scholarly journals Long-Term Optical Photometry of the Dwarf Nova VW Hyi

1987 ◽  
Vol 93 ◽  
pp. 127-134
Author(s):  
S.F. Van Amerongen ◽  
J. Van Paradijs
Keyword(s):  
Secular Change ◽  
Optical Photometry ◽  
Dwarf Nova ◽  
Upper Limits

AbstractLong-term five-colour photometry of the dwarf nova VW Hyi shows no evidence for a secular change of the flux during the quiescent interval between normal outbursts (3σ upper limits between 0.16 and 0.20 mag in the five passbands). However, the amplitudes in the orbital B-U and U-W colour curves change during quiescence. A delay in the progress of normal outbursts toward higher frequencies confirms the delay, seen with IUE, in the onset of a normal outburst toward higher frequencies. Just after outburst, the system is substantially bluer than later in quiescence.

Long-term optical photometry of the dwarf nova VW Hyi

1987 ◽  
Vol 130 (1-2) ◽  
pp. 127-134
Author(s):  
S. F. Van Amerongen ◽  
J. Van Paradijs
Keyword(s):  
Optical Photometry ◽  
Dwarf Nova

Simultaneous infrared and optical photometry of the Eclipsing Dwarf Nova V2051 Ophiuchi

1986 ◽  
Vol 6 (3) ◽  
pp. 306-308 ◽  
Author(s):  
D. J. Watts ◽  
R. D. Watson
Keyword(s):  
Light Curve ◽  
Optical Photometry ◽  
Dwarf Nova

AbstractA complete orbital light-curve of V2051 Oph in the IR H band is presented, together with a second eclipse in the J band. Simultaneous Rc band data were obtained. Eclipse depths in Rc, J and H are 1.8 mag, 1.0 mag and 0.8 mag respectively. No evidence for ellipsoidal variations due to the secondary was seen and constraints on the secondary are discussed.

scholarly journals Observed Auroral Ovals Secular Variation Inferred from Auroral Boundary Data

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 351
Author(s):  
Bruno Zossi ◽  
Hagay Amit ◽  
Mariano Fagre ◽  
Ana G. Elias
Keyword(s):  
High Frequency ◽  
Field Model ◽  
Geomagnetic Latitude ◽  
Auroral Zone ◽  
Secular Change ◽  
Polar Cap ◽  
High Frequency Signal ◽  
Area Increase ◽  
Northern And Southern Hemispheres

We analyze the auroral boundary corrected geomagnetic latitude provided by the Auroral Boundary Index (ABI) database to estimate long-term changes of core origin in the area enclosed by this boundary during 1983–2016. We design a four-step filtering process to minimize the solar contribution to the auroral boundary temporal variation for the northern and southern hemispheres. This process includes filtering geomagnetic and solar activity effects, removal of high-frequency signal, and additional removal of a ~20–30-year dominant solar periodicity. Comparison of our results with the secular change of auroral plus polar cap areas obtained using a simple model of the magnetosphere and a geomagnetic core field model reveals a decent agreement, with area increase/decrease in the southern/northern hemisphere respectively for both observations and model. This encouraging agreement provides observational evidence for the surprising recent decrease of the auroral zone area.

scholarly journals Determination of standards of raw timber natural losses due to shrinkage at long-term dry storage

2021 ◽  
Vol 67 (No. 5) ◽  
pp. 195-203
Author(s):  
Dalibor Šafařík ◽  
Petra Hlaváčková ◽  
David Březina
Keyword(s):  
Woody Plants ◽  
Mean Value ◽  
The Czech Republic ◽  
Long Term Storage ◽  
Upper Limits ◽  
Natural Losses ◽  
Term Storage

The aim of the article is to describe the issue of determining the characteristics and parameters of raw timber natural losses due to shrinkage at long-term storage, defining the theoretical basis for creating standards, and verify its finding by means of a case study in raw timber storing. This issue is very topical in forestry practice in the Czech Republic as well as in other countries. The lower and upper limits of the standards were calculated, and the proposed mean value was grouped according to woody plants that reflected the most frequent commercial usage with respect to subsequent processing. Subsequently, experimental verification was carried out on a representative sample of 2 209.99 m3 of raw timber of Norway spruce (Picea abies /L./ H. Karst.) at selected forest administrations. Furthermore, the article addresses the related accounting and tax issues of the standards of natural losses of raw timber. Currently, no legislation mandates an entity to establish standards.

Constraints by Experimental Data for Modeling of Radionuclide Release from Spent Fuel

1989 ◽  
Vol 176 ◽  
Author(s):  
Bernd Grambow ◽  
L.O. Werme ◽  
R.S. Forsyth ◽  
J. Bruno
Keyword(s):  
Experimental Data ◽  
Product Layer ◽  
Spent Fuel ◽  
Upper Limits ◽  
The Matrix ◽  
The Usa ◽  
Oxidant Production ◽  
Release Data ◽  
Radionuclide Release

ABSTRACTComparison of spent fuel corrosion data from nuclear waste management projects in Canada, Sweden and the USA strongly suggests that the release of 90Sr to the leachant can be used as a measure of the degradation (oxidation/dissolution) of the fuel matrix. A surprisingly quantitative similarity in the 90 Sr release data for fuel of various types (BWR, PWR, Candu), linear power ratings and burnups leached under oxic conditions was observed in the comparison. After 1000 days of leachant contact, static or sequential, the fractional release rates for 90Sr (and for cesium nuclides) were of the order of 10−7/d.The rate of spent fuel degradation (alteration) under oxic conditions can be considered to be controlled either by the growth rates of secondary alteration products, by oxygen diffusion through a product layer, by the rate of formation of radiolytic oxidants or by solubility-controlled dissolution of the matrix. These processes are discussed. Methods for determining upper limits for long-term 90Sr release, and hence fuel degradation, have been derived from the experimental data and consideration of radiolytic oxidant production.

scholarly journals The Hunt for Pulsating Ultraluminous X-ray Sources

2019 ◽  
Author(s):  
X Song ◽  
D J Walton ◽  
G B Lansbury ◽  
P A Evans ◽  
A C Fabian ◽  
...  
Keyword(s):  
Next Generation ◽  
X Ray ◽  
Monitoring Programs ◽  
Final Sample ◽  
Upper Limits ◽  
Flux Variability ◽  
Order Of Magnitude

Abstract Motivated by the recent discoveries that six Ultraluminous X-ray Sources (ULXs) are powered by highly super-Eddington X-ray pulsars, we searched for additional pulsating ULX (PULX) candidates by identifying sources that exhibit long-term flux variability of at least an order of magnitude (a common feature seen in the 6 known PULXs, which may potentially be related to transitions to the propeller regime). Expanding on previous studies, we used the available fluxes from XMM-Newton, Swift and Chandra, along with carefully computed upper limits in cases of a non-detection, to construct long-term lightcurves for a sample of 296 ULXs selected from the XMM-Newton archive. Among these 296, we find 25 sources showing flux variability larger than a factor of 10, of which 17 show some evidence for (or are at least consistent with) exhibiting bi-modal flux distributions, as would be expected for sources undergoing propeller transitions. These sources are excellent candidates for continued monitoring programs to further test for this behaviour. There are 3 sources in our final sample with fluxes similar to NGC 5907 ULX1, currently the faintest known PULX, which would also be good targets for deeper observations with current facilities to search for pulsations. For the rest of the PULX candidates identified here, the next generation of X-ray telescopes (such as Athena) may be required to determine their nature owing to their lower peak fluxes.

scholarly journals Conditions of formation of seismogenic landslides on Sakhalin Island

2019 ◽  
Vol 265 ◽  
pp. 04012
Author(s):  
Nikolay Kazakov ◽  
Sergey Kudryavtsev
Keyword(s):  
Water Cycle ◽  
High Water ◽  
High Humidity ◽  
Increased Risk ◽  
Upper Limits ◽  
Landslide Processes ◽  
Low Humidity ◽  
The Stability ◽  
Moisture Increase

There is no direct connection between landslide and seismic processes. The increase in humidity of rocks during a long period of high humidity (6-7 years) with a large amount of precipitation causes an increase in the humidity of rocks in landslides to the upper limits of plasticity (or fluidity) of soils, which leads to a decrease in their stability and activation of landslide processes. The consequence of reducing the stability of landslide arrays is to increase the probability of activation of landslide processes under seismic effects on landslide arrays. Strong hydration of rocks during the previous cycle of high humidity is maintained for at least 2 years. Therefore, in the first 2 years after the beginning of the low humidity cycle, the conditions for the activation of landslide processes in an earthquake remain. Similarly, in the first 2 years after the beginning of the high-water cycle, the rocks of landslide massifs are still not sufficiently moistened, and the probability of landslides formation in earthquakes is low. Long-term forecast of seismogenic landslides can be made as a forecast of periods of increased risk of landslides based on the account of the cycles of moisture (increase in precipitation) and physical and mechanical characteristics of rocks of landslides.

Long-Term Activity of a Little Known Dwarf Nova DT Octantis

2019 ◽  
Vol 74 (4) ◽  
pp. 490-496
Author(s):  
V. Šimon ◽  
H. Edelmann
Keyword(s):  
Dwarf Nova
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