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A statistical analysis of the detection limits of fast photometry
This work investigates the statistical limits for the detection ofstellar variability using ground based fast photometry. We show thatwhen sky transparency variations are very low or have been efficientlyremoved from the raw light curve, the overall noise is of a MixedPoisson (MP) nature (photon noise mixed by scintillation). As aconsequence, three regimes appear for the detection of photometricvariations depending on the star's brightness (scintillation,scintillation and photon noise, photon noise and sky background). Theproposed analysis is mainly applied to the Indian sites of Manora Peak(existing 104 cm telescope) and Devasthal (future 1 m automatedtelescope, and 3 m telescope project). As shown by some examples, it canbe applied to any site with the corresponding parameters. For 1 m classtelescopes at an altitude of about 2000 m, the frontier magnitudesbetween the different detection regimes are about 10 mag and 15 mag. Byanalysing the corresponding statistics of the MP noise periodogram, theminimum amplitude variation that one can detect with a given confidencelevel is evaluated for each observational setting. For example, with a 3m telescope at about 2500 m, ≈120 μmag variations would bedetected in 2 h with a 99% confidence level for stars brighter thanmagnitude 12. For a star of 15th magnitude, ≈400 μmag oscillationswould still be detected at that level. These detection limits arediscussed in the light of observations obtained in Manora peak, andcompared to results obtained at different astronomical sites.
| Mesures de vitesses radiales. VII. Accompagnement AU sol DU programme d'observation DU satellite Hipparcos. Radial velocities. VII. Ground based measurements for Hipparcos.
We publish 734 radial velocities of stars distributed in 28 fields of4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot etal. 1990 and 1992), using the Fehrenbach objective prism method.
| Estimation of spectral classifications for bright northern stars with interesting Stromgren indices
The purpose of this investigation is to provide spectroscopic observerswith finding lists of potentially interesting objects. From anunpublished UVBY catalogue of 7026 northern stars (mostly brighter than8.3m) 1094 objects with interesting combinations of UVBY indices havebeen selected. Most stars with post-HD classifications have beenexcluded, as well as late F dwarfs belonging to the intermediatepopulation II. For the 792 remaining stars estimated spectralclassifications are given. The techniques and experience from a previouspaper dealing with southern stars have been utilized here. Among thepredicted spectral classifications are 40 OB stars; 262 Ap, Am, or Fmstars; 16 supergiants of types A to G; 110 bright giants of types A to K(class II); 156 double stars or objects with composite spectra; 26 lateF dwarfs; 91 weak-lined dwarf and giant stars of types F to K, includingearly F-type population II field blue stragglers; and a few possiblefield horizontal branch stars, lambda Bootis-type stars, and late-typehalo giants.
| Photoelectric measurements of lunar occultations. VII - Further observational results
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..689A&db_key=AST
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