30 research outputs found
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
Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups
We present here high resolution echelle spectra taken during three observing
runs of 14 single late-type stars identified in our previous studies (Montes et
al. 2001b, hereafter Paper I) as possible members of different young stellar
kinematic groups (Local Association (20 - 150 Myr), Ursa Major group (300 Myr),
Hyades supercluster (600 Myr), and IC 2391 supercluster (35 Myr)). Radial
velocities have been determined by cross correlation with radial velocity
standard stars and used together with precise measurements of proper motions
and parallaxes taken from Hipparcos and Tycho-2 Catalogues, to calculate
Galactic space motions (U, V, W) and to apply Eggen's kinematic criteria. The
chromospheric activity level of these stars have been analysed using the
information provided for several optical spectroscopic features (from the Ca II
H & K to Ca II IRT lines) that are formed at different heights in the
chromosphere. The Li I 6707.8 AA line equivalent width (EW) has been determined
and compared in the EW(Li I) versus spectral type diagram with the EW(Li I) of
stars members of well known young open clusters of different ages, in order to
obtain an age estimation. All these data allow us to analyse in more detail the
membership of these stars in the different young stellar kinematic groups.
Using both kinematic and spectroscopic criteria we have confirmed PW And, V368
Cep, V383 Lac, EP Eri, DX Leo, HD 77407, and EK Dra as members of the Local
Association and V834 Tau, pi^{1} UMa, and GJ 503.2 as members of the Ursa Major
group. A clear rotation-activity dependence has been found in these stars.Comment: Latex file with 19 pages, 7 figures tar'ed gzip'ed. Full postscript
(text, figures and tables) available at
http://www.ucm.es/info/Astrof/p_skg_stars_I_fv.ps.gz Accepted for publication
in: Astronomy & Astrophysics (A&A
Direct imaging of the young spectroscopic binary HD 160934
We report on the direct detection of a close companion to HD 160934, a young
active star, SB1 spectroscopic binary, and suggested member of the AB Doradus
moving group. High angular resolution at the Calar Alto 2.2m telescope was
achieved by means of the Lucky Imaging technique, allowing direct imaging close
to the diffraction limit in the SDSS z' band. Our results are combined with
pre-discovery HST archive data, own UBVRI broadband photometry, published JHK
magnitudes, and available radial velocity measurements to constrain the
physical properties of the HD 160934 close binary. We suggest that the direct
detection may be identical to the spectroscopically discovered companion.Comment: 5 pages, 1 figure, submitted to A&
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
A review of the application of adverse possession within the Torrens system of land regulation in Australia
The doctrine of adverse possession is but one method of resolving boundary discrepancies in Australia. An abundance of research is available on the common law concepts of the doctrine. However little research has been conducted on how adverse possession is applied in Australian jurisdictions.
The aim of this research is to conduct a review of the application of adverse possession within the Torrens system of land regulation in Australia by comparing and contrasting
variations in legislation between states, and also forming recommendations of best practice.
Comparing and contrasting legislation of Australian jurisdictions required the underlying Torrens statutes, case law, and other relevant statutes. Key to understanding
the efficiency of a jurisdiction’s approach to the application of adverse possession is performing a brief analysis of the number of disputes related to adverse possession. This has been done over a limited time period of 15 years due to time constraints.
Results showed that there are many differences between the four schemes used by Australian jurisdictions. Various strengths, weaknesses, and limitations were discovered
when analysing the approaches. One of the more important findings is the fact that when adverse possession of less than a whole parcel is permitted by itself with no
alternative boundary repair mechanism, more boundary disputes occur. This was evident in the results of the disputes analysis for Victoria. Four elements of ‘best
practice’ were identified from the research performed. One such element identified is that if adverse possession of less than a whole parcel is permitted in a jurisdiction, than statutory encroachment should be offered as an alternative.
When identifying ‘best practice’, it may not be possible to put together a set of criteria in which everybody is satisfied. However, components have been identified which work well and which may minimise disputes over land boundaries, being a fundamental objective of the Torrens system
Zeta Coronae Borealis, A Spectroscopic Triple System Including an Asynchronous Close Binary
Sustainable engineering of sewers and sewage treatment plants for scenarios with urine diversion.
Urine diversion (UD) has been studied for decades as a way to enable distributed sanitation and to recycle nutrients onto land to fuel circular economies. No study to date has attempted a quantitative technical and economic analysis of the downstream effects of UD on sewage transport and treatment. This work used the SeweX model to reveal for the first time that through UD, hydrogen sulfide concentration in sewer headspaces can be reduced, and consequently sewer corrosion can be reduced. For a long rising main of 5Â km, sewer headspace H2S can be reduced from 280Â ppm to 200Â ppm by diverting 75% of the urine. The same scenario enables the reduction of sewer corrosion from 12 to 10Â mm/yr. Modeling sewage treatment plants with BioWin showed that sewage treatment responds to UD with a sharp reduction of the anoxic volume and a decrease of energy requirement by up to 50% at 75% UD. An upgrade of bioreactors to increase capacity by 20% can be completely avoided if 7% of the catchment's urine is diverted. Reductions in upgrade expenditure by up to 75% can provide the economic incentive for the uptake of UD