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Absolute parameters of the Algol binary V505 Sgr from infrared JK light curves
We present the first light curves of V505 Sgr in the infrared (IR) J andK bands. The light curves are analysed with a code based on Rochegeometry and stellar model atmosphere fluxes in order to determine a newset of stellar and orbital parameters. From the visual-IR photometry wefind no evidence of IR excess in the system. We study the effect of thenon-synchronous rotation of the primary star in the light and radialvelocity curves. The distance of the system is estimated as 112 +/- 4pc,in close agreement with the Hipparcos parallax.
| High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere
We present the results of 8 yr of infrared photometric monitoring of alarge sample of stars visible from Teide Observatory (Tenerife, CanaryIslands). The final archive is made up of 10,949 photometric measuresthrough a standard InSb single-channel photometer system, principally inJHK, although some stars have measures in L'. The core of this list ofstars is the standard-star list developed for the Carlos SánchezTelescope. A total of 298 stars have been observed on at least twooccasions on a system carefully linked to the zero point defined byVega. We present high-precision photometry for these stars. The medianuncertainty in magnitude for stars with a minimum of four observationsand thus reliable statistics ranges from 0.0038 mag in J to 0.0033 magin K. Many of these stars are faint enough to be observable with arraydetectors (42 are K>8) and thus to permit a linkage of the bright andfaint infrared photometric systems. We also present photometry of anadditional 25 stars for which the original measures are no longeravailable, plus photometry in L' and/or M of 36 stars from the mainlist. We calculate the mean infrared colors of main-sequence stars fromA0 V to K5 V and show that the locus of the H-K color is linearlycorrelated with J-H. The rms dispersion in the correlation between J-Hand H-K is 0.0073 mag. We use the relationship to interpolate colors forall subclasses from A0 V to K5 V. We find that K and M main-sequence andgiant stars can be separated on the color-color diagram withhigh-precision near-infrared photometry and thus that photometry canallow us to identify potential mistakes in luminosity classclassification.
| The BV light and it O-C curves analyses of the triple system V505 Sagittarii
The new UBV light curves and times of minimum light for V505 Sgr arepresented. The B and V band light curves were analyzed by theWilson-Devinney code and the contribution of the third star to the totallight of the triple system was found to be 2.62% for the B and 3.56% forV band. The colour and absolute visual magnitude of the third star wereestimated to be 0m.46 and 4m.00, respectively. Theapparent visual magnitude of the third star seems fainter by about3m.6 than the eclipsing pair. Only photoelectric times ofminimum light were used to determine the parameters for the light-timeorbit. The semi-major axis of the third star's orbit around theeclipsing pair was found to be 18.8 AU. The third body completes arevolution on this orbit in 38.13 yr. The semi-amplitude of the radialvelocity of the eclipsing pair's mass center was estimated to be 2.37 kms-1 while 6.4 km s-1 was found for the third starwhich agrees with the spectroscopic measurements.
| Towards a fundamental calibration of stellar parameters of A, F, G, K dwarfs and giants
I report on the implementation of the empirical surface brightnesstechnique using the near-infrared Johnson broadband { (V-K)} colour assuitable sampling observable aimed at providing accurate effectivetemperatures of 537 dwarfs and giants of A-F-G-K spectral-type selectedfor a flux calibration of the Infrared Space Observatory (ISO). Thesurface brightness-colour correlation is carefully calibrated using aset of high-precision angular diameters measured by moderninterferometry techniques. The stellar sizes predicted by thiscorrelation are then combined with the bolometric flux measurementsavailable for a subset of 327 ISO standard stars in order to determineone-dimensional { (T, V-K)} temperature scales of dwarfs and giants. Theresulting very tight relationships show an intrinsic scatter induced byobservational photometry and bolometric flux measurements well below thetarget accuracy of +/- 1 % required for temperature determinations ofthe ISO standards. Major improvements related to the actual directcalibration are the high-precision broadband { K} magnitudes obtainedfor this purpose and the use of Hipparcos parallaxes for dereddeningphotometric data. The temperature scale of F-G-K dwarfs shows thesmallest random errors closely consistent with those affecting theobservational photometry alone, indicating a negligible contributionfrom the component due to the bolometric flux measurements despite thewide range in metallicity for these stars. A more detailed analysisusing a subset of selected dwarfs with large metallicity gradientsstrongly supports the actual bolometric fluxes as being practicallyunaffected by the metallicity of field stars, in contrast with recentresults claiming somewhat significant effects. The temperature scale ofF-G-K giants is affected by random errors much larger than those ofdwarfs, indicating that most of the relevant component of the scattercomes from the bolometric flux measurements. Since the giants have smallmetallicities, only gravity effects become likely responsible for theincreased level of scatter. The empirical stellar temperatures withsmall model-dependent corrections are compared with the semiempiricaldata by the Infrared Flux Method (IRFM) using the large sample of 327comparison stars. One major achievement is that all empirical andsemiempirical temperature estimates of F-G-K giants and dwarfs are foundto be closely consistent between each other to within +/- 1 %. However,there is also evidence for somewhat significant differential effects.These include an average systematic shift of (2.33 +/- 0.13) % affectingthe A-type stars, the semiempirical estimates being too low by thisamount, and an additional component of scatter as significant as +/- 1 %affecting all the comparison stars. The systematic effect confirms theresults from other investigations and indicates that previousdiscrepancies in applying the IRFM to A-type stars are not yet removedby using new LTE line-blanketed model atmospheres along with the updatedabsolute flux calibration, whereas the additional random component isfound to disappear in a broadband version of the IRFM using an infraredreference flux derived from wide rather than narrow band photometricdata. Table 1 and 2 are only available in the electronic form of thispaper
| A U, B, V photoelectric investigation of the eclipsing-binary system V505 Sagittarii.
Abstract image available at:http://adsabs.harvard.edu/abs/1972AJ.....77..672C
| Lettera alla Direzione - Minimi di alcune variabili
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| Computation of the elements of the eclipsing variable V 505 Sagittarii from photo-electric observations made by Prof. P. Th. Oosterhoff
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