J/A+A/694/A15 KOBE-1 activity indicators and RVs (Balsalobre-Ruza+, 2025)
KOBE-1: The first planetary system from the KOBE survey.
Two planets likely in the sub-Neptune mass regime around a late K-dwarf.
Balsalobre-Ruza O., Lillo-Box J., Silva A.M., Grouffal S., Aceituno J.,
Castro-Gonzalez A., Cifuentes C., Standing M.R., Faria J.P., Figueira P.,
Santerne A., Marfil E., Abreu A., Aguichine A., Gonzalez-Ramirez L.,
Morales J.C., Santos N., Huelamo N., Delgado Mena E., Barrado D.,
Adibekyan V., Barros S.C.C., Berihuete A., Morales-Calderon M., Nagel E.,
Solano E., Sousa S.G., Aguei Fernandez J.F., Azzaro M., Bergond G.,
Cikota S., Fernandez-Martin A., Flores J., Gongora S., Guijarro A.,
Hermelo I., Pinter V., Vico Linares J.I.
<Astron. Astrophys. 694, A15 (2025)>
=2025A&A...694A..15B 2025A&A...694A..15B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Stars, K-type ;
Spectroscopy ; Radial velocities ; Optical
Keywords: techniques: radial velocities - surveys -
planets and satellites: detection - stars: late-type -
Abstract:
K-dwarf stars are promising targets in the exploration of potentially
habitable planets. Their properties, falling between G and M dwarfs,
provide an optimal trade off between habitability prospect and ease of
detection. The KOBE experiment is a blind-search survey exploiting
this niche, monitoring the radial velocity of 50 late-type K-dwarf
stars using the CARMENES spectrograph with an observational strategy
designed to detect planets in the habitable zone of their system. In
this paper, we exploited the KOBE data set to characterize planetary
signals in the K7 V star HIP 5957 (KOBE-1) and to constrain the
planetary population within its habitable zone. We used 82 CARMENES
spectra with a time span of three years. We employed the generalized
Lomb-Scargle periodogram to search for significant periodic signals
compatible with Keplerian motion on KOBE-1. We conducted model
comparison in a Bayesian framework to ensure the significance of the
planetary model over alternative configurations of lower complexity.
We also inspected two available TESS sectors in search of planetary
signals. We identified two signals at Pb=8.5d and Pc=29.7d. We
confirmed their planetary nature through ruling out other
non-planetary configurations. Their minimum masses are
8.80±0.76M⊕ (KOBE-1 b), and 12.4±1.1M⊕ (KOBE-1 c),
corresponding to absolute masses within the planetary regime to a high
certainty (>99.7%). By analyzing the sensitivity of the CARMENES time
series to additional signals, we discarded planets above 8.5M⊕
within the habitable zone. We identified a single transit-like feature
in TESS whose origin is still uncertain, but it is compatible within
1-sigma with a transit from planet c. The KOBE-1 multi-planetary
system, consisting of a relatively quiet K7-dwarf hosting two
sub-Neptune-minimum-mass planets, sets the first discovery of the KOBE
experiment. We explored future prospects for characterizing this
system, concluding that Gaia DR4 will be insensitive to their
astrometric signature, while nulling interferometry with LIFE could be
capable of directly imaging both planets and characterize their
atmospheres.
Description:
We used the CARMENES 2014) instrument to monitor the RV of KOBE-1 (GJ
9048, TIC 16917838, HIP 5957). These observations are part of the KOBE
experiment survey (PI: Lillo-Box; Lillo-Box et al,.
2020A&A...642A.121L 2020A&A...642A.121L), running at the Calar Alto Observatory since
January 2021. The CARMENES instrument is fed by the 3.5-m telescope of
this observatory and is located in an isolated chamber with active
environmental control.
Objects:
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RA (2000) DE Designation(s)
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01 16 39.35 +25 19 53.3 KOBE-1 = HIP 5957
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablef1.dat 133 82 KOBE-1 activity indicators
tablef2.dat 112 82 KOBE-1 radial velocities
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Byte-by-byte Description of file: tablef1.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d Time Observing time (BJD-2400000)
20- 24 F5.3 m/s FWHM FWHM
26- 30 F5.3 m/s e_FWHM Uncertainty of the FWHM
32- 36 F5.3 m/s Bis Bisector span
38- 44 F7.5 m/s e_Bis Uncertainty of the bisector span
46- 52 F7.3 m2/s2 dlw Differential line width
54- 58 F5.3 m2/s2 e_dlw Uncertainty of the dLW
60- 66 F7.3 m/s Crx Chromatic index
68- 73 F6.3 m/s e_Crx Uncertainty of the chromatic index
75- 79 F5.3 --- Ha Halpha index
81- 85 F5.3 --- e_Ha Uncertainty of the Halpha index
87- 91 F5.3 --- Ca1 CaIRT1 index
93- 97 F5.3 --- e_Ca1 Uncertainty of the CaIRT1 index
99-103 F5.3 --- Ca2 CaIRT2 index
105-109 F5.3 --- e_Ca2 Uncertainty of the CaIRT2 index
111-115 F5.3 --- Na1 NaD1 index
117-121 F5.3 --- e_Na1 Uncertainty of the NaD1 index
123-127 F5.3 --- Na2 NaD2 index
129-133 F5.3 --- e_Na2 Uncertainty of the NaD2 index
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Byte-by-byte Description of file: tablef2.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d Time Observing time (BJD-2400000)
20- 38 F19.12 m/s RV Radial velocity
40- 57 F18.16 m/s e_RV Uncertainty of the radial velocity
59- 78 F20.17 m/s NZP Nightly zero point
80- 98 F19.17 m/s e_NZP Uncertainty of the nightly zero point
100-106 F7.3 m/s Drift Drift
108-112 F5.3 m/s e_Drift Uncertainty of the drift
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Acknowledgements:
Olga Balsalobre-Ruza, obalsalobre(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 18-Dec-2024