SDSS J0349-0059 is a GW Virginis star

High speed photometric observations of the spectroscopically-discovered PG 1159 star SDSS J034917.41-005917.9 in 2007 and 2009 reveal a suite of pulsation frequencies in the range of 1038 - 3323 microHz with amplitudes between 3.5 and 18.6 mmag. SDSS J034917.41-005917.9 is therefore a member of the GW Vir class of pulsating pre-white dwarfs. We have identified 10 independent pulsation frequencies that can be fitted by an asymptotic model with a constant period spacing of 23.61 +/- 0.21 s, presumably associated with a sequence of l = 1 modes. The highest amplitude peak in the suite of frequencies shows evidence for a triplet structure, with a frequency separation of 14.4 microHz. Five of the identified frequencies do not fit the l = 1 sequence, but are, however, well-modeled by an independent asymptotic sequence with a constant period spacing of 11.66 +/- 0.13 s. It is unclear to which l mode these frequencies belong.Comment: Accepted for publication in MNRAS; 5 pages, 6 figures and 4 table

Nova Scorpii 1941 (V697 Sco): A Probable Intermediate Polar

V697 Sco, the remnant of Nova Scorpii 1941 and currently at V ~ 20.0, is found from photometric observations to have the characteristics of an intermediate polar (IP) with an orbital period (Porb) of 4.49 h and a rotation period (Prot) of 3.31 h. It therefore appears to be a member of the rare class of IPs where Prot ~ Porb, which are probably discless systems. The prominence of the modulation at 0.5 Prot, and its orbital sidebands, indicates two-pole accretion.Comment: To appear in the November 2002 issue of PAS

Stability studies of Sasol Synfuels Transmission and Distribution network under fault conditions and N-1 supply contingency

Includes abstract.Includes bibliographical references (leaves 129-130).The aim of the work is to perform a transient stability analysis of the Sasol Synfuels Transmission and Distribution network when the power system is subjected to fault conditions and N-1 supply contingency conditions. The work provides an overview of the problem of power system stability as well as discussing issues related to the problem of power system stability; which include power system control and power system modelling

Farm economic sustainability in the European Union: A pilot study

The measurement of farm economic sustainability has received intermittent academic interest in recent times, while the conceptual discussions are often quite limited. Moreover, this concept receives more attention at periods of diffi culty for the sector. The measurement of farm viability is an important precondition to enrich these discussions. Therefore, it is necessary todevelop more comprehensive and detailed measurement techniques to provide more clarity on viability and vulnerability levels in the sector. This paper refocuses attention on this issue, using a pilot dataset collected at farm level across a range of EU Member States which facilitates the assessment of an additional category of viability, namely that of economically sustainablefarms, i.e. farms that are economically vulnerable but which are deemed sustainable by the presence of off-farm income. Differences in viability and economic sustainability across the eight surveyed Member States are shown. The analysis is sensitive to the factors included in the measurement of viability as well as to the threshold income used to defi ne viability. Although this is a pilot study, it enhances our understanding of the factors affecting cross-country evaluation of viability and sustainability, and the policy instruments that could improve viability levels

High Speed photometry of faint Cataclysmic Variables: I. V359 Cen, XZ Eri, HY Lup, V351 Pup, V630 Sgr, YY Tel, CQ Vel, CE-315

The first results of a photometric survey of faint Cataclysmic Variables are presented. V359 Cen is an SU UMa star with a period of 112 min. Even though observed at quiescence, the mass transfer rate in this old nova may be sufficiently high that in such a short period system (with its implied small mass ratio) the disc may be excited into an elliptical shape with the result that the observed brightness modulation gives a superhump period rather than an orbital period. XZ Eri is an eclipsing dwarf nova with an orbital period (P(orb)) of 88.1 min. HY Lup has only slight variability. V351 Pup, the remnant of Nova Puppis 1991, has P(orb) = 2.837 h and a light curve that strongly resembles that of the magnetic Nova Cyg 1975. V630 Sgr is the first nova remnant that has both positive superhumps (P(sh) = 2.980 h) and eclipses (P(orb) = 2.831 h). The YY Tel identification is somewhat uncertain. The correct identification for CQ Vel is provided from discovery of its flickering activity. The light curve of CE-315, a recently discovered AM CVn star, shows similarities to that of GP Com, with no apparent orbital modulation.Comment: 8 pages, 12 figures, accepted for publication in MNRA

57 second oscillations in Nova Centauri 1986 (V842 Cen)

High speed photometry in 2008 shows that the light curve of V842 Cen possesses a coherent modulation at 56.825 s, with sidebands at 56.598 s and 57.054 s. These have appeared since this nova remnant was observed in 2000 and 2002. We deduce that the dominant signal is the rotation period of the white dwarf primary and the sidebands are caused by reprocessing from a surface moving with an orbital period of 3.94 h. Thus V842 Cen is an intermediate polar (IP) of the DQ Herculis subclass, is the fastest rotating white dwarf among the IPs and is the third fastest known in a cataclysmic variable. As in other IPs we see no dwarf nova oscillations, but there are often quasi-periodic oscillations in the range 350 - 1500 s. There is a strong brightness modulation with a period of 3.78 h, which we attribute to negative superhumps, and there is an even stronger signal at 2.886 h which is of unknown origin but is probably a further example of that seen in GW Lib and some other systems. We used the Swift satellite to observe V842 Cen in the ultra-violet and in X-rays, although no periodic modulation was detected in the short observations. The X-ray luminosity of this object appears to be much lower than that of other IPs in which the accretion region is directly visible.Comment: 6 pages, 10 figures, accepted for publication in MNRA

Suspended and bedload transport in the surfzone : implications for sand transport models

ACKNOWLEDGMENTS The research presented in this paper is conducted within the SINBAD project, funded by STW (12058) and EPSRC (EP/J00507X/1, EP/J005541/1), and received additional funding through the European Community’s FP7 project Hydralab IV (contract no. 261520).Publisher PD

Dwarf nova oscillations and quasi-periodic oscillations in cataclysmic variables - VII. OY Carinae and oscillations in dwarf novae in quiescence

We have observed dwarf nova oscillations (DNOs) in OY Car during outburst, down through decline and beyond; its behaviour is similar to what we have previously seen in VW Hyi, making it only the second dwarf nova to have DNOs late in outburst that continue well into quiescence. There are also occasional examples of DNOs in deep quiescence, well away from outburst - they have properties similar to those during outburst, indicating similar physical causes and structures. We discuss the occurrence of DNOs in other dwarf novae and conclude that DNOs during quiescence are more common than often supposed and exhibit properties similar to those seen in outburst.Comment: Accepted for publication in MNRAS; paper contains 11 figures and 2 tables. This paper has become paper VII in the serie

High speed photometry of faint cataclysmic variables - VI. Car2, V1040 Cen, Ha 075648, IL Nor (Nova Nor 1893), HS Pup (Nova Pup 1963), SDSS J2048-06, CSS 081419-005022 and CSS 112634-100210

We have observed 8 faint cataclysmic variable stars photometrically. The nova-like Car2 was extensively sampled but showed little variability. V1040 Cen was observed near the end of a dwarf nova outburst and possessed dwarf nova and quasi-periodic oscillations. Ha 075648 has strong large amplitude flickering and a possible orbital modulation at 3.49 h. The correct identification for the nova remnant IL Nor (Nova Nor 1893) has been established. HS Pup (Nova Pup 1963) has a possible orbital period of 3.244 h. SDSS J2048-06 is a low mass transfer dwarf nova that in quiescence shows slow variations at 7.67 h (though poorly sampled with our observations) and an orbital modulation at 87.26 min. The dwarf nova CSS 081419-005022 has an orbital period of 1.796 h and the eclipsing dwarf nova CSS 112634-100210 has an orbital period of 1.8581 h.Comment: 7 pages, 15 figures. Accepted for publication in MNRA