exoclock

KELT-21b (LOW)

Discovered by: Johnson et al. 2018

The Star
Simbad
GAIA
2MASS		 HD 332124
DR2 2054523105274216704
J20191200+3234517
RA 20:19:12.0049 DEC +32:34:51.762
Parallax
2.095 mas		 P.M. RA
2.239 mas/y		 P.M. DEC
-0.113 mas/y
MagV
10.48		 MagR*
10.453		 MagI*
10.24		 MagJ
10.149		 MagH
10.121		 MagK
10.09
MagG
10.541		 MagGBP
10.642		 MagGRP
10.381
*Calculated from GAIA magnitudes.

Ephemeris - Verified True
Kokori et al. 2025
Mid-time
2459091.48021 ± 0.00011 BJDTDB
Period
3.61277072 ± 8.8e-07 days
Transit Parameters
Johnson et al. 2018
Rp/Rs
0.09952 ± 0.00071		 a/Rs
6.86 +0.13 -0.12
 i
86.46 +0.38 -0.34 deg
e
-		 ω
- deg
DepthR*
12.2 mmag		 Duration*
4.11 hours
*Calculated from the other parameters, using PyLightcurve.
**Adjusted based on the space observations.

Limb Darkening Parameters
Johnson et al. 2018
Teff
7598.0 +81.0 -84.0 K
 Log(g)
4.173 +0.015 -0.014 cm/s2
 Fe/H
-0.405 +0.032 -0.033 dex
ExoClock Status
Observing Priority LOW
Minimum aperture 5.0"
Total Observations (Recent) 47 (7)
O-C 0.79 ± 0.43 minutes
ExoClock Observations (Recent) 22 (7)
Space Observations (Recent) 12 (0)
ETD Observations (Recent) 0 (0)
Literature Mid-times (Recent) 13 (0)
Kepler Rp/Rs -
TESS Rp/Rs 0.09944 ± 0.00031

KELT-21b


ExoClock Observations
Planet
Observation Date		 Observer
Observatory		 Telescope
Camera / Filter / Exp [s]		 O-C
minutes
KELT-21b (LOW)
2025-09-11		Paolo Arcangelo Matassa
P:M.P.H.R. Deep Sky (K81)		Ritchey Chretien 40cm-F5.3
CCD ICX453AQ / Lum / 45.0		-0.15 ± 1.87
KELT-21b (LOW)
2025-08-13		Vojtěch Školník
Broumov NM Observatory		Meade LX90 ACF
MI C2-7000A / Clear / 30.0		3.4 ± 1.87
KELT-21b (LOW)
2025-08-13		Stefan Brenner
NOE Volkssternwarte AST		Martini-Truss mit Zambuto 11“ f/4,7
Omegon veTEC 571 C / Clear / 60.0		-2.51 ± 1.58
KELT-21b (LOW)
2025-06-28		Paolo Arcangelo Matassa
P:M.P.H.R. Deep Sky (K81)		Ritchey Chretien 40cm-F5.3
CCD ICX453AQ / Lum / 30.0		3.86 ± 1.58
KELT-21b (LOW)
2025-06-28		Matthieu Bachschmidt
Gonachon		Celestron C11
SBIG ST8XME / R / 60.0		2.27 ± 1.73
KELT-21b (LOW)
2025-06-28		Miguel Ángel Álava Amat
Sarriguren		Meade SC 8"
Asi 1600 MM / rpr / 180.0		0.69 ± 1.87
KELT-21b (LOW)
2025-06-28		Giovanni Calapai
Home Astronomical Observatory		Celestron 11 Schmidt-Cassegrain
Atik 314L+ / Clear / 90.0		-3.92 ± 2.3
KELT-21b (LOW)
2024-07-27		Ramon Naves
Montcabrer		Meade LX200 12" ACF
Moravian G4-9000 / rpr / 120.0		1.85 ± 1.14
KELT-21b (LOW)
2024-07-27		Ian Sharp
PixelSkies		Celestron C11 Edge HD
Starlight Xpress Trius Pro SX694 / R / 45.0		-0.21 ± 1.44
KELT-21b (LOW)
2024-07-08		Deborah Smith
Complejo Astronomico Los Coloraos, Gorafe		Celestron C11
QHY9 / I / 60.0		1.74 ± 2.16
KELT-21b (LOW)
2024-07-08		Anaël Wünsche
Observatoire des Baronnies Provençales		CDK Planewave 2
ZWO ASI6200 / R / 120.0		1.54 ± 0.85
KELT-21b (LOW)
2024-07-08		Yves Jongen
Rasteau Observatory		Plane Wave CDK 17"
SBIG STXL 11002 / R / 90.0		-1.86 ± 1.73
KELT-21b (LOW)
2024-06-10		Deborah Smith
Complejo Astronomico Los Coloraos, Gorafe		Celestron C11 EdgeHD
ASI2600MM / R / 120.0		-3.64 ± 2.59
KELT-21b (LOW)
2023-06-22		Guillaume Biesse
Observatoire de la colline Tossius		Ritchey Chretien GSO
ASI 533 MM - Gain=0 / rpr / 180.0		2.6 ± 3.17
KELT-21b (LOW)
2022-10-04		Adam Popowicz
Observatory Pyskowice		RC12" GSO
ASI ZWO 1600 MM / ATIK 11000M / R / 60.0		0.86 ± 2.3
KELT-21b (LOW)
2022-07-21		Jean-Baptiste Marquette
MrKite47		Newton Sky-Watcher 200/1000
ZWO ASI183MM Pro / R / 70.0		4.87 ± 2.02
KELT-21b (LOW)
2022-07-21		Marianna Michelagnoli
Osservatorio Polifunzionale del Chianti		Ritchey-Chretien
Moravian G4-9000 / V / 40.0		1.56 ± 0.58
KELT-21b (LOW)
2022-07-21		Yves Jongen
Rasteau Observatory		Plane Wave CDK 17"
SBIG STXL 11002 / R / 90.0		0.84 ± 2.02
KELT-21b (LOW)
2022-07-02		Fran Campos
Puig d'Agulles Observtory		RC14" on EQ8 German mount
SBIG ST-8XME / R / 90.0		6.1 ± 1.73
KELT-21b (LOW)
2022-07-02		Thomas SALOMON
Astroqueyras		Ritchey chretien 500 F/8
160803 / R / 60.0		2.64 ± 1.44
KELT-21b (LOW)
2022-07-02		Claudio Lopresti
Claudio Lopresti		Meade LX200 12"
CCD Sbig ST9xe / Lum / 180.0		-0.52 ± 2.45
KELT-21b (LOW)
2022-07-02		Claudio Lopresti
Claudio Lopresti		Mak-Newton
CCD Sbig ST10xme / I / 180.0		-3.69 ± 2.74

Space Observations
Planet
Observation Date		 Mission O-C
minutes
KELT-21b (LOW)
2022-08-26		TESS-1.29 ± 0.85
KELT-21b (LOW)
2022-08-22		TESS1.13 ± 0.88
KELT-21b (LOW)
2022-08-11		TESS0.76 ± 0.81
KELT-21b (LOW)
2022-08-08		TESS0.6 ± 0.81
KELT-21b (LOW)
2021-08-19		TESS0.42 ± 0.69
KELT-21b (LOW)
2021-08-15		TESS-1.17 ± 0.73
KELT-21b (LOW)
2021-08-11		TESS-0.75 ± 0.73
KELT-21b (LOW)
2021-08-08		TESS0.0 ± 0.73
KELT-21b (LOW)
2021-08-04		TESS0.61 ± 0.73
KELT-21b (LOW)
2021-07-31		TESS0.0 ± 0.85
KELT-21b (LOW)
2021-07-28		TESS1.04 ± 0.69
KELT-21b (LOW)
2021-07-24		TESS-0.5 ± 0.79

Literature Mid-times
Planet
Observation Date		 Reference O-C
minutes
2020-08-26 Garai et al. 2022 -1.09 ± 0.66
2020-07-24 Garai et al. 2022 -0.18 ± 0.12
2020-07-24 Garai et al. 2022 -0.72 ± 0.3
2020-07-21 Garai et al. 2022 1.85 ± 1.02
2020-07-03 Garai et al. 2022 0.89 ± 0.46
2017-05-29 Johnson et al. 2018 1.23 ± 1.15
2017-05-29 Johnson et al. 2018 0.8 ± 0.72
2016-08-24 Johnson et al. 2018 2.02 ± 1.15
2016-08-24 Johnson et al. 2018 0.58 ± 1.15
2016-08-24 Johnson et al. 2018 -3.02 ± 1.01
2016-07-19 Johnson et al. 2018 0.01 ± 1.15
2014-10-25 Johnson et al. 2018 6.17 ± 1.44
2014-08-29 Johnson et al. 2018 -0.55 ± 2.88
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