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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.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| Supplement to the Second Catalogue of Am Stars with Known Spectral Types (end 1981)
Not Available
| Spectral types of stars with unusual photometric indices
The Kitt Peak 2.1-m Cassegrain spectrograph was used to obtain spectraof 92 A5-G0 stars measured by Olsen in the Stromgren four-color systemand predicted to be abnormal in the sense of excessive reddening, highluminosity, or abnormal composition. Of the five stars predicted to bereddened B or A stars, four were indeed such while for the fifth Olsenobserved the blended components. Of twelve stars predicted to besupergiants, one is a supergiant, four are giants, two are subgiants,three are Ap stars, and two are Am stars. Thus photometrically predictedsupergiants are actually stars above main sequence in two out of threecases but mostly much less luminous than expected. Of ten predictedweak-lined stars, only two were found to be really so. Am stars werewell predicted, though detection is contaminated with Ap and luminousstars. It is concluded that four-color photometry is useful in selectinginteresting stars, but is often unable to tell the specific type ofabnormality present.
| Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
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Observation and Astrometry data
| Constellation: | Sextans |
| Right ascension: | 10h23m27.36s |
| Declination: | +02°15'14.1" |
| Apparent magnitude: | 8.688 |
| Proper motion RA: | 9.6 |
| Proper motion Dec: | -1.4 |
| B-T magnitude: | 9.155 |
| V-T magnitude: | 8.727 |
Catalogs and designations:
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INHABITED SKY
