J/A+A/689/L8 K2-399 b is not a planet (Lillo-Box+, 2024)
K2-399 b is not a planet. The Saturn that wandered through the Neptune desert is
actually a hierarchical eclipsing binary.
Lillo-Box J., Latham D.W., Collins K.A., Armstrong D.J., Gandolfi D.,
Jensen E.L.N., Castro-Gonzalez A., Balsalobre-Ruza O., Montesinos B.,
Sousa S.G., Aceituno J., Schwarz R.P., Narita N., Fukui A., Cabrera J.,
Hadjigeorghiou A., Kuzuhara M., Hirano T., Fridlund M., Hatzes A.P.,
Barragan O., Batalha N.M.
<Astron. Astrophys. 689, L8 (2024)>
=2024A&A...689L...8L 2024A&A...689L...8L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Radial velocities ; Optical
Keywords: planets and satellites: general, individual: K2-399 -
techniques: radial velocity, photometric
Abstract:
The transit technique has been very efficient in detecting planet
candidate signals over the past decades. The so-called statistical
validation approach has become a popular way of verifying a
candidate's planetary nature. However, the incomplete consideration of
false positive scenarios and data quality can lead to the
misinterpretation of the results.
In this work we revise the planetary status of K2-399 b, a validated
planet with an estimated false positive probability of 0.078% located
in the middle of the so-called Neptunian desert, and hence a potential
key target for atmospheric prospects. We use radial velocity data from
the CARMENES, HARPS and TRES spectrographs, as well as ground-based
multi-band transit photometry LCOGT MuSCAT3 and broad band photometry
to test the planetary scenario.
Our analysis of the available data does not support the existence of
this (otherwise key) planet, and instead points to a scenario composed
of an early G-dwarf orbited in a 846.62+0.22-0.28days period by a
pair of eclipsing M-dwarfs (hence a hierarchical eclipsing binary)
likely in the mid-type domain. We thus demote K2-399 b as a planet.
We conclude that the validation process, while very useful to
prioritise follow-up efforts, must always be conducted with careful
attention to data quality while ensuring that all possible scenarios
have been properly tested to get reliable results. We also encourage
developers of validation algorithms to ensure the accuracy of a priori
probabilities for different stellar scenarios that can lead to this
kind of false validation. We further encourage the use of follow-up
observations when possible (such as radial velocity and/or multi-band
light curves) to confirm the planetary nature of detected transiting
signals rather than only relying on validation tools.
Description:
Demotion of the planet K2-399b.
Objects:
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RA (2000) DE Designation(s)
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10 32 17.62 +02 14 16.5 K2-399 = EPIC 248472140
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 66 80 Radial velocity measurements of EPIC 248472140
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See also:
J/AJ/156/89 : K2-24 system RVs & predicted transit-times (Petigura+, 2018)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d BJD Barycentric Julian date (TBD)
18- 35 F18.15 km/s RV Radial velocity
37- 55 F19.17 km/s e_RV Radial velocity uncertainty
57- 66 A10 --- Inst Instrument (1)
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Note (1): Instruments are CARMENES, CARMENES18, HARPS, HARPSN and TRES.
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Acknowledgements:
Jorge Lillo-Box, jlillo(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 07-Sep-2024