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I. Horváth B. G. Tóth J. Hakkila L. V. Tóth L. G. Balázs I. I. Rácz S. Pintér Z. Bagoly 《Astrophysics and Space Science》2018,363(3):53
GRB 170817A, associated with the LIGO-Virgo GW170817 neutron-star merger event, lacks the short duration and hard spectrum of a Short gamma-ray burst (GRB) expected from long-standing classification models. Correctly identifying the class to which this burst belongs requires comparison with other GRBs detected by the Fermi GBM. The aim of our analysis is to classify Fermi GRBs and to test whether or not GRB 170817A belongs—as suggested—to the Short GRB class. The Fermi GBM catalog provides a large database with many measured variables that can be used to explore gamma-ray burst classification. We use statistical techniques to look for clustering in a sample of 1298 gamma-ray bursts described by duration and spectral hardness. Classification of the detected bursts shows that GRB 170817A most likely belongs to the Intermediate, rather than the Short GRB class. We discuss this result in light of theoretical neutron-star merger models and existing GRB classification schemes. It appears that GRB classification schemes may not yet be linked to appropriate theoretical models, and that theoretical models may not yet adequately account for known GRB class properties. We conclude that GRB 170817A may not fit into a simple phenomenological classification scheme. 相似文献
44.
S. Jejčič P. Heinzel N. Labrosse A. N. Zhukov A. Bemporad S. Fineschi S. Gunár 《Solar physics》2018,293(2):33
We determine the optimal width and shape of the narrow-band filter centered on the He?i D3 line for prominence and coronal mass ejection (CME) observations with the ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy) satellite, to be launched in 2020. We analyze He?i D3 line intensities for three representative non-local thermal equilibrium prominence models at temperatures 8, 30, and 100 kK computed with a radiative transfer code and the prominence visible-light (VL) emission due to Thomson scattering on the prominence electrons. We compute various useful relations at prominence line-of-sight velocities of 0, 100, and 300 km?s?1 for 20 Å wide flat filter and three Gaussian filters with a full-width at half-maximum (FWHM) equal to 5, 10, and 20 Å to show the relative brightness contribution of the He?i D3 line and the prominence VL to the visibility in a given narrow-band filter. We also discuss possible signal contamination by Na?i D1 and D2 lines, which otherwise may be useful to detect comets. Our results mainly show that i) an optimal narrow-band filter should be flat or somewhere between flat and Gaussian with an FWHM of 20 Å in order to detect fast-moving prominence structures, ii) the maximum emission in the He?i D3 line is at 30 kK and the minimal at 100 kK, and iii) the ratio of emission in the He?i D3 line to the VL emission can provide a useful diagnostic for the temperature of prominence structures. This ratio is up to 10 for hot prominence structures, up to 100 for cool structures, and up to 1000 for warm structures. 相似文献
45.
Sacit Özdemir Cahit Yeşilyaprak Bahadır Aktuğ Derya Öztürk Deniz Çoker Recep Balbay 《Experimental Astronomy》2018,46(2):323-336
We present preliminary statistics on the precipitable water vapor (PWV) content over the Karakaya Hills in Erzurum city, where the largest optical and near-infrared astronomical telescope in Turkey will be operated. Since the observatory will observe in the near-infrared (NIR), it is intended to perform PWV measurements of the atmosphere above the site by using signal delays in Global Positioning System (GPS) communication. The analysis of the GPS data recorded on the summit for almost one year shows that the atmosphere over the site of the observatory, which has an altitude of 3170 m, has favorable conditions for NIR observations. From GPS measurements, we report that the site had an average PWV of 3.2 mm and a median PWV of 2.7 mm between October 6, 2016, and June 15, 2017. We also present the time dependency of the PWV content and the correlations between the amount of PWV and the other meteorological records gathered from radiosonde flights and ground-based measurements. 相似文献
46.
Recursive algorithms for the computation of the potential harmonic coefficients of a constant density polyhedron 总被引:1,自引:0,他引:1
Dimitrios Tsoulis Olivier Jamet Jérôme Verdun Nicolas Gonindard 《Journal of Geodesy》2009,83(10):925-942
The gravitational potential of a constant density general polyhedron can be expressed both in terms of a closed analytical expression and as a series expansion involving the corresponding spherical harmonic coefficients. The latter can be obtained from two independent algorithms, which differ not only in their algorithmic architecture but in their efficiency and overall performance, especially when computing the coefficients of higher degree and order. In the present paper a comparative study of all these three approaches is carried out focusing on the numerical implementation of the recursive relations appearing in the two algorithms for the computation of the polyhedral potential harmonic coefficients. The performed numerical investigations show that the linear algorithm proposed by Jamet and Thomas (Proceedings of the second international GOCE user workshop, ‘GOCE, The Geoid and Oceanography’, ESA-ESRIN, Frascati, Italy, 8–10 March 2004, ESA SP-569, 2004), but so far not implemented, achieves a reasonable accuracy at a computational expense that opens to practical applications, for instance in the field of satellite gravimetry/gradiometry interpretation. The convergence behavior of the linear recursion algorithm is studied thoroughly and a computational procedure is proposed that enables the stable computation of potential harmonic coefficients up to degree 60 when referring to an arbitrarily shaped polyhedral body. 相似文献
47.
The Arctic is more vulnerable to climate change than are mid latitudes. Therefore, palaeolimnological studies from the High Arctic are important in providing insights into the dynamics of the climate system. Here we present a multi‐proxy study from one of the world's northernmost lakes: Bliss Lake, Peary Land, Greenland. The early Holocene (10 850–10 480 cal. a BP) is characterized by increased erosion and gradually more marine conditions. Full marine conditions developed from 10 480 cal. a BP until the lake was isolated at 7220 cal. a BP. From its marine isolation at 7220 cal. a BP Bliss Lake becomes a lacustrine environment. Evidence from geochemical proxies (δ13C and total organic carbon) suggests that warmer conditions prevailed between 7220 and 6500 cal. a BP, corresponding to the Holocene thermal maximum, and from 3300 until 910 cal. a BP. From 850 to 500 cal. a BP colder climate conditions persisted. The transition from warmer to colder climate conditions taking place around 850 cal. a BP may be associated with the transition from the Medieval Warm Period to the Little Ice Age. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
48.
Dr. T. H. C. Nutte Dr. T. Oberthür Dr. R. Saager Dr. H. -P. Tomschi 《Mineralogy and Petrology》1988,39(2):145-162
Summary At Broomstock Mine, three types of gold mineralization have been identified: (i) jaspilite-hosted ore, (ii) ore confined to shear zones within meta-basalts, and (iii) supergene ore. The present study, which is focused on the jaspilite-hosted ore, revealed that areas carrying economic gold grades are characterized by fracturing, brecciation and abundant arsenopyrite-pyrite mineralization. The mineralization was introduced by hydrothermal fluids which used dilatant fractures in the jaspilites as channelways. Deposition of gold and sulfides occurred in response to changing P-T conditions and through chemical reactions of the fluids with the iron-rich jaspilites. Gold and accompanying elements may either originate from processes of intraformational remobilization, or they were derived from external, distant sources.r>
Geologie, Mineralogie und Geochemie der Goldlagerstätte Broomstock im Kwekwe Greenstone Belt, Zimbabwe: Bedeutung für Goldvererzung in jaspitischen Eisenformationen
Zusammenfassung In der Broomstock Mine treten drei Typen von Goldmineralisationen auf: (i) Vererzungen in Jaspiliten, (ii) Vererzungen in Scherzonen, die Metabasalte durchsetzen, und (iii) supergene Vererzungen.Die vorliegende Untersuchung befaßt sich vornehmlich mit den Vererzungen der Jaspilite. Kartierungen und Beprobungen zeigten, daß ökonomische Goldgehalte an Be-reiche der Jaspilite gebunden sind, die tektonisch zerbrochen und brekziiert sind. Zudem treten in diesen Bereichen Arsenkies und Pyrit in hohen Konzentrationen auf. Die Mineralisation stellt den Absatz hydrothermaler Lösungen dar, die dilatante Bruchzonen innerhalb der Jaspilite als Zufuhrkanäle benutzten. Der Absatz der Sulfide und des Goldes erfolgte aufgrund sich ändernder P-T-Bedingungen und durch chemische Reaktionen zwischen den Lösungen und den eisenreichen Jaspiliten. Als Modell zur Herkunft des Goldes und der begleitenden Elemente wird entweder eine intraformationale Umlagerung, oder eine Zufuhr aus externen, entfernteren Quellen angenommen.相似文献
49.
Theo de Crook Vladimír Schenk M. S. Barbano F. Colombo J. J. Egozcue M. García-Fernández P. Kottnauer G. Leydecker F. Mantlík Z. Schenková G. Zonno 《Natural Hazards》1989,2(3-4):229-236
The algorithms to evaluate seismic hazard, used and/or developed by five teams participating in the TERESA project, applied to the low seismicity area rc="/content/w7q55275771x8532/xxlarge8216.gif" alt="lsquo" align="BASELINE" BORDER="0">Belgium, The Netherlands and NW Germanyrc="/content/w7q55275771x8532/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> are compared. The main differences in the results can be explained by the majority criterion of Egozcue et al. (1989), the differences in the upper bound and zonification and, in some cases, by a higher attenuation. 相似文献
50.
Summary The Alcsutdoboz-2 (AD-2) core contains 12 magmatic dykes which belong to the Late Cretaceous lamprophyric-carbonatitic association of NE Transdanubia, Hungary. Petrographically, 11 dykes can be considered alkaline lamprophyre (mainly monchiquite), and the remainder might be called carbonatite. The lamprophyre dykes are similar to both alkaline lamprophyres and ultramafic lamprophyres in major element composition, whereas the carbonatite dyke has some features that are similar to carbonatites but others that are dissimilar. Nevertheless, both of the two types of AD-2 dykes possess higher LILE content than the ultramafc lamprophyres and kimberlites, but strongly differ from average carbonatite. Based on the REE pattern, crystal fractionation (mainly of olivine) and separation of a carbonate phase from the parental lamprophyric magma are proposed for genesis of the carbonatite dyke. These characteristics and the compositional zoning of clinopyroxene and mica suggest a complex crystallization history for these dykes. The likeliest origin for the parental lamprophyric melt is through a very small degree of partial melting of metasomatized mantle.r>
Alkalische Lamprophyre und assoziierte Ganggesteine in Nordost-Transdanubien, Ungarn: die Bohrung Alcsutdoboz-2 (AD-2)
Zusammenfassung Der Kern der Bohrung Alcsutdoboz-2 (AD-2) enthält zwölf magmatische Gänge, die zu der jung-kretazischen Lamprophyr-Karbonatit-Assoziation des nordöstlichen Transdanubiens in Ungarn gehören. Petrographisch gesehen gehören elf Gänge zu den alkalischen Lamprophyren (hauptsächlich Monchiquit), und der Rest kann als Karbonatit bezeichnet werden. Die Lamprophyrgänge sind in ihrer Hauptelementzusammensetzung sowohl alkalischen Lamprophyren wie ultramafschen Lamprophyren ähnlich. Der Karbonatitgang hingegen zeigt Parameter, die denen von Karbonatiten teilweise, aber nicht durchwegs, ähnlich sind. Beide Typen der AD-2-Gänge zeigen höhere LILE-Gehalte als ultramafische Lamprophre und Kimberlite, unterscheiden sich aber deutlich vom durchschnittlichen Karbonatit. Auf der Basis der Seltenen ErdVerteilung, werden Kristallfraktionierung (hauptsächlich von Olivin) und Abtrennung einer Karbonatphase von lamprophyrischen Magma als Vorgänge gesehen, die für die Entstehung der Karbonatit-Gänge relevant sind. Diese Aspekte und die Zonierung der Zusammensetzungen von Klinopyroxen und Glimmer weisen auf eine komplexe Kristallisationsgeschichte dieser Gänge hin. Sehr wahrscheinlich ist die lamprophyrische Ausgangsschmelze durch eine geringfügige teilweise Aufschmelzung von metasomatisiertem Mantel entstanden.相似文献