J/AJ/168/294 Predicted transit times of Kepler-51b, c, and d (Masuda+, 2024)
A fourth planet in the Kepler-51 system revealed by transit timing variations.
Masuda K., Libby-Roberts J.E., Livingston J.H., Stevenson K.B., Gao P.,
Vissapragada S., Fu G., Han Te, Greklek-McKeon M., Mahadevan S., Agol E.,
Bello-Arufe A., Berta-Thompson Z., Canas C.I., Chachan Y., Hebb L., Hu R.,
Kawashima Y., Knutson H.A., Morley C.V., Murray C.A., Ohno K.,
Tokadjian A., Zhang Xi, Welbanks L., Nixon M.C., Freedman R., Narita N.,
Fukui A., de Leon J.P., Mori M., Palle E., Murgas F., Parviainen H.,
Esparza-Borges E., Jontof-Hutter D., Collins K.A., Benni P., Barkaoui K.,
Pozuelos F.J., Gillon M., Jehin E., Benkhaldoun Z., Hawley S., Lin A.S.J.,
Stefansson G., Bieryla A., Yilmaz M., Senavci H.V., Girardin E.,
Marino G., Wang G.
<Astron. J., 168, 294 (2024)>
=2024AJ....168..294M 2024AJ....168..294M
ADC_Keywords: Exoplanets; Photometry, infrared; Optical
Keywords: Exoplanet astronomy ; Hubble Space Telescope ; Transit photometry ;
Transit timing variation method ; Transits ;
James Webb Space Telescope
Abstract:
Kepler-51 is a ≤1Gyr old Sun-like star hosting three transiting
planets with radii ∼6-9R⊕ and orbital periods ∼45-130days.
Transit timing variations (TTVs) measured with past Kepler and Hubble
Space Telescope (HST) observations have been successfully modeled by
considering gravitational interactions between the three transiting
planets, yielding low masses and low mean densities (≤0.1g/cm3) for
all three planets. However, the transit time of the outermost
transiting planet Kepler-51d recently measured by the James Webb Space
Telescope 10yr after the Kepler observations is significantly
discrepant from the prediction made by the three-planet TTV model,
which we confirmed with ground-based and follow-up HST observations.
We show that the departure from the three-planet model is explained by
including a fourth outer planet, Kepler-51e, in the TTV model. A wide
range of masses (≤MJup) and orbital periods (≤10yr) are possible
for Kepler-51e. Nevertheless, all the coplanar solutions found from
our brute-force search imply masses ≤10M⊕ for the inner
transiting planets. Thus, their densities remain low, though with
larger uncertainties than previously estimated. Unlike other possible
solutions, the one in which Kepler-51e is around the 2:1 mean motion
resonance with Kepler-51d implies low orbital eccentricities (≤0.05)
and comparable masses (∼5M⊕) for all four planets, as is seen
in other compact multiplanet systems. This work demonstrates the
importance of long-term follow-up of TTV systems for probing
longer-period planets in a system.
Description:
Midtransit times of all three Kepler-51 transiting planets were pulled
from a wide range of observations spanning 14yr (2010-2024) of
measurements made both from the ground and from space.
Space telescopes:
James Webb Space Telescope (JWST): We observed a single transit of
Kepler-51d with the JWST/NIRSpec-PRISM on 2023 June 26 (Cycle 1) using
NIRSpec's Bright Object Time Series with an overall exposure time of
2.9s and 18,082 total integrations across the ∼14hr of observing time.
Hubble Space Telescope (HST): Two full transits each of Kepler-51b and
d were observed with HST between 2015 and 2017 and were analyzed by
Libby-Roberts+2020 (J/AJ/159/57; Cycle 23). For these transits, we
adopted the transit times reported therein. More recently, HST
observed a single transit each of Kepler-51c and d using the WFC3/G141
mode (Cycle 30). Each observation lasted six HST orbits (∼8.8hr).
Kepler: Transit times based on the Kepler observations have been
reported in multiple works (e.g., Masuda, 2014ApJ...783...53M 2014ApJ...783...53M;
Holczer+2016, J/ApJS/225/9; Libby-Roberts+2020, J/AJ/159/57). Here we
reanalyze the whole set of available Kepler light curves in a uniform
manners. All available Pre-search Data Conditioning light curves for
Kepler-51 were downloaded from the Mikulski Archive for Space
Telescopes.
Transiting Exoplanet Survey Satellite (TESS): TESS observed Kepler-51
in six different sectors. The transits of Kepler-51b were caught in
Sectors 14 (07/18/19-08/15/19), 54 (07/09/22-08/05/22), and
55 (08/05/22-09/01/22) and Kepler-51d in Sector 14 (07/18/19-08/15/19).
However, we could not clearly identify the expected transits of
Kepler-51b in Sectors 54 and 55, so they are not included in our
timing analysis.
Ground-based facilities:
Teide Observatory: We used the MuSCAT2 multiband imager installed at
the 1.52m Telescopio Carlos Sanchez (TCS) at the Teide Observatory,
Spain, to observe transits of the Kepler-51 planets simultaneously in
g, r, i, and zs. Transits of planet b were observed on the nights of
UT 2018 August 2 and 2019 June 14 , planet c was observed on 2019 May 22
and 2021 September 21, and planet d was observed on 2018 June 29.
Exposure times were typically 30-60s.
Las Cumbres Observatory Global Telescope (LCOGT): We used the SBIG
camera mounted on a 0.4m telescope of the LCOGT network to observe a
transit of Kepler-51b on 2018 August 2. The telescope we used was
physically located at Teide Observatory in Spain. We observed in r
band with an exposure time of 150s. We also used the MuSCAT3 multiband
imager mounted on the LCOGT 2m Faulkes Telescope North at Haleakala
Observatory on Maui, Hawaii, to observe a transit of Kepler-51b on UT
2022 October 15 simultaneously in the g, r, i, zs bands, using
exposure times of 60s.
Oukaimeden Observatory: We observed an egress of Kepler-51d on
2020 August 18 with the TRAnsiting Planets and PlanetesImals Small
Telescope (TRAPPIST-North) 60cm robotic telescope at the Oukaimeden
Observatory in Morocco as part of TESS Follow-up Observing Program
(TFOP-SG1) photometric follow-up. The transit was observed in the
I+z filter with an exposure time of 120s.
Acton Sky Portal Observatory: The same 2020 August 18 egress of
Kepler-51d was observed using the 0.36m telescope on the Acton Sky
Portal private observatory in Acton, Massachusetts, with a blue
blocking clear Astrodon exoplanet filter. We used 60s exposure times.
Ankara University Kreiken Observatory (AUKR): We observed the same
2020 August 18 transit of Kepler-51d in g' and r' filters with the
Apogee Alta U47 CCD camera attached to the T80 Telescope located at
the Ankara University Kreiken Observatory (AUKR) in Turkey. The
exposure time for both g' and r' filters is 90 s.
KeplerCam: We used the KeplerCam CCD mounted on the 1.2m telescope at
the Fred Lawrence Whipple Observatory (FLWO) at Mount Hopkins,
Arizona, to observe the same 2020 August 18 transit of Kepler-51d.
The observation covered a part of the egress as well as a long
out-of-transit baseline. Images were taken in the Sloan i band with
100s exposure time.
Apache Point Observatory (APO): We observed partial transits of
Kepler-51b and d with the ARCTIC optical CCD camera attached to the
3.5m ARC telescope at the APO in Sunspot, New Mexico, on 2023 May 30
and 2023 June 26, respectively - simultaneous with the JWST
observations. We caught the transit egress baseline for Kepler-51b and
ingress transit for Kepler-51d. We used the Sloan Digital Sky Survey
(SDSS) r' filter with 15s exposures.
Palomar: We observed a transit of Kepler-51c in J with the Wide-field
Infrared Camera (WIRC) on the Hale Telescope at Palomar Observatory in
California. Palomar/WIRC is a 5.08m telescope equipped with a near-IR
detector. We observed the transit of Kepler-51c on UT 2024 April 17
from 08:10 to 12:38. We collected a total of 302 science images with
an exposure time of 45s per image.
Objects:
--------------------------------------------------------------------
RA (2000) DE Designation(s)
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19 45 55.13 +49 56 15.6 Kepler-51b = KOI-620.01
19 45 55.14 +49 56 15.6 Kepler-51c = KOI-620.03
19 45 55.15 +49 56 15.6 Kepler-51d = KOI-620.02
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 76 177 Future predicted transit times of Kepler-51b, c,
and d based on the 2:1 solutions and all solutions
from the brute-force search
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See also:
I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)
VII/233 : 2MASS All-Sky Extended Src Cat. (XSC) (IPAC/UMass, 2003-2006)
J/A+A/546/A14 : Limb-darkening for CoRoT, Kepler, Spitzer (Claret+, 2012)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/MNRAS/436/1883 : Properties of KOI host stars (Walkowicz+, 2013)
J/ApJ/790/146 : Planets in Kepler's multi-transiting systems (Fabrycky+, 2014)
J/ApJ/787/80 : 139 Kepler planets transit time variations (Hadden+, 2014)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/ApJS/225/9 : Kepler TTVs. IX. The full long-cadence dataset (Holczer+, 2016)
J/AJ/154/5 : Transit timing variations of 145 Kepler planets (Hadden+, 2017)
J/AJ/154/107 : California-Kepler Survey (CKS). I. 1305 stars (Petigura+, 2017)
J/ApJS/237/38 : Extended abundance analysis of KOIs (Brewer+, 2018)
J/AJ/155/48 : California-Kepler Survey (CKS).V. Masses & radii (Weiss+, 2018)
J/AJ/157/43 : WASP-161b, WASP-163b and WASP-170b (Barkaoui+, 2019)
J/AJ/157/52 : Radial velocity obs. in super-Earth systems (Bryan+, 2019)
J/AJ/158/133 : Transit timing and light curves for K2-146 (Hamann+, 2019)
J/AJ/159/57 : HST spec. LCs of Kepler 51b & 51d (Libby-Roberts+, 2020)
J/MNRAS/505/1293 : Duration measurements analysis KOIs planets (Shahaf+, 2021)
J/AJ/163/179 : The California-Kepler Survey. X. (Petigura+, 2022)
J/AJ/165/33 : HIRES TOI-1136s planets & planet b RVs (Dai+, 2023)
J/AJ/165/48 : Transit times for Kepler-289 b, c and d (Greklek-McKeon+, 2023)
J/AJ/168/93 : Phot. follow-up of TOI-2015 & discov. of TOI-2015b (Jones+, 2024)
http://archive.stsci.edu/ : Mikulski Archive for Space Telescopes
Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- ID Planet identifier
12- 24 F13.5 d BJD-out Mean Barycentric Julian Date of transit time
for outside 2:1 solution
26- 32 F7.5 d e_BJD-out Standard deviation in BJD-out
34- 46 F13.5 d BJD-in Mean Barycentric Julian Date of transit time
for inside 2:1 solution
48- 54 F7.5 d e_BJD-in Standard deviation in BJD-in
56- 68 F13.5 d BJD-all Mean Barycentric Julian Date of transit time
for all solutions from the brute-force search
70- 76 F7.5 d e_BJD-all Standard deviation in BJD-all
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 17-Sep-2025