J/A+A/632/A37 Well sampled stars FEROS+HARPS radial velocities (Brems+, 2019)
Radial velocity jitter of stars as a function of observational timescale and
stellar age.
Brems S.S., Kuerster M., Trifonov T., Reffert S., Quirrenbach A.
<Astron. Astrophys. 632, A37 (2019)>
=2019A&A...632A..37B 2019A&A...632A..37B (SIMBAD/NED BibCode)
ADC_Keywords: Radial velocities ; Stars, normal
Keywords: stars: activity - methods: data analysis -
techniques: radial velocities
Abstract:
Stars show various amounts of Radial Velocity (RV) jitter due to
varying stellar activity levels. The typical amount of RV jitter as a
function of stellar age and observational timescale has not been
systematically quantified so far, although it is often larger than the
instrumental precision of modern high-resolution spectrographs used
for Doppler planet detection and characterization. We aim to
empirically determine the intrinsic stellar RV variation for mostly G
and K dwarf stars on different timescales and for different stellar
ages independently of stellar models. We also focus on young stars
(~<30Myr), where the RV variation is known to be large. We use
archival FEROS and HARPS RV data of stars which were observed at least
30 times spread over at least two years. We then apply the Pooled
Variance (PV) technique to these data sets to identify the periods and
amplitudes of underlying, quasiperiodic signals. We show that the PV
is a powerful tool to identify quasiperiodic signals in highly
irregularly sampled data sets. We derive activity-lag functions for 20
assumingly single stars stars, where lag is the timescale on which the
stellar jitter is measured. Since the ages of all stars are known, we
also use this to formulate an activity-age-lag relation which can be
used to predict the expected RV jitter of a star given its age and the
timescale to be probed. The maximum RV jitter on timescales of decades
decreases from over 500m/s for 5Myr old stars to 2.3m/s for stars
with ages around 5Gyr. The decrease in RV jitter when considering a
time scale of only 1d instead of 1yr is smaller by roughly a factor
of 4 for stars with an age of about 5Myr, and a factor of 1.5 for
stars with an age of 5Gyr. How fast the RV jitter increases with lag
strongly depends on stellar age and reaches 99% of the maximum RV
jitter between a few days for a few Myr old stars up to presumably
decades or longer for stars with an age of a few Gyr.
Description:
HARPS and FEROS Radial velocities for 27 F6 to M0 stars with ages
ranging from 3Myr to 7.2Gyr. The spectroscopic data from HARPS was
analyzed using SERVAL and the data from FEROS was analyzed using
CERES. All values are as they are those pipelines.
Note that SERVAL does by contstruction not return absolute RV values,
but only relative ones in between the measurements. They are thus
chosen to be roughly zero.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 52 27 List of studied stars
tablee1.dat 62 6004 Radial velocity data for all 27 stars
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Target Stellar ID
25- 26 I2 h RAh Simbad right ascension (J2000)
28- 29 I2 min RAm Simbad right ascension (J2000)
31- 35 F5.2 s RAs Simbad right ascension (J2000)
37 A1 --- DE- Simbad declination sign (J2000)
38- 39 I2 deg DEd Simbad declination (J2000)
41- 42 I2 arcmin DEm Simbad declination (J2000)
44- 47 F4.1 arcsec DEs Simbad declination (J2000)
49- 52 I4 --- Nobs Number of radial velocity measurements
in table E1 (tablee1.dat)
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Byte-by-byte Description of file: tablee1.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Target Stellar ID
23- 27 A5 --- Inst [HAPRS, FEROS] Instrument
29- 44 F16.8 d BJD Barycentric Julian Date
46- 55 F10.3 m/s RV Radial Velocity
57- 62 F6.3 m/s e_RV Error (std) of the Radial Velocity
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Acknowledgements:
Stefan Sebastian Brems, sbrems(at)lsw.uni-heidelberg.de
(End) Stefan S. Brems [Univ. Heidelberg], Patricia Vannier [CDS] 09-Oct-2019