ST ScI Preprint #1380

Evidence for a Population of Numerous Binaries with Comparably Bright Components among HIPPARCOS "Single" F Stars

We find evidence for the presence of a population of numerous binaries with comparably bright components (C-binaries) among HIPPARCOS F stars that are flagged in the HIPPARCOS catalogue as single. We propose a criterion that identifies such binaries. The criterion is based on comparison of absolute magnitude M V obtained from the HIPPARCOS parallax and Johnson V magnitude with absolute magnitude derived from the dereddened uvby luminosity index c₀, M_c0. For photometrically unresolved binaries, M_V must be brighter because it represents the integrated flux of a binary system while M_c0 is determined by the integrated spectrum and is thus close to the absolute magnitude of the primary. We have conducted a series of tests that have revealed the presence of C-binaries among HIPPARCOS "single" F stars and confirmed that the proposed criterion is quite effective at identifying these stars. The C-binary candidates have been found to be, on average, older than the candidates comprising single stars and binaries with disparate components (D-binaries).

Status:

Appeared in: The Astrophysical Journal, Letters

Affiliations:

¹⁾ Space Telescope Science Institute, 3700 San Martin Drive Baltimore, MD 21218