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121.
A. Smith R. W. Atkins S. Bradbury O. Celik Y. C. K. Chow P. Cogan C. Dowdall S. J. Fegan P. Fortin D. Gall G. H. Gillanders J. Grube K. J. Gutierrez T. A. Hall D. Hanna J. Holder D. Horan S. B. Hughes T. B. Humensky I. Jung P. Kaaret G. Kenny M. Kertzman D. B. Kieda A. Konopelko H. Krawczynski F. Krennrich M. J. Lang S. Le Bohec G. Maier J. Millis P. Moriarty R. A. Ong J. S. Perkins K. Ragan G. H. Sembroski J. A. Toner L. Valcarcel V. V. Vassiliev R. G. Wagner S. P. Wakely T. C. Weekes R. J. White D. A. Williams 《Astrophysics and Space Science》2007,309(1-4):299-303
In this paper we present the results of the past two years observations on the galactic microquasar LS I +61 303 with the
Whipple 10 m gamma-ray telescope. The recent MAGIC detection of the source between 200 GeV and 4 TeV suggests that the source
is periodic with very high energy (VHE) gamma-ray emission linked to its orbital cycle. The entire 50-hour data set obtained
with Whipple from 2004 to 2006 was analyzed with no reliable detection resulting. The upper limits obtained in the 2005–2006
season covered several of the same epochs as the MAGIC Telescope detections, albeit with lower sensitivity. Upper limits are
placed on emission during the orbital phases of 0→0.1 and 0.8→1, phases which are not included in the MAGIC data set.
相似文献
122.
Douglas S. Hall Gregory W. Henry Dietmar Böhme Peter A. Brooks Sandy Chang Ales Dolzan George L. Fortier Robert E. Fried Russell M. Genet Bruce S. Grim James Hannon Darrel B. Hoff Kevin Krisciunas Howard J. Landis Howard P. Louth Larry P. Lovell Paul Nielsen Bobby E. Powell Harry D. Powell Don Pray Thomas R. Renner Charles W. Rogers Stephen Shervais Douglas M. Slauson Samuel Slote Harold J. Stelzer Arthur J. Stokes Jack C. Troeger Louis C. Turner Norman F. Wasson Kenneth W. Zeigler 《Journal of Astrophysics and Astronomy》1991,12(4):281-287
We present photoelectric photometry of λ And never before published, obtained between February 1982 and December 1990 at 29
different observatories. Then we combine it with all other photometry available to us (previously published, contained in
the I.A.U. Commission 27 Archives, and obtained with the Vanderbilt 16-inch automatic telescope but not yet published), to
yield a 14.8-year data base. Analysis reveals a long-term cycle in mean brightness, with a full range of 0m.15 and a period of 11.4 ± 0.4 years. Because most of our new photometry was concentrated in the 1983-84 observing season,
we analyze that one well-defined light curve with a two-spot model. Spot A keeps a 0m.04 amplitude throughout four rotation cycles whereas the amplitude of spot B diminishes from 0m.09 down almost to 0m.03. The spot rotation periods were 55d.9 ± 0d.6 and 520d.8 ± 1d.0, respectively. 相似文献
123.
Acoustic signals from small explosive charges have been measured with sonobuoys on twelve tracks in Australian northern shallow waters with the aim of assessing whether useful geoacoustic information could be obtained. Using the frequency band from 14 to 70 Hz, travel times of head waves were monitored, and the sound speeds and depths of corresponding interfaces in the seabed were derived. The water sound speed varied a little with range, and its depth dependence was allowed for by using its average value. Head waves from interfaces indistinguishable from the seafloor (the water/seabed interface) were detected on only three of the tracks, with derived sound speeds of 2100 to 2300 m/s. The first sub-bottom interfaces were from 50 to 600 m beneath the seafloor, and their sound speeds ranged from around 2000 m/s to 6400 m/s. Thus the head waves were from chalk or limestone, cemented sediments in which sound-speed gradients would be small. The amount of data obtained for the seafloor was limited by incoherence of the signals and, for some tracks, by excessive spacing between shots. The incoherence is generally attributed to multiple head waves that are individually unresolvable, while on two tracks there were indications of medal ground waves. Occasional anomalous data were obtained, but generally the assumptions of the simple interpretation method were found to be valid. Since no curvature in the range-time lines was observed, there was no evidence of sub-bottom sound-speed gradients being significant 相似文献
124.
125.
We present evidence of a large lake (Glacial Lake Victoria) that existed in Victoria Valley in the dry valleys region of Antarctica between at least 20 000 and 8600 14C yr BP. At its highstands, Glacial Lake Victoria covered 100 km2 and was ca. 200 m deep. The chronology for lake‐level changes comes from 87 AMS radiocarbon dates of lacustrine algae preserved in deltas and glaciolacustrine deposits that extend up to 185 m above present‐day lakes on the valley floor. The existence of Glacial Lake Victoria, as well as other large lakes in the dry valleys, indicates a climate regime significantly different from that of today at the last glacial maximum and in the early Holocene. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
126.
Gosselin Jeremy M. Dosso Stan E. Askan Aysegul Wathelet Marc Savvaidis Alexandros Cassidy John F. 《Journal of Seismology》2022,26(4):781-821
Journal of Seismology - Seismic site characterization attempts to quantify seismic wave behavior at a specific location based on near-surface geophysical properties, for the purpose of mitigating... 相似文献
127.
128.
BO Husφy 《极地研究(英文版)》2002,13(1)
1 IntroductionAtlatitudesaround 80°Nandinthemesosphere /lowerthermosphere (MLT) ,therehavebeenfewmeasurementsofneutraldynamics.ArequirementwasseenforlongtermcontinualmonitoringandaVHFmeteorradarwasidentifiedasbeingamostsuitableinstrument.RadarsliketheEISCA… 相似文献
129.
Microfossils in isolation basin sediments are frequently used to reconstruct sea‐level change, but preservation problems and non‐analogue situations can limit their usefulness. Here we investigate the potential of stable carbon isotopes (δ13C) and C/N ratios from bulk organic matter, as an alternative proxy of salinity within isolation basin sediments from a basin in northwest Scotland. Within the Holocene sediment δ13C and C/N are determined largely by the mean weighted values of the predominant source of the organic material. Analysis of modern materials and comparison with the diatom record shows that the marine parts of the sequence are dominated by high δ13C and variable C/N. In the fresh water sequences the organic material is a mixture of both freshwater aquatic and terrestrial plant input that have relatively low δ13C and high C/N. The application of δ13C and C/N ratios in the studied basin in general follow the environmental change recorded by the diatoms and shows the potential of bulk organic matter in the investigation of salinity change in isolation basins. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
130.
Y.-F. Yuan Jeremy S. Heyl † 《Monthly notices of the Royal Astronomical Society》2005,360(4):1493-1505
We study the evolution of a rigidly rotating protoneutron star (PNS) with hyperons and nucleons or solely nucleons in its core due to the escape of trapped neutrinos. As the neutrinos escape, the core nucleonic neutron star (NS) expands and the stellar rotation slows. After the neutrinos escape, the range of the spin periods is narrower than the initial one, but the distribution is still nearly uniform. A PNS with hyperons, at the late stage of its evolution, keeps shrinking and spinning up until all the trapped neutrinos escape. Consequently, the distribution of the stellar initial spin periods is skewed towards shorter periods. If the hyperonic star is metastable, its rotational frequency accelerates distinguishedly before it collapses to a black hole. 相似文献