J/A+A/696/A28 TOI-238 and TOI-1685 light curves (Egger+, 2025)
Searching for hot water world candidates with CHEOPS. Refining the radii and
analysing the internal structures and atmospheric lifetimes of TOI-238 b and
TOI-1685 b.
Egger J.A., Kubyshkina D., Alibert Y., Osborn H.P., Bonfanti A.,
Wilson T.G., Brandeker A., Guenther M.N., Lendl M., Kitzmann D.,
Fossati L., Mordasini C., Sousa S.G., Adibekyan V., Fridlund M.,
Pezzotti C., Gandolfi D., Ulmer-Moll S., Alonso R., Barczy T.,
Barrado Navascues D., Barros S.C., Baumjohann W., Benz W., Billot N.,
Borsato L., Broeg C., Collier Cameron A., Correia A.C.M., Csizmadia Sz.,
Cubillos P.E., Davies M.B., Deleuil M., Deline A., Demangeon O.D.S.,
Demory B.-O., Derekas A., Edwards B., Ehrenreich D., Erikson A., Fortier A.,
Gazeas K., Gillon M., Guedel M., Heitzmann A., Helling C., Isaak K.G.,
Kiss L., Korth J., Lam K.W.F., Laskar J., Lecavelier des Etangs A.,
Luntzer A., Luque R., Magrin D., Maxted P.F.L., Merin B., Munari M.,
Nascimbeni V., Olofsson G., Ottensamer R., Pagano I., Palle E., Peter G.,
Piazza D., Piotto 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.,
Van Grootel V., Venturini J., Villaver E., Walton N.A., Wolf S., Wolter D.
<Astron. Astrophys. 696, A28 (2025)>
=2025A&A...696A..28E 2025A&A...696A..28E (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ; Optical
Keywords: techniques: photometric - planets and satellites: formation -
planets and satellites: interior -
planets and satellites: individual: TOI-238 -
planets and satellites: individual: TOI-1685
Abstract:
Studying the composition of exoplanets is one of the most promising
approaches to observationally constrain planet formation and evolution
processes. However, this endeavour is complicated for small exoplanets
by the fact that a wide range of compositions is compatible with their
observed bulk properties. To overcome this issue, we identify
triangular regions in the mass-radius space where part of this
intrinsic degeneracy is lifted for close-in planets, since low-mass
H/He envelopes would not be stable due to high-energy stellar
irradiation. Planets in these Hot Water World triangles need to
contain at least some heavier volatiles and are therefore interesting
targets for atmospheric follow-up observations. We perform a
demographic study to show that only few well-characterised planets in
these regions are currently known and introduce our CHEOPS GTO
programme aimed at identifying more of these potential hot water
worlds. Here, we present CHEOPS observations for the first two targets
of our programme, TOI-238 b and TOI-1685 b. Combined with TESS
photometry and published RVs, we use the precise radii and masses of
both planets to study their location relative to the corresponding Hot
Water World triangles, perform an interior structure analysis and
study the possible lifetimes of H/He and water-dominated atmospheres
under these conditions. We find that TOI-238 b lies, at the 1sigma
level, inside the corresponding triangle. While a pure H/He atmosphere
would have evaporated after 0.4-1.3Myr, it is likely that a
water-dominated atmosphere would have survived until the current age
of the system, which makes TOI-238 b a promising candidate for a hot
water world. Conversely, TOI-1685 b lies below the mass-radius model
for a pure silicate planet, meaning that even though a water-dominated
atmosphere would be compatible both with our internal structure and
evaporation analysis, we cannot rule out the planet to be a bare core.
Description:
We present raw and detrended CHEOPS (extracted using PIPE) and TESS
photometry of TOI-238 and TOI-1685.
Objects:
----------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------
23 16 55.51 -18 36 23.9 TOI-238 = TIC 9006668
04 34 22.49 +43 02 14.6 TOI-1685 = TIC 28900646
----------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
ctoi238.dat 844 1748 CHEOPS photometry and model fits for TOI-238
ttoi238.dat 520 48229 TESS photometry and model fits for TOI-238
ctoi1685.dat 817 4160 CHEOPS photometry and model fits for TOI-238
ttoi1685.dat 402 33290 TESS photometry and model fits for TOI-238
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ctoi238.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Index Index (index)
6- 23 F18.10 d Time BJD time (time)
25- 47 F23.20 10-3 Flux Normalised flux (in ppt unit) (flux)
49- 67 F19.17 10-3 e_Flux Normalised flux error (in ppt unit)
(flux_err)
69- 89 F21.17 deg phi Roll angle (phi)
91-108 F18.14 e- bg Background (bg)
110-127 F18.14 pix CentroidX PSF X centroid (centroidx)
129-146 F18.14 pix CentroidY PSF Y centroid (centroidy)
148-166 F19.15 --- deltaT Temperature change (deltaT)
168-190 E23.16 pix Xoff PSF X centroid offset (xoff)
192-214 E23.16 pix Yoff PSF Y centroid offset (yoff)
216-238 A23 --- Filekey CHEOPS file key (filekey)
240 I1 --- nphimodel Index for rollangle model (nphimodel)
242-263 F22.19 --- Cpredsp-2sig Spline detrend model (-2sig)
(cheopspredspline_-2sig)
265-287 E23.16 --- Cpredsp-1sig Spline detrend model (-1sig)
(cheopspredspline_-1sig)
289-311 E23.16 --- Cpredspmed Spline detrend model (median)
(cheopspredspline_med)
313-335 F23.20 --- Cpredsp+1sig Spline detrend model (+1sig)
(cheopspredspline_+1sig)
337-360 E24.17 --- Cpredsp+2sig Spline detrend model (+2sig)
(cheopspredspline_+2sig)
362-383 E22.16 --- Cldetre-2sig Decorrelation detrend model (-2sig)
(cheopslindetrend-2sig)
385-406 E22.16 --- Calldet-2sig Sum of detrend models (-2sig)
(cheopsalldetrend-2sig)
408-430 E23.16 --- Cbmodel-2sig Planet b model (-2sig)
(cheopsbmodel-2sig)
432-434 F3.1 --- Ccmodel-2sig Planet c model (-2sig)
(cheopscmodel-2sig)
436-458 E23.16 --- Callplmodel-2sig Sum of planet models (-2sig)
(cheopsallplmodel-2sig)
460-483 E24.17 --- Cldetre-1sig Decorrelation detrend model (-1sig)
(cheopslindetrend-1sig)
485-507 E23.17 --- Calldet-1sig Sum of detrend models (-1sig)
(cheopsalldetrend-1sig)
509-530 F22.19 --- Cbmodel-1sig Planet b model (-1sig)
(cheopsbmodel-1sig)
532-534 F3.1 --- Ccmodel-1sig Planet c model (-1sig)
(cheopscmodel-1sig)
536-557 F22.19 --- Callplmodel-1sig Sum of planet models (-1sig)
(cheopsallplmodel-1sig)
559-581 E23.17 --- Cldetremed Decorrelation detrend model (median)
(cheopslindetrendmed)
583-604 E22.16 --- Calldetmed Sum of detrend models (median)
(cheopsalldetrendmed)
606-627 F22.19 --- Cbmodelmed Planet b model (median)
(cheopsbmodelmed)
629-631 F3.1 --- Ccmodelmed Planet c model (median)
(cheopscmodelmed)
633-654 F22.19 --- Callplmodelmed Sum of planet models (median)
(cheopsallplmodelmed)
656-678 F23.20 --- Cldetre+1sig Decorrelation detrend model (+1sig)
(cheopslindetrend+1sig)
680-702 E23.17 --- Calldet+1sig Sum of detrend models (+1sig)
(cheopsalldetrend+1sig)
704-725 F22.19 --- Cbmodel+1sig Planet b model (+1sig)
(cheopsbmodel+1sig)
727-729 F3.1 --- Ccmodel+1sig Planet c model (+1sig)
(cheopscmodel+1sig)
731-752 F22.19 --- Callplmodel+1sig Sum of planet models (+1sig)
(cheopsallplmodel+1sig)
754-773 F20.18 --- Cldetre+2sig Decorrelation detrend model (+2sig)
(cheopslindetrend+2sig)
775-796 F22.19 --- Calldet+2sig Sum of detrend models (+2sig)
(cheopsalldetrend+2sig)
798-818 F21.18 --- Cbmodel+2sig Planet b model (+2sig)
(cheopsbmodel+2sig)
820-822 F3.1 --- Ccmodel+2sig Planet c model (+2sig)
(cheopscmodel+2sig)
824-844 F21.18 --- Callplmodel+2sig Sum of planet models (+2sig)
(cheopsallplmodel+2sig)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ttoi238.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Index Index (index)
7- 24 F18.10 d Time BJD time (time)
26- 49 E24.17 10-3 Flux Normalised flux (in ppt unit) (flux)
51- 69 F19.17 10-3 e_Flux Normalised flux error (in ppt unit)
(flux_err)
71- 74 A4 --- Mask Boolean flux mask (mask)
76- 80 A5 --- NearTrans All planet near-transit mask
(near_trans)
82- 86 A5 --- inTransb In-transit mask of planet b
(intransb)
88- 92 A5 --- inTransc In-transit mask of planet c
(intransc)
94- 98 A5 --- inTransall All planet in-transit mask
(intransall)
100-123 E24.17 --- spline Transit-masked flux bspline (spline)
125-147 E23.16 --- Fluxflat Spline-flattened flux (flux_flat)
149-172 E24.17 --- Tgpmodelmed GP detrend model (median)
(tessgpmodelmed)
174-196 E23.16 --- Tbmodel-2sig Planet b model (-2sig)
(tessbmodel-2sig)
198-218 F21.18 --- Tcmodel-2sig Planet c model (-2sig)
(tesscmodel-2sig)
220-242 E23.16 --- Tallplmodel-2sig Sum of planet models (-2sig)
(tessallplmodel-2sig)
244-266 E23.16 --- Tbmodel-1sig Planet b model (-1sig)
(tessbmodel-1sig)
268-289 F22.19 --- Tcmodel-1sig Planet c model (-1sig)
(tesscmodel-1sig)
291-313 E23.16 --- Tallplmodel-1sig Sum of planet models (-1sig)
(tessallplmodel-1sig)
315-336 F22.19 --- Tbmodelmed Planet b model (median)
(tessbmodelmed)
338-360 E23.16 --- Tcmodelmed Planet c model (median)
(tesscmodelmed)
362-384 E23.16 --- Tallplmodelmed Sum of planet models (median)
(tessallplmodelmed)
386-407 E22.15 --- Tbmodel+1sig Planet b model (+1sig)
(tessbmodel+1sig)
409-429 F21.18 --- Tcmodel+1sig Planet c model (+1sig)
(tesscmodel+1sig)
431-452 E22.15 --- Tallplmodel+1sig Sum of planet models (+1sig)
(tessallplmodel+1sig)
454-475 F22.19 --- Tbmodel+2sig Planet b model (+2sig)
(tessbmodel+2sig)
477-497 F21.18 --- Tcmodel+2sig Planet c model (+2sig)
(tesscmodel+2sig)
499-520 F22.19 --- Tallplmodel+2sig Sum of planet models (+2sig)
(tessallplmodel+2sig)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ctoi1685.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Index Index (index)
6- 23 F18.10 d Time BJD time (time)
25- 46 F22.19 10-3 Flux Normalised flux (in ppt unit) (flux)
48- 65 F18.16 10-3 e_Flux Normalised flux error (in ppt unit)
(flux_err)
67- 87 F21.17 deg phi Roll angle (phi)
89-106 F18.14 e- bg Background (bg)
108-125 F18.14 pix CentroidX PSF X centroid (centroidx)
127-144 F18.14 pix CentroidY PSF Y centroid (centroidy)
146-164 F19.15 mK deltaT Temperature change (deltaT)
166-188 E23.16 pix Xoff PSF X centroid offset (xoff)
190-212 E23.16 pix Yoff PSF Y centroid offset (yoff)
214-236 A23 --- Filekey CHEOPS file key (filekey)
238 I1 --- nphimodel Index for rollangle model
(nphimodel)
240-261 F22.19 --- Cpredsp-2sig Spline detrend model (-2sig)
(cheopspredspline_-2sig)
263-286 E24.17 --- Cpredsp-1sig Spline detrend model (-1sig)
(cheopspredspline_-1sig)
288-311 E24.17 --- Cpreds-pmed Spline detrend model (median)
(cheopspredspline_med)
313-334 F22.19 --- Cpredsp+1sig Spline detrend model (+1sig)
(cheopspredspline_+1sig)
336-359 E24.17 --- Cpredsp+2sig Spline detrend model (+2sig)
(cheopspredspline_+2sig)
361-382 F22.19 --- Cldetre-2sig Decorrelation detrend model (-2sig)
(cheopslindetrend-2sig)
384-406 F23.20 --- Calldet-2sig Sum of detrend models (-2sig)
(cheopsalldetrend-2sig)
408-430 F23.20 --- Cbmodel-2sig Planet b model (-2sig)
(cheopsbmodel-2sig)
432-454 F23.20 --- Callplmodel-2sig Sum of planet models (-2sig)
(cheopsallplmodel-2sig)
456-477 F22.19 --- Cldetre-1sig Decorrelation detrend model (-1sig)
(cheopslindetrend-1sig)
479-500 F22.19 --- Calldet-1sig Sum of detrend models (-1sig)
(cheopsalldetrend-1sig)
502-522 F21.18 --- Cbmodel-1sig Planet b model (-1sig)
(cheopsbmodel-1sig)
524-544 F21.18 --- Callplmodel-1sig Sum of planet models (-1sig)
(cheopsallplmodel-1sig)
546-567 F22.19 --- Cldetre-med Decorrelation detrend model (median)
(cheopslindetrendmed)
569-590 F22.19 --- Calldet-med Sum of detrend models (median)
(cheopsalldetrendmed)
592-612 F21.18 --- Cbmodel-med Planet b model (median)
(cheopsbmodelmed)
614-634 F21.18 --- Callplmodel-med Sum of planet models (median)
(cheopsallplmodelmed)
636-657 F22.19 --- Cldetre+1sig Decorrelation detrend model (+1sig)
(cheopslindetrend+1sig)
659-680 E22.16 --- Calldet+1sig Sum of detrend models (+1sig)
(cheopsalldetrend+1sig)
682-702 F21.18 --- Cbmodel+1sig Planet b model (+1sig)
(cheopsbmodel+1sig)
704-724 F21.18 --- Callplmodel+1sig Sum of planet models (+1sig)
(cheopsallplmodel+1sig)
726-748 F23.20 --- Cldetre+2sig Decorrelation detrend model (+2sig)
(cheopslindetrend+2sig)
750-771 F22.19 --- Calldet+2sig Sum of detrend models (+2sig)
(cheopsalldetrend+2sig)
773-794 F22.19 --- Cbmodel+2sig Planet b model (+2sig)
(cheopsbmodel+2sig)
796-817 F22.19 --- Callplmodel+2sig Sum of planet models (+2sig)
(cheopsallplmodel+2sig)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ttoi1685.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Index Index (index)
7- 24 F18.10 d Time BJD time (time)
26- 47 E22.16 10-3 Flux Normalised flux (in ppt unit) (flux)
49- 66 F18.16 10-3 e_Flux Normalised flux error (in ppt unit)
(flux_err)
68- 71 A4 --- Mask Boolean flux mask (mask)
73- 77 A5 --- NearTrans All planet near-transit mask
(near_trans)
79- 83 A5 --- inTransb In-transit mask of planet b
(intransb)
85- 89 A5 --- inTransall All planet in-transit mask
(intransall)
91-114 E24.17 --- spline Transit-masked flux bspline (spline)
116-137 E22.16 --- Fluxflat Spline-flattened flux (flux_flat)
139-162 E24.17 --- Tgpmodelmed GP detrend model (tessgpmodelmed)
164-187 E24.17 --- Tbmodel-2sig Planet b model (-2sig)
(tessbmodel-2sig)
189-212 E24.17 --- Tallplmodel-2sig Sum of planet models (-2sig)
(tessallplmodel-2sig)
214-236 F23.20 --- Tbmodel-1sig Planet b model (-1sig)
(tessbmodel-1sig)
238-260 F23.20 --- Tallplmodel-1sig Sum of planet models (-1sig)
(tessallplmodel-1sig)
262-284 E23.16 --- Tbmodel-med Planet b model (median)
(tessbmodelmed)
286-308 E23.16 --- Tallplmodel-med Sum of planet models (median)
(tessallplmodelmed)
310-332 E23.16 --- Tbmodel-+1sig Planet b model (+1sig)
(tessbmodel+1sig)
334-356 E23.16 --- Tallplmodel-+1sig Sum of planet models (+1sig)
(tessallplmodel+1sig)
358-379 F22.19 --- Tbmodel-+2sig Planet b model (+2sig)
(tessbmodel+2sig)
381-402 F22.19 --- Tallplmodel-+2sig Sum of planet models (+2sig)
(tessallplmodel+2sig)
--------------------------------------------------------------------------------
Acknowledgements:
Jo Ann Egger, jo-ann.egger(at)unibe.ch
(End) Patricia Vannier [CDS] 14-Feb-2025