Temporal X-ray astronomy with a pinhole camera     

Stephen S. Holt 《Astrophysics and Space Science》1976,42(1):123-141

The first preliminary results from the Ariel-5 All-Sky X-Ray Monitor are presented, along with sufficient experiment details to define the experiment sensitivity. Periodic modulation of the X-ray emission is investigated from three sources with which specific periods have been associated, with the results that the 4.8 h variation from Cyg X-3 is confirmed, a long-term average 5.6 day variation from Cyg X-1 is discovered, and no detectable 0.787 day modulation of Sco X-1 is observed. Consistency of the long-term Sco X-1 emission with a shot-noise model is discussed, wherein the source behavior is shown to be interpretable as 100 flares per day, each with a duration of several hours. A sudden increase in the Cyg X-1 intensity by almost a factor of three on 22 April, 1975 is reported, after 5 months of relative source constancy. The light curve of a bright nova-like transient source in Triangulum is presented, and compared with previously observed transient sources. Preliminary evidence for the existence of X-ray bursts with duration <1 h is offered, with the caveat that there is not yet any supporting evidence to guarantee that the effect is truly astronomical.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.  相似文献   

The dynamics of western North America: stress magnitudes and the relative role of gravitational potential energy, plate interaction at the boundary and basal tractions     

Lucy M. Flesch  William E. Holt  A. John Haines  Lianxing Wen  Bingming Shen-Tu 《Geophysical Journal International》2007,169(3):866-896

  相似文献   

A Seasonal Statistical Evaluation of COAMPS® over the Arabian Gulf Region     

Rebecca E. Eager  Sethu Raman  Teddy R. Holt  Douglas Westphal  Jeffrey Reid  Jason Nachamkin  Ming Liu  Abdulla Al Mandoos 《Pure and Applied Geophysics》2007,164(8-9):1747-1764

A statistical evaluation of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS^®) was performed over the Arabian Gulf region for the period, 1 August to 5 October, 2004. Verification skill scores of bias and root-mean-square error were estimated for surface variables and for vertical profiles to investigate any diurnal variations. The model predictions of boundary-layer heights are compared with the observations at Abu Dhabi, United Arab Emirates. The Middle East presents challenges to numerical weather prediction due to complex land-ocean-land mesoscale processes. An independent data set of surface measurements from 50 stations in the UAE was available from the Department of Water Resources Studies, Abu Dhabi for model verification. The results indicate a diurnal variation in the model errors. The errors are small considering the magnitudes of the observed variables. Errors in the coastal region can be attributed to the differences in the timing of the onset of sea and land breeze circulations in the simulations as compared to the observations. Errors are relatively smaller in the offshore locations.  相似文献   

Microwave links: The future for urban rainfall measurement?     

G.J.G. Upton  A.R. Holt  R.J. Cummings  A.R. Rahimi  J.W.F. Goddard   《Atmospheric Research》2005,77(1-4):300

Microwave links are ideally suited to the urban environment, since there are many suitable vandal-free locations to which the receiver and transmitter can be attached. A signal sent along a link is received with reduced power as a consequence of scattering and absorption by intervening water droplets. Thus a measurement of the power loss can be transformed into a measure of total path rainfall. This paper discusses the requirements for the estimation process to be accurate. The paper presents results using a single frequency, together with the improved results from a dual-frequency link. Potential future applications of microwave links are presented.  相似文献   

Letter     

Sidney J. Holt 《Marine pollution bulletin》1984,15(4):161-162

  相似文献   

Highly extinguished emission line outflows in the young radio source PKS 1345+12     

J. Holt  C. N. Tadhunter  R. Morganti 《Monthly notices of the Royal Astronomical Society》2003,342(1):227-238

  相似文献   

Chandra observations of Tycho’s supernova remnant     

U. Hwang  R. Petre  A. E. Szymkowiak  S. S. Holt 《Journal of Astrophysics and Astronomy》2002,23(1-2):81-87

We present a newChandra observation of Tycho’s supernova remnant with the Advanced CCD Imaging Spectrometer. Multicolor Xray imaging reveals new details of the outer shock and ejecta. At energies between 4 and 6 keV, the outline of the outer shock is clearly revealed in X-rays for the first time. The distribution of the emission from lines of Si and Fe are confirmed to have a different morphology from each other, and the Si ejecta are shown to extend to the blast shock at several locations. Characteristic spectra of the outer shock and ejecta are also presented.  相似文献   

High-redshift QSOs in the FIRST survey     

C.R. Benn  M. Vigotti  M. Pedani  J. Holt  K.-H. Mack  R. Curran  S.F. Sánchez 《Monthly notices of the Royal Astronomical Society》2002,329(1):221-226

In a pilot search for high-redshift radio quasi-stellar objects (QSOs), we have obtained spectra of 55 FIRST sources     with very red     starlike optical identifications. 10 of the candidates are QSOs with redshifts     (four were previously known), six with     . The remaining 45 candidates comprise: one     broad-absorption-line (BAL) QSO; three low-redshift galaxies with narrow emission lines; 18 probable radio galaxies; and 23 M stars (mainly misidentifications). The success rate (high-redshift QSOs / spectroscopically-observed candidates) for this search is 1/2 for     , and 1/9 for     . With an effective search area of 4030 deg², the surface density of high-redshift     QSOs discovered with this technique is 0.0015 deg⁻².  相似文献   

Can saltwater toxicity be predicted from freshwater data?   总被引：3，自引：0，他引：3  

K M Leung  D Morritt  J R Wheeler  P Whitehouse  N Sorokin  R Toy  M Holt  M Crane 《Marine pollution bulletin》2001,42(11):1007-1013

The regulation of substances discharged to estuarine and coastal environments relies upon data derived from ecotoxicity tests. Most such data are generated for freshwater rather than saltwater species. If freshwater toxicity data are related to saltwater toxic effects in a systematic and predictable way, the former can be used to predict the latter. This would have economic advantages due to a reduction in toxicity testing of saltwater species. If toxicity data are plotted as species sensitivity distributions, four theoretical relationships between freshwater and saltwater can be envisaged. Examples show that each one of these relationships is supported by empirical data. These examples show that although there is considerable potential for freshwater to saltwater prediction, species parity and representativeness need to be examined for each chemical substance to avoid bias.  相似文献   

Calving retreat and proglacial lake growth at Hooker Glacier,Southern Alps,New Zealand     

Clare M. Robertson  Martin S. Brook  Kat A. Holt  Ian C. Fuller  Douglas I. Benn 《New Zealand geographer》2013,69(1):14-25

Hooker Glacier in the central Southern Alps of New Zealand has undergone significant downwasting and recession (～2.14 km) during the last two centuries. High retreat rates (51 m a^?1 1986–2001, 43 m a^?1 2001–2011) have produced a large (1.22 km²) proglacial lake. We present a retreat scenario for Hooker Glacier. A retreat scenario predicts that the glacier terminus will stabilise >3 km up‐valley of the current lake outlet after 2028 when ice velocity equals calving rate.  相似文献