Comparing X-ray color selection in separating X-ray binary classes using color-color-intensity diagrams

•Color-Color-Intensity diagrams are used for classifying X-ray binaries.•Different X-ray colors are tested for CCI diagrams of separate classes of XRBs.•X-ray binaries with black holes are separated from neutron stars in all X-ray colors.•Soft BH XRBs spectral states are separated in X-ray colors wi...

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Bibliographic Details
Published inNew astronomy Vol. 85; p. 101514
Main Authors Islam, N., Vrtilek, S.D., Boroson, Bram, Kim, D.-W., O’Sullivan, E., McCollough, M.L., Fabbiano, G., Anderson, C., Burke, D.J., D’Abrusco, R., Fruscione, A., Lauer, J.L., Morgan, D., Mossman, A., Paggi, A., Trinchieri, G.
Format Journal Article
LanguageEnglish
Published Goddard Space Flight Center Elsevier B.V 01.05.2021
Elsevier
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Summary:•Color-Color-Intensity diagrams are used for classifying X-ray binaries.•Different X-ray colors are tested for CCI diagrams of separate classes of XRBs.•X-ray binaries with black holes are separated from neutron stars in all X-ray colors.•Soft BH XRBs spectral states are separated in X-ray colors with lowest energyband. X-ray binaries exhibit a wide range of properties but there are few accepted methods to determine the nature of the compact object. Color-Color-Intensity diagrams have been suggested as a means of distinguishing between systems containing black holes from those containing neutron stars. However, this technique has been verified with data from only one instrument (RXTE/ASM) with a single set of X-ray colors defined using data available only in pre-determined energy bands. We test a selection of X-ray colors with a more sensitive instrument to determine the reliability of this method. We use data from the MAXI/Gas Slit Camera, which allows users to specify energy-bands. We test X-ray colors that have been previously defined in the literature as well as ones that we define specifically in this paper. A representative set of systems are used to construct Color-Color-Intensity diagrams in each set of colors to determine which are best for separating different classes. For studying individual sources certain bands are more effective than others. For a specified energy range, the separation of soft states in black hole binaries was possible only where both soft and hard colors included information from the lowest energy band. We confirm that Color-Color-Intensity diagrams can distinguish between systems containing black holes or neutron stars in all X-ray colors tested; this suggests an universality in the accretion processes governing these different classes. We suggest possible physical processes driving different classes of X-ray binaries to different locations in Color-Color-Intensity diagrams.
Bibliography:GSFC
Goddard Space Flight Center
ISSN:1384-1076
1384-1092
DOI:10.1016/j.newast.2020.101514