J/A+A/636/A119 YZ Ceti CARMENES and HARPS radial velocity curve (Stock+, 2020)
The CARMENES search for exoplanets around M dwarfs.
Characterization of the nearby ultra-compact multiplanetary system YZ Cet.
Stock S., Kemmer J., Reffert S., Trifonov T., Kaminski A., Dreizler S.,
Quirrenbach A., Caballero J.A., Reiners A., Jeffers S.V., Anglada-Escude G.,
Ribas I., Amado P.J., Barrado D., Barnes J.R., Bauer F.F., Berdinas Z.M.,
Bejar V.J.S., Coleman G.A.L., Cortes-Contreras M., Diez-Alonso E.,
Dominguez-Fernandez A.J., Espinoza N., Haswell C.A., Hatzes A., Henning T.,
Jenkins J.S., Jones H.R.A., Kossakowski D., Kuerster M., Lafarga M.,
Lee M.H., Lopez Gonzalez M.J., Montes D., Morales J.C., Morales N.,
Palle E., Pedraz S., Rodriguez E., Rodriguez-Lopez C., Zechmeister M.
<Astron. Astrophys. 636, A119 (2020)>
=2020A&A...636A.119S 2020A&A...636A.119S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Exoplanets ; Radial velocities ; Optical
Keywords: techniques: radial velocities - stars: individual: YZ Ceti -
stars: late-type - planets and satellites: terrestrial planets -
planets and satellites: dynamical evolution and stability -
planetary systems
Abstract:
The nearby ultra-compact multiplanetary system YZ Ceti consists of at
least three planets, and a fourth tentative signal. The orbital period
of each planet is the subject of discussion in the literature due to
strong aliasing in the radial velocity data. The stellar activity of
this M dwarf also hampers significantly the derivation of the
planetary parameters.
With an additional 229 radial velocity measurements obtained since the
discovery publication, we reanalyze the YZ Ceti system and resolve the
alias issues.
We use model comparison in the framework of Bayesian statistics and
periodogram simulations based on a method by Dawson and Fabrycky to
resolve the aliases. We discuss additional signals in the RV data, and
derive the planetary parameters by simultaneously modeling the stellar
activity with a Gaussian process regression model. To constrain the
planetary parameters further we apply a stability analysis on our
ensemble of Keplerian fits.
We find no evidence for a fourth possible companion. We resolve the
aliases: the three planets orbit the star with periods of 2.02d,
3.06d, and 4.66d. We also investigate an effect of the stellar
rotational signal on the derivation of the planetary parameters, in
particular the eccentricity of the innermost planet. Using photometry
we determine the stellar rotational period to be close to 68d and we
also detect this signal in the residuals of a three-planet fit to the
RV data and the spectral activity indicators. From our stability
analysis we derive a lower limit on the inclination of the system with
the assumption of coplanar orbits which is imin=0.9deg. From the
absence of a transit event with TESS, we derive an upper limit of the
inclination of imax=87.43deg.
YZ Ceti is a prime example of a system where strong aliasing hindered
the determination of the orbital periods of exoplanets. Additionally,
stellar activity influences the derivation of planetary parameters and
modeling them correctly is important for the reliable estimation of
the orbital parameters in this specific compact system. Stability
considerations then allow additional constraints to be placed on the
planetary parameters.
Description:
We acquired spectra with CARMENES (Quirrenbach et al., 2014, in Proc.
SPIE, Vol. 9147, Ground-based and Airborne Instrumentation for
Astronomy V, 91471F), a high-resolution precise echelle spectrograph
mounted at the 3.5m telescope at the Calar Alto Observatory in Spain.
We combined this data with 334 high-resolution spectra from HARPS, of
which 59 were collected by the Red Dots program (Dreizler et al.,
2019, arXiv e-prints, arXiv:1908.04717) and the remaining by
Astudillo-Defru et al. (2017A&A...605L..11A 2017A&A...605L..11A, Cat. J/A+A/605/L11).
Objects:
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RA (2000) DE Designation(s)
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01 12 30.64 -16 59 56.4 YZ Cet = V* YZ Cet
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 68 440 Radial velocity data
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See also:
J/A+A/605/L11 : YZ Ceti radial velocity curve (Astudillo-Defru+, 2017)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d BJD Barycentric Julian date
15- 35 F21.17 m/s RV Radial velocity
38- 55 F18.16 m/s e_RV Radial velocity uncertainty
59- 68 A10 --- Inst Instrument
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Acknowledgements:
Stephan Stock, sstock(at)lsw.uni-heidelberg.de
(End) Patricia Vannier [CDS] 06-Feb-2020