J/A+A/693/A7 BD+00 444 (TOI-2443) RV curves (Naponiello+, 2025)
The GAPS programme at TNG. LXIV.
An inner eccentric sub-Neptune and an outer sub-Neptune-mass candidate
around BD+00 444 (TOI-2443).
Naponiello L., Bonomo A.S., Mancini L., Steinmeyer M.-L., Biazzo K.,
Polychroni D., Dorn C., Turrini D., Lanza A.F., Sozzetti A., Desidera S.,
Damasso M., Collins K.A., Carleo I., Collins K.I., Colombo S., D'Arpa M.C.,
Dumusque X., Gonzalez M., Guilluy G., Lorenzi V., Mantovan G.,
Nardiello D., Pinamonti M., Schwarz R.P., Singh V., Watkins C.N.,
Zingales T.
<Astron. Astrophys. 693, A7 (2025)>
=2025A&A...693A...7N 2025A&A...693A...7N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Optical
Keywords: instrumentation: photometers - instrumentation: spectrographs -
methods: data analysis - techniques: photometric -
techniques: radial velocities; occultations
Abstract:
Super-Earths and sub-Neptunes are the most common types of planets
outside the Solar System and likely represent the link between
terrestrial planets and gas giants. Characterizing their physical and
orbital properties and studying their multiplicity are key steps in
testing and understanding their formation, migration, and evolution.
We examined the star BD+00 444 (GJ 105.5, TOI-2443; V=9.5mag;
d=23.9pc) in depth, with the aim of characterizing and confirming the
planetary nature of its small companion, the planet candidate
TOI-2443.01, which was discovered by the TESS space telescope and
subsequently validated by a follow-up statistical study.
We monitored BD+00 444 with the HARPS-N spectrograph for 1.5 years to
search for planet-induced radial-velocity (RV) variations, and then
analyzed the RV measurements jointly with TESS and ground-based
photometry.
We determined that the host is a quiet K5 V star with a radius of
R*=0.631-0.014+0.013R☉ and a mass of
M*=0.642-0.025+0.026M☉. We revealed that the sub-Neptune
BD+00 444 b has a radius of Rb=2.36±0.05R⊕, a mass of
Mb=4.8±1.1M⊕, and consequently a rather low-density value of
ρb=2.00-0.45+0.49g/cm3, which makes it compatible with both an
Earth-like rocky interior with a thin H-He atmosphere and a
half-rocky, half-water composition with a small amount of H-He. With
an orbital period of about 15.67 days and an equilibrium temperature
of about 519K, BD+00 444 b has an estimated transmission spectroscopy
metric (TSM) of 159-31+46, which makes it ideal for atmospheric
follow-up with the James Webb Space Telescope. Notably, it is the
second most eccentric inner transiting planet among those with
well-determined eccentricities, with e=0.302-0.035+0.051, and a
mass of below 20M⊕. We estimated that tidal forces from the
host star affect both the rotation and eccentricity of planet b, and
strong tidal dissipation may signal intense volcanic activity.
Furthermore, our analysis suggests the presence of a sub-Neptune-mass
planet candidate, BD+00 444 c, which would have an orbital period of
Pc=96.6±1.4 days and a minimum mass of
Mcsini=9.3-2.0+1.8M⊕. With an equilibrium temperature of
about 283K, BD+00 444 c is inside the habitable zone; however,
confirmation of this candidate would require further observations and
stronger statistical evidence. We explored the formation and migration
of both planets by means of population synthesis models, which reveal
that both planets started their formation beyond the water snowline
during the earliest phases of the life of their protoplanetary disk.
Description:
Between 18 July 2021 and 18 January 2023, we collected a total of 97
high-resolution spectra of BD+00 444 with HARPS-N (Sect. 6) with a
variable exposure time of 15-20 min. The RVs and activity indices were
extracted from the spectra reduced using version 3.0.1 of the HARPS-N
Data Reduction Software (DRS), available on the Data Analysis Center
for Exoplanets (DACE) web platform. In the following analysis, we
employed all the RVs, including a few with relatively lower
signal-to-noise ratio (S/N), as their removal did not influence the
results. Overall, the measurements have an average error of 1.6m/s, a
root mean square error of 3.3m/s, and an S/N~=70, measured at a
reference wavelength of 5500Å.
Objects:
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RA (2000) DE Designation(s)
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2 40 42.87 +01 11 55.2 BD+00 444 = TOI-2443
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 78 97 HARPS-N RV data points and activity indices
obtained with the DRS pipeline
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d BJD Barycentric Julian date (BJD-2457000)
13- 20 F8.2 m/s RV Radial velocity
22- 25 F4.2 m/s e_RV Radial velocity error
27- 33 F7.2 m/s FWHM Full Width Half Maximum of the CCF
35- 39 F5.2 m/s e_FWHM Full Width Half Maximum of the CCF error
41- 45 F5.2 m/s BIS Bisector span
47- 51 F5.2 m/s e_BIS Bisector span error
53- 58 F6.3 --- Cont Contrast of the CCF
60- 64 F5.3 --- e_Cont Contrast of the CCF error
66- 71 F6.4 --- Sindex S-index
73- 78 F6.4 --- e_Sindex S-index error
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History:
Copied at https://zenodo.org/records/14161511
(End) Patricia Vannier [CDS] 20-May-2025