J/A+A/690/A349 K2-24 planetary system revisited by CHEOPS (Nascimbeni+, 2024)
The K2-24 planetary system revisited by CHEOPS.
Nascimbeni V., Borsato L., Leonardi P., Sousa S.G., Wilson T.G., Fortier A.,
Heitzmann A., Mantovan G., Luque R., Zingales T., Piotto G., Alibert Y.,
Alonso R., Barczy T., Barrado Navascues D., Barros S.C., Baumjohann W.,
Beck T., Benz W., Billot N., Biondi F., Brandeker A., Broeg C., Busch M.-D.,
Collier Cameron A., Correia A.C.M., Csizmadia Sz., Cubillos P.E.,
Davies M.B., Deleuil M., Deline A., Delrez L., Demangeon O.D.S.,
Demory B.-O., Derekas A., Edwards B., Ehrenreich D., Erikson A., Fossati L.,
Fridlund M., Gandolfi D., Gazeas K., Gillon M., Guedel M., Guenther M.N.,
Helling C., Isaak K.G., Kerschbaum F., Kiss L., Korth J., Lam K.W.F.,
Laskar J., Lecavelier des Etangs A., Lelue A., Lendl M., Magrin D.,
Maxted P.F.L., Merin B., Mordasini C., Olofsson G., Ottensamer R.,
Pagano I., Palle E., Peter G., Pollacco D., Queloz D., Ragazzoni R.,
Rando N., Rauer H., Ribas I., Santos N.C., Scandariato G., Segransan D.,
Simon A.E., Smith A.M.S., Southworth R., Stalport M., Sulis S.,
Szabo M.Gy., Udry S., Ulmer B., Van Grootel V., Venturini J., Villaver E.,
Walton N.A.
<Astron. Astrophys. 690, A349 (2024)>
=2024A&A...690A.349N 2024A&A...690A.349N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ; Optical
Keywords: techniques: photometric - techniques: spectroscopic -
planets and satellites: detection -
planets and satellites: dynamical evolution and stability -
planets and satellites: gaseous planets
Abstract:
K2-24 is a planetary system composed of two transiting low-density
Neptunians locked in an almost perfect 2:1 resonance and showing large
TTVs, i.e., an excellent laboratory to search for signatures of
planetary migration. Previous studies performed with K2, Spitzer and
RV data tentatively claimed a significant non-zero eccentricity for
one or both planets, possibly high enough to challenge the scenario of
pure disk migration through resonant capture. With 13 new CHEOPS light
curves (seven of planet -b, six of planet -c), we carried out a global
photometric and dynamical (RV+TTV) re-analysis by including all the
available literature data as well. We got the most accurate set of
planetary parameters to date for the K2-24 system, including radii and
masses at 1% and 5% precision (now essentially limited by the
uncertainty on stellar parameters) and non-zero eccentricities
eb=0.0498+0.0011-0.0018, ec=0.0282+0.0003-0.0007 detected
at very high significance for both planets. Such relatively large
values imply the need for an additional physical mechanism of
eccentricity excitation during or after the migration stage. Also,
while the accuracy of the previous TTV model had drifted by up to 0.5
days at the current time, we constrained the orbital solution firmly
enough to predict the forthcoming transits for the next ∼15 years,
thus enabling an efficient follow-up with top- level facilities such
as JWST or ESPRESSO.
Description:
a) Photometric time series of K2-24 obtained by CHEOPS, K2, HST during
the transits of planets -b and -c. The provided flux for the CHEOPS
light curves corresponds to the roll-angle detrended normalized flux;
b) transit times of K2-24b and -c analyzed in the previous work (Table
3 of the paper; c) transit times of K2-24b and -c for the 2024-2029
period as predicted by our dynamical best-fit model.
Objects:
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RA (2000) DE Designation(s)
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16 10 17.69 -24 59 25.2 CD-24 12581 = K2-24
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 51 24 Central transit time of K2-24b and K2-24c
lcs.dat 85 6460 Light curves of K2-24b and K2-24c
predtt.dat 64 156 Transit times of K2-24b and K2-24c
predicted by our dynamic model
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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: table3.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Planet [-b -c] Name of the planet (-b or -c)
4- 10 A7 --- Inst Instrument name
12- 24 F13.5 d T0 Central transit time T0, BJD-TDB standard
26- 40 E15.7 d e_T0 Symmetrized 1-sigma error on T0
42- 51 A10 --- Id ID of the corresponding light curve (1)
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Note (1): b1-b7 for CHEOPS -b observations, c1-c6 for CHEOPS -c observations,
hst_b1 for HST -b observations,
k2b1-k2b4 for K2 -b observations, k2c1-k2c2 for K2 -c observations,
spitzerb1-spitzerb2 for Spitzer -b observations,
spitzerc1-spitzerc2 for Spitzer -c observations.
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Byte-by-byte Description of file: lcs.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Planet [-b -c] Name of the planet (-b or -c)
4- 17 F14.6 d Time Time of the observation, BJD-TDB standard
19- 26 F8.6 --- Flux Detrended flux, normalized
28- 35 E8.3 --- e_Flux 1-sigma error on the detrended flux
37- 44 F8.6 --- Model Best-fit PyORBIT model
46- 55 E10.4 --- Res Flux residuals from the best-fit model
57- 58 I2 --- N Numerical ID, for plotting
60- 64 A5 --- Id ID of the corresponding light curve (1)
66- 71 A6 --- Inst Instrument name
73- 85 F13.5 --- T0 Best-fit transit time T0, for stacking
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Note (1): b1-b7 for CHEOPS -b observations, c1-c6 for CHEOPS -c observations,
k2b1-k2b4 for K2 -b observations, k2c1-k2c2 for K2 -c observations.
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Byte-by-byte Description of file: predtt.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Planet [-b -c] Name of the planet (-b or -c)
4- 16 F13.5 d T0BJDTDB T0 predicted by our model,
in BJD-TDB standard
18- 34 F17.9 d T0JD T0 predicted by our model, in JD
36- 44 E9.3 d e_T0 1-sigma error on T0
46- 64 A19 "datime" T0UTC T0 predicted by our model,
in ISO UTC standard
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Acknowledgements:
Valerio Nascimbeni, valerio.nascimbeni(at)inaf.it
(End) Patricia Vannier [CDS] 07-Sep-2024