The Spectroscopic Orbit of the Evolved Binary HD 197770

We have used spectra taken between 1992 and 1997 to derive the spectroscopic orbit of the eclipsing double-lined spectroscopic binary HD 197770. This binary has a period of 99.69 +/- 0.02 days and K amplitudes of 31.2 +/- 0.8 and 47.1 +/- 0.4 km s^{-1} for components A & B, respectively. The msin^{3}i values for A & B are 2.9 and 1.9, respectively, and are close to the actual masses due to the eclipsing nature of this binary. Both components of HD 197770 have spectral types near B2 III. This means both components are undermassive by about a factor of five and, thus, evolved stars. Additional evidence of the evolved nature of HD 197770 is found in 25, 60, and 100 micron IRAS images of HD 197770. These images show 2 apparent shells centered on HD 197770; a bright 60 micron shell with a 14' diameter and a larger (1.2 degeree diameter) bubble-like feature. At least one of the components of HD 197770 is likely to be a post-AGB star.Comment: will be published in the AJ (1998 June), also availible at http://snake.phys.lsu.edu/~gordon/papers/hd197770.htm

The young active star SAO 51891 (V383 Lac)

Our aim is investigating surface inhomogeneities of the young late-type star SAO51891, from photosphere to upper chromosphere, analyzing contemporaneous high-resolution spectra and broad-band photometry. The FOCES@CAHA spectral range is used to determine spectral classification and derive vsini and Vrad. The Li abundance is measured to estimate the age. The BVRIJHKs bands are used to construct the SED. The variations of our BV fluxes and Teff are used to infer the presence of photospheric spots and observe their behavior over time. The chromospheric activity is studied applying the spectral subtraction technique to Halpha, CaII H&K, Heps, and CaII IRT lines. We find SAO51891 to be a young K0-1V star with Li abundance close to the Pleiades upper envelope, confirming its youth (~100 Myr), also inferred from its kinematical membership to the Local Association. We detect no IR excess from SED analysis, and rotational modulation of luminosity, Teff, CaII, and Heps total fluxes. A spot model with two active regions, ~240 K cooler than the surrounding photosphere, fits our light/Teff curves, and reproduces the small-amplitude Vrad variations. The anti-correlation of light curves and chromospheric diagnostics indicates plages spatially associated with spots. The large amplitude observed in the Heps-flux curve suggests that this line is very sensitive to the plage presence. Finally, SAO51891 is a young active star, lacking significant amounts of circumstellar dust or any evidence for low mass companions. The spots turn out to be larger and warmer than those in less active MS stars. The Vrad variation produced by spots has an amplitude comparable with those induced by Jupiter-mass planets orbiting close to the star. SAO51891 is a good example of star where the detection of planets may be hampered by the high activity level.Comment: 16 pages, 12 figures, 7 tables, accepted by Astronomy and Astrophysics; abstract here was shortene

The Identification of Thresholds of Acceptability and Danger: The Biological Route

The application of scientific concepts to management decisions is a clear need nowadays. The regulation of environmental pollutants requires the application of cost/benefit analysis. Human health and ecosystem status can be seriously affected and, therefore, are essential parts of the cost assessment. Ecotoxicology must provide the scientific basis for the prediction, control, monitoring and diagnosis of the expected/observed effects of chemical substances on the structure and function of ecosystems. The basic problem is to select which levels of risk/alteration can be accepted, taken into account the degree of uncertainty in the assessment. This paper summarizes some biologically based approaches that try to reduce the level of uncertainty and/or to improve the decisions on the basic thresholds acceptable/unacceptable and safe/dangerous. The presentation will focus on two specific aspects. Starting with prediction related topics, the first aspect will regard on the evolution of Hazard and Risk Assessments and the biological developments that try to improve these evaluations. The discussion will cover ecotoxicological concepts included in the adopted criteria for different regulatory aspects, i.e. setting Water Quality Objectives, classifying potential hazards using the "inherent" toxicity of a substance, or predicting Non Effect Concentration in risk characterization procedures. The second aspect will cover the use of biologically based systems as complementary and even alternative tools in management decisions related to the control, monitoring and diagnosis of the environmental alterations produced by highly toxic chemicals on biological systems

Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry

peer reviewedWith the objective of investigating the wind-wind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the massive, highly eccentric O9III+B1III binary Iota Orionis. Successfully separating the spectra of the components, we refine the orbital elements and confirm the rapid apsidal motion in the system. We also see strong interaction between the components during periastron passage and detect phase-locked variability in the spectrum of the secondary star. However, we find no unambiguous signs of the bow shock crashing on the surface of the secondary, despite the predictions of hydrodynamic simulations. Combining all available photometric data, we find rapid, phase-locked variations and model them numerically, thus restricting the orbital inclination to 50°<~i<~70°