J/A+A/615/A69 K2-3 system characterized with HARPS-N & HARPS (Damasso+, 2018)
Eyes on K2-3: A system of three likely sub-Neptunes characterized with
HARPS-N and HARPS.
Damasso M., Bonomo A.S., Astudillo-Defru N., Bonfils X., Malavolta L.,
Sozzetti A., Lopez E., Zeng L., Haywood R.D., Irwin J.M., Mortier A.,
Vanderburg A., Maldonado J., Lanza A.F., Affer L., Almenara J.-M.,
Benatti S., Biazzo K., Bignamini A., Borsa F., Bouchy F., Buchhave L.A.,
Cameron A.C., Carleo I., Charbonneau D., Claudi R., Cosentino R.,
Covino E., Delfosse X., Desidera S., Di Fabrizio L., Dressing C.,
Esposito M., Fares R., Figueira P., Fiorenzano A.F.M., Forveille T.,
Giacobbe P., Gonzalez-Alvarez E., Gratton R., Harutyunyan A.,
Asher Johnson J., Latham D.W., Leto G., Lopez-Morales M., Lovis C.,
Maggio A., Mancini L., Masiero S., Mayor M., Micela G., Molinari E.,
Motalebi F., Murgas F., Nascimbeni V., Pagano I., Pepe F., Phillips D.F.,
Piotto G., Poretti E., Rainer M., Rice K., Santos N.C., Sasselov D.,
Scandariato G., Segransan D., Smareglia R., Udry S., Watson C., Wuensche A.
<Astron. Astrophys. 615, A69 (2018)>
=2018A&A...615A..69D 2018A&A...615A..69D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Exoplanets ;
Radial velocities
Keywords: stars: individual: K2-3 - planets and satellites: detection -
planets and satellites: composition - techniques: radial velocities -
stars: individual: EPIC 201367065 -
stars: individual: 2MASS 11292037-0127173
Abstract:
M-dwarf stars are promising targets for identifying and characterizing
potentially habitable planets. K2-3 is a nearby (45pc), early-type M
dwarf hosting three small transiting planets, the outermost of which
orbits close to the inner edge of the stellar (optimistic) habitable
zone. The K2-3 system is well suited for follow-up characterization
studies aimed at determining accurate masses and bulk densities of the
three planets. Using a total of 329 radial velocity measurements
collected over 2.5 years with the HARPS-N and HARPS spectrographs and
a proper treatment of the stellar activity signal, we aim to improve
measurements of the masses and bulk densities of the K2-3 planets. We
use our results to investigate the physical structure of the planets.
We analysed radial velocity time series extracted with two independent
pipelines using Gaussian process regression. We adopted a
quasi-periodic kernel to model the stellar magnetic activity jointly
with the planetary signals. We used Monte Carlo simulations to
investigate the robustness of our mass measurements of K2-3 c and
K2-3 d, and to explore how additional high-cadence radial velocity
observations might improve these values. Even though the stellar
activity component is the strongest signal present in the radial
velocity time series, we are able to derive masses for both planet b
(Mb=6.6±1.1M⊕) and planet c (Mc=3.1+1.3-1.2M⊕).
The Doppler signal from K2-3 d remains undetected, likely because of
its low amplitude compared to the radial velocity signal induced by
the stellar activity. The closeness of the orbital period of K2-3 d to
the stellar rotation period could also make the detection of the
planetary signal complicated. Based on our ability to recover injected
signals in simulated data, we tentatively estimate the mass of K2-3 d
to be Md=2.7+1.2-0.8M⊕. These mass measurements imply that
the bulk densities and therefore the interior structures of the three
planets may be similar. In particular, the planets may either have
small H/He envelopes (<1percent) or massive water layers, with a water
content >50 percent of their total mass, on top of rocky cores.
Placing further constraints on the bulk densities of K2-3 c and d is
difficult; in particular, we would not have been able to detect the
Doppler signal of K2-3 d even by adopting a semester of intense,
high-cadence radial velocity observations with HARPS-N and HARPS.
Description:
Radial velocities of K2-3, collected with HARPS-N and HARPS and
extracted with two algorithms (TERRA and the alternative pipeline
described in Astudillo-Defru et al. 2015A&A...575A.119A 2015A&A...575A.119A,
2017A&A...602A..88A 2017A&A...602A..88A), are presented . Also included is the time series
of the spectroscopic activity indicator based on the H-alpha line, as
extracted from the HARPS-N and HARPS spectra.
Objects:
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RA (2000) DE Designation(s)
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11 29 20.39 -01 27 17.2 K2-3 = 2MASS J11292037-0127173
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 26 197 Radial velocities of K2-3 extracted from
HARPS-N spectra using the TERRA algorithm
tablea2.dat 26 132 Radial velocities of K2-3 extracted from
HARPS spectra using the TERRA algorithm
tablea3.dat 28 197 Radial velocities of K2-3 extracted from
HARPS-N spectra using the alternative pipeline
tablea4.dat 28 132 Radial velocities of K2-3 extracted from HARPS
spectra using the alternative pipeline
tablea5.dat 30 329 Time series of the activity indicator based on
the H-alpha line extracted from
HARPS-N and HARPS spectra
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Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d Time Epoch of observation (BJD-2400000)
15- 20 F6.2 m/s RV Radial velocity (1)
23- 26 F4.2 m/s e_RV Radial velocity error
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Note (1): Radial velocities are relative to a high S/N template
For table5.dat, Radial velocities starting from epoch BJD 2457199 were
collected after the upgrade of the instrument. An offset between the pre- and
post-upgrade datasets should be included in fitting model.
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Byte-by-byte Description of file: tablea3.dat tablea4.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d Time Epoch of observation (BJD-2400000)
15- 22 F8.2 m/s RV Radial velocity (1)
25- 28 F4.2 m/s e_RV Radial velocity error
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Note (1): Radial velocities include the systemic velocity.
For table7.dat, Radial velocities starting from epoch BJD 2457199 were
collected after the upgrade of the instrument. An offset between the
pre- and post-upgrade datasets should be included in fitting model.
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Byte-by-byte Description of file: tablea5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 d Time Epoch of observation (BJD-2400000)
15- 21 F7.5 m/s ActInd H-alpha activity indicator
24- 30 F7.5 m/s e_ActInd H-alpha activity indicator error
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Acknowledgements:
Mario Damasso, mario.damasso(at)inaf.it
(End) Mario Damasso [INAF-OATo, Italy], Patricia Vannier [CDS] 11-May-2018