J/A+A/705/A252 HD 176986 HARPS Rvs and activity indicators (Nari+, 2026)
The RoPES project with HARPS and HARPS-N.
II. A third planet in the multi-planetary system HD 176986.
Nari N., Suarez Mascareno A., Gonzalez Hernandez J.I., Stefanov A.K.,
Rebolo R., Mestre J.M., Dumusque X., Cretignier M., Passegger V.M.,
Mignon L.
<Astron. Astrophys. 705, A252 (2026)>
=2026A&A...705A.252N 2026A&A...705A.252N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Optical ; Spectroscopy
Keywords: planets and satellites: detection -
planets and satellites: terrestrial planets -
stars: individual: HD 176986
Abstract:
Earth-like planets orbiting in the habitable zone of K- to G-type
stars create an RV effect in amplitude of less than 1m/s and have
orbital periods of hundreds of days. Only long-term RV surveys with
sub-meter per second precision instruments can explore the outer
regions of Sun-like stars and look for Earth-like planets and
super-Earths. Detecting Earth-like or super-Earth planets in the
habitable zone of Sun-like stars is crucial to provide targets to the
next generation of direct imaging facilities.
We present the analysis of the K-type star HD 176986. It has a
brightness of V=8.45mag and a distance from the Sun of d=27.88pc.
This star hosts a known planetary system of two super-Earths. We
utilize historical and recently collected RV measurements to
investigate the presence of Earth- and super-Earth-like planets in the
habitable zone of HD 176986.
We monitored the system with HARPS and HARPS-N. We joined historical
datasets with new data collected in an ongoing blind search program.
We took advantage of recently developed tools for RV extraction and
stellar activity filtering. The analysis of activity indicators
permits us to determine the period of the magnetic cycle of the star
alongside its rotation period. We performed a joint analysis of RVs
and activity indicators through multidimensional GPs to better
constrain the activity model in RVs and avoid overfitting.
We detected a new planet orbiting the star and retrieved the two known
planets. HD 176986 b has an orbital period of
6.49164-0.00029+0.00030d and a minimum mass of
5.36±0.44M⊕. HD 176986 c has an orbital period of
Pc=16.8124±0.0015d and a minimum mass of
9.75-0.64+0.65M⊕. HD 176986 d has an orbital period of
61.376_-0.049+0.051d and a minimum mass of
6.76-0.92+0.91M⊕. From the analysis of activity
indicators, we find evidence of a magnetic cycle with a period of
2432-59+64d, along with a rotation period of 36.05-0.71+0.67d.
We discover a new planet in the multi-planet system orbiting the
K-type star HD 176986. All the planets have minimum masses compatible
with super-Earths or mini-Neptunes.
Description:
We report the discovery of a system of two super-Earths orbiting the
moderately active K-dwarf HD 176986. This work is part of the RoPES RV
program of G- and K-type stars, which combines radial velocities (RVs)
from the HARPS and HARPS-N spectrographs to search for short-period
terrestrial planets. HD 176986 b and c are super-Earth planets with
masses of 5.74 and 9.18M⊕, orbital periods of 6.49 and 16.82
days, and distances of 0.063 and 0.119 AU in orbits that are
consistent with circular. The host star is a K2.5 dwarf, and despite
its modest level of chromospheric activity
(log10(RHK)=-4.90±0.04), it shows a complex activity pattern.
Along with the discovery of the planets, we study the magnetic cycle
and rotation of the star. HD 176986 proves to be suitable for testing
the available RV analysis technique and further our understanding of
stellar activity.
Tables contain RV and activity indicators used in our analysis. We
provide the YARARA RV and activity indicators calculated either before
and after the stellar activity correction. yararava.dat are without
stellar activity correction and derived with the CCF-technique.
yararav1.dat are calculated after stellar activity correction and are
derived with the LBL technique.
Objects:
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RA (2000) DE Designation(s)
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19 03 05.87 -11 02 38.1 HD 176986 = BD-11 4849
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
yararava.dat 317 330 YARARA RV and activity indicators calculated
without stellar activity correction and derived
with the CCF-technique
yararav1.dat 317 330 YARARA RV and activity indicators calculated
after stellar activity correction and are
derived with the LBL technique
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See also:
J/A+A/612/A41 : HD 176986 HARPS + HARPS-N data (Suarez Mascareno+, 2018)
Byte-by-byte Description of file: yararava.dat yararav1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d BJD Baricentric Julian date (BJD-2400000)
14- 28 F15.11 m/s RV Radial velocity
30- 40 F11.9 m/s e_RV Radial velocity error
42- 51 F10.8 m/s FWHM FWHM of the CCF
53- 66 F14.12 m/s e_FWHM FWHM error
68- 80 F13.11 m/s BISspan Bisector span velocity
82- 95 F14.12 m/s e_BISspan Bisector span velocity error
97-107 F11.9 --- Contrast Contrast of the CCF
109-123 F15.13 --- e_Contrast Contrast of the CCF error
125-135 F11.9 --- SMW Mont Wilson S activity indicator
137-149 F13.11 --- e_SMW Mont Wilson S activity indicator error
151-161 F11.9 --- Ha Hα activity indicator
163-176 F14.12 --- e_Ha Hα activity indicator error
178-188 F11.9 --- Na Na activity indicator
190-203 F14.12 --- e_Na Na activity indicator error
205-215 F11.9 --- Ca Ca activity indicator
217-230 F14.12 --- e_Ca Ca activity indicator error
232-242 F11.8 --- RHK RHK activity indicator
244-256 F13.11 --- e_RHK RHK activity indicator error
258-270 F13.9 --- BERV Baricentric Earth Radial Velocity
272-282 F11.7 --- SNCaII Signal-to-noise ratio from CaII line
284-297 E14.9 --- Model Model value
299-311 A13 --- Inst Instrument name
313-317 A5 --- Ver Instrument DRS version
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Acknowledgements:
Nicola Nari, nicola.nari(at)lightbridges.es
(End) Patricia Vannier [CDS] 04-Dec-2025