J/A+A/707/A93 Multiplanet system GJ 887 (Hartogh+, 2026)
RedDots: Multiplanet system around M dwarf GJ 887 in the solar neighborhood.
Hartogh C., Jeffers S.V., Dreizler S., Barnes J.R., Haswell C.A.,
Liebing F., Collier Cameron A., Gorrini P., Del Sordo F., Cortes-Zuleta P.
<Astron. Astrophys. 707, A93 (2026)>
=2026A&A...707A..93H 2026A&A...707A..93H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Optical
Keywords: methods: data analysis - techniques: radial velocities -
planets and satellites: detection - stars: activity -
stars: low-mass - stars: individual: GJ 887
Abstract:
GJ 877 is a bright M dwarf in the solar neighborhood with two
currently reported nontransiting exoplanets with periods of 9d and
21d, along with an additional unconfirmed signal at 50d. We reanalyzed
the system with 101 new HARPS and 12 new ESPRESSO radial velocities
(RVs) secured with a cadence to confirm or refute the origin of the 50
d signal. To do so, we searched for signals related to stellar
activity in photometric data and spectroscopic indicators. We modeled
the stellar activity in the RVs with Gaussian processes (GPs). With
the Bayesian analysis, we confirmed a four-planet model, including the
two previously known planets at periods of 9.2619±0.0005d and
21.784±0.004d, as well as two newly confirmed exoplanets: an
Earth-mass planet, with a 4.42490±0.00014d period and a
sub-meter-per-second amplitude, and a super-Earth with a 50.77±0.05d
period located in the habitable zone (HZ). This super-Earth is the
second closest planet in the HZ, after Proxima Cen b. We found an
additional signal in a 2:1 resonance with the 4.4d planet at
2.21661±0.00010d with an amplitude of 0.37±0.09m/s, which could be
related to an additional planet. However, other explanations of its
origin are also plausible. This signal remains a candidate, as further
investigation is required to confirm its true nature. If the signal is
caused by a planet, its minimum mass would be half that of Earth. We
measured the stellar rotation period with the characteristic periodic
timescale of the GP. We found a period of 38.7±0.5d, which is
consistent with the rotation period determined from photometry and
other activity indices.
Description:
Radial velocity measurements of GJ887 with ESPRESSO and radial
velocity and activity indicators of GJ887 with HARPS.
Objects:
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RA (2000) DE Designation(s)
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23 05 52.03 -35 51 11.0 GJ 887 = HD 217987
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablee1.dat 34 11 Radial velocity ESPRESSO
tablee2.dat 221 356 Radial velocity and activity indicators HARPS
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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- 15 F15.7 d BJD Barycentric Julian Date
17- 25 F9.4 m/s RV Radial velocity
27- 34 F8.4 m/s e_RV Uncertainty on RV
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Byte-by-byte Description of file: tablee2.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian Date
16- 26 F11.6 m/s RV Radial velocity serval
28- 37 F10.6 m/s e_RV Radial velocity error serval
39- 50 F12.6 m/s DRS DRS radial velocity
52- 61 F10.6 m/s e_DRS DRS radial velocity error
63- 72 F10.6 km/s FWHM Full width half maximum of CCF
74- 84 F11.6 km/s BIS Bisector span of CCF
86- 97 F12.6 --- dLW Differential line width
99-108 F10.6 --- e_dLW Differential line width error
110-120 F11.6 m/s crx Chromatic index
122-131 F10.6 m/s e_crx Chromatic index error
133-142 F10.6 --- Halpha Halpha index
144-153 F10.6 --- e_Halpha Halpha index error
155-164 F10.6 --- NaD1 NaD1 index
166-175 F10.6 --- e_NaD1 NaD1 index error
177-186 F10.6 --- NaD2 NaD2 index
188-197 F10.6 --- e_NaD2 NaD2 index error
199-209 F11.6 m/s Drift CARACAL Drift
211-221 F11.6 m/s SA Secular acceleration
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Acknowledgements:
Christian Hartogh, ch395(at)st-andrews.ac.uk
(End) Patricia Vannier [CDS] 27-Jan-2026