Discovery of Solar Rieger periodicities in another star

Massi, M.; Neidhoefer, J.; Carpentier, Y.; Ros, E.

doi:10.1051/0004-6361:200500097

Cited by 20 publications

(19 citation statements)

References 25 publications

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“…Future studies of the modulation of chromospheric indicators, like the flux in the cores of Ca II H and K lines, may provide further support for this interaction. We note that the detection of a short-term periodicity in a young latetype main-sequence star other than the Sun is a new result, since such short-term (or Rieger) cycles have been reported only in the RS CVn binary system UX Arietis, consisting of more evolved stars (Massi et al 2005).…”

Section: Discussionmentioning

confidence: 60%

Magnetic activity in the photosphere of CoRoT-Exo-2a

Lanza¹,

Pagano²,

Leto³

et al. 2008

A&A

158

206

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Context. The space experiment CoRoT has recently detected transits by a hot Jupiter across the disc of an active G7V star (CoRoTExo-2a) that can be considered as a good proxy for the Sun at an age of approximately 0.5 Gyr. Aims. We present a spot modelling of the optical variability of the star during 142 days of uninterrupted observations performed by CoRoT with unprecedented photometric precision. Methods. We apply spot modelling approaches previously tested in the case of the Sun by modelling total solar irradiance variations, a good proxy for the optical flux variations of the Sun as a star. The best results in terms of mapping of the surface brightness inhomogeneities are obtained by means of maximum entropy regularized models. To model the light curve of CoRoT-Exo-2a, we take into account the photometric effects of both cool spots and solar-like faculae, adopting solar analogy. Results. Two active longitudes initially on opposite hemispheres are found on the photosphere of CoRoT-Exo-2a with a rotation period of 4.522 ± 0.024 days. Their separation changes by ≈80• during the time span of the observations. From this variation, a relative amplitude of the surface differential rotation lower than ∼1 percent is estimated. Individual spots form within the active longitudes and show an angular velocity ∼1 percent lower than that of the longitude pattern. The total spotted area shows a cyclic oscillation with a period of 28.9 ± 4.3 days, which is close to 10 times the synodic period of the planet as seen by the rotating active longitudes. We discuss the effects of solar-like faculae on our models, finding indications of a facular contribution to the optical flux variations of CoRoT-Exo-2a being significantly smaller than in the present Sun. Conclusions. The implications of such results for the internal rotation of CoRoT-Exo-2a are discussed, based on solar analogy. A possible magnetic star-planet interaction is suggested by the cyclic variation of the spotted area. Alternatively, the 28.9-d cycle may be related to Rossby-type waves propagating in the subphotospheric layers of the star.

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Section: Discussionmentioning

confidence: 60%

Magnetic activity in the photosphere of CoRoT-Exo-2a

Lanza¹,

Pagano²,

Leto³

et al. 2008

A&A

158

206

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“…Those oscillations of the spotted area may be associated with hydromagnetic Rossby-type waves propagating in the upper part of the convection zone or at the interface between the radiative interior and the convection zone where the dynamo is probably located (Lou 2000;Zaqarashvili et al 2010). Since only a few examples of stars displaying Rieger-type cycles are known (cf., Massi et al 2005;Lanza et al 2009a), the new results on Kepler-17 are particularly interesting for a better understanding of this phenomenon in the framework of the solar-stellar connection.…”

Section: Discussionmentioning

confidence: 90%

Starspot activity and rotation of the planet-hosting star Kepler-17

Bonomo

Lanza

2012

A&A

101

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Context. Kepler-17 is a G2V sun-like star accompanied by a transiting planet with a mass of ≈2.5 Jupiter masses and an orbital period of 1.486 d, recently discovered by the Kepler space telescope. This star is highly interesting as a young solar analogue. It is also a good candidate for a test of the tidal theories for solar-like stars. Aims. We used about 500 days of high-precision, high-duty-cycle optical photometry collected by Kepler to study the rotation of the star and the evolution of its photospheric active regions.Methods. We applied a maximum-entropy light curve inversion technique to model the flux rotational modulation induced by active regions that consist of dark spots and bright solar-like faculae with a fixed area ratio. Their configuration was varied after a fixed time interval to take their evolution into account. Active regions were used as tracers to study stellar differential rotation, and planetary occultations were used to constrain the latitude of some spots. Results. Our modelling approach reproduces the light variations of Kepler-17 with a standard deviation of the residuals comparable with the precision of Kepler photometry. We find several active longitudes where individual active regions appear, evolve, and decay with lifetimes comparable to those observed in the Sun, although the star has a spotted area ≈10−15 times larger than the Sun at the maximum of the 11-yr cycle. Kepler-17 shows a solar-like latitudinal differential rotation, but the fast spot evolution prevents a precise determination of its amplitude. Moveover, the star shows a cyclic variation of the starspot area with a period of 47.1 ± 4.5 d, particularly evident during the last 200 days of the observations, similar to the solar Rieger cycles. Possible effects of the close-in massive planet on stellar photospheric activity cannot be excluded, but require a long-term monitoring to be unambiguously detected.

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“…in a single star, flares occur when new emerging loops from below the stellar surface move into older, already-existing loops (Heyvaerts et al 1977;Massi et al 2005). Such intruding loops have indeed been observed on the Sun in high-resolution maps obtained with the Nobeyama Radio Interferometer (Nishio et al 1996); 2. in protostars or young (pre-main sequence) stellar systems, which are still surrounded by a dense accretion disk, flares can occur because of stretching, disruption, and reconnection of magnetic field lines between the star and its disk (Feigelson & Montmerle 1999); 3. in close binary systems consisting of late spectral type stars, much higher magnetic activity is expected compared to the Sun (because tidal synchronism increases the rotation rate and therefore the dynamo efficiency).…”

Section: Introductionmentioning

confidence: 95%

Synchrotron emission from the T Tauri binary system V773 Tauri A

Massi¹,

Forbrich²,

Menten³

et al. 2006

A&A

Self Cite

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The pre-main sequence binary system V773 Tau A shows remarkable flaring activity around periastron passage. Here, we present the observation of such a flare at a wavelength of 3 mm (90 GHz) performed with the Plateau de Bure Interferometer . We examine different possible causes for the energy losses responsible for the e-folding time of 2.31 ± 0.19 h of that flare. We exclude synchrotron, collisional, and inverse Compton losses because they are not consistent with observational constraints, and we propose that the fading of the emission is due to the leakage of electrons themselves at each reflection between the two mirror points of the magnetic structure partially trapping them. The magnetic structure compatible with both our leakage model and previous observations is that of a helmet streamer that, as in the solar case, can occur at the top of the X-ray-emitting, stellar-sized coronal loops of one of the stars. The streamer may extend up to ∼20 R * and interact with the corona of the other star at periastron passage, causing recurring flares. The inferred magnetic field strength at the two mirror points of the helmet streamer is in the range 0.12−125 G, and the corresponding Lorentz factor, γ, of the partially trapped electrons is in the range 20 < γ < 632. We therefore rule out that the emission could be of gyro-synchrotron nature: the derived high Lorentz factor proves that the nature of the emission at 90 GHz from this pre-main binary system is synchrotron radiation.

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Discovery of Solar Rieger periodicities in another star

Cited by 20 publications

References 25 publications

Magnetic activity in the photosphere of CoRoT-Exo-2a

Magnetic activity in the photosphere of CoRoT-Exo-2a

Starspot activity and rotation of the planet-hosting star Kepler-17

Synchrotron emission from the T Tauri binary system V773 Tauri A

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