Spectroscopy of Early F Stars: γ Doradus Candidates and Possible Metallic Shell Stars

Abstract

We obtained high-resolution spectroscopic observations of 34 Doradus candidates. From the redwavelength spectra, we determined spectral classes, radial velocities, and projected rotational velocities. The spectra of seven late A or early F stars show metallic lines that have composite profiles consisting of a narrow component near the center of a broad line, indicating that they may be shell stars or binaries. Several stars, including HD 152896, HD 173977, HD 175337, and HD 195068/9, show large line profile asymmetries. Two stars, HD 11443 (= Trianguli) and HD 149420, are ellipsoidal variables and not Doradus stars. The percentage of binary systems in our sample may be as high as 74%.

Long-term photometric monitoring with the Mercator telescope

“…The frequency given by Koen & Eyer (2002) for the Hipparcos data (1.78085 d −1 ) is not present in any of the significant threefrequency solutions. Fekel et al (2003) observed no velocity changes in the 2 spectra they obtained, but Mathias et al (2004) did. The latter also mentioned possible line-profile variations in the blue wing of the lines.…”

HD 173977: An ellipsoidal δ Scuti star variable

“…The large line asymmetries described by Fekel et al (2003) are certainly due to the presence of the weak lines of the companion, the residual flux of which are about 1/3 that of the main component. We measured the lines of the components using a Gaussian fit to both Ti  and Fe  lines.…”

“…The average of the derived velocities are listed in Table 1. We also considered the two velocity values given by Fekel et al (2003) to derive the parameters of the binary orbit that are provided in Table 2. This orbit is represented, for both components, in Fig.…”

“…From the angular frequency of the system, we can estimate a projected radius of 2.6 R for the main component and 1.3 R for its companion. The spectral type of the system provided in the literature is F2 (CDS) or F1 (Fekel et al 2003). Unfortunately, our spectral domain is not convenient to determine precisely the spectral characteristics of the two components.…”

“…Fekel et al (2003) obtained 2 spectra and found large variations both in line profile and in radial velocity, which led them to classify the star as a single line spectroscopic binary. This star was included in an observational photometric and spectroscopic campaign (Mathias et al, 2004) to compare its photometric and spectroscopic periods and to determine its pulsational modes from the line profile and radial velocity variations.…”