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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
| Radial velocity measurements. IV - Ground-based accompaniment to the HIPPARCOS observation program
The paper presents 396 radial velocities of stars distributed in 19fields of 4 x 4 degrees. The study employs the Fehrenbach objectiveprism method and the same measuring technique used in a previous paper(Fehrenbach et al., 1987).
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| Optical variability of V 1668 Cygni - Nova Cygni 1978 during the Nova and Post-Nova phase
Photoelectric observations of Nova Cygni 1978, obtained during 18 nightsin 1978 and one night in 1981 at the Bologna Observatory with the 152-cmtelescope equipped with a fast double-head UBV photometer are presentedand analyzed. The light curve is typical of a fast nova, without a clearpresence of a transition phase connected to dust formation. During themaximum and the first decay the nova sometimes shows a fairly smoothlight curve and sometimes rapid fluctuations, but no stable pulsationshave been found. In August 1981, when its magnitude was about 17, someevidence of a periodicty of 0.070d is present. The same period wasguessed by Voloshina and Cherepashchuk (1980) from observations inOctober 1978. Photographic observations in July 1983 show that themagnitude of the Nova was greater than 19.
| Interstellar reddening and distance of Nova Cygni 1978
Observations of Nova Cygni 1978 at 7699 A (a potassium line) are used toestimate the nova distance. The distance seems to be 3.3 plus or minus0.6 kpc with a corresponding absolute visual magnitude at maximum lightof approximately -7.5. The nova is classified as a fast galactic nova onthe basis of its absolute magnitude at maximum light and the rate ofdecline towards minimum light. The color excess deduced from theobservations is reported, application of the distance-reddening law tothe nova is explained, and a composite light curve is presented.
| Note on the Absolute Magnitude and Reddening of SS Cygni.
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Observation and Astrometry data
| Constellation: | Cygnus |
| Right ascension: | 21h35m08.64s |
| Declination: | +43°42'11.9" |
| Apparent magnitude: | 6.794 |
| Distance: | 383.142 parsecs |
| Proper motion RA: | 0.9 |
| Proper motion Dec: | 3.4 |
| B-T magnitude: | 6.674 |
| V-T magnitude: | 6.785 |
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