Photometry and line profile variations of the peculiar variable γ Doradus

Balona, L. A.; Hearnshaw, John; Koen, C.; Collier, Angela; Machi, I.; Mkhosi, M.; Steenberg, Conrad

doi:10.1093/mnras/267.1.103

Cited by 26 publications

(30 citation statements)

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“…After prewhitening, there is still power near 0.5842 d, 0.9647 d, and 0.4234 d. We are clearly dealing with a multi-periodic γ Dor star, but the aliasing is too strong to continue our period search. For γ Dor (=HD 27290), three periods are commonly present in photometry and spectroscopy: 0.75701 d, 0.73339 d, and 0.67797 d (Balona et al 1994a(Balona et al ,b, 1996. However, we find a δ Sct like period instead: 0.1103 d reduces the variance with 90% while the variance reduction for the known periods are all below 45% (Fig.…”

Section: Spectroscopic Variations Not Compatible With Photometric Periodmentioning

confidence: 57%

A spectroscopic study of southern (candidate) γ Doradus stars

Cat

Eyer

Cuypers³

et al. 2006

A&A

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We present the results of a spectroscopic study of 37 southern (candidate) γ Doradus stars based on échelle spectra. The observed spectra were cross-correlated with the standard template spectrum of an F0-type star for easier detection of binary and intrinsic variations. We identified 15 objects as spectroscopic binaries, including 7 new ones, while another 3 objects are binary suspects. At least 12 objects show composite spectra. We could determine the orbital parameters for 9 binaries, of which 4 turned out to be ellipsoidal variables. For 6 binaries, we estimated the expected time-base of the orbital variations. Clear profile variations were observed for 17 objects, pointing towards stellar pulsation. For 8 of them, we have evidence that the main spectroscopic and photometric periods coincide. Our results, in combination with prior knowledge from the literature, lead to the classification of 10 objects as new bona fide γ Doradus stars, 1 object as a new bona fide δ Scuti star, and 8 objects as constant stars. Finally, we determined the projected rotational velocity by two independent methods. The resulting v sin i values range from 3 to 135 km s −1 . For the bona fide γ Doradus stars, the majority has v sin i below 60 km s −1 .

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Section: Spectroscopic Variations Not Compatible With Photometric Periodmentioning

confidence: 57%

A spectroscopic study of southern (candidate) γ Doradus stars

Cat

Eyer

Cuypers³

et al. 2006

A&A

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“…According to its spectral type, 57 Tau is situated on HR diagram near to the cool border of the instability strip, exactly in the region where γ Dor stars are located. The g−mode frequencies of γ Dor stars discovered in the last few years (Abt et al 1983;Antonello & Mantegazza 1986;Krisciunas & Guinan 1990;Balona et al 1994;Breger et al 1997;Zerbi et al 1997;Kaye et al 1998;Kaye et al 1999a) occur in the same frequency range as in the low frequency domain of 57 Tau's amplitude spectrum. If this interpretation is correct 57 Tau would be the first δ Scuti type star where both p & high overtone g modes are excited, i.e.…”

Section: Discussionmentioning

confidence: 92%

A comprehensive study of the δ Scuti star, 57 Tauri (= HR 1351) in the Hyades cluster

Paparó

Rodríguez²,

McNamara

et al. 2000

Astron. Astrophys. Suppl. Ser.

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Abstract.A comprehensive frequency analysis of 57 Tau, supposed only a static pulsational arrangement, is presented based on 54 nights of photometric data collected between 1981 and 1995 (althogether 232 hours). The presence of individual frequencies is confirmed by intercomparing four subsets of this data set, however, the uncertainties in data coming from the sparse nights and low signal weaken the conclusion on some results. The entire data base is then used to resolve closely spaced peaks. Twelve frequencies are indentified using this process. Further multisite observations are recommended to confirm the present frequency solution. Two periods, with a high probability of being real, are found in the low frequency domain. They are suggested to arise from binarity or g modes, as in γ Dor stars. Single unusual cycles, possessing large amplitude, or displaying asymmetry, have been localized. A coherent frequency at 29.83 c/d with variable amplitude was found. The nonstandard behaviour of the light variation indicates that nonlinear and/or nonstationary processes could be very important in the investigation of δ Scuti observations.

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“…(2.19), γ is by definition directly proportional to the power supplied to or released from the mode by some external forces during a cycle. The work integral approach then consists in calculating the time derivative of the work by Cousins and Warren (1963), identified as a new class by Balona et al (1994) Red-giant stars p modes…”

Section: Work Integral Approachmentioning

confidence: 99%

Stellar oscillations - II - The non-adiabatic case

Samadi

Belkacem

Sonoi

2015

EAS Publications Series

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Abstract. A leap forward has been performed due to the space-borne missions, MOST, CoRoT and Kepler. They provided a wealth of observational data, and more precisely oscillation spectra, which have been (and are still) exploited to infer the internal structure of stars. While an adiabatic approach is often sufficient to get information on the stellar equilibrium structures it is not sufficient to get a full understanding of the physics of the oscillation. Indeed, it does not permit one to answer some fundamental questions about the oscillations, such as: What are the physical mechanisms responsible for the pulsations inside stars? What determines the amplitudes? To what extent the adiabatic approximation is valid? All these questions can only be addressed by considering the energy exchanges between the oscillations and the surrounding medium.This lecture therefore aims at considering the energetical aspects of stellar pulsations with particular emphasis on the driving and damping mechanisms. To this end, the full non-adiabatic equations are introduced and thoroughly discussed. Two types of pulsation are distinguished, namely the self-excited oscillations that result from an instability and the solar-like oscillations that result from a balance between driving and damping by turbulent convection. For each type, the main physical principles are presented and illustrated using recent observations obtained with the ultra-high precision photometry space-borne missions (MOST, CoRoT and Kepler). Finally, we consider in detail the physics of scaling relations, which relates the seismic global indices with the global stellar parameters and gave birth to the development of statistical (or ensemble) asteroseismology. Indeed, several of these relations rely on the same cause: the physics of non-adiabatic oscillations.

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Photometry and line profile variations of the peculiar variable γ Doradus

Cited by 26 publications

References 0 publications

A spectroscopic study of southern (candidate) γ Doradus stars

A spectroscopic study of southern (candidate) γ Doradus stars

A comprehensive study of the δ Scuti star, 57 Tauri (= HR 1351) in the Hyades cluster

Stellar oscillations - II - The non-adiabatic case

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