2019A&A...621A..21R


Query : 2019A&A...621A..21R

2019A&A...621A..21R - Astronomy and Astrophysics, volume 621A, 21-21 (2019/1-1)

Transition from spot to faculae domination. An alternate explanation for the dearth of intermediate Kepler rotation periods.

REINHOLD T., BELL K.J., KUSZLEWICZ J., HEKKER S. and SHAPIRO A.I.

Abstract (from CDS):


Context. The study of stellar activity cycles is crucial to understand the underlying dynamo and how it causes magnetic activity signatures such as dark spots and bright faculae. Having knowledge about the dominant source of surface activity might allow us to draw conclusions about the stellar age and magnetic field topology, and to put the solar cycle in context.
Aims. We investigate the underlying process that causes magnetic activity by studying the appearance of activity signatures in contemporaneous photometric and chromospheric time series.
Methods. Lomb-Scargle periodograms are used to search for cycle periods present in the photometric and chromospheric time series. To emphasize the signature of the activity cycle we account for rotation-induced scatter in both data sets by fitting a quasi-periodic Gaussian process model to each observing season. After subtracting the rotational variability, cycle amplitudes and the phase difference between the two time series are obtained by fitting both time series simultaneously using the same cycle period.
Results. We find cycle periods in 27 of the 30 stars in our sample. The phase difference between the two time series reveals that the variability in fast-rotating active stars is usually in anti-phase, while the variability of slowly rotating inactive stars is in phase. The photometric cycle amplitudes are on average six times larger for the active stars. The phase and amplitude information demonstrates that active stars are dominated by dark spots, whereas less-active stars are dominated by bright faculae. We find the transition from spot to faculae domination to be at the Vaughan-Preston gap, and around a Rossby number equal to one.
Conclusions. We conclude that faculae are the dominant ingredient of stellar activity cycles at ages ≥2.55Gyr. The data further suggest that the Vaughan-Preston gap cannot explain the previously detected dearth of Kepler rotation periods between 15 and 25 days. Nevertheless, our results led us to propose an explanation for the lack of rotation periods to be due to the non-detection of periodicity caused by the cancelation of dark spots and bright faculae at ∼800Myr.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: activity - stars: rotation

VizieR on-line data: <Available at CDS (J/A+A/621/A21): table1.dat tableb1.dat>

Simbad objects: 30

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Number of rows : 30
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 * 9 Cet BY* 00 22 51.7884553555 -12 12 33.969921319 7.29 7.05 6.39     G2.5V 471 0
2 * 107 Psc PM* 01 42 29.7625251280 +20 16 06.645657710 6.57 6.08 5.24 4.55 4.12 K1V 532 0
3 * 64 Cet PM* 02 11 21.0787585632 +08 34 11.305868808   6.189 5.623 6.81   G0IV 117 0
4 * rho Ari PM* 02 56 26.1717266513 +18 01 23.665188613   6.02 5.58 5.3   F6V 152 0
5 * kap01 Cet BY* 03 19 21.6964175772 +03 22 12.714979884 5.71 5.52 4.85 4.27 3.91 G5V 860 0
6 * 50 Per RS* 04 08 36.6171573432 +38 02 23.058806100 7.78 5.97   5.2   F8V 213 0
7 * 111 Tau BY* 05 24 25.4632701888 +17 23 00.726415944   5.52   4.7   F8V 327 0
8 * chi01 Ori RS* 05 54 22.9829893 +20 16 34.222038 5.08 5.00 4.40 3.90 3.59 G0V 831 0
9 * pi.01 UMa BY* 08 39 11.7046112880 +65 01 15.263122512 6.33 6.26 5.64 5.12 4.79 G0.5V 548 0
10 * 5 LMi PM* 08 50 32.2228174512 +33 17 06.195898140   6.738 6.210     F7Vs 165 0
11 HD 81809 SB* 09 27 46.8088908054 -06 04 17.008787302           G1.5IV-V 288 0
12 HD 82443 BY* 09 32 43.7594578944 +26 59 18.706023348   7.78   6.6   G9V(k) 237 1
13 * 11 LMi RS* 09 35 39.5021937366 +35 48 36.477051175 6.560 6.110 5.340 4.79 4.42 G8Va 359 0
14 HD 103095 Pe* 11 52 58.7673387755 +37 43 07.254113125 7.38 7.20 6.45 5.80 5.35 K1V_Fe-1.5 776 1
15 * e Vir PM* 13 16 46.5148594512 +09 25 26.960139646   5.81   4.8   G0V 534 1
16 HD 115404 PM* 13 16 51.0514297623 +17 01 01.840901307   7.69 6.66     K2V 264 0
17 * tau Boo Ro* 13 47 15.7381720026 +17 27 24.809555600 5.02 4.98 4.49 4.09 3.85 F7IV-V 953 1
18 * 14 Boo ** 14 14 05.1793499304 +12 57 33.996726108   6.08   5.2   F8V 167 0
19 V* EK Dra BY* 14 39 00.2104038120 +64 17 29.979649860   8.243 7.604     G1.5V 424 0
20 * ksi Boo A PM* 14 51 23.3884659504 +19 06 01.619801424   5.40 4.675     G7Ve 520 0
21 * rho CrB PM* 16 01 02.6604891411 +33 18 12.639472357   6.01   5.0   G0+VaFe-1 615 1
22 * 12 Oph BY* 16 36 21.4496896968 -02 19 28.513024233 7.00 6.55 5.77 5.13 4.74 K1V 468 0
23 HD 158614 SB* 17 30 23.79699 -01 03 46.4882 6.34 6.03 5.31 5.52   G9-IV-VHdel1 288 0
24 * 84 Her PM* 17 43 21.5645208624 +24 19 40.156969404   6.394 5.729     G2IIIb 142 0
25 * b Aql PM* 19 24 58.1999714302 +11 56 39.888480530 6.35 5.93   4.7   G7IVHdel1 476 0
26 * sig Dra PM* 19 32 21.5902098601 +69 39 40.235805206 5.860 5.460 4.680 4.04 3.63 K0V 610 0
27 HD 190007 BY* 20 02 47.0456863896 +03 19 34.265904204   8.60   6.8   K5V 212 0
28 * 61 Cyg A BY* 21 06 53.9395895022 +38 44 57.902349973 7.50 6.39 5.21 4.19 3.54 K5V 1005 0
29 * 61 Cyg B Er* 21 06 55.2638444466 +38 44 31.358519864 8.63 7.40 6.03 4.86 3.55 K7V 702 1
30 V* HN Peg BY* 21 44 31.3299461136 +14 46 18.983292600       6.16   G0V+ 489 0

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2023.01.31-08:22:24

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