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Multiperiodicity, modulations and flip-flops in variable star light curves II. Analysis of II Peg photometry during 1979-2010
Solar and Stellar Astrophysics · Submitted 15 Apr 2013
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim As a result, we confirm the earlier results of the spot activity having been dominated by one primary spotted region almost through the entire data set, and the existence of a persistent, nearly linear drift.
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The abstract, sentence by sentence
According to earlier Doppler images of the magnetically active primary giant component of the RS CVn binary II Peg, the surface of the star was dominated by one single active longitude that was clearly drifting in the rotational frame of the binary system during 1994-2002; later imaging for 2004-2010, however, showed decreased and chaotic spot activity, with no signs of the drift pattern. Here we set out to investigate from a more extensive photometric dataset whether such a drift is a persistent phenomenon, in which case it could be due to either an azimuthal dynamo wave or an indication of the binary system orbital synchronization still being incomplete. We analyse the datasets using the Carrier Fit method (hereafter CF), especially suitable for analyzing time series in which a fast clocking frequency (such as the rotation of the star) is modulated with a slower process (such as the stellar activity cycle). We combine all collected photometric data into one single data set, and analyze it with the CF method. As a result, we confirm the earlier results of the spot activity having been dominated by one primary spotted region almost through the entire data set, and the existence of a persistent, nearly linear drift. Disruptions of the linear trend and complicated phase behavior are also seen, but the period analysis reveals a rather stable periodicity with P(spot)=6.71054d plus/minus 0.00005d. After the linear trend is removed from the data, we identify several abrupt phase jumps, three of which are analyzed in more detail with the CF method. These phase jumps closely resemble what is called flip-flop event, but the new spot configurations do not, in most cases, persist for longer than a few months.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | According to earlier Doppler images of the magnetically active primary giant component of the RS CVn binary II Peg, the surface of the star was dominated by one single active longitude that was clearly drifting in the rotational frame of the binary system during 1994-2002; later imaging for 2004-2010, however, showed decreased and chaotic spot activity, with no signs of the drift pattern. | background 1.00 | 0.06 | 0.03 | asserted 1.00 |
| s1 | Here we set out to investigate from a more extensive photometric dataset whether such a drift is a persistent phenomenon, in which case it could be due to either an azimuthal dynamo wave or an indication of the binary system orbital synchronization still being incomplete. | contribution 0.70 | 0.33 | 0.03 | hedged possibility 0.82 |
| s2 | We analyse the datasets using the Carrier Fit method (hereafter CF), especially suitable for analyzing time series in which a fast clocking frequency (such as the rotation of the star) is modulated with a slower process (such as the stellar activity cycle). | method 1.00 | 0.82 | 0.02 | asserted 0.98 |
| s3 | We combine all collected photometric data into one single data set, and analyze it with the CF method. | method 0.98 | 0.95 | 0.02 | asserted 0.88 |
| s4 | As a result, we confirm the earlier results of the spot activity having been dominated by one primary spotted region almost through the entire data set, and the existence of a persistent, nearly linear drift. | result 1.00 | 0.93 | 0.80 | asserted 1.00 |
| s5 | Disruptions of the linear trend and complicated phase behavior are also seen, but the period analysis reveals a rather stable periodicity with P(spot)=6.71054d plus/minus 0.00005d. | result 1.00 | 0.95 | 0.16 | asserted 1.00 |
| s6 | After the linear trend is removed from the data, we identify several abrupt phase jumps, three of which are analyzed in more detail with the CF method. | result 0.52 | 0.96 | 0.04 | asserted 1.00 |
| s7 | These phase jumps closely resemble what is called flip-flop event, but the new spot configurations do not, in most cases, persist for longer than a few months. | result 0.65 | 0.93 | 0.07 | asserted 0.95 |
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The paper
Original abstract
According to earlier Doppler images of the magnetically active primary giant component of the RS CVn binary II Peg, the surface of the star was dominated by one single active longitude that was clearly drifting in the rotational frame of the binary system during 1994-2002; later imaging for 2004-2010, however, showed decreased and chaotic spot activity, with no signs of the drift pattern. Here we set out to investigate from a more extensive photometric dataset whether such a drift is a persistent phenomenon, in which case it could be due to either an azimuthal dynamo wave or an indication of the binary system orbital synchronization still being incomplete. We analyse the datasets using the Carrier Fit method (hereafter CF), especially suitable for analyzing time series in which a fast clocking frequency (such as the rotation of the star) is modulated with a slower process (such as the stellar activity cycle). We combine all collected photometric data into one single data set, and analyze it with the CF method. As a result, we confirm the earlier results of the spot activity having been dominated by one primary spotted region almost through the entire data set, and the existence of a persistent, nearly linear drift. Disruptions of the linear trend and complicated phase behavior are also seen, but the period analysis reveals a rather stable periodicity with P(spot)=6.71054d plus/minus 0.00005d. After the linear trend is removed from the data, we identify several abrupt phase jumps, three of which are analyzed in more detail with the CF method. These phase jumps closely resemble what is called flip-flop event, but the new spot configurations do not, in most cases, persist for longer than a few months.
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1 arXiv paper cite this in 4 sentences
Papers citing it · 3 sentences without a confident label
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In active rapid rotators, the reported pattern speeds are of the same order (in absolute terms) as reported in this study, see [ref] .
Azimuthal dynamo wave in spherical shell convection · Conclusions · 1.00
What it cites · 2 sentences without a confident label
Uses the method or tool of 1 paper
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Next, we divide the data into shorter segments, and perform a 'local' CF analysis [ref] .
Flip-flops of FK Comae Berenices · Stage 3: analysis of short segments · 0.98
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