On the Binarity of the F0p Magnetic Stars <i>ϒ</i> Equ and 49 Cam

Mkrtichian, D. E.; Samus, N. N.; Gorynya, N. A.; North, P.; Hatzes, A. P.

doi:10.1017/s0252921100048740

Cited by 2 publications

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“…The binary hypothesis was supported by Scholz et al (1997), who observed a temporary drop in radial velocity for γ Equ during 4 consecutive nights. Their results are however contradicted by Mkrtichian et al (1998Mkrtichian et al ( , 1999. Magnetic field data spanning more than 58 years indicate that the variation is most likely due to rotation and therefore P mag = P rot (Bychkov et al 2006).…”

Section: Introduction -The History Of γ Equmentioning

confidence: 92%

MOST photometry and modeling of the rapidly oscillating (roAp) starγEquulei

Gruberbauer

Saio

Huber

et al. 2008

A&A

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Aims. Despite photometry and spectroscopy of its oscillations obtained over the past 25 years, the pulsation frequency spectrum of the rapidly oscillating Ap (roAp) star γ Equ has remained poorly understood. Better time-series photometry, combined with recent advances to incorporate interior magnetic field geometry into pulsational models, enable us to perform improved asteroseismology of this roAp star. Methods. We obtained 19 days of continuous high-precision photometry of γ Equ with the Most (Microvariability & Oscillations of STars) satellite. The data were reduced with two different reduction techniques and significant frequencies were identified. Those frequencies were fitted by interpolating a grid of pulsation models that include dipole magnetic fields of various polar strengths. Results. We identify 7 frequencies in γ Equ that we associate with 5 high-overtone p-modes and 1st and 2nd harmonics of the dominant p-mode. One of the modes and both harmonics are new discoveries for this star. Our best model solution (1.8 M , log T eff ∼ 3.882; polar field strength ∼8.1 kG) leads to unique mode identifications for these frequencies ( = 0, 1, 2 and 4). This is the first purely asteroseismic fit to a grid of magnetic models. We measure amplitude and phase modulation of the primary frequency due to beating with a closely spaced frequency that had never been resolved. This casts doubts on theories that such modulation -unrelated to the rotation of the star -is due to a stochastic excitation mechanism.

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Section: Introduction -The History Of γ Equmentioning

confidence: 92%

MOST photometry and modeling of the rapidly oscillating (roAp) starγEquulei

Gruberbauer

Saio

Huber

et al. 2008

A&A

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Multiplicity among chemically peculiar stars

Carrier¹,

North²,

Babel³

2002

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Abstract. We present new orbits for sixteen Ap spectroscopic binaries, four of which might in fact be Am stars, and give their orbital elements. Four of them are SB2 systems: HD 5550, HD 22128, HD 56495 and HD 98088. The twelve other stars are: HD 9996, HD 12288, HD 40711, HD 54908, HD 65339, HD 73709, HD 105680, HD 138426, HD 184471, HD 188854, HD 200405 and HD 216533. Rough estimates of the individual masses of the components of HD 65339 (53 Cam) are given, combining our radial velocities with the results of speckle interferometry and with Hipparcos parallaxes. Considering the mass functions of 74 spectroscopic binaries from this work and from the literature, we conclude that the distribution of the mass ratio is the same for cool Ap stars and for normal G dwarfs. Therefore, the only differences between binaries with normal stars and those hosting an Ap star lie in the period distribution: except for the case of HD 200405, all orbital periods are longer than (or equal to) 3 days. A consequence of this peculiar distribution is a deficit of null eccentricities. There is no indication that the secondary has a special nature, like e.g. a white dwarf.

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On the Binarity of the F0p Magnetic Stars ϒ Equ and 49 Cam

Cited by 2 publications

References 1 publication

MOST photometry and modeling of the rapidly oscillating (roAp) starγEquulei

MOST photometry and modeling of the rapidly oscillating (roAp) starγEquulei

Multiplicity among chemically peculiar stars

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