Access to Astronomical Catalogues

← Click to display the menu
J/A+A/511/A54   Magnetic cycles and radial-velocity for 8 stars  (Santos+, 2010)

Do stellar magnetic cycles influence the measurement of precise radial velocities? Santos N.C., Gomes da Silva J., Lovis C., Melo C. <Astron. Astrophys. 511, A54 (2010)> =2010A&A...511A..54S
ADC_Keywords: Stars, G-type ; Radial velocities Keywords: planetary systems - stars: fundamental parameters - techniques: spectroscopic - techniques: radial velocities - stars: activity - starspots Abstract: The ever increasing level of precision achieved by present and future radial velocity instruments is opening the way to the discovery of very low mass, long period planets (e.g. solar-system analogs). These systems will be detectable as low amplitude signals in radial-velocity (RV). However, an important obstacle to their detection may be the existence of stellar magnetic cycles with similar timescales. Here we present the results of a long term program to measure simultaneously radial-velocities and stellar activity indicators (CaII, Hα, HeI) for a sample of stars with known activity cycles. Our results suggest that all these stellar activity indexes can be used to trace the stellar magnetic cycle in solar-type stars. Further to this, we find clear indications that different parameters of the HARPS cross-correlation function (BIS, FWHM, and Contrast) are also sensitive to activity level variations. Finally, we show that though in a few cases slight correlations or anti-correlations between radial-velocity and the activity level of the star exist, their origin is still not clear. We can however conclude that for our targets (early-K dwarfs) we do not find evidence for radial-velocity variations induced by variations of the stellar magnetic cycle with amplitudes significantly above 1m/s. Description: Tables contain the data used to produce figures 2, 3, and 8. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 59 8 List of target stars table5.dat 37 241 CaII S activity level as a function of time table6.dat 39 275 Hα activity level as a function of time table7.dat 39 275 HeI D3 activity level as a function of time table8.dat 125 35 Yearly averages of CaII-S, RV, BIS, FWHM, and Contrast
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HD] 3- 8 I6 --- HD Star HD number 9 A1 --- m_HD Multiplicity index on HD 11- 14 F4.2 mag Vmag V magnitude 16- 20 F5.3 mag B-V B-V colour index 22- 28 A7 --- SpType MK spectral type 30- 31 I2 d Prot Rotational period (1) 33- 42 A10 "YYYY/MM/DD" ObsF First observation date 44- 53 A10 "YYYY/MM/DD" ObsL Last observation date 55- 56 I2 --- N Number of nights each star was observed 58- 59 I2 --- <S/N> Average signal-to-noise ratio of individual spectra in HARPS order 6 (near λ=4000Å)
Note (1): From Baliunas et al., 1996ApJ...457L..99B.
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HD] 3- 8 I6 --- HD Star HD number 10- 23 F14.6 d BJD Barycentric Julian date 25- 30 F6.4 --- SMW CaII activity level in MW scale (SMW scale, see Baliunas et al. 1995ApJ...438..269B) 32- 37 F6.4 --- e_SMW Statistical error in SMW
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HD] 3- 8 I6 --- HD Star HD number 10- 23 F14.6 d BJD Barycentric Julian date 25- 31 F7.5 --- Halpha Hα activity level 33- 39 F7.5 --- e_Halpha Statistical error in Hα
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HD] 3- 8 I6 --- HD Star HD number 10- 23 F14.6 d BJD Barycentric Julian date 25- 31 F7.5 --- HeI HeI activity level 33- 39 F7.5 --- e_HeI Statistical error in HeI
Byte-by-byte Description of file: table8.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HD] 3- 8 I6 --- HD Star HD number 10- 13 I4 yr Year Year of the measurements 15- 28 F14.6 d BJD1 ?=- Average Barycentric Julian Date for SMW values 30- 43 F14.6 d BJD2 Average Barycentric Julian Date for RV, FWHM, BIS, and Contrast values 45- 51 F7.5 --- <SMW> ?=- Average activity level in MW scale 53- 59 F7.5 --- e_<SMW> ?=- rms uncertainty on <SMW> 61- 68 F8.4 km/s <RV> Average radial velocity 70- 75 F6.4 km/s e_<RV> rms uncertainty on <RV> 77- 84 F8.5 km/s <BIS> Average Bisector Inverse Slope (BIS) value (1) 86- 92 F7.5 km/s e_<BIS> rms uncertainty on <BIS> 94-101 F8.5 % <Cont> Average Cross-Correlation Function's Contrast value (1) 103-109 F7.5 % e_<Cont> rms uncertainty on <Contrast> 111-117 F7.5 km/s <FWHM> Average FWHM value (1) 119-125 F7.5 km/s e_<FWHM> rms uncertainty on <FWHM>
Note (1): Parameters of the HARPS cross-correlation function.
Acknowledgements: Nuno Santos, nuno(at)astro.up.pt
(End) Patricia Vannier [CDS] 28-Dec-2009
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

catalogue service

© UDS/CNRS

Contact