The FK Comae stars

Bopp, B. W.; Stencel, R. E.

doi:10.1086/183606

Cited by 159 publications

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“…The Hα emission intensity and profile are variable over the rotation period. The strongest emission occurs at photometric minimum, in accord with the presence of cool starspots on the rapidly rotating K giant (v sin i ≈ 90 km s −1 ; Bopp & Stencel 1981). Modelling photometric data, Olah et al (2002) found a surprisingly well-defined phase coherence of the light curve minima for eight consecutive years.…”

Section: Introductionmentioning

confidence: 66%

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X-ray spectroscopy of UZ Librae

Gondoin

2003

A&A

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Abstract. UZ Librae is the giant primary of a close binary system with extremely fast rotation and revolution. Its distinctive characteristics include an optical light curve with a large amplitude and a high X-ray luminosity. UZ Librae was observed twice at five months interval in August 2000 and January 2001 by the XMM-Newton space observatory. Serie of lines of highly ionized Fe and several lines of the Ly and He series are visible in the reflection grating spectra, most notably from C, O and Ne. The corresponding ions are associated with plasma components with temperature in the range 3-8 MK. Bremstrahlung emission from plasma at high temperature (T > 3 × 10 7 K) indicates an intense flaring activity on UZ Librae. This is also supported by a Ne abundance enhancement relative to oxygen reminiscent of abundance anomalies observed during stellar and solar flares. In contrast to oxygen and neon, the abundance of Fe in the corona of UZ Librae is determined to be a tenth of the solar photospheric value. We conjecture that the large fluid kinetic helicity induced by the rapid rotation of the star currently generates magnetic fields with two characteristic scales comparable with compact loops within solar active regions and with larger cooler loops interconnecting solar active regions. The X-ray emission of UZ Librae would be strongly enhanced not only due to the occurrence of these magnetic structures, but mainly due to their large surface coverage and to their permanent interactions responsible for heating UZ Librae plasma to high temperatures. A rotational modulation effect could have contributed to the luminosity variation between the two XMM-Newton observations since a large fraction of the X-ray emitting material might be located above large photospheric spots detected on Doppler images of the star.

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Section: Introductionmentioning

confidence: 66%

“…It is among the most active binary systems of the RSCVn class (Bopp & Stencel 1981). Dempsey et al (1997) present X-ray observations of evolved binary systems including UZ Librae, obtained with the Position Sensitive Proportional Counter (PSPC) during the ROSAT AllSky Survey phase of the mission.…”

Section: Introductionmentioning

confidence: 99%

X-ray spectroscopy of UZ Librae

Gondoin

2003

A&A

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“…Bopp et al (1985) have recently found that this FK Com star is a close binary with a 4.77-day orbital period and nearly synchronous stellar rotation. Except for a broad Ha emission line, UZ Librae closely resembles an RS CVn system.…”

Section: H the Datamentioning

confidence: 92%

On the coronae of rapidly rotating star. V - The other stars

Walter

1985

PASP

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“…F K Comae (HD 117555) is an extremely rapidly rotating single late-type giant (Bopp and Stencel, 1981;McCarthy and Ramsay, 1984: G2 III; P p hot = 2?4000; v sini = 1 2 0 k m / s ; u ra d = -21.3±6.2km/s). It is also the prototype for the definition of the F K Comae class, which originally contained two other candidates, UZ Librae and HD 199178 proposed by Bopp and Stencel (1981).…”

Section: Introductionmentioning

confidence: 99%

“…It is also the prototype for the definition of the F K Comae class, which originally contained two other candidates, UZ Librae and HD 199178 proposed by Bopp and Stencel (1981). A long-term photometric study of FK Comae has now been performed using basically the same methods as those presented by Jetsu et al (1990a,b) for HD 199178.…”

Section: Introductionmentioning

confidence: 99%

The Spot Activity of FK Comae Berenices

Jetsu

Pelt

Tuominen

et al. 1991

International Astronomical Union Colloquium

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A b s t r a c t : The active regions of FK Comae Berenices show a flip-flop behaviour, i.e. the concentrated part of spot-activity shifts exactly to the other side of stellar surface, and then remains on the same longitude for a time interval from a few years to a decade. The activity shows excellent phase coherence with respect to these two active longitudes separated 180 degrees from each other. FK Comae may provide a physical example of a non-linear dynamo, which shows surprisingly simple observational changes in the pattern of the magnetically induced spot configurations.

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The FK Comae stars

Cited by 159 publications

References 0 publications

X-ray spectroscopy of UZ Librae

X-ray spectroscopy of UZ Librae

On the coronae of rapidly rotating star. V - The other stars

The Spot Activity of FK Comae Berenices

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