J/A+A/399/1167 Hipparcos Variability-Induced Movers (Pourbaix+, 2003)
How many Hipparcos Variability-Induced Movers are genuine binaries ?
Pourbaix D., Platais I., Detournay S., Jorissen A., Knapp G., Makarov V.V.
<Astron. Astrophys. 399, 1167 (2003)>
=2003A&A...399.1167P 2003A&A...399.1167P
ADC_Keywords: Stars, variable ; Parallaxes, trigonometric
Keywords: stars: binaries: close - astrometry - stars: variable: general
Abstract:
Hipparcos observations of some variable stars, and especially of
long-period (e.g. Mira) variables, reveal a motion of the photocenter
correlated with the brightness variation (variability-induced mover,
VIM), suggesting the presence of a binary companion. A re-analysis of
the Hipparcos photometric and astrometric data (Cat. I/239) does not
confirm the VIM solution for 62 among the 288 VIM objects (21%) in the
Hipparcos catalogue. Most of these 288 VIMs are long-period (e.g.
Mira) variables (LPV). The effect of a revised chromaticity
correction, which accounts for the color variations along the light
cycle, was then investigated. It is based on "instantaneous" V-I color
indices derived from Hipparcos and Tycho-2 (Cat. I/259) epoch
photometry. Among the 188 LPVs flagged as VIM in the Hipparcos
catalogue, 89 (47%) are not confirmed as VIM after this improved
chromaticity correction is applied. This dramatic decrease in the
number of VIM solutions is not surprising, since the chromaticity
correction applied by the Hipparcos reduction consortia was based on a
fixed V-I color. Astrophysical considerations lead us to adopt a more
stringent criterion for accepting a VIM solution (first-kind risk of
0.27% instead of 10% as in the Hipparcos catalogue). With this more
severe criterion, only 27 LPV stars remain VIM, thus rejecting 161 of
the 188 (86%) of the LPVs defined as VIMs in the Hipparcos catalogue.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 64 188 *188 red Variability-Induced Movers (VIM) from
the Hipparcos catalogue
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Note on table1.dat : 188 red VIM from the Hipparcos catalogue, for which
epoch (V-I) indices are available from the (V-I, Hp-VT2) color
transformation (Platais et al., 2003, Cat. J/A+A/397/997),
reprocessed with an improved chromaticity correction.
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See also:
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/250 : The Tycho Reference Catalogue (Hog+ 1998)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
J/A+A/397/997 : Hipparcos red stars (Platais+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HIP Hipparcos Catalogue number (Cat. I/239)
9- 20 A12 --- GCVS GCVS variable star name or Bayer name
25- 29 A5 --- Var Variability type from GCVS
32- 38 F7.2 mas plxHIP Hipparcos parallax
40- 43 F4.2 mas e_plxHIP Sigma of Hipparcos parallax
46 A1 --- Sol [5V] Type of solution (1)
49- 55 F7.2 mas plx Revised parallax
57- 60 F4.2 mas e_plx Sigma of revised parallax
62- 64 I3 % alpha Confidence level that the parallax is
different from zero (Eq. (6))
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Note (1): Type of solution:
V: VIM model significantly better than single-star model, and
then adopted
5: standing for 5-parameter, single-star solution, means that our
reprocessing does not confirm the VIM nature of the object, at
the 0.27% confidence level (FD<3.44 in Eq. (2)).
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Acknowledgements: Dimitri Pourbaix
(End) Patricia Bauer [CDS] 17-Dec-2002