Pre-maximum and maximum of Novae: The spectroscopic observations of Nova ASASSN-17hx

The coverage of the pre-maximum stage of novae is sparse, with the exception of a few slow novae where the pre-maximum duration is of the order of some weeks. This paper discusses the main features of novae during the pre-maximum and the maximum stages and reports the preliminary results of an investigation of ASASSN-17hx, a peculiar nova that showed a long pre-maximum and secondary brightenings.Comment: Proceedings of a talk given at the conference "The Golden Age of Cataclysmic Variables and Related Objects IV (GOLDEN 2017)", 11-16 September, 2017, Palermo, Italy; 9 pages, 8 figure

Multifrequency Behaviour of Galactic and Extragalactic Novae

The outbursts of novae are among the strongest explosions in the Universe. The eruptions involve physical processes that span the whole electromagnetic spectrum, demanding multifrequency observations. The photometric and spectroscopic observations in the optical domain are combined with radio, infrared, X-ray and gamma ray observations, allowing to discover new phenomena, like the GeV gamma ray emission.Comment: Proceedings of a talk given at the conference on "XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop", 2017, 12-17 June Palermo, Italy; 22 pages, 9 figures, 2 table

The importance of transient X-ray sources for gravitational wave physics

The recent discovery of gravitational waves has opened a new window in observational astronomy. The X-ray sources are interesting targets of gravitational astronomy, among them X-ray binaries. Accreting neutron stars are candidates for continuous emission of gravitational waves in the sensitivity band of the advanced LIGO/Virgo interferometers. The X-ray binaries are also potential emitters of low frequency gravitational radiation in the frequency band of the forthcoming space based interferometer eLISA. The accurate knowledge of the orbital period of the X-ray binaries is necessary to estimate the gravitational emission at low frequency and to reduce the computational cost of searching the signal from accreting neutron stars. The systematic search for periodicities in the archives of X-ray missions can detect the required orbital periods and, in addition, superorbital periods. The preliminary results of a search for periodicities in the Swift/BAT and RXTE/ASM archives is presented, showing also how the estimated periodicities can provide information about the characteristics of the astrophysical sources

Galactic and extragalactic novae - A Review

The outbursts of classical novae are among the strongest explosions in the Universe. The multifrequency observations are contributing to understanding the process of explosions and of the long term evolution. In this review, I discuss the observations of novae over the electromagnetic spectrum, focusing on the morphology of the decline light curves, the spectroscopic investigations, the long term evolution, the recurrent novae, the gamma ray emission in novae, extragalactic novae and the gravitational emission of novae

The transient OT J213806.6+261957 in Pegasus - Possible emitter of gravitational waves

The transient OT J213806.6+261957 in Pegasus showed an outburst in 2010 and an unexpected new outburst in 2014. The system has been classified as a SU UMa system and as a possible member of the WZ Sge subclass. The present paper reports about the spectroscopic monitoring of OT J213806.6+261957 (secured at Loiano Observatory, Italy) during the 2014 outburst and the potential of the system as a gravitational wave emitter. Since the system has an orbital period of 82 minutes and is at a distance of 70 pc only, it could be a strong gravitational source for the forthcoming space based interferometers

Biogeoquímica de uma microbacia após o corte raso de uma plantação de eucalipto de 7 anos de idade

This work studied the effect on nutrient cycling and quantities of mineral nutrients exported with the woody biomass after the clearcutting of a 7-year old plantation of Eucalyptus saligna Smith. The experiment was carried out on lands of Votorantim Celulose e Papel S/A, Fazenda Bela Vista III, located in the municipality of Santa Branca, State of São Paulo, with coordinates 25°25' South and 45°54' West from Greenwich, and 695m average altitude. The climate is classified as Cwa type, according to Köeppen, and is characterized by dry winter temperatures, and by an annual average precipitation of 1,562mm. The soils in the region are predominantly of the Hapludulf type. The experimental catchment has an area of7.0 ha,3.3% of which is covered with riparian vegetation, with average slope of 19.6%. The total experimental period comprised eight years, with comparison of the results being made between data from the 7 years before the clearcutting and data obtained during the first year after the clearcutting. Rain water and streamflow samples were obtained weekly during the experimental period, and were analyzed for N, K+, Ca++, and Mg++, with the purpose of quantifying the catchment geochemical cycling. The amount of nutrients exported with the harvesting of the woody biomass was obtained from the estimates of the arboreous biomass and the nutrients content (phytomass and mineralmass, respectively). The total, above soil biomass production of theE. saligna plantation for the seven years amounted to 178.1t.ha, distributed as follows: 145.2t as wood, 14.7t as bark, 13.62t as branches and4.6t as leaves. The nutrients contents in the total biomass were: N 200.8Kg, P 52.8Kg, K 308.3Kg, Ca 796.1Kg, Mg 133.33kg, and S3.06Kg. The nutrient concentrations for the different parts of the tree, respectively, wood, bark, branches, and leaves, were as follows: N0.07,0.21,0.19,0.92 (%); P0.02,0.09,0.04,0.11 (%); K0.11,0.38,0.34,1.01 (%); Ca0.10,3.34,0.90,0.84 (%); Mg0.03,0.39,0.15,0.26 (%); S0.01,0.05,0.02, and0.13 (%). For the entire eight-year period, total inputs in precipitation, in Kg.ha-1, were as follows: N=77.6, K=32.2, Ca=46.7 and Mg=11.9. For the same period, total outputs in streamflow were: N=7.1, K=24.1, Ca=31.7 and Mg=7.4. Results are discussed in terms of maintenance of site productivity considering the exchangeable amount contained in the soil catchment, as well as the harvesting method, that is whole-tree x wood only harvesting

The variable finesse locking technique

Virgo is a power recycled Michelson interferometer, with 3 km long Fabry-Perot cavities in the arms. The locking of the interferometer has been obtained with an original lock acquisition technique. The main idea is to lock the instrument away from its working point. Lock is obtained by misaligning the power recycling mirror and detuning the Michelson from the dark fringe. In this way, a good fraction of light escapes through the antisymmetric port and the power build-up inside the recycling cavity is extremely low. The benefit is that all the degrees of freedom are controlled when they are almost decoupled, and the linewidth of the recycling cavity is large. The interferometer is then adiabatically brought on to the dark fringe. This technique is referred to as variable finesse, since the recycling cavity is considered as a variable finesse Fabry-Perot. This technique has been widely tested and allows us to reach the dark fringe in few minutes, in an essentially deterministic way