J/MNRAS/517/5050 K2-18 HARPS time-series (Radica+, 2022)
Revisiting radial velocity measurements of the K2-18 system with the
line-by-line framework.
Radica M., Artigau E., Lafreniere D., Cadieux C., Cook N.J., Doyon R.,
Amado P.J., Caballero J.A., Henning T., Quirrenbach A., Reiners A., Ribas I.
<Mon. Not. R. Astron. Soc. 517, 5050-5062 (2022)>
=2022MNRAS.517.5050R 2022MNRAS.517.5050R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Optical
Keywords: techniques: radial velocities -
planets and satellites: detection -
planets and satellites: fundamental parameters -
planets and satellites: individual: K2-18
Abstract:
The cross-correlation function and template matching techniques have
dominated the world of precision radial velocities for many years.
Recently, a new technique, named line-by-line, has been developed as
an outlier resistant way to efficiently extract radial velocity
content from high resolution spectra. We apply this new method to
archival HARPS and CARMENES datasets of the K2-18 system. After
reprocessing the HARPS dataset with the line-by-line framework, we are
able to replicate the findings of previous studies. Furthermore, by
splitting the full wavelength range into sub-domains, we were able to
identify a systematic chromatic correlation of the radial velocities
in the reprocessed CARMENES dataset. After post-processing the radial
velocities to remove this correlation, as well as rejecting some
outlier nights, we robustly uncover the signal of both K2-18b and
K2-18c, with masses that agree with those found from our analysis of
the HARPS dataset. We then combine both the HARPS and CARMENES
velocities to refine the parameters of both planets, notably resulting
in a revised mass and period for K2-18c of 6.99±0.97 Earth masses
and 9.2072±0.0065d, respectively. Our work thoroughly demonstrates
the power of the line-by-line technique for the extraction of
precision radial velocity information.
Description:
HARPS spectroscopic time-series of K2-18 reprocessed with the
line-by-line framework.
Objects:
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RA (2000) DE Designation(s)
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11 30 14.52 +07 35 18.3 K2-18 = EPIC 201912552
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 82 100 K2-18 HARPS time-series
tablea3.dat 102 64 K2-18 CARMENES time-series
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See also:
J/A+A/608/A35 : K2-18 HARPS time-series (Cloutier+, 2017)
J/AJ/155/257 : Photometry + RV follow-up observations of K2-18 (Sarkis+, 2018)
J/A+A/621/A49 : K2-18 HARPS time-series (Cloutier+, 2019)
J/A+A/634/L4 : HST/STIS FUV spectra of K2-18 (dos Santos+, 2020)
Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d Time Timestamp (BJD-2400000)
13- 19 F7.3 m/s RV Radial velocity
21- 25 F5.3 m/s e_RV Radial velocity uncertainty
27- 34 F8.3 m/s RV-u Radial Velocity (u band)
36- 42 F7.3 m/s e_RV-u Radial Velocity uncertainty (u band)
44- 50 F7.3 m/s RV-g Radial Velocity (g band)
52- 57 F6.3 m/s e_RV-g Radial Velocity uncertainty (g band)
59- 65 F7.3 m/s RV-r Radial Velocity (r band)
67- 71 F5.3 m/s e_RV-r Radial Velocity uncertainty (r band)
73- 82 F10.3 m2/s2 dLW Differential line width
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d Time Timestamp (BJD-2400000)
13- 20 F8.3 m/s RV Radial velocity
22- 27 F6.3 m/s e_RV Radial velocity uncertainty
29- 36 F8.3 m/s RV-g Radial Velocity (g band)
38- 43 F6.3 m/s e_RV-g Radial Velocity uncertainty (g band)
45- 52 F8.3 m/s RV-r Radial Velocity (r band)
54- 59 F6.3 m/s e_RV-r Radial Velocity uncertainty (r band)
61- 68 F8.3 m/s RV-i Radial Velocity (i band)
70- 75 F6.3 m/s e_RV-i Radial Velocity uncertainty (i band)
77- 83 F7.3 m/s RV-z Radial Velocity (z band)
85- 90 F6.3 m/s e_RV-z Radial Velocity uncertainty (z band)
92-102 F11.3 m2/s2 dLW Differential line width
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Acknowledgements:
Michael Radica, michael.radica(at)umontreal.ca
(End) Michael Radica [UdeM, Canada], Patricia Vannier [CDS] 18-Oct-2022