Astrophys Space Sci (2011) 335:105–111 DOI 10.1007/s10509-011-0613-1
O R I G I N A L A RT I C L E
Single-binary star separation by ultraviolet color index diagrams Oleg Malkov · Aleksej Mironov · Sergej Sichevskij
Received: 22 October 2010 / Accepted: 11 January 2011 / Published online: 28 January 2011 © Springer Science+Business Media B.V. 2011
Abstract Detection of a composite flux in photometry can serve as an indication of a photometrically unresolved binarity and can contribute to the parameterization of the components of binary systems. A main goal of the present study is to develop a method of automatic photometric detection of binaries, based on multi-color photometry, theoretical stellar spectral energy distributions and general understanding of binary evolution. In particular, we consider an ultraviolet photometry where, in combination with optical and infrared photometry, interstellar reddening can be easier distinguished from temperature reddening. The following procedure is applied to achieve the declared goal. One can compose possible pairs of components, based on evolution concept. This can be done for various stages of binary evolution. Theoretical spectral energy distributions and response functions of ultraviolet photometric bands in appropriate sky surveys allow us to compute color-indices of such pairs, when they are unresolved, as well as of single stars. Usage of an interstellar extinction law gives us theoretical color-indices of reddened objects, both single stars and unresolved binaries. When plotted on a multidimensional color space, they allow us to indicate areas, where unresolved binaries can be easily separated from single stars, and identify binaries among objects, crossmatched in photometric surveys. Keywords Unresolved binaries · Ultraviolet · Very large databases O. Malkov () · S. Sichevskij Institute of Astronomy, Moscow, Russia e-mail:
[email protected] A. Mironov Sternberg Astronomical Institute, Moscow State University, Moscow, Russia
1 Introduction
Color index diagrams can serve as powerful tools for determination of stellar intrinsic energy distribution and, hence, for parameterization of stars. This is tightly related to the study of interstellar extinction, because the SED investigation can be examined only once the observed spectra are corrected for interstellar reddening. Interstellar extinction affects the continuous energy distributions of astronomical objects to some degree, and its effects are particularly strong for observations at ultraviolet wavelengths. The most frequent obstacle to an object parameterization from color index diagrams is to separate extinction reddening and temperature reddening. In other words, curves, representing stars of a particular luminosity class (e.g., MSband), are hardly detached from reddening curves, at least for optical and IR photometric bands. The task is however facilitated at wavelength, where a significant deviation from monotonic function is observed in stellar spectrum (e.g., Balmer jump area for B5-G0 stars or molecular bands in the spectrum of M stars) or/and in interstellar extinction law. The strongest known interstellar extinction law feature is by far a broad bump observed at about 2175 A. It represents an extremely high extinction region with an equivalent width of ≈ 1000 A and allows us to use color index diagrams with UV bands for stellar parameterization. The procedure of color index diagrams construction is described in Sect. 2. Simulation of various types of unresolved binaries is discussed in Sect. 3, and results of the application of the procedure to reddened stars are summarized in Sect. 4. In Sect. 5 we draw our conclusions.
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Astrophys Space Sci (2011) 335:105–111
Fig. 1 SDSS photometry. Filled black circles—Pickles (1998) models recalculated into the AB magnitude system. Open black circles—the same models but reddened by EB−V = 1. Red arrow—reddening curve. SDSS objects in Boo (l = 353°, b = +68°, r = 0.1°) area: gray points—all objects, blue points—objects with photometric u, g, r accuracy better than 0.1 mag
2 Construction of UV color index diagrams To simulate stars on color index diagrams we used Pickles (1998) spectral library and Fluks et al. (1994) interstellar extinction law Aλ /EB−V (λ). SDSS, GALEX and Gaia response curves were taken from Gunn et al. (1998), Morrissey et al. (2005) and Jordi and Carrasco (2007), respectively. In Fig. 1 we show theoretical and observational points in the u-g–g-r plane, while combined SDSS and GALEX photometry is shown in Fig. 2. Here u, g, r are SDSS photometric bands, and FUV, NUV are GALEX photometric bands.
3 Unresolved binaries simulation There is a number of reasons for the observed disagreement between the empirical and theoretical points in Figs. 1–2: observational photometric uncertainties, catalogs misprints, cross-match errors, variability or non-stellar nature of objects, non-standard behaviour of the interstellar extinction law in the area, etc. One of possible reasons is unresolved binaries: close binaries, which can be resolved neither photometrically (unless they exhibit mutual eclipses) nor astrometrically. Unresolved binaries with components of different temperature can exhibit colors different enough from ones of single stars. Such binaries can be separated from single stars in some color index diagrams. One of the goals of the present study is to specify color index diagrams, where the single-binary star separation is possible.
Fig. 2 SDSS/GALEX photometry. Blue squares—SDSS/GALEX objects in Boo (l = 353°, b = +68°, r = 0.1°, crossed squares) and Hya (l = 228°, b = +27°, r = 0.1°, open squares) areas. The other curves and symbols are the same as shown in Fig. 1
In Fig. 3 we show an example of theoretical consideration of the location of a A0V+K0III binary system (with components of approximately equal masses, around 2–2.5 solar mass) in the C1M468-C1M716–C1M379-C1M395 plane, where C1Mxxx are Gaia photometric bands. Here the binary can be easily detected. Simulations of unresolved binaries on color index diagrams were made for all combinations (pairings) of spectral types available in Pickles (1998) spectral library. Some pairings can be unfiled, as follows. • Evolutionary meaningless pairs. • Binaries with components of very different luminosity (m > 3m ). • Binaries with components of similar temperature (Sp < 1/2 spectral type, this approximately gives log Teff < 0.1 for hot stars, and log Teff < 0.02 for cool stars). However, such pairs are recognizable on color-magnitude plots, as they have an increased luminosity for a given color.
Astrophys Space Sci (2011) 335:105–111
107
Table 1 Two-color Gaia diagrams, where a separation of a given binary from the nearest single star is a maximum. Columns are: 1—spectral type of components; 2—best two-color diagram for separation; 3—separation from the nearest single star 1
2
3
1
2
3
B0V+F5I
C1M348-C1M515–C1M861-C1M965
0.06m
G8III+M3III
C1M410-C1M549–C1M656-C1M965
0.21m
B0V+F8I
C1M348-C1M395–C1M716-C1M965
0.11m
G8III+M4III
C1M410-C1M656–C1M549-C1M965
0.30m
B0V+G0I
C1M348-C1M515–C1M506-C1M716
0.24m
G8III+M5III
C1M379-C1M656–C1M549-C1M965
0.40m
C1M348-C1M549–C1M506-C1M965
0.39m
G8III+M6III
C1M395-C1M747–C1M656-C1M965
0.52m
C1M348-C1M549–C1M468-C1M965
0.45m
K0III+M1III
C1M515-C1M549–C1M716-C1M747
0.04m
B0V+G8I
C1M348-C1M515–C1M468-C1M965
0.62m
K0III+M2III
C1M410-C1M468–C1M716-C1M747
0.08m
B0V+K2I
C1M348-C1M468–C1M515-C1M965
0.86m
K0III+M3III
C1M515-C1M716–C1M716-C1M965
0.11m
C1M348-C1M549–C1M468-C1M965
0.89m
K0III+M4III
C1M410-C1M656–C1M656-C1M965
0.25m
C1M348-C1M515–C1M515-C1M965
1.13m
K0III+M5III
C1M395-C1M656–C1M549-C1M965
0.39m
B0V+M2I
C1M348-C1M515–C1M515-C1M965
1.23m
K0III+M6III
C1M395-C1M747–C1M656-C1M965
0.52m
B0V+M0III
C1M348-C1M515–C1M515-C1M965
1.13m
K1III+M1III
C1M506-C1M549–C1M861-C1M965
0.03m
C1M348-C1M515–C1M506-C1M965
1.17m
K1III+M2III
C1M515-C1M549–C1M747-C1M965
0.04m
C1M348-C1M515–C1M515-C1M965
1.23m
K1III+M3III
C1M506-C1M656–C1M716-C1M825
0.09m
C1M348-C1M515–C1M515-C1M965
1.23m
K1III+M4III
C1M410-C1M656–C1M656-C1M965
0.22m
B1V+M0III
C1M348-C1M515–C1M515-C1M965
1.03m
K1III+M5III
C1M410-C1M825–C1M656-C1M965
0.25m
B1V+M1III
C1M348-C1M515–C1M515-C1M965
1.03m
K1III+M6III
C1M395-C1M716–C1M716-C1M965
0.41m
C1M348-C1M515–C1M515-C1M965
1.03m
K2III+M0III
C1M348-C1M395–C1M549-C1M861
0.13m
C1M348-C1M515–C1M549-C1M965
1.11m
K2III+M1III
C1M348-C1M395–C1M515-C1M825
0.13m
B1V+M4III
C1M348-C1M549–C1M549-C1M965
1.41m
K2III+M2III
C1M348-C1M395–C1M549-C1M861
0.13m
B1V+M2I
C1M348-C1M515–C1M515-C1M965
1.23m
K2III+M3III
C1M348-C1M379–C1M515-C1M656
0.12m
C1M348-C1M656–C1M468-C1M965
1.56m
K2III+M4III
C1M515-C1M656–C1M656-C1M965
0.15m
C1M348-C1M656–C1M549-C1M965
1.64m
K2III+M5III
C1M379-C1M716–C1M656-C1M965
0.25m
B8V+K0III
C1M395-C1M410–C1M747-C1M825
0.04m
K2III+M6III
C1M395-C1M747–C1M656-C1M965
0.39m
B8V+K1III
C1M395-C1M410–C1M747-C1M965
0.09m
K3III+M0III
C1M348-C1M395–C1M716-C1M825
0.08m
C1M395-C1M468–C1M716-C1M965
0.16m
K3III+M1III
C1M348-C1M379–C1M515-C1M716
0.06m
C1M395-C1M410–C1M747-C1M965
0.09m
K3III+M3III
C1M348-C1M379–C1M515-C1M716
0.06m
B8V+K4III
C1M395-C1M549–C1M515-C1M965
0.35m
K3III+M4III
C1M515-C1M656–C1M716-C1M965
0.11m
B8V+K5III
C1M395-C1M549–C1M549-C1M965
0.53m
K3III+M5III
C1M468-C1M656–C1M747-C1M965
0.18m
C1M395-C1M468–C1M656-C1M965
0.48m
K3III+M6III
C1M395-C1M747–C1M656-C1M965
0.26m
C1M395-C1M656–C1M549-C1M965
0.60m
K4III+M4III
C1M395-C1M410–C1M861-C1M965
0.07m
B8V+M2III
C1M379-C1M515–C1M549-C1M965
0.74m
K4III+M5III
C1M348-C1M395–C1M410-C1M468
0.11m
B8V+M3III
C1M395-C1M549–C1M549-C1M965
0.89m
K4III+M6III
C1M348-C1M468–C1M747-C1M965
0.24m
C1M379-C1M549–C1M549-C1M965
1.11m
K5III+M0III
C1M348-C1M395–C1M716-C1M861
0.12m
C1M395-C1M549–C1M656-C1M965
1.18m
K5III+M1III
C1M348-C1M395–C1M656-C1M861
0.11m
C1M348-C1M656–C1M549-C1M965
1.41m
K5III+M2III
C1M348-C1M395–C1M395-C1M468
0.13m
B9V+K1III
C1M395-C1M410–C1M747-C1M965
0.09m
K5III+M3III
C1M348-C1M379–C1M410-C1M549
0.12m
B9V+K2III
C1M395-C1M410–C1M747-C1M965
0.09m
K5III+M4III
C1M348-C1M379–C1M410-C1M506
0.15m
C1M395-C1M410–C1M747-C1M965
0.09m
K5III+M5III
C1M348-C1M379–C1M348-C1M468
0.21m
C1M395-C1M515–C1M515-C1M861
0.30m
K5III+M6III
C1M348-C1M716–C1M656-C1M965
0.25m
B9V+K5III
C1M395-C1M716–C1M549-C1M965
0.40m
M0III+M5III
C1M348-C1M379–C1M348-C1M468
0.24m
B9V+M0III
C1M395-C1M716–C1M549-C1M965
0.40m
M0III+M6III
C1M348-C1M716–C1M656-C1M965
0.25m
C1M379-C1M549–C1M549-C1M965
0.60m
M1III+M6III
C1M348-C1M716–C1M656-C1M965
0.25m
C1M379-C1M515–C1M549-C1M965
0.74m
B0I+F5I
C1M348-C1M379–C1M861-C1M965
0.06m
B9V+M3III
C1M395-C1M549–C1M549-C1M965
0.89m
B0I+F8I
C1M348-C1M395–C1M656-C1M965
0.11m
B9V+M4III
C1M395-C1M549–C1M549-C1M965
1.03m
B0I+G0I
C1M348-C1M515–C1M468-C1M716
0.29m
C1M348-C1M656–C1M549-C1M965
1.05m
B0I+G2I
C1M348-C1M549–C1M506-C1M965
0.39m
B0V+G2I B0V+G5I
B0V+K3I B0V+K4I
B0V+M1III B0V+M2III B0V+M3III
B1V+M2III B1V+M3III
B1V+M5III B1V+M6III
B8V+K2III B8V+K3III
B8V+M0III B8V+M1III
B8V+M4III B8V+M5III B8V+M6III
B9V+K3III B9V+K4III
B9V+M1III B9V+M2III
B9V+M5III
108
Astrophys Space Sci (2011) 335:105–111
Table 1 (Continued) 1
2
3
1
2
3
B9V+M6III
C1M379-C1M656–C1M549-C1M965
1.39m
B0I+G5I
C1M348-C1M549–C1M410-C1M716
0.47m
A0V+K0III
C1M379-C1M395–C1M549-C1M861
0.03m
B0I+G8I
C1M348-C1M515–C1M468-C1M965
0.62m
A0V+K1III
C1M379-C1M395–C1M515-C1M656
0.08m
B0I+K2I
C1M348-C1M515–C1M468-C1M965
0.82m
C1M379-C1M395–C1M515-C1M656
0.08m
B0I+K3I
C1M348-C1M468–C1M515-C1M965
0.86m
C1M395-C1M410–C1M825-C1M965
0.09m
B0I+K4I
C1M348-C1M468–C1M515-C1M965
1.03m
A0V+K4III
C1M395-C1M468–C1M656-C1M965
0.21m
B0I+M2I
C1M348-C1M515–C1M515-C1M965
1.23m
A0V+K5III
C1M395-C1M656–C1M549-C1M965
0.40m
B1I+F5I
C1M379-C1M395–C1M861-C1M965
0.04m
C1M395-C1M549–C1M716-C1M965
0.41m
B1I+F8I
C1M348-C1M410–C1M515-C1M716
0.18m
C1M395-C1M549–C1M549-C1M965
0.53m
B1I+G0I
C1M348-C1M468–C1M468-C1M747
0.34m
A0V+M2III
C1M395-C1M549–C1M549-C1M965
0.71m
B1I+G2I
C1M348-C1M549–C1M410-C1M656
0.43m
A0V+M3III
C1M379-C1M549–C1M549-C1M965
0.79m
B1I+G5I
C1M348-C1M549–C1M410-C1M747
0.47m
C1M395-C1M506–C1M656-C1M965
0.93m
B1I+G8I
C1M348-C1M468–C1M515-C1M965
0.52m
C1M348-C1M656–C1M549-C1M965
1.01m
B1I+K2I
C1M348-C1M515–C1M468-C1M965
0.82m
A0V+M6III
C1M395-C1M656–C1M549-C1M965
1.37m
B1I+K3I
C1M348-C1M468–C1M506-C1M825
0.83m
A2V+G8III
C1M379-C1M395–C1M515-C1M716
0.08m
B1I+K4I
C1M348-C1M515–C1M515-C1M965
1.03m
C1M379-C1M395–C1M515-C1M716
0.08m
B1I+M2I
C1M348-C1M506–C1M515-C1M965
1.19m
C1M379-C1M395–C1M515-C1M656
0.08m
B3I+F5I
C1M348-C1M410–C1M861-C1M965
0.06m
A2V+K2III
C1M348-C1M395–C1M716-C1M965
0.11m
B3I+F8I
C1M348-C1M395–C1M515-C1M716
0.11m
A2V+K3III
C1M395-C1M410–C1M825-C1M965
0.09m
B3I+G0I
C1M348-C1M468–C1M515-C1M965
0.34m
C1M395-C1M468–C1M549-C1M861
0.24m
B3I+G2I
C1M348-C1M506–C1M410-C1M716
0.40m
C1M395-C1M656–C1M549-C1M965
0.40m
B3I+G5I
C1M348-C1M515–C1M468-C1M965
0.41m
C1M395-C1M549–C1M716-C1M965
0.41m
B3I+G8I
C1M348-C1M468–C1M468-C1M747
0.52m
A2V+M1III
C1M395-C1M549–C1M549-C1M965
0.53m
B3I+K2I
C1M348-C1M468–C1M515-C1M965
0.69m
A2V+M2III
C1M395-C1M549–C1M549-C1M965
0.71m
B3I+K3I
C1M348-C1M468–C1M515-C1M965
0.69m
C1M379-C1M515–C1M549-C1M965
0.74m
B3I+K4I
C1M348-C1M549–C1M506-C1M965
0.70m
C1M395-C1M506–C1M656-C1M965
0.93m
B3I+M2I
C1M348-C1M549–C1M515-C1M965
1.13m
A2V+M5III
C1M348-C1M656–C1M549-C1M965
1.01m
B5I+F8I
C1M348-C1M410–C1M861-C1M965
0.06m
A2V+M6III
C1M395-C1M656–C1M549-C1M965
1.37m
B5I+G0I
C1M348-C1M410–C1M515-C1M716
0.21m
C1M379-C1M395–C1M468-C1M656
0.07m
B5I+G2I
C1M348-C1M468–C1M468-C1M825
0.34m
C1M379-C1M395–C1M515-C1M656
0.08m
B5I+G5I
C1M348-C1M549–C1M410-C1M656
0.43m
A3V+K0III
C1M379-C1M395–C1M515-C1M656
0.08m
B5I+G8I
C1M348-C1M468–C1M515-C1M965
0.52m
A3V+K1III
C1M379-C1M395–C1M515-C1M656
0.08m
B5I+K2I
C1M348-C1M468–C1M549-C1M965
0.52m
C1M379-C1M395–C1M410-C1M716
0.08m
B5I+K3I
C1M348-C1M468–C1M549-C1M965
0.52m
C1M395-C1M410–C1M825-C1M965
0.09m
B5I+K4I
C1M348-C1M515–C1M515-C1M965
0.62m
A3V+K4III
C1M348-C1M395–C1M549-C1M716
0.16m
B5I+M2I
C1M379-C1M549–C1M549-C1M965
1.01m
A3V+K5III
C1M379-C1M549–C1M549-C1M965
0.40m
B8I+F8I
C1M348-C1M410–C1M395-C1M716
0.18m
C1M379-C1M549–C1M549-C1M965
0.40m
B8I+G0I
C1M348-C1M410–C1M549-C1M861
0.18m
C1M395-C1M549–C1M549-C1M965
0.53m
B8I+G2I
C1M348-C1M410–C1M549-C1M861
0.18m
A3V+M2III
C1M395-C1M716–C1M549-C1M965
0.60m
B8I+G5I
C1M348-C1M410–C1M549-C1M965
0.18m
A3V+M3III
C1M379-C1M506–C1M549-C1M965
0.72m
B8I+G8I
C1M379-C1M410–C1M515-C1M656
0.22m
C1M395-C1M506–C1M716-C1M965
0.87m
B8I+K2I
C1M379-C1M468–C1M549-C1M965
0.30m
C1M348-C1M656–C1M549-C1M965
1.01m
B8I+K3I
C1M348-C1M515–C1M515-C1M965
0.41m
C1M395-C1M656–C1M549-C1M965
1.27m
B8I+K4I
C1M348-C1M549–C1M506-C1M965
0.47m
A5V+G5III
C1M348-C1M379–C1M395-C1M515
0.07m
B8I+M2I
C1M379-C1M549–C1M549-C1M965
1.01m
A5V+G8III
C1M348-C1M379–C1M395-C1M506
0.07m
A0I+G5I
C1M395-C1M410–C1M549-C1M656
0.09m
C1M379-C1M395–C1M515-C1M656
0.07m
A0I+G8I
C1M395-C1M410–C1M549-C1M656
0.14m
C1M379-C1M395–C1M410-C1M716
0.08m
A0I+K2I
C1M395-C1M468–C1M515-C1M716
0.24m
A0V+K2III A0V+K3III
A0V+M0III A0V+M1III
A0V+M4III A0V+M5III
A2V+K0III A2V+K1III
A2V+K4III A2V+K5III A2V+M0III
A2V+M3III A2V+M4III
A3V+G5III A3V+G8III
A3V+K2III A3V+K3III
A3V+M0III A3V+M1III
A3V+M4III A3V+M5III A3V+M6III
A5V+K0III A5V+K1III
Astrophys Space Sci (2011) 335:105–111
109
Table 1 (Continued) 1
2
3
1
2
3
A5V+K2III
C1M348-C1M379–C1M747-C1M965
0.10m
A0I+K3I
C1M395-C1M549–C1M549-C1M965
0.35m
C1M348-C1M379–C1M747-C1M965
0.09m
A0I+K4I
C1M379-C1M549–C1M515-C1M965
0.43m
A5V+K4III
C1M348-C1M395–C1M549-C1M716
0.16m
A0I+M2I
C1M379-C1M549–C1M549-C1M965
1.01m
A5V+K5III
C1M379-C1M515–C1M549-C1M965
0.37m
A2I+G5I
C1M506-C1M656–C1M825-C1M861
0.02m
C1M395-C1M468–C1M716-C1M965
0.41m
A2I+G8I
C1M395-C1M410–C1M549-C1M656
0.09m
C1M395-C1M549–C1M549-C1M965
0.53m
A2I+K2I
C1M395-C1M410–C1M825-C1M965
0.14m
A5V+M2III
C1M379-C1M549–C1M549-C1M965
0.60m
A2I+K3I
C1M395-C1M468–C1M549-C1M965
0.24m
A5V+M3III
C1M395-C1M506–C1M656-C1M965
0.74m
A2I+K4I
C1M379-C1M656–C1M549-C1M965
0.40m
C1M395-C1M716–C1M656-C1M965
0.82m
A2I+M2I
C1M379-C1M549–C1M549-C1M965
0.95m
C1M379-C1M549–C1M656-C1M965
0.95m
F0I+G0I
C1M348-C1M395–C1M468-C1M549
0.13m
C1M395-C1M656–C1M549-C1M965
1.27m
F0I+G2I
C1M348-C1M395–C1M515-C1M716
0.16m
A7V+G8III
C1M379-C1M395–C1M549-C1M656
0.05m
F0I+G5I
C1M348-C1M395–C1M468-C1M549
0.19m
A7V+K0III
C1M379-C1M395–C1M410-C1M656
0.07m
F0I+G8I
C1M348-C1M395–C1M468-C1M656
0.32m
C1M379-C1M395–C1M410-C1M656
0.07m
F0I+K2I
C1M348-C1M395–C1M549-C1M861
0.32m
C1M379-C1M395–C1M410-C1M656
0.07m
F0I+K3I
C1M348-C1M395–C1M515-C1M656
0.39m
A7V+K3III
C1M395-C1M410–C1M747-C1M965
0.09m
F0I+K4I
C1M348-C1M395–C1M716-C1M965
0.40m
A7V+K4III
C1M395-C1M410–C1M747-C1M965
0.14m
F0I+M2I
C1M395-C1M506–C1M656-C1M965
0.70m
C1M395-C1M549–C1M549-C1M965
0.35m
F5I+G5I
C1M348-C1M395–C1M515-C1M656
0.16m
C1M395-C1M549–C1M656-C1M965
0.37m
F5I+G8I
C1M348-C1M395–C1M515-C1M656
0.24m
A7V+M4III
C1M395-C1M716–C1M656-C1M965
0.74m
F5I+K2I
C1M348-C1M379–C1M549-C1M656
0.24m
A7V+M5III
C1M379-C1M716–C1M549-C1M965
0.94m
F5I+K3I
C1M348-C1M395–C1M515-C1M716
0.32m
C1M395-C1M656–C1M549-C1M965
1.21m
F5I+K4I
C1M379-C1M549–C1M549-C1M965
0.40m
C1M379-C1M395–C1M395-C1M656
0.05m
F5I+M2I
C1M379-C1M515–C1M656-C1M965
0.61m
F0V+K1III
C1M379-C1M395–C1M395-C1M656
0.05m
F8I+G8I
C1M348-C1M410–C1M410-C1M656
0.21m
F0V+K3III
C1M395-C1M410–C1M825-C1M965
0.07m
F8I+K2I
C1M348-C1M395–C1M515-C1M656
0.24m
C1M395-C1M410–C1M747-C1M965
0.14m
F8I+K3I
C1M348-C1M379–C1M515-C1M716
0.25m
C1M395-C1M515–C1M549-C1M965
0.30m
F8I+K4I
C1M348-C1M379–C1M515-C1M861
0.30m
F0V+M5III
C1M379-C1M716–C1M549-C1M965
0.94m
F8I+M2I
C1M379-C1M468–C1M549-C1M861
0.44m
F0V+M6III
C1M395-C1M656–C1M549-C1M965
1.21m
G0I+G8I
C1M348-C1M379–C1M515-C1M656
0.12m
C1M395-C1M410–C1M747-C1M861
0.07m
G0I+K2I
C1M348-C1M379–C1M515-C1M861
0.12m
C1M395-C1M410–C1M747-C1M965
0.09m
G0I+K3I
C1M348-C1M379–C1M515-C1M861
0.12m
C1M395-C1M410–C1M747-C1M965
0.14m
G0I+K4I
C1M379-C1M410–C1M716-C1M965
0.13m
F2V+K5III
C1M395-C1M549–C1M656-C1M965
0.25m
G0I+M2I
C1M379-C1M656–C1M549-C1M965
0.40m
K0V+K7V
C1M468-C1M515–C1M515-C1M656
0.07m
G2I+G8I
C1M348-C1M379–C1M515-C1M716
0.12m
C1M395-C1M515–C1M747-C1M965
0.13m
G2I+K2I
C1M348-C1M379–C1M515-C1M861
0.12m
C1M468-C1M506–C1M515-C1M549
0.05m
G2I+K3I
C1M348-C1M379–C1M515-C1M716
0.12m
K2V+M1V
C1M410-C1M656–C1M716-C1M747
0.08m
G2I+K4I
C1M348-C1M379–C1M515-C1M656
0.12m
K3V+M1V
C1M410-C1M549–C1M716-C1M747
0.08m
G2I+M2I
C1M379-C1M549–C1M549-C1M965
0.32m
C1M379-C1M549–C1M656-C1M965
0.16m
G5I+K4I
C1M379-C1M410–C1M716-C1M861
0.05m
C1M379-C1M549–C1M716-C1M965
0.16m
G5I+M2I
C1M348-C1M379–C1M506-C1M656
0.09m
G5III+M3III
C1M379-C1M549–C1M656-C1M965
0.25m
G8I+K2I
C1M348-C1M379–C1M515-C1M716
0.15m
G5III+M4III
C1M379-C1M549–C1M549-C1M965
0.40m
G8I+K3I
C1M348-C1M379–C1M395-C1M825
0.15m
C1M348-C1M656–C1M468-C1M965
0.53m
G8I+K4I
C1M348-C1M379–C1M515-C1M656
0.12m
C1M348-C1M656–C1M410-C1M965
0.63m
G8I+M2I
C1M348-C1M379–C1M410-C1M515
0.12m
G8III+M1III
C1M410-C1M549–C1M825-C1M965
0.06m
K2I+M2I
C1M348-C1M395–C1M395-C1M468
0.17m
G8III+M2III
C1M410-C1M549–C1M716-C1M747
0.08m
K3I+M2I
C1M348-C1M395–C1M395-C1M468
0.21m
A5V+K3III
A5V+M0III A5V+M1III
A5V+M4III A5V+M5III A5V+M6III
A7V+K1III A7V+K2III
A7V+K5III A7V+M0III
A7V+M6III F0V+K0III
F0V+K4III F0V+K5III
F2V+K2III F2V+K3III F2V+K4III
K0V+M0V K2V+K7V
G5III+M1III G5III+M2III
G5III+M5III G5III+M6III
110
Astrophys Space Sci (2011) 335:105–111
Fig. 3 Theoretical location of a A0V+K0III binary (circle) and single stars of various luminosity class in a Gaia color index diagram. Solid line—V (MS), dashed line—III (giants), dotted line—I (supergiants). Location of an A0V star (cross) and a K0III star (triangle) is also indicated. Note the different axis scale
Fig. 5 Theoretical location of a B1V+M5III binary (circle) and single stars of various luminosity class in a two-color (top) and three-color (bottom) Gaia diagrams. The curves and symbols are the same as shown in Fig. 4
For remaining ≈ 280 types of pairs color index diagrams can be found, where a separation of such a binary from the nearest single star is a maximum. The resulting list of twocolor Gaia diagrams is presented in Table 1. It was found, in particular, that extreme (C1M348 and C1M985) Gaia bands are very important for the single-binary star separation.
4 Interstellar reddening
Fig. 4 Theoretical location of a A0V+K0III binary (circle) and single stars of various luminosity class in a two-color (top) and three-color (bottom) SDSS/GALEX diagrams. Line of increasing reddening is shown by arrow. The other curves and symbols are the same as shown in Fig. 3
Obviously, the reddening will complicate the identification of unresolved binaries in color index diagrams. To overcome this problem one can indicate diagrams where interstellar reddening does not prevent to discover the pair. Example of SDSS/GALEX color index diagrams is shown in Fig. 4, where the A0V+K0III binary system even being reddened can be separated from single stars. It should be noted that the observed colors can be significantly distorted due to extinction. For other binaries, color index diagrams can also be found where interstellar reddening does not prevent to discover the pair. An example is shown in Fig. 5. Here a B1V+M5III binary system can be separated from single stars in the C1M348-C1M965–C1M515-C1M965 (top) and
Astrophys Space Sci (2011) 335:105–111
C1M348-C1M965–C1M515-C1M965–C1M515-C1M747 (bottom) areas. Note: this pair was/is not a detached binary, as the more evolved component is the less massive one: mass of B1V and M5III stars are approximately 15 and 1 solar mass, respectively.
5 Conclusions A main goal of the present study was to develop a method for indication of an unresolved binarity from a composite flux in ultraviolet photometry. We have constructed a tool for simulation of color index diagrams, and we have snown that GALEX/SDSS photometry and Gaia photometry can be used for single-binary star separation and for parameterization of (even reddened) stars. Particularly, we have found Gaia color indices, most suitable for single-binary star separation. The developed procedure can be also applied to data to be generated from other future space observatories: WSOUV (Shustov et al. 2009), Lira-B, Svecha. Determination of
111
extinction value in a given area and construction of a 3D galactic interstellar extinction map is also envisaged. Acknowledgements We thank Dimitri Pourbaix and Frederic Arenou for collaboration and valuable comments. We are also grateful to Sergej Karpov for the SDSS/GALEX cross-matching. This work has been supported by Russian Foundation for Fundamental Research grants 08-02-00371, 09-02-00520, 10-02-00426 and 10-0700342, by the Federal Science and Innovations Agency under contract 02.740.11.0247, by the Federal target-oriented program “Scientific and pedagogical staff for innovation Russia” under contract P1195 and by the Presidium RAS program “Leading Scientific Schools Support” 4354.2008.2.
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