887 research outputs found

    Simultaneous IUE, EXOSAT and optical observations of the unusual AM Her type variable H058+608

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    Simultaneous observations of the AM Her type variable H0538+608 made with IUE, EXOSAT, and a 1.3 m ground based telescope, and subsequent optical spectrophotometry at high and low resolution are discussed. The X-ray and optical data show clear evidence of a 3.30 + or - 0.03 hr period. Three SWP spectra were taken outside of eclipse and during overlapping phase intervals. The UV spectra contain strong emission lines characteristic of this class of objects and a flat continuum which appears to be deficient, given the brightness of source at optical and X-ray wavelengths. There is evidence for intensity variations in emission lines, particularly C IV. The X-ray light curves for H0538+608 reveal behavior which may be related to irregularities in its accretion flow

    Role of Nitrogen, Phosphorus and Potassium fertilizers in continuous corn culture on Nicollet and Webster soils

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    The possibility of growing continuous corn is receiving increasing consideration with the changing agricultural patterns. Farmers are devoting more and more acres to intensive cropping sequences in which corn follows corn more often. The practice of continuous corn-growing consecutive corn crops on the same land-is on the increase. This is because corn is the most profitable crop generally grown in the Corn Belt, because limitations in production technology have been eased, and because farm product demands or values have altered. Early research with crop rotations generally resulted in conclusions that continuous culture of inter tilled crops, especially of corn, was less profitable than other alternatives and resulted in decreasing soil fertility and continuously declining yields. The early experiments indicated that a crop rotation, including a nitrogen-fixing legume, was needed to increase or even maintain fertility levels. These experiments usually did not explore the use of N, and, if they did, the N usually was used in low amounts, probably because of the high cost. Forage-producing crops were also necessary for the livestock program, which then included draft horses, and the manure byproduct from the animals helped maintain fertility levels

    What Fertilizers for Crop Rotation?

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    No one can predict the exact response of a single crop in a given year or at a specific location. Price relationships change, too. What should you do in a cropping sequence? Here are some clues from our long-term research

    XTE J1550-564: INTEGRAL Observations of a Failed Outburst

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    The well known black-hole X-ray binary transient XTE J1550-564 underwent an outburst during the spring of 2003 which was substantially underluminous in comparison to previous periods of peak activity in that source. In addition, our analysis shows that it apparently remained in the hard spectral state over the duration of that outburst. This is again in sharp contrast to major outbursts of that source in 1998/1999 during which it exhibited an irregular light curve, multiple state changes and collimated outflows. This leads us to classify it as a "failed outburst." We present the results of our study of the spring 2003 event including light curves based on observations from both INTEGRAL and RXTE. In addition, we studied the evolution of the high-energy 3-300 keV continuum spectrum using data obtained with three main instruments on INTEGRAL. These spectra are consistent with typical low-hard-state thermal Comptonization emission. We also consider the 2003 event in the context of a multi-source, multi-event period-peak luminosity diagram in which it is a clear outlyer. We then consider the possibility that the 2003 event was due to a discrete accretion event rather than a limit-cycle instablility. In that context, we apply model fitting to derive the timescale for viscous propagation in the disk, and infer some physical characteristics.Comment: 22 pages, 8 figures, to be published in The Astrophysical Journa

    Long-term variability of AGN at hard X-rays

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    Variability at all observed wavelengths is a distinctive property of AGN. Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by absorption along the line of sight. Swift/BAT offers the unique opportunity to follow, on time scales of days to years and with a regular sampling, the 14-195 keV emission of the largest AGN sample available up to date for this kind of investigation. We study the amplitude of the variations, and their dependence on sub-class and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. About 80% of the AGN in the sample are found to exhibit significant variability on months to years time scales, radio loud sources being the most variable. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes of the absorption column density. In general, the variations in the 14-24 and 35-100 keV bands are well correlated, suggesting a common origin of the variability across the BAT energy band. However, radio quiet AGN display on average 10% larger variations at 14-24 keV than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on month time scale. In addition, sources with harder spectra are found to be more variable than softer ones. These properties are generally consistent with a variable power law continuum, in flux and shape, pivoting at energies >~ 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at hard X-rays are comparable to those at lower energies, with at least some of the differences possibly ascribable to components contributing differently in the two energy domains (e.g., reflection, absorption).Comment: 17 pages, 11 figures, accepted for publication in A&

    STANDARDIZATION OF DOE DISPOSAL FACILITIES WASTE ACCEPTANCE PROCESSES

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    ABSTRACT On February 25, 2000, the U.S. Department of Energy (DOE) issued the Record of Decision (ROD) for the Waste Management Programmatic Environmental Impact Statement (WM PEIS) for low-level and mixed low-level wastes (LLW/ MLLW) treatment and disposal. The ROD designated the disposal sites at Hanford and the Nevada Test Site (NTS) to dispose of LLW/MLLW from sites without their own disposal facilities. DOE's Richland Operations Office (RL) and the National Nuclear Security Administration's Nevada Operations Office (NV) have been charged with effectively implementing the ROD. To accomplish this task NV and RL, assisted by their operating contractors Bechtel Nevada (BN), Fluor Hanford (FH), and Bechtel Hanford (BH) assembled a task team to systematically map out and evaluate the current waste acceptance processes and develop an integrated, standardized process for the acceptance of LLW/MLLW. A structured, systematic, analytical process using the Six Sigma system identified disposal process improvements and quantified the associated efficiency gains to guide changes to be implemented. The review concluded that a unified and integrated Hanford/NTS Waste Acceptance Process would be a benefit to the DOE Complex, particularly the waste generators. The Six Sigma review developed quantitative metrics to address waste acceptance process efficiency improvements, and provides an initial look at development of comparable waste disposal cost models between the two disposal sites to allow quantification of the proposed improvements

    Now you see it, now you don't - the circumstellar disk in the GRO J1008--57 system

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    Multiwavelength observations are reported here of the Be/X-ray binary pulsar system GRO J1008-57. Over ten years worth of data are gathered together to show that the periodic X-ray outbursts are dependant on both the binary motion and the size of the circumstellar disk. In the first instance an accurate orbital solution is determined from pulse periods, and in the second case the strength and shape of the Halpha emission line is shown to be a valuable indicator of disk size and its behaviour. Furthermore, the shape of the emission line permits a direct determination of the disk size which is in good agreement with theoretical estimates. A detailed study of the pulse period variations during outbursts determined the binary period to be 247.8, in good agreement with the period determined from the recurrence of the outbursts.Comment: Accepted for publication in MNRA
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