The On/Off nature of star-planet interactions in the HD 179949 and υ And systems

AbstractEvidence suggesting an observable magnetic interaction between a star and its hot Jupiter (Porb< 7 days,a< 0.1 AU,Mpsini> 0.2MJ) appears as a cyclic variation of stellar activity synchronized to the planet's orbit. HD 179949 has been observed almost every year since 2001. Synchronicity of the Ca II H & K emission with the orbit is clearly seen in four out of six epochs, while rotational modulation withProt=7 days is apparent in the other two seasons. We observe a similar phenomenon on υ And, which displays rotational modulation (Prot=12 days) in September 2005, while in 2002 and 2003 variations appear to correlate with the planet's orbital period. This on/off nature of star-planet interaction (SPI) in the two systems is likely a function of the changing stellar magnetic field structure throughout its activity cycle. The tentative correlation between this activity in the 13 stars we have observed to date and the ratio ofMpsinito the planet's rotation period, a quantity proportional to the hot Jupiter's magnetic moment, first presented in Shkolniket al. (2005) remains viable. This work furthers the characterization of SPI, improving its potential as a probe of extrasolar planetary magnetic fields.

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Magnetic characterization of the SPB/β Cep hybrid pulsator HD 43317

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731012 ◽

2017 ◽

Vol 605 ◽

pp. A104 ◽

Cited By ~ 10

Author(s):

B. Buysschaert ◽

C. Neiner ◽

M. Briquet ◽

C. Aerts

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Rotation Axis ◽

Rotation Period ◽

Line Of Sight ◽

Rotational Modulation ◽

Stellar Pulsation ◽

Deep Interior ◽

Rotating Surface

Large-scale magnetic fields at the surface of massive stars do not only influence the outer-most layers of the star, but also have consequences for the deep interior, only observationally accessible through asteroseismology. We performed a detailed characterization of the dipolar magnetic field at the surface of the B3.5V star HD 43317, a SPB/β Cep hybrid pulsator, by studying the rotationally modulated magnetic field of archival and new Narval spectropolarimetry. Additionally, we employed a grid-based approach to compare the Zeeman signatures with model profiles. By studying the rotational modulation of the He lines in both the Narval and HARPS spectroscopy caused by co-rotating surface abundance inhomogeneities, we updated the rotation period to 0.897673 ± 0.000004 d. The inclination angle between the rotation axis and the observer’s line of sight remains ill-defined, because of the low level of variability in Stokes V and deformations in the intensity profiles by stellar pulsation modes. The obliquity angle between the rotation and magnetic axes is constrained to β ∈ [ 67,90 ] °, and the strength of the dipolar magnetic field is of the order of 1 kG to 1.5 kG. This magnetic field at the stellar surface is sufficiently strong to warrant a uniformly rotating radiative envelope, causing less convective core overshooting, which should be visible in future forward seismic modeling.

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The Magnetic Be Star Sigma Orionis E

International Astronomical Union Colloquium ◽

10.1017/s0252921100116057 ◽

1987 ◽

Vol 92 ◽

pp. 82-83 ◽

Cited By ~ 3

Author(s):

C. T. Bolton ◽

A. W. Fullerton ◽

D. Bohlender ◽

J. D. Landstreet ◽

D. R. Gies

Keyword(s):

Magnetic Field ◽

Field Structure ◽

High Signal ◽

Rotational Period ◽

Magnetic Field Structure ◽

The Past ◽

Distribution Of Elements ◽

Be Star ◽

Hα Emission ◽

The Magnetic Field

Over the past two years, we have obtained high resolution high signal/noise (S/N) spectra of the magnetic Be star σ Ori E at the Canada-France-Hawaii Telescope and McDonald Observatory. These spectra, which cover the spectral regions 399-417.5 and 440-458.5 nm and the Hα line and have typical S/N>200 and spectral resolution ≃0.02 nm, were obtained at a variety of rotational phases in order to study the magnetic field structure, the distribution of elements in the photosphere, and the effects of the magnetic field on the emission envelope. Our analysis of these spectra confirms, refines and extends the results obtained by Landstreet & Borra (1978), Groote & Hunger (1982 and references therein), and Nakajima (1985).The Hα emission is usually double-peaked, but it undergoes remarkable variations with the 1.19081 d rotational period of the star, which show that the emitting gas is localized into two regions which co-rotate with the star.

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Propagation of an MHD Shock in the Vicinity of a Magnetic Neutral Sheet

Symposium - International Astronomical Union ◽

10.1017/s0074180900067802 ◽

1980 ◽

Vol 91 ◽

pp. 323-326

Author(s):

D. J. Mullan ◽

R. S. Steinolfson

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Solar Corona ◽

Large Scale ◽

Field Structure ◽

Neutral Sheet ◽

Solar Cosmic Rays ◽

Magnetic Field Structure ◽

Large Scale Magnetic Field ◽

Highly Correlated

The acceleration of solar cosmic rays in association with certain solar flares is known to be highly correlated with the propagation of an MHD shock through the solar corona (Svestka, 1976). The spatial structure of the sources of solar cosmic rays will be determined by those regions of the corona which are accessible to the flare-induced shock. The regions to which the flare shock is permitted to propagate are determined by the large scale magnetic field structure in the corona. McIntosh (1972, 1979) has demonstrated that quiescent filaments form a single continuous feature (a “baseball stitch”) around the surface of the sun. It is known that helmet streamers overlie quiescent filaments (Pneuman, 1975), and these helmet streamers contain large magnetic neutral sheets which are oriented essentially radially. Hence the magnetic field structure in the low solar corona is characterized by a large-scale radial neutral sheet which weaves around the entire sun following the “baseball stitch”. There is therefore a high probability that as a shock propagates away from a flare, it will eventually encounter this large neutral sheet.

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