J/ApJ/898/L11 TESS and NGTS LCs and RVs of NGTS-11 (Gill+, 2020)
NGTS-11 b (TOI-1847 b): a transiting warm Saturn recovered from a TESS
single-transit event.
Gill S., Wheatley P.J., Cooke B.F., Jordan A., Nielsen L.D., Bayliss D.,
Anderson D.R., Vines J.I., Lendl M., Acton J.S., Armstrong D.J., Bouchy F.,
Brahm R., Bryant E.M., Burleigh M.R., Casewell S.L., Eigmuller P.,
Espinoza N., Gillen E., Goad M. R, Grieves N., Gunther M.N., Henning T.,
Hobson M.J., Hogan A., Jenkins J.S., McCormac J., Moyano M., Osborn H.P.,
Pollacco D., Queloz D., Rauer H., Raynard L., Rojas F., Sarkis P.,
Smith A.M.S., Tala Pinto M., Tilbrook R.H., Udry S., Watson C.A., West R.G.
<Astrophys. J., 898, L11 (2020)>
=2020ApJ...898L..11G 2020ApJ...898L..11G
ADC_Keywords: Exoplanets; Stars, K-type; Photometry; Radial velocities; Optical
Keywords: Exoplanet astronomy ; Exoplanet detection methods ; Exoplanets ;
Extrasolar gas giants ; Photometry ; High resolution spectroscopy
Abstract:
We report the discovery of NGTS-11 b (=TOI-1847b), a transiting Saturn
in a 35.46 day orbit around a mid K-type star (Teff=5050±80K). We
initially identified the system from a single-transit event in a TESS
full-frame image light curve. Following 79 nights of photometric
monitoring with an NGTS telescope, we observed a second full transit
of NGTS-11 b approximately one year after the TESS single-transit
event. The NGTS transit confirmed the parameters of the transit signal
and restricted the orbital period to a set of 13 discrete periods. We
combined our transit detections with precise radial-velocity
measurements to determine the true orbital period and measure the mass
of the planet. We find NGTS-11 b has a radius of
0.817-0.032+0.028RJup, a mass of 0.344-0.073+0.092MJup,
and an equilibrium temperature of just 435-32+34K, making it one
of the coolest known transiting gas giants. NGTS-11 b is the first
exoplanet to be discovered after being initially identified as a TESS
single-transit event, and its discovery highlights the power of
intense photometric monitoring in recovering longer-period transiting
exoplanets from single-transit events.
Description:
The K-dwarf TIC-54002556 (NGTS-11, T=11.62) was observed at a 30min
cadence with TESS Camera 1 in Sector 3 of the mission (2018/Sep/20 -
2018/Oct/18). See Section 2.1.
We used the Next Generation Transit Survey (NGTS) facility (see NGTS
project; Wheatley+ 2018MNRAS.475.4476W 2018MNRAS.475.4476W) located at the ESO Paranal
Observatory in Chile to monitor NGTS-11 photometrically.
We started monitoring NGTS-11 with a single NGTS telescope on the
night of 2019 August 11. We observed NGTS-11 for 79 nights
(105642 exposures) before a second transit event was detected
(ΔlogL=364) on the UT night of 2019 October 24. The transit
event was centered at JD 2458780.712, which is 390 days after the
initial TESS single-transit. See Section 2.2.
Following the NGTS transit detection, we immediately began
radial-velocity follow-up using the CORALIE fiber-fed Echelle
spectrograph installed on the 1.2m Leonard Euler telescope at the ESO
La Silla Observatory. We made three 600s observations of NGTS-11 over
54 days (2019 October 29, November 28, and December 25), the first
just 5 days after the NGTS transit detection.
Those observations were followed by an additional nine 1800s
radial-velocity measurements spanning 63 days with the HARPS
spectrograph (R=115000) on the 3.6m ESO telescope, and six
measurements spanning 11 days with the FEROS spectrograph (R=48000) on
the MPG/ESO 2.2m Telescope.
See Section 2.4.
Objects:
--------------------------------------------------
RA (ICRS) DE Designation(s)
--------------------------------------------------
01 34 05.14 -14 25 09.2 NGTS-11b = TOI-1847b
--------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
coralie.dat 168 3 CORALIE radial velocity time series
(data behind Figure 1)
feros.dat 26 6 FEROS radial velocity time series
(data behind Figure 1)
harps.dat 116 9 HARPS radial velocity time series
(data behind Figure 1)
tess.dat 18 1275 TESS light curve (data behind Figure 1)
ngts.dat 75 105642 NGTS light curve (data behind Figure 1)
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/616/A39 : Power-2 limb-darkening law from STAGGER-grid (Maxted, 2018)
J/AJ/157/55 : RVs and light curves for HATS-60-HATS-69 (Hartman+, 2019)
J/AJ/159/241 : TESS-Keck Survey. I. HD332231 RVs (Dalba+, 2020)
J/MNRAS/495/2713 : TIC-231005575 photometric and RV curves (Gill+, 2020)
J/AJ/159/173 : Phot. & RVs of 4 dwarfs hosting giant planets (Hartman+, 2020)
J/ApJS/254/39 : Exoplanet candidates from TESS first 2yr obs (Guerrero+, 2021)
Byte-by-byte Description of file: coralie.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 F17.11 d BJD [58785.6/58839.6] Barycentric Julian Date
in TDB; BJD-2400000.5
19- 30 F12.6 m/s HRV [21364/21439] Barycentric radial velocity
32- 40 F9.6 m/s e_HRV [48/56] Uncertainty in HRV
42- 52 F11.6 m/s FWHM FWHM of the cross-correlation function
54- 62 F9.6 m/s e_FWHM Uncertainty in FWHM
64- 73 F10.6 m/s BS Bisector span
75- 83 F9.6 m/s e_BS Uncertainty in BS
85- 93 F9.6 % Contrast Contrast
95-102 F8.6 % e_Contrast Uncertainty in Contrast
104-111 F8.6 --- Halpha H-alpha index
113-120 F8.6 --- e_Halpha Uncertainty in Halpha
122-129 F8.6 --- NaID NaID index
131-138 F8.6 --- e_NaID Uncertainty in NaID
140-148 F9.6 --- CaHK CaHK index
150-157 F8.6 --- e_CaHK Uncertainty CaHK
159-168 F10.6 km/s beRV Barycentric Earth radial velocity
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Byte-by-byte Description of file: feros.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.5 d BJD [58802.6/58813.7] Barycentric Julian Date
in TDB; BJD-2400000.5
13- 19 F7.4 km/s HRV [21.35/21.43] Heliocentric radial velocity
21- 26 F6.4 km/s e_HRV [0.006/0.01] Uncertainty in HRV
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Byte-by-byte Description of file: harps.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 d BJD [58837.6/58900.6] Barycentric Julian Date
in TDB; BJD-2400000.5
14- 21 F8.5 km/s HRV [21.38/21.43] Barycentric radial velocity
23- 29 F7.5 km/s e_HRV [0.0028/0.012] Uncertainty in HRV
31- 37 F7.5 km/s FWHM FWHM of the cross-correlation function
39- 44 F6.3 % Contrast Contrast
46- 53 F8.5 km/s BS Bisector span
55- 61 F7.5 km/s Noise Photon Noise
63- 70 F8.6 --- Sindex Mount Wilson S index
72- 79 F8.6 --- e_Sindex Uncertainty in Sindex
81- 87 F7.4 --- logRHK Stellar Activity index, Ca II HK
89- 94 F6.4 --- e_logRHK Uncertainty in logRHK
96- 99 F4.2 --- snCaII Signal-to-noise, CaII line
101-104 F4.2 --- sn10 sn10
106-110 F5.2 --- sn50 sn50
112-116 F5.2 --- sn60 sn60
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Byte-by-byte Description of file: tess.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.5 d BJD [1382/1409.4] Barycentric Julian Date;
BJD-2457000
12- 18 F7.5 --- Flux [0.29/1.01] Normalized Flux
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Byte-by-byte Description of file: ngts.dat
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Bytes Format Units Label Explanations
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1- 24 E24.18 d BJD [2.4587e+06/2.45879e+06] Barycentric Julian Date
26- 50 E25.18 mag mag [-0.378/0.326] Relative magnitude
52- 75 E24.18 mag e_mag [0.0075/0.008] Uncertainty in mag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Dec-2021