Archival light curves from the Bamberg Sky Patrol: CF Octantis, 1964-76

Innis, J. L.; Borisova, Ana; Coates, D. W.; Tsvetkov, Milcho

doi:10.1111/j.1365-2966.2004.08345.x

Cited by 5 publications

(10 citation statements)

References 14 publications

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“…Kroll et al 2001), as has been demonstrated by the work of Phillips & Hartmann (1978), Hartmann et al (1979), Hartmann et al (1981), Bondar' (1995, Alekseev & Bondar' (1998), Fröhlich et al (2002), and Innis et al (2004. Even though the photometric accuracy of a photographic brightness measure is low, averaging over dozens of measures nevertheless gives an accurate long-term mean light curve.…”

Section: Introductionmentioning

confidence: 76%

The RS CVn binary HK Lacertae: long-term photometry from Sonneberg sky-patrol plates

Fröhlich

Kroll²,

Strassmeier

2006

A&A

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Long-term photographic photometry of the active long-period RS CVn binary HK Lac (HD 209813) was obtained from more than 2000 Sonneberg Sky-Patrol plates taken between 1956 and 1996. We achieve an internal accuracy of 0. m 07. The correspondence with contemporaneous high-precision photoelectric photometry from automatic telescopes is striking and successfully demonstrates the feasibility of our approach. Based on a Bayesian time series analysis, we improve the previously published cycle period to 13.37 ± 0.08 years, and present evidence of an additional period of 9.48 ± 0.13 years. This establishes the multi-periodicity of dynamo action in these overactive stars as compared to the Sun. The already known 6.7-years cycle turns out to be an overtone of the dominating 13.4-years cycle. Our long-term photographic photometry even allowed the detection of the star's mean rotational period of 24.35 days.

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Section: Introductionmentioning

confidence: 76%

The RS CVn binary HK Lacertae: long-term photometry from Sonneberg sky-patrol plates

Fröhlich

Kroll²,

Strassmeier

2006

A&A

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“…In the GCVS (Samus et al 2010), the star is described as an RS CVn‐type variable with maximal brightness V = 8.27 mag and relatively large photometric variations ∼0.3 mag. Early archival observations from the BOSSS were recently digitized and analysed by Innis et al (2004).…”

Section: Cf Oct An Active Spotted Giant Starmentioning

confidence: 99%

“…CF Oct was observed on 352 plates in the period 1964–1976. Innis et al (2004) performed aperture photometry and phase dispersion minimization (PDM) light‐curve analysis. In Innis et al (2004) we discussed the methods for photographic plate digitization, the plate photometry and the transformation from B to V magnitude of the star.…”

Section: Observationsmentioning

confidence: 99%

“…Innis et al (2004) performed aperture photometry and phase dispersion minimization (PDM) light‐curve analysis. In Innis et al (2004) we discussed the methods for photographic plate digitization, the plate photometry and the transformation from B to V magnitude of the star. Plate data (BAM) are collected in more then six seasons relatively well covered by observations, separated by significant intervals with a lack of observations.…”

Section: Observationsmentioning

confidence: 99%

“…The phase shift of the minimal or maximal light suggested by Pollard et al (1989) and Innis et al (2004) led us to the idea of studying time‐residuals. The time‐residuals represent the difference between the observed and model‐predicted times of signal minima (or maxima) and are an analogue of the ( O − C ) terms in the light curves of binary stars.…”

Section: Long‐term Variability Of Cf Octmentioning

confidence: 99%

See 2 more Smart Citations

Bayesian approach to the cyclic activity of CF Oct

Borisova

Hambaryan

Innis³

2012

Monthly Notices of the Royal Astronomical Society

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The Bayesian statistical methods of Gregory–Loredo and the Bretthorst generalization of the Lomb–Scargle periodogram are used to study the activity cycles of the early K‐type subgiant star CF Oct. We use a ∼45‐yr‐long data set derived from archival photographic observations, published photoelectric photometry, the Hipparcos data series and the All Sky Automated Survey archive. We confirm the already known rotational period for the star of 20.16 d and provide evidence that it has exhibited changes from 19.90 to 20.45 d. This is an indication of stellar surface differential rotation. The Bayesian magnitude and time‐residual analysis clearly reveals at least one long‐term cycle. The posterior distributions of the cycle length appear to be multimodal with pronounced peaks at a period of 7.1 yr with a full width at half‐maximum (FWHM) of 54 d for time‐residuals and at a period of 9.8 yr with a FWHM of 184 d for magnitude data. These results are consistent with the previously postulated cycle of 9 ± 3 yr.

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Measuring the Spin of the Primary Black Hole in Oj287

Valtonen

Mikkola

Merritt

et al. 2010

ApJ

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The compact binary system in OJ287 is modelled to contain a spinning primary black hole with an accretion disk and a non-spinning secondary black hole. Using Post Newtonian (PN) accurate equations that include 2.5PN accurate non-spinning contributions, the leading order general relativistic and classical spin-orbit terms, the orbit of the binary black hole in OJ287 is calculated and as expected it depends on the spin of the primary black hole. Using the orbital solution, the specific times when the orbit of the secondary crosses the accretion disk of the primary are evaluated such that the record of observed outbursts from 1913 up to 2007 is reproduced. The timings of the outbursts are quite sensitive to the spin value. In order to reproduce all the known outbursts, including a newly discovered one in 1957, the Kerr parameter of the primary has to be 0.28 ± 0.08. The quadrupole-moment contributions to the equations of motion allow us to constrain the 'no-hair' parameter to be 1.0 ± 0.3 where 0.3 is the one sigma error. This supports the 'black hole no-hair theorem' within the achievable precision.It should be possible to test the present estimate in 2015 when the next outburst is due. The timing of the 2015 outburst is a strong function of the spin: if the spin is 0.36 of the maximal value allowed in general relativity, the outburst begins in early November 2015, while the same event starts in the end of January 2016 if the spin is 0.2.

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Archival light curves from the Bamberg Sky Patrol: CF Octantis, 1964-76

Cited by 5 publications

References 14 publications

The RS CVn binary HK Lacertae: long-term photometry from Sonneberg sky-patrol plates

The RS CVn binary HK Lacertae: long-term photometry from Sonneberg sky-patrol plates

Bayesian approach to the cyclic activity of CF Oct

Measuring the Spin of the Primary Black Hole in Oj287

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