The spot activity of FK Comae Berenices

Jetsu, L.; Pelt, J.; Tuominen, I.; Nations, H. L.

doi:10.1007/3-540-53955-7_161

Cited by 124 publications

(195 citation statements)

References 3 publications

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“…Indication of the flip-flop effect in LO Peg is quite similar to that observed by Korhonen, Berdyugina & Tuominen (2002) and Järvinen, Berdyugina & Strassmeier (2005). The flip-flop phenomenon has been noticed for the first time by Jetsu et al (1991) in the giant star FK Com. Later it was found to be cyclic in RS CVn and FK Comtype stars, as well as in some young solar analogues (e.g.…”

Section: Discussionsupporting

confidence: 82%

LO Peg: surface differential rotation, flares, and spot-topographic evolution

Karmakar

Pandey

Саванов

et al. 2016

Mon. Not. R. Astron. Soc.

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Using the wealth of ∼24 yr multiband data, we present an in-depth study of the starspot cycles, surface differential rotations (SDR), optical flares, evolution of star-spot distributions, and coronal activities on the surface of young, single, main-sequence, ultrafast rotator (UFR) LO Peg. From the long-term V -band photometry, we derive rotational period of LO Peg to be 0.4231 ± 0.0001 d. Using the seasonal variations on the rotational period, the SDR pattern is investigated, and shows a solar-like pattern of SDR. A cyclic pattern with period of ∼2.7 yr appears to be present in rotational period variation. During the observations, 20 optical flares are detected with a flare frequency of ∼1 flare per two days and with flare energy of ∼10 31−34 erg. The surface coverage of cool spots is found to be in the range of ∼9-26 per cent. It appears that the high-and low-latitude spots are interchanging their positions. Quasi-simultaneous observations in X-ray, UV, and optical photometric bands show a signature of an excess of X-ray and UV activities in spotted regions.

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Section: Discussionsupporting

confidence: 82%

LO Peg: surface differential rotation, flares, and spot-topographic evolution

Karmakar

Pandey

Саванов

et al. 2016

Mon. Not. R. Astron. Soc.

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“…These jumps are possibly a sign for some flip-flop scenario as already claimed for other stars (Jetsu et al 1993;Korhonen et al 2001), where the relative strength between two active longitudes is changing suddenly and periodically. The timescale of these "jump periods" derived from our global brightness map is roughly 10 stellar rotations; however, this is not seen in the transit map.…”

Section: Longitudinal Movement / Differential Rotationsupporting

confidence: 59%

Planetary eclipse mapping of CoRoT-2a

Huber

Czesla

Wolter

et al. 2010

A&A

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The lightcurve of CoRoT-2 shows substantial rotational modulation and deformations of the planet's transit profiles caused by starspots. We consistently model the entire lightcurve, including both rotational modulation and transits, stretching over approximately 30 stellar rotations and 79 transits. The spot distribution and its evolution on the noneclipsed and eclipsed surface sections are presented and analyzed, making use of the high resolution achievable under the transit path. We measure the average surface brightness on the eclipsed section to be (5 ± 1)% lower than on the noneclipsed section. Adopting a solar spot contrast, the spot coverage on the entire surface reaches up to 19% and a maximum of almost 40% on the eclipsed section. Features under the transit path, i.e. close to the equator, rotate with a period close to 4.55 days. Significantly higher rotation periods are found for features on the noneclipsed section indicating a differential rotation of ΔΩ > 0.1. Spotted and unspotted regions in both surface sections concentrate on preferred longitudes separated by roughly 180°.

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“…Finally, we note that the ''flip-flop'' effect, first discussed by Jetsu et al (1991) in FK Com, also appears to be present in HD 37824 and HD 181809. Korhonen et al (2002) found that FK Com shows two persistent active longitudes, separated by 180 , and that the dominant spot activity switches back and forth or flip-flops between the two longitudes.…”

Section: Spot Cyclesmentioning

confidence: 54%

Chromospherically Active Stars. XXIV. The Giant, Single-lined Binaries HD 37824, HD 181809, and HD 217188

Fekel

Henry

2005

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We have obtained spectroscopy and photometry of three chromospherically active, single-lined spectroscopic binaries, HD 37824 (V1149 Ori), HD 181809 (V4138 Sgr), and HD 217188 (AZ Psc). HD 37824 has a circular orbit with a period of 53.57 days. Its primary is a K0 III star, while the secondary is likely a G or K dwarf. HD 181809 has an orbit with a period of 13.04667 days and a low eccentricity of 0.040. The primary has a spectral type of K0 III-IV, and its secondary is probably an M dwarf. The orbit of HD 217188 has a period of 47.1209 days and a moderately high eccentricity of 0.470. The spectral type of the primary is K0 III, while the secondary is likely an M dwarf. All three systems are estimated to have near solar iron abundances. Photometric observations spanning 15-16 years for all three stars yield mean photometric periods of 53.12, 59.85, and 90.89 days for HD 37824, HD 181809, and HD 217188, respectively. Thus, HD 37824 is rotating synchronously with the orbital period, while HD 181809 and HD 217188 are both rotating considerably slower than synchronously. All three stars show longterm variations in mean brightness and photometric amplitude, but no correlations are observed between the seasonal mean brightness, photometric amplitude, and seasonal photometric period in any of the stars. No clear evidence for long-term periodic variations in any of these parameters is present. The circular orbit of HD 37824 and the synchronous rotation of its K giant argue that the star is in the core helium-burning phase of its evolution. The giant components of HD 181809 and HD 217188 are asynchronous rotators, and both systems have eccentric orbits. Thus, those two stars are likely first-ascent giants.

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The spot activity of FK Comae Berenices

Cited by 124 publications

References 3 publications

LO Peg: surface differential rotation, flares, and spot-topographic evolution

LO Peg: surface differential rotation, flares, and spot-topographic evolution

Planetary eclipse mapping of CoRoT-2a

Chromospherically Active Stars. XXIV. The Giant, Single-lined Binaries HD 37824, HD 181809, and HD 217188

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