Main final dvi
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- Bu səhifədəki naviqasiya:
- Period [days]
- Signal searches on the assymetry of the spectral lines.
2 5 10 20 50 100 300 1000
Period [days] 0 10 20 30 40 ∆ ln L 1% FAP P 1 = 82.9 days P 2 = 85 days ~317 days m 2 - HARPS pre-2016 a 2 5 10 20 50 100 300
1000 Period [days] 0 10 20 30 40 ∆ ln L 1% FAP P 1 ~ 75 days P 2 ~ 38 days 8.39 days m 2 - HARPS PRD b Extended Data Figure 4: Signal searches on the width of the spectral lines. Likelihood peri- odogram searches on the width of the mean spectral line as measured by m 2
(panel a) and HARPS PRD data (panel b). The signals in the HARPS pre-2016 data are comparable to the photometric period reported in the literature and the variability in the HARPS PRD run com- pares quite well to the photometric variability. Black, red and blue lines represent the search for a first, second and third signal respectively. correlations.
2
The m
measurement contains a strong variability that closely mirrors the measurements from the photometric time-series (see Figure 3 in the main manuscript). As in the photometry, the rotation period and its first harmonic (∼ 40 days) are clearly detected in the PRD campaign (see Extended data Figure 4). This apparently good match needs to be verified on other stars as it might become a strong diagnostic for stellar activity in M-stars. The analysis of the HARPS pre-2016 also shows very strong evidence that m 2 is tracing the photometric rotation period of 83 days. The modelling of this HARPS pre-2016 requires a second sinusoid with P 2
close it is to P 1 . We suspect this is caused by photospheric features on the surface changing over time.
5.5 Asymmetry of the mean spectral lines as monitored by m 3 The periodogram analysis of m 3 of the PRD run suggests a signal at 24 days which is close to twice the Doppler signal of the planet candidate (see Extended Data Figure 5). However, line asymmetries are expected to be directly correlated with Doppler signals, not at twice nor integer multiples of the Doppler period. In addition, the peak has a FAP∼ 5% which makes it non-significantly different from white noise. When looking at the HARPS pre-2016 data, some strong beating is observed at 179 and 360 days, which is likely caused by a poorly sampled signal at that period or longer (magnetic cycle?), or some residual systematic effect (contamination by tellurics?). In summary, m 3
24 2 5 10 20 50 100 300 1000
Period [days] 0 10 20 30 40 50 60 ∆ ln L 1% FAP P 1 =179 or 360 days 16.9 days m 3 - HARPS pre-2016 a 2 5 10 20 50 100 300
1000 Period [days] 0 5 10 15 20 25 ∆
1% FAP 24.2 days m 3 - HARPS PRD b Extended Data Figure 5: Signal searches on the assymetry of the spectral lines. Likelihood periodogram searches on the line asymmetry as measured by m 3
a) and HARPS PRD (panel b) datasets. A signal beating at ∼ 1 year and 1/2 year is detected in the HARPS pre-2016 data, possibly related to instrumental systematic effects or telluric contamination. No signals are detected above 1% threshold in the HARPS PRD campaign. Black and red lines represent the search for first and second signals respectively. 5.6 Signal searches in S-index. While H
α 52 and other lines like the sodium doublet (NaD1 and NaD2) 63 have been shown to be the best tracers for activity on M-dwarfs, analyzing the time-series of the S-index is also useful because of its historical use in long term monitoring of main-sequence stars. 64 In Extended Data Figure 6 we show the likelihood ratio periodograms for the S-indices of the HARPS pre-2016 and PRD time-series. As can be seen, no signals were found around the 11 day period of the radial velocity signal, however two peaks were found close the 1% false alarm probability threshold with periods of ∼170 and 340 days. In order to further test the reality of these possible signals, we performed a Lomb-Scargle (LS) periodogram analysis 44 of the combined PRD and pre-2016 HARPS data. This test resulted in the marginal recovery of both the 170 and 340 day peaks seen in the likelihood periodograms, with no emerging peaks around the proposed 11 day Doppler signal. The LS tests revealed some weak evidence for a signal at much lower periods, ∼7 days and ∼30 days. Given that there is evidence for significant peaks close to periods of 1 yr, its first harmonic, and the lunar period, we also analysed the window function of the time-series to check if there was evidence that these peaks are artefacts from the combination of the window function pattern interfering with a real long-period activity signal in the data. The dominant power in the window function is found to increase at periods greater than 100 days, with a forest of strong peaks found in that domain, in comparison to sub-100 day periods which is very flat, representing the noise floor of the time-series. This indicates that there is likely to be strong interference patterns from the sampling in this region, and that the signal in the radial velocity data is also not due to the sampling of the data. A similar study in the context of the HARPS M-dwarf program was also done on Proxima. 63 They compared several indices and finally decided to use the intensity of the chromospheric sodium 25 Yüklə 354,89 Kb. Dostları ilə paylaş:
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