J/AJ/155/106 New Doppler velocity measurements of GJ 876 (Millholland+, 2018)
New constraints on Gliese 876 - Exemplar of mean-motion resonance.
Millholland S., Laughlin G., Teske J., Butler R.P., Burt J., Holden B.,
Vogt S., Crane J., Shectman S., Thompson I.
<Astron. J., 155, 106 (2018)>
=2018AJ....155..106M 2018AJ....155..106M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Radial velocities ; Exoplanets
Keywords: planets and satellites: detection -
planets and satellites: dynamical evolution and stability -
planets and satellites: general - stars: individual (GJ 876)
Abstract:
Gliese 876 harbors one of the most dynamically rich and well-studied
exoplanetary systems. The nearby M4V dwarf hosts four known planets,
the outer three of which are trapped in a Laplace mean-motion
resonance. A thorough characterization of the complex resonant
perturbations exhibited by the orbiting planets, and the chaotic
dynamics therein, is key to a complete picture of the system's
formation and evolutionary history. Here we present a reanalysis of
the system using 6 yr of new radial velocity (RV) data from four
instruments. These new data augment and more than double the size of
the decades-long collection of existing velocity measurements. We
provide updated estimates of the system parameters by employing a
computationally efficient Wisdom-Holman N-body symplectic integrator,
coupled with a Gaussian process (GP) regression model to account for
correlated stellar noise. Experiments with synthetic RV data show that
the dynamical characterization of the system can differ depending on
whether a white-noise or correlated-noise model is adopted. Despite
there being a region of stability for an additional planet in the
resonant chain, we find no evidence for one. Our new parameter
estimates place the system even deeper into resonance than previously
thought and suggest that the system might be in a low-energy,
quasi-regular double apsidal corotation resonance. This result and
others will be used in a subsequent study on the primordial migration
processes responsible for the formation of the resonant chain.
Description:
The data set we consider here consists of two decades of RV measurements
from four spectrographs: Keck/HIRES, HARPS, the Automated Planet Finder
(APF) Levy Spectrograph, and the Carnegie Planet Finder Spectrograph (PFS)
on the Magellan Telescope. Note that the 54 new Keck/HIRES velocities
correspond to the same observations presented by Nelson et al.
(2016MNRAS.455.2484N 2016MNRAS.455.2484N), but the observations presented here were reduced by
the Lick-Carnegie Exoplanet Survey (LCES) team while those in Nelson et al.
(2016MNRAS.455.2484N 2016MNRAS.455.2484N) were reduced by the California Planet Search (CPS)
group. The Keck/HIRES, APF, and PFS RVs were obtained using the iodine cell
technique and spectral synthesis procedure described by Butler et al.
(1996PASP..108..500B 1996PASP..108..500B). We retrieved the new HARPS spectra from the
ESO-HARPS public archive and used the Template-Enhanced Radial velocity
Re-analysis Application (TERRA) pipeline for the RV measurement extraction
(Anglada-Escude & Butler 2012, J/ApJS/200/15).
Objects:
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RA (ICRS) DE Designation(s)
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22 53 16.73 -14 15 49.3 GJ 876 = BD-15 6290
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 54 552 New Doppler velocity measurements of the GJ 876
system from four instruments
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See also:
J/ApJ/634/625 : Radial velocities and photometry of GJ 876 (Rivera+, 2005)
J/A+A/511/A21 : Radial velocities of GJ876 planetary system (Correia+, 2010)
J/ApJ/719/890 : Keck radial velocities of GJ 876 (Rivera+, 2010)
J/ApJS/200/15 : HARPS-TERRA project. I. (Anglada-Escude+, 2012)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 I1 --- Sample [1/6] RV sample (1)
3 I1 --- f_Sample [0/1] Flag on Sample indicating new observations
(1=New)
5- 15 F11.3 d BJD Barycentric Julian Date of observation
17- 30 F14.9 m/s RV [-333.2757062/423.62] Radial velocity
32- 42 F11.9 m/s e_RV [0.399202018/8.01] Uncertainty in RV
44- 54 F11.9 --- S [0.3439/1.8697] Mount Wilson Ca HK activity index
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Note (1): Doppler velocity sample and instrumentation are defined as follows:
1 = ESO/HARPS, Correia et al. (2010A&A...511A..21C 2010A&A...511A..21C);
2 = ESO/HARPS, new;
3 = Keck/HIRES pre-upgrade;
4 = Keck/HIRES post-upgrade;
5 = Automated Planet Finder (APF) Levy Spectrograph;
6 = Carnegie Planet Finder Spectrograph (PFS) on Magellan.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 19-Oct-2018