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The Fall and Rise of V854 Centauri: Long-Term Ultraviolet Spectroscopy of a Highly Active R Coronae Borealis Star
We examine long-term low-dispersion International Ultraviolet ExplorerSWP and LWP spectroscopy of the R Coronae Borealis (RCB) star V854 Cen,obtained across the deep (DeltaV>6 mag) 1991, 1992-1993, and 1994declines. We also report the optical light curve for the star in theinterval 1987-1998, including multicolor photometry obtained during1989-1998. The light curve includes at least eight major declines wherethe amplitude exceeds 5 mag, many of which appear to be multiple declineevents. Analysis of the UV emission-line spectra indicates most linesdecay during the deep declines on characteristic timescales comparableto that reported for optical features. Fe, Mg, and neutral C lines decayon timescales of typically 50-100 days. Other lines, notably ionized Clines, decay on longer timescales (>200 days) or appear to beunaffected by the declines. The general nature of the UV emission linesand other UV features during the declines is consistent with theE1/E2/BL line region model developed from the behavior of opticalspectral features during declines. However, the detailed line behaviorindicates large intrinsic variability between decline eventsinconsistent with the simple E1/E2/BL model. Limited temporal coverageprevents detailed examination of the geometry of the emission-lineregion or the obscuring dust. We also report the first detection of thetransition-region line C IV] lambda1550 in the spectrum of an RCB star.We fit the onset times of all declines from maximum light within the1987-1998 interval, irrespective of decline amplitude, with a 43.23 daylinear solution, thus improving the decline ephemeris. The linear termis probably the pulsation period of V854 Cen, further supporting thesuspected link between radial pulsations and mass loss in these types ofstars.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
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Osservazione e dati astrometrici
| Costellazione: | Dragone |
| Ascensione retta: | 18h53m01.33s |
| Declinazione: | +64°47'15.6" |
| Magnitudine apparente: | 8.213 |
| Distanza: | 781.25 parsec |
| Moto proprio RA: | 2.3 |
| Moto proprio Dec: | 9.1 |
| B-T magnitude: | 9.792 |
| V-T magnitude: | 8.344 |
Cataloghi e designazioni:
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