A search for SB2 systems among selected Am binaries

Abstract

Abstract. We report on the detection of secondary spectra in five spectroscopic binary systems: HD 434, HD 861, HD 108642, HD 178449, and HD 216608. High signal-to-noise high resolution spectroscopic observations were carried out at the Bulgarian NAO Rozhen as part of an extended project concerned mainly with Am stars in binary systems. Our knowledge about early type binaries has serious gaps. This is true especially when it is only based on older photographic techniques. We concluded that photographic data involving longer orbital periods (where Doppler shifts due to the orbital motion are comparable or even less than the rotational broadening of the spectral lines) and early type stars (that have only a few and usually broad lines) should be revisited or at least used with caution. We demonstrate that for the five systems how CCD observations made with 2-m class telescopes can discover the binary nature or secondary spectra of many currently unresolved SB1 systems. Important astrophysical information such as the atmospheric parameters and the mass ratios are used to unravel previous misinterpretations of the data leading often to spurious orbits.

New Precision Orbits of Bright Double-Lined Spectroscopic Binaries. V. The Am Stars Hd 434 and 41 Sextantis

“…Walker (1966) estimated a v sin i value of 60 ± 25 km s −1 . However, the significantly higher resolution observations of Iliev et al (2001) resulted in values of about 32 and 27 km s −1 for the primary and secondary, respectively. Cowley et al (1969) included 41 Sex (α = 10 h 50 m 18. s 06, δ = −08 • 53 51.…”

“…Both Sreedhar Rao & Abhyankar (1992) and Margoni et al (1992) collected additional observations, and using previous velocity observations, the two groups independently revised the preliminary orbit of Hube & Gulliver (1985). As part of an extended project on Am binaries, Iliev et al (2001) reobserved HD 434 and announced the discovery of its secondary spectrum. From those spectra, Budaj et al (2003) obtained a mass ratio of 1.19 for the primary relative to the secondary.…”

“…More recently Abt (2004) also identified the combined spectrum as that of a classical Am star and provided spectral classes for its Ca K, hydrogen, and metal lines of A2, A6, and F0, respectively. Examining their red wavelength spectra where both components of the binary were in evidence, Iliev et al (2001) concluded that both stars have Am peculiarities. Walker (1966) estimated a v sin i value of 60 ± 25 km s −1 .…”

Observations of nonmagnetic CP stars: crossing boundaries

“…As a result of improvements in the quality of spectra, companions to HgMn stars continue to be identified, and we should expect to find additional cases of binarity among currently known Am and HgMn stars (see, e.g., Iliev et al 2005) Most literature still cites older statistics that claim binarity among HgMn stars to be no more prevalent than among the general field stars, which is to say about 50%. However, this conflicts with published statements claiming a lower limit perhaps as high as 67% and the general impression that binarity is more prevalent since companions continue to be discovered.…”

Search for Tidally Driven Anomalies in the Atmospheres of Am Stars

“…We started a systematic study (Budaj & Iliev 2003, hereafter Paper I); and Iliev et al 2006, hereafter Paper II) of the Am peculiarity in binary stars in order to search for abundance anomalies driven by the tidal interaction in these systems.…”