Line profile variations in   Doradus

Abstract

We present data from high-dispersion echelle spectra and simultaneous uvby photometry for γ Doradus. These data were obtained from several sites during 1994 November as part of the MUSICOS-94 campaign. The star has two closely-spaced periods of about 0.75 d and is the brightest member of a new class of variable early F-type stars. A previously suspected third period, very close to the other two, is confirmed. Previous observations indicated that sudden changes could be expected in the spectrum, but none were found during the campaign. The radial velocities rule out the possibility of a close companion. The phasing between the radial velocity and light curve of the strongest periodic component rules out the starspot model. The only viable mechanism for understanding the variability is nonradial pulsation. We used the method of moments to identify the modes of pulsation of the three periodic components. These appear to be sectorial retrograde modes with spherical harmonic degrees, (ℓ, m), as follows: f 1 = (3,3), f 2 = (1,1) and f 4 = (1,1). The angle of inclination of the star is found to be i ≈ 70 • .

Non-radial pulsations in the γ Doradus star HD 195068

“…From line profile variations in γ Doradus itself and using the moments method to identify the pulsational modes of the three periodic components, Balona et al (1996) Krisciunas et al (1995), Aerts & Krisciunas (1996) found with the moments method that they are a manifestation of the = 3, |m| = 1 spheroidal mode and its toroidal corrections due to the rotation of the star. Investigating two frequencies (1.32 d −1 and 1.40 d −1 ) deduced from multisite photometry of HD 108100, Breger et al (1997) concluded that amplitude ratios and phase differences between the light curves at different wavelengths are consistent with g-mode pulsation of = 1, rather than = 2.…”

Evidence of theγDoradus nature for a group of candidates

“…Their discovery among field stars is almost only Send offprint requests to: S. Martín, e-mail: susana@merate.mi.astro.it achievable serendipitously and, once discovered, they need multi-longitude observing campaigns to conveniently sample their curves. Examples are the works published by Balona et al (1996), Breger et al (1997) and Zerbi et al (1999).…”

Asteroseismology of γ Doradus Variables: Past, Present, and Future

“…Despite these minor setbacks, the γ Dor variables were defined as a class by Kaye et al (1999a) who, based on informal discussions at a conference held in 1995 at Cape Town, South Africa (Stobie & Whitelock 1995), and upon several papers in the literature (e.g., Krisciunas et al 1993;Balona et al 1996;Zerbi et al 1997aZerbi et al , 1997bPoretti et al 1997;Kaye 1998a;Kaye et al 1999b), defined the class to consist of "variable stars with an implied range in spectral type A7-F5 and in luminosity class IV, IV-V, or V; their variations are consistent with the model of high-order (n), low-degree ( ), nonradial, gravity-mode oscillations. "…”

“…While some may suspect that this is due to the intrinsically difficult nature of analysing γ Dor data, this particular issue has been verified with double-blind tests using different software and different analytical and numerical techniques on the same sets of data. Interested readers are encouraged to examine the published literature on 9 Aurigae (see, e.g., Krisciunas et al 1991;Krisciunas et al 1993;Balona, Krisciunas & Cousins 1994; Krisciunas et al 1995a;Aerts & Krisciunas 1996;Balona et al 1996;Zerbi et al 1997a); in addition, more than 10 years of BV differential photometry is now available on this object, yet the temporal dependence of the various modes is not understood.4 The "mystery" of HD 8801 and the recently discovered similar objects are discussed in the previous section. …”

“…Variable star class namesake: γ Doradus 2 (Cousins & Warren 1963) Brightest γ Dor star in the Northern Hemisphere: 9 Aurigae (Krisciunas & Guinan 1990) γ Dor stars with identified pulsation modes: γ Doradus (Balona et al 1996), 9 Aurigae (Aerts & Krisciunas 1996), HD 207223 (Aerts & Kaye 2001), HD 12901 (Dupret et al 2005a; see also Moya et al 2005), HD 48501 (Dupret et al 2005a; see also Suárez et al 2005) Chemically peculiar (λ Boötis-type): HR 8799 (Gray & Kaye 1999) Chemically peculiar (Am-type): HD 8801 , HD 100215 (Grenier et al 1999), HD 221866 (Kaye, Gray & Griffin 2004) Part of a confirmed binary system: HD 7169 ), HD 19684 (Henry & Fekel 2002, HD 23874 , HD 62454 (Kaye et al 1998b), HD 86358 (Henry & Fekel 2003), HD 100215 (Griffin 2006), HD 105085 (Henry & Fekel 2003), HD 113867 (Henry & Fekel 2003), HD 160295 (Henry & Fekel 2003), HD 167858 (De Cat et al 2006), HD 209295 (Handler et al 2002, HD 221866 (Kaye, Gray & Griffin 2004) Also show p-mode pulsations: HD 8801 , HD 209295 3 It is interesting to note that although HD 8801 is reported to be an Am star , it is not among the list of confirmed binary γ Dor stars. If this is verified, HD 8801 will be a very unique object, showing both γ Dor and δ Sct variations as well as being one of a very few single Am stars (see Abt 1961, Abt 1965, and the more recent discussions in Noels, Montalbán & Maceroni 2004 and references therein).…”