Optical spectroscopy and Doppler tomography of Cygnus X-2     

P. Elebert  P. J. Callanan  M. A. P. Torres  M. R. Garcia 《Monthly notices of the Royal Astronomical Society》2009,395(4):2029-2038

We present phase resolved optical spectroscopy and Doppler tomography of V1341 Cygni, the optical counterpart to the neutron star low-mass X-ray binary (LMXB) Cygnus X-2 (Cyg X-2). We derive a radial velocity (RV) curve for the secondary star, finding a projected RV semi-amplitude of   K ₂= 79 ± 3 km s⁻¹  , leading to a mass function of  0.51 ± 0.06 M_⊙, ∼30  per cent lower than the previous estimate. We tentatively attribute the lower value of K ₂ (compared to that obtained by other authors) to variations in the X-ray irradiation of the secondary star at different epochs of observations. The limited phase coverage and/or longer timebase of previous observations may also contribute to the difference in K ₂. Our value for the mass function implies a primary mass of  1.5 ± 0.3 M_⊙  , somewhat lower than previous dynamical estimates, but consistent with the value found by analysis of type-I X-ray bursts from this system. Our Doppler tomography of the broad He  ii λ4686 line reveals that most of the emission from this line is produced on the irradiated face of the donor star, with little emission from the accretion disc. In contrast, the Doppler tomogram of the N  iii λ4640.64 Bowen blend line shows bright emission from near the gas stream/accretion disc impact region, with fainter emission from the gas stream and secondary star. This is the first LMXB for which the Bowen blend is dominated by emission from the gas stream/accretion disc impact region, without comparable emission from the secondary star. This has implications for the interpretation of Bowen blend Doppler tomograms of other LMXBs for which the ephemeris may not be accurately known.  相似文献   

The severe zonda wind event of 11 July 2006 east of the Andes Cordillera (Argentine): a case study using the BRAMS model     

Federico Augusto Norte  Ana Graciela Ulke  Silvia Carmen Simonelli  Maximiliano Viale 《Meteorology and Atmospheric Physics》2008,102(1-2):1-14

  相似文献   

A less disastrous disaster: Managing response to climate-driven hazards in the Cayman Islands and NE Brazil     

Emma L. Tompkins  Maria Carmen Lemos  Emily Boyd 《Global Environmental Change》2008,18(4):736

This paper explores the relationship between disaster risk reduction and long-term adaptive capacity building in two climate vulnerable areas—the Cayman Islands in the Caribbean and Ceará, in NE Brazil. Drawing on past applications of the disaster risk reduction framework, we identify four critical factors that have led to reductions in risk: flexible, learning-based, responsive governance; committed, reform-minded and politically active actors; disaster risk reduction integrated into other social and economic policy processes; and a long-term commitment to managing risk. We find that while the presence of these factors has reduced overall risk in both regions, in Ceará, disaster response as it is currently practiced, has fallen short of addressing the fundamental causes of vulnerability that leave those prone to hazards able to cope in the short term, yet enmeshed in poverty and at risk from the longer-term changes associated with climate change. Although calls for integration of disaster risk management with poverty eradication are not new, there has been insufficient attention paid in the literature on how to foster such integration. Based on the two case studies, we argue that the adoption of good governance mechanisms (such as stakeholder participation, access to knowledge, accountability and transparency) in disaster risk reduction policy may create the policy environment that is conducive to the kind of structural reform needed to build long-term adaptive capacity to climate-driven impacts. We conclude that without a synergistic two-tiered approach that includes both disaster risk reduction and structural reform, disaster risk reduction, in the face of climate changes, will prove to be an expensive and ineffective palliative treatment of changing risks.  相似文献   

Integrated spectroscopic study of 7 star clusters in the Small Magellanic Cloud     

M.L. Talavera  A.V. Ahumada  J.F.C. Santos  Jj. Clari  E. Bica  M.C. Parisi  M.C. Torres 《Astronomische Nachrichten》2010,331(3):323-329

  相似文献   

Andalusite and Na- and Li-rich cordierite in the La Costa pluton, Sierras Pampeanas, Argentina: textural and chemical evidence for a magmatic origin     

Pablo H. Alasino  Juan A. Dahlquist  Carmen Galindo  Cesar Casquet  Julio Saavedra 《International Journal of Earth Sciences》2010,99(5):1051-1065

The La Costa pluton in the Sierra de Velasco (NW Argentina) consists of S-type granitoids that can be grouped into three igneous facies: the alkali-rich Santa Cruz facies (SCF, SiO₂ ~67 wt%) distinguished by the presence of andalusite and Na- and Li-rich cordierite (Na₂O = 1.55–1.77 wt% and Li₂O = 0.14–0.66 wt%), the Anillaco facies (SiO₂ ~74 wt%) with a significant proportion of Mn-rich garnet, and the Anjullón facies (SiO₂ ~75 wt%) with abundant albitic plagioclase. The petrography, mineral chemistry and whole-rock geochemistry of the SCF are compatible with magmatic crystallization of Na- and Li-rich cordierite, andalusite and muscovite from the peraluminous magma under moderate P–T conditions (~1.9 kbar and ca. 735°C). The high Li content of cordierite in the SCF is unusual for granitic rocks of intermediate composition.  相似文献   

Collective effects of stellar winds and unidentified gamma-ray sources     

Diego F. Torres  Eva Domingo-Santamaría 《Astrophysics and Space Science》2007,309(1-4):345-350

We study collective wind configurations produced by a number of massive stars, and obtain densities and expansion velocities of the stellar wind gas that is to be target, in this model, of hadronic interactions. We study the expected γ-ray emission from these regions, considering in an approximate way the effect of cosmic ray modulation. We compute secondary particle production (electrons from knock-on interactions and electrons and positrons from charged pion decay), and solve the loss equation with ionization, synchrotron, bremsstrahlung, inverse Compton, and expansion losses. We provide examples where configurations can produce sources for GLAST satellite, and the MAGIC, HESS, or VERITAS telescopes in non-uniform ways, i.e., with or without the corresponding counterparts. We show that in all cases we studied no EGRET source is expected.  相似文献   

The white dwarf luminosity function – II. The effect of the measurement errors and other biases     

Santiago Torres  Enrique García-Berro  Jordi Isern 《Monthly notices of the Royal Astronomical Society》2007,378(4):1461-1470

The disc white dwarf luminosity function is an important tool for studying the solar neighbourhood, since it allows the determination of several Galactic parameters, the most important one being the age of the Galactic disc. However, only the     method has been employed so far for observationally determining the white dwarf luminosity function, whereas for other kind of luminosity functions several other methods have been frequently used. Moreover, the procedures to determine the white dwarf luminosity function are not free of biases. These biases have two different origins: they can either be of statistical nature or a consequence of the measurement errors. In a previous paper we carried out an in-depth study of the first category of biases for several luminosity function estimators. In this paper we focus on the biases introduced by the measurement errors and on the effects of the degree of contamination of the input sample used to build the disc white dwarf luminosity function by different kinematical populations. To assess the extent of these biases we use a Monte Carlo simulator to generate a controlled synthetic population and analyse the behaviour of the disc white dwarf luminosity function for several assumptions about the magnitude of the measurement errors and for several degrees of contamination, comparing the performances of the most robust luminosity function estimators under such conditions.  相似文献   

Time series of multivariate data in aquatic ecology     

Miguel Alvarez Cobelas  María Verdugo  Carmen Rojo 《Aquatic Sciences - Research Across Boundaries》1995,57(3):185-198

Coupling of multivariate methods and time series analysis can be ueful for studying dynamics of aquatic communities. This is demonstratred with a data set from the pelagic area of an oligo-mesotrophic lake in Central Spain during 61 consecutive days of Autumn overturn. Abiotic variables, phytoplankton species and their total biomass were traced. Species abundance and specific biomass were considered as indices of community structure and resource partitioning, respectively. Abiotic and algal data sets were subjected to factor analyses of cases separately. Atmospheric forcing and nitrogen could be considered as the main (2) driving variables of the abiotic matrix. The coupling of motile abilities and cell size was associated to the main factors of the community structure matrix whereas phosphorus limitation and species responses to buoyancy represented the main factors of the biomass matrix. Coordinates of the two first factors could be used to mimic the trajectories in the data space. Significant short term lags (1–4 days) were found in most time series. Lagged responses of atmospheric forcing and nitrogen on phytoplankton community structure and resource partitioning at scales of 1–7 days were also shown. Overall phytoplankton biomass did not show significant delayed responses, thereby suggesting that it might be resulting from the interplay of other non-studied factors.  相似文献   

Station Correction of the seismic station Kašperské Hory for short-periodP waves     

Carmen Sobotová  Jiří Vaněk  Reviewer K. Pěč 《Studia Geophysica et Geodaetica》1973,17(3):260-261

Summary The magnitude station correction of the seismic station Kaperské Hory, related to Prhonice, was determined for the vertical component of short-period P waves.  相似文献   

Wirkungen elektrischer Felder und Strahlungen atmosphärischen und kosmischen Ursprungs auf das Wasser     

Carmen Boute 《Theoretical and Applied Climatology》1955,7(1):146-155

Ohne ZusammenfassungMit 6 Textabbildungen  相似文献