Magnetic activity and dynamics of close binaries

Lanza, A. F.; Rodonò, M.

doi:10.1002/asna.200310239

Cited by 40 publications

(45 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The present results are qualitatively consistent with the torsional oscillation model discussed by Lanza & Rodono (2004). Further simultaneous radial velocity measurements and photometry are needed to determine more accurately the ratio of the periods of spot activity cycle and orbital period modulation.…”

Section: Discussionsupporting

confidence: 89%

“…The mechanism proposed by Applegate (1992), where the orbital motion is gravitationally coupled to variations in the shape of the magnetically active star due to variations in its internal angular velocity as it goes through its activity cycle, was later found to be inadequate on both observational and theoretical grounds (Lanza & Rodono 2004;Lanza 2005). The most direct prediction of the Applegate mechanism is that the modulations in the orbital period and spot activity should have the same timescale.…”

Section: Discussionmentioning

confidence: 99%

“…3 indicates that the ΔP/P has a near-sinusoidal modulation with a period around 36.3 ± 1.9 yr, while the spot activity varies with an average period around 14.1 ± 0.3 yr, which is clearly inconsistent with the mechanism. Lanza et al (1998) and Lanza & Rodono (2004) suggested improvements to the Applegate's mechanism, where they proposed that the anisotropic magnetic tension associated with the toroidal magnetic field also plays a role in distorting the shape of the star. According to their model, the magnetic energy, which is a measure of the total spot area, goes through two maxima during a cycle of orbital period variation.…”

Section: Discussionmentioning

confidence: 99%

“…Based on a study of the eclipse-times of a few RS CVn binaries that have simultaneous information about the spot area on the active component, Lanza & Rodono (2004) found that the lengths of the orbital period and spot activity cycles are, probably, in the ratio 2:1. A clear picture of the nature of orbital period variation and its relationship with the photometric variation is essential in understanding the basic physical mechanism that produces the cyclic variation in the orbital periods of chromospherically active binaries.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Muneer

Jayakumar

Rosario

et al. 2010

A&A

View full text Add to dashboard Cite

Aims. We attempt to establish the real nature of the orbital period variation and its relation to the spot activity of V711 Tau, and determine why the (B − V) colour of the star appears to be nearly independent of its V magnitude. We wish to verify whether existing predictions in the literature for the long-term spot activity of the star are true or not by making extended photometric observations, and whether the broad component of Hα emission originates in more localised active regions, as suggested by some chromospheric models, by searching for any correlation between the base-line width of the emission and the light modulation. Methods. We obtained new radial velocities of the G-type component of V711 Tau on 42 nights during 2004−09, and BV photometry of V711 Tau on 202 nights during the years 1993−2009. We measured the equivalent widths of two well resolved lines of the G-type component from 13 of the spectra obtained by us. We also measured the equivalent widths and base-line widths of Hα emission from 21 spectra obtained during 2008−09. We analyse these along with relevant information available in the literature. Results. The available radial velocity data of V 711 Tau are consistent with a sinusoidal modulation of its orbital period; the period of modulation is found to be 36.3 ± 1.9 yr. The fractional light-loss over a photometric cycle is found to vary with an average period of 14.1 ± 0.3 yr. It appears that physical processes linked to the magnetic activity of the spotted star are responsible for the variation in the orbital period. The excess reduction in the B band flux relative to that in V band caused by spot activity is almost compensated for by the fractional increase in the contribution by the hotter companion to the total light in the blue spectral region, and thereby makes the (B − V) colour of the binary system nearly independent of its V magnitude. We find that the ratio of the radii of the components derived from their v sin i values, which is usually quoted in the literature, is substantially larger than that implied by the ratio of their brightnesses in V band. There is a slight indication from the V band data that the spot activity in V711 Tau has a component that is fixed in the orbital frame of reference. The equivalent width and base-line width of Hα emission do not show any obvious correlation with the V band light curve.

show abstract

Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Muneer

Jayakumar

Rosario

et al. 2010

A&A

View full text Add to dashboard Cite

show abstract

“…This indicates that the common understanding of mechanisms driving the (O-C) in HU Aqr may be in fact incomplete. Indeed, Lanza et al (1998); Lanza & Rodonò (1999, 2002, 2004; Lanza (2005Lanza ( , 2006 derived a mechanism of the orbital period modulations in close binaries due to magnetic activity cycles in one component, extending the idea of Applegate (1992). This theory is build upon a hypothesis that the action of the hydromagnetic dynamo and the Lorentz force in the convective zone of the active star may cyclically change its quadrupole moment.…”

Section: Introductionmentioning

confidence: 97%

The HU Aqr planetary system hypothesis revisited

Goździewski

Słowikowska

Dimitrov

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We study the mid-egress eclipse timing data gathered for the cataclysmic binary HU Aquarii during the years 1993-2014. The (O-C) residuals were previously attributed to a single ∼ 7 Jupiter mass companion in ∼ 5 au orbit or to a stable 2-planet system with an unconstrained outermost orbit. We present 22 new observations gathered between June, 2011 and July, 2014 with four instruments around the world. They reveal a systematic deviation of ∼ 60-120 seconds from the older ephemeris. We re-analyse the whole set of the timing data available. Our results provide an erratum to the previous HU Aqr planetary models, indicating that the hypothesis for a third and fourth body in this system is uncertain. The dynamical stability criterion and a particular geometry of orbits rule out coplanar 2-planet configurations. A putative HU Aqr planetary system may be more complex, e.g., highly non-coplanar. Indeed, we found examples of 3-planet configurations with the middle planet in a retrograde orbit, which are stable for at least 1 Gyr, and consistent with the observations. The (O-C) may be also driven by oscillations of the gravitational quadrupole moment of the secondary, as predicted by the Lanza et al. modification of the Applegate mechanism. Further systematic, long-term monitoring of HU Aqr is required to interpret the (O-C) residuals.

show abstract

CK Bootis: a W UMa system with a small mass ratio

Kalci¹,

Derman

2005

Astron. Nachr.

View full text Add to dashboard Cite

Abstract.We present an analysis of BV R light curves of an eclipsing binary CK Bootis, a system with a very small mass ratio. The light curves appear to exhibit a typical O'Connell effect. The light curves are analyzed by means of the latest version of the WD program. The asymmetry of the light curves is explained by a cool star spot model. The simultaneous BV R synthetic light curve analysis gives a tiny mass ratio of 0.12, an extremely large fill-out factor of 0.65, and a very small difference between the component temperatures of 90 K. The absolute parameters of the system were also derived by combining the photometric solutions with the radial velocity data. The mass of the secondary is very low (0.15 M ) and it continues losing mass. Thirty seven new times of minimum are reported. It is found that the orbital period of the system has a quasi periodic variation, superimposed on a period increase. The long-term period increase rate is deduced to be dP/dt = 3.54x10 −7 d yr −1 , which can be interpreted as being due to mass transfer from the less massive star to the more massive component.

show abstract

Magnetic activity and dynamics of close binaries

Cited by 40 publications

References 46 publications

Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

The HU Aqr planetary system hypothesis revisited

CK Bootis: a W UMa system with a small mass ratio

Contact Info

Product

Resources

About