Single-binary star separation by ultraviolet color index diagrams

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.

Unresolved Binaries and Multiples in the Intermediate Mass Range in Open Clusters: Pleiades, Alpha Per, Praesepe, and NGC 1039

“…The identification and classification of unresolved binary systems in star clusters based on multicolor stellar photometry have been the subject of a number of relatively recent papers. Malkov et al (2010) exploit the Gaia photometric system and suggest using photometric bands in the ultraviolet range to search for unresolved binary systems (Malkov et al 2011), but, unfortunately, there are currently no available deep enough photometric data sets in the ultraviolet range. Bardalez Gagliuffi et al (2014) have proposed methods to identify the unresolved binaries among the very low-mass stars and brown dwarfs using spectroscopic observations.…”

Astrometric microlensing of primordial black holes with Gaia

“…In case it is found that the predicted binary background is sufficiently small after such a study, and if the number of detected candidate AML events with Gaia is also sufficiently small, follow up observation of the detected candidates (possibly with terrestrial or other space-based telescopes) could be further used to identify binary companions. If the binary companions are in different spectral classes, photometric follow ups could detect intensity peaks in two widely separated bands [78][79][80][81], thus identifying it as a binary system. Although this technique would have low efficacy, other additional techniques such as spectroscopic measurements (either to detect different spectral types [82] or time-domain spectroscopy to measure Doppler shifts [83][84][85]) or high resolution imaging [86][87][88], can be used to identify binary systems among candidate lensing events.…”

Virtual Observatory for stellar astronomy

“…Construction of resulting color-index diagrams and parameterization of objects are discussed in Malkov et al (2011) andSichevskij (2012).…”