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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.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Objective-prism discoveries in the northern sky. I
Attention is given to 175 northern hemisphere stars whose newlyrecognized peculiar, or otherwise prepossessing characteristics havebeen noted in a preliminary inspection of moderate dispersion objectiveprism plates. The plates were obtained with a 10-deg prism. The starlist gives HD or BD, alpha and delta values, magnitude, and type.
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