via the internal dynamo motion, during rapid rotation of the component stars generates magnetic fields. The magnetic activity heats the tenuous coronal plasma, and the reconnection of energetic particles leads to stellar flare formation. Cyclic-variation signatures in brightness and emission lines are indicators of coronal/chromospheric activities. The spatial population densities of CABs are large, and their hard energy spectral characteristics are prominent in our galaxy. Photo-ionization/collisional excitation processes in the coronae of CABs generate a strong thermal emission line at 6.7 keV. In the present work, we re-analyzed stellar flare data of two CABs (Algol & GT Muscae) observed with Suzaku. We resolved the 6.7 keV emission spectrum and equivalent width (EW) in each source’s stellar flare data. The resolved energy spectra are remarkably similar to that of the hard energy spectra at 6.7 keV of X-ray point sources observed in different Galactic regions. The EW of the 6.7 keV emission line obtained in this work compares favorably with the EW range (260 eV – 980 eV) of the 6.7 keV energy spectra of Galactic point sources. Hence, cumulative X-ray emission lines of coronal plasma (and their EWs) emitted by numerous point sources in different Galactic plane positions give clues on the Galactic Ridge X-ray Emission (GRXE) mechanism. We are of the view that CABs could account for a large number of fast-transient X-ray sources that emit thermal emission line at 6.7 keV during their quiescent and flared phases, and these underlying population sources could contribute significantly to the total luminosity of 6.7 keV GRXE.

Published
2022
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30. Modern optical measurements

Author

Brosch, Noah, Burton, W. B., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Ehrenfreund, P., editor, Engvold, O., editor, Heck, A., editor, Van Der Heuvel, E.P.J., editor, Kaspi, V. M., editor, Kuijpers, J. M. E., editor, Van Der Laan, H., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Somov, B. V., editor, Sunyaev, R. A., editor, and Brosch, Noah

Published
2008
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32. Spectroscopy of QSO Pairs

Author

Ellison, Sara L., Leibundgut, Bruno, editor, Santos, Nuno C., editor, Pasquini, Luca, editor, Correia, Alexandre C. M., editor, and Romaniello, Martino, editor

Published
2008
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34. Upper limits on the escape fraction of ionizing radiation from galaxies at 2 ≲ z < 6

Author

L. J. Prichard, Emma V. Ryan-Weber, J. Cooke, U. Meštrić, Marc Rafelski, and Robert Bassett

Subjects
Physics, 010308 nuclear & particles physics, Flux, Astronomy and Astrophysics, Astrophysics, Join (topology), Lambda, 01 natural sciences, Redshift, Galaxy, Space and Planetary Science, 0103 physical sciences, Dark Ages, 010303 astronomy & astrophysics, Reionization, Equivalent width
Abstract

In this work, we investigate upper limits on the global escape fraction of ionizing photons ($f_{\rm esc/global}^{\rm abs}$) from a sample of galaxies probed for Lyman-continuum (LyC) emission characterized as non-LyC and LyC leakers. We present a sample of nine clean non-contaminated (by low-redshift interlopers, CCD problems, and internal reflections of the instrument) galaxies that do not show significant (>3σ) LyC flux in the range 880

Published
2021
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35. Estimating Teff, radius, and luminosity of M-dwarfs using high-resolution optical and NIR spectral features

Author

Ramkrishna Das, Dhrimadri Khata, T. Baug, and Soumen Mondal

Subjects
Physics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Radius, Effective temperature, Spectral line, Luminosity, Root mean square, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Equivalent width, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Line (formation)
Abstract

We estimate effective temperature ($T_{\rm eff}$), stellar radius, and luminosity for a sample of 271 M-dwarf stars (M0V-M7V) observed as a part of CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) radial-velocity planet survey. For the first time, using the simultaneously observed high resolution (R$\sim90000$) spectra in the optical (0.52 - 0.96 $\mu$m) and near-infrared (0.96 - 1.71 $\mu$m) bands, we derive empirical calibration relationships to estimate the fundamental parameters of these low-mass stars. We select a sample of nearby and bright M-dwarfs as our calibrators for which the physical parameters are acquired from high-precision interferometric measurements. To identify the most suitable indicators of $T_{\rm eff}$, radius, and luminosity (log $L/L_{\odot}$), we inspect a range of spectral features and assess them for reliable correlations. We perform multivariate linear regression and find that the combination of pseudo equivalent widths and equivalent width ratios of the Ca II at 0.854 $\mu$m and Ca II at 0.866 $\mu$m lines in the optical and the Mg I line at 1.57 $\mu$m in the NIR give the best fitting linear functional relations for the stellar parameters with root mean square errors (RMSE) of 99K, 0.06 $R_{\odot}$ and 0.22 dex respectively. We also explore and compare our results with literature values obtained using other different methods for the same sample of M dwarfs., Comment: 12 pages, 7 figures and 7 tables; accepted on July 24, 2021 for publication in MNRAS

Published
2021
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36. Assessing the sources of reionization: a spectroscopic case study of a 30× lensed galaxy at z ∼ 5 with Lyα, C <scp>iv</scp>, Mg <scp>ii</scp>, and [Ne <scp>iii</scp>]

Author

Mark Swinbank, Nicolas Laporte, Mirko Curti, Johan Richard, Richard Massey, Roberto Maiolino, Renske Smit, Joris Witstok, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Active galactic nucleus, Metallicity, first stars, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, galaxies: high-redshift, 0103 physical sciences, dark ages, 010303 astronomy & astrophysics, Reionization, Astrophysics::Galaxy Astrophysics, Physics, Very Large Telescope, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, gravitational lensing: strong, Astronomy and Astrophysics, Galaxy, Redshift, Gravitational lens, [SDU]Sciences of the Universe [physics], Space and Planetary Science, reionization, methods: observational, Equivalent width, techniques: spectroscopic
Abstract

We present a detailed spectroscopic analysis of a galaxy at z ≃ 4.88 that is, by chance, magnified ∼30× by gravitational lensing. Only three sources at z ≳ 5 are known with such high magnification. This particular source has been shown to exhibit widespread, high equivalent width ${{\rm C\, \small {IV}}}\ \lambda 1549\, \mathring{\rm A}$ emission, implying it is a unique example of a metal-poor galaxy with a hard radiation field, likely representing the galaxy population responsible for cosmic reionization. Using ultraviolet (UV) nebular line ratio diagnostics, Very Large Telescope (VLT)/X-shooter observations rule out strong active galactic nuclei (AGN) activity, indicating a stellar origin of the hard radiation field instead. We present a new detection of ${[{\rm Ne\, \small {III}}]}\ \lambda 3870\, \mathring{\rm A}$ and use the [${\rm Ne\, \small {III}}$]/[${\rm O\, \small {II}}$] line ratio to constrain the ionization parameter and gas-phase metallicity. Closely related to the commonly used [${\rm O\, \small {III}}$]/[${\rm O\, \small {II}}$] ratio, our [${\rm Ne\, \small {III}}$]/[${\rm O\, \small {II}}$] measurement shows this source is similar to local ‘Green Pea’ galaxies and Lyman-continuum leakers. It furthermore suggests this galaxy is more metal poor than expected from the fundamental metallicity relation, possibly as a consequence of excess gas accretion diluting the metallicity. Finally, we present the highest redshift detection of ${{\rm Mg\, \small {II}}}\ \lambda 2796\, \mathring{\rm A}$, observed at high equivalent width in emission, in contrast to more evolved systems predominantly exhibiting ${\rm Mg\, \small {II}}$ absorption. Strong ${\rm Mg\, \small {II}}$ emission has been observed in most z ∼ 0 Lyman-continuum leakers known and has recently been proposed as an indirect tracer of escaping ionizing radiation. In conclusion, this strongly lensed galaxy, observed just $300\, \mathrm{Myr}$ after reionization ends, enables testing of observational diagnostics proposed to constrain the physical properties of distant galaxies in the James Webb Space Telescope (JWST)/Extremely Large Telescope (ELT) era.

Published
2021
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38. Stellar Spectra and Radiation Fields

Author

Kogure, Tomokazu, Leung, Kam-Ching, Burton, W. B., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Ehrenfreund, P., editor, Engvold, O., editor, Heck, A., editor, van den Heuvel, E. P. J., editor, Kaspi, V. M., editor, Kuijpers, J. M. E., editor, van der Laan, H., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Kogure, Tomokazu, and Leung, Kam-Ching

Published
2007
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43. Stellar Spectra

Author

Karttunen, Hannu, editor, Kröger, Pekka, editor, Oja, Heikki, editor, Poutanen, Markku, editor, and Donner, Karl Johan, editor

Published
2007
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46. Automated Spectral Classification of QSOs and Galaxies by Radial Basis Function Network with Dynamic Decay Adjustment

Author

Zhao, Mei-fang, Yang, Jin-fu, Wu, Yue, Wu, Fu-chao, Luo, Ali, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Wang, Jun, editor, Yi, Zhang, editor, Zurada, Jacek M., editor, Lu, Bao-Liang, editor, and Yin, Hujun, editor

Published
2006
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48. THE HIDDEN LIFE OF MASSIVE STARS

Author

Lenorzer, A., Bik, A., Mokiem, M.R., de Koter, A., Kaper, L., Waters, L.B.F.M., Del Toro Iniesta, J.C., editor, Alfaro, E.J., editor, Gorgas, J.G., editor, Salvador-Solé, E., editor, and Butcher, H., editor

Published
2006
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49. Near-IR Super Star Clusters in Starburst and Luminous Infrared Galaxies

Author

Alonso-Herrero, Almudena, Burton, W.B., editor, Kuijpers, J. M. E., editor, Van Den Heuvel, E. P. J., editor, Van Der Laan, H., editor, Bahcall, J. N., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Engvold, O., editor, Heck, A., editor, McCray, R., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Sato, K., editor, Shu, F. H., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Tanaka, Y., editor, Tremaine, S., editor, Weiss, N. O., editor, De Grijs, Richard, editor, and González Delgado, Rosa M., editor

Published
2005
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