J/A+A/680/A78 CHEOPS observations of HD 139139 (Alonso+, 2023)
No random transits in CHEOPS observations of HD 139139.
Alonso R., Hoyer S., Deleuil M., Simon A.E., Beck M., Benz W., Floren H.-G.,
Guterman P., Borsato L., Brandeker A., Gandolfi D., Wilson T.G.,
Zingales T., Alibert Y., Anglada G., Barczy T., Barrado Navascues D.,
Barros S.C.C., Baumjohann W., Beck T., Billot N., Bonfils X., Broeg C.,
Charnoz S., Collier Cameron A., Corral van Damme C., Csizmadia Sz.,
Cubillos P.E., Davies M.B., Deline A., Delrez L., Demangeon O.D.S.,
Demory B.-O., Ehrenreich D. , Erikson A., Fortier A., Fossati L.,
Fridlund M., Gillon M., Guedel M., Guenther M.N., Heitzmann A., Helling C.,
Isaak K.G., Kiss L.L., Kopp E., Lam K.W.F., Laskar J.,
Lecavelier des Etangs A., Lendl M., Magrin D., Maxted P.F.L., Mordasini C.,
Nascimbeni V., Olofsson G., Ottensamer R., Pagano I., Palle E., Peter G.,
Piotto G., Pollacco D., Queloz D., Ragazzoni R., Rando N., Rauer H.,
Ribas I., Santos N.C., Scandariato G., Segransan D., Smith A.M.S.,
Sousa S.G., Stalport M., Szabo Gy.M., Thomas N., Udry S., Ulmer B.,
Van grootel V., Venturini J., Verrecchia F., Walton N.A.
<Astron. Astrophys. 680, A78 (2023)>
=2023A&A...680A..78A 2023A&A...680A..78A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, peculiar ; Photometry ; Optical
Keywords: stars: peculiar - planets and satellites: detection -
techniques: photometric
Abstract:
The star HD 139139 (a.k.a. 'The Random Transiter') is a star that
exhibited enigmatic transit-like features with no apparent periodicity
in K2 data. The shallow depth of the events (∼200ppm -- equivalent to
transiting objects with radii of ∼1.5R☉ in front of a Sun-like
star), and their non- periodicity, constitutes a challenge for the
photometric follow-up of this star.
The goal of this study is to confirm with independent measurements the
presence of shallow, non-periodic transit-like features on this
object.
We performed observations with CHEOPS, for a total accumulated time of
12.75d, distributed in visits of roughly 20h in two observing
campaigns in years 2021 and 2022. The precision of the data is
sufficient to detect 150 ppm features with durations longer than 1.5h.
We use the duration and times of the events seen in the K2 curve to
estimate how many should have been detected in our campaigns, under
the assumption that their behaviour during the CHEOPS observations
would be the same as in the K2 data of 2017.
We do not detect events with depths larger than 150 ppm in our data
set. If the frequency, depth, and duration of the events were the same
as in the K2 campaign, we estimate the probability of having missed
all events due to our limited observing window would be 4.8%.
We suggest three different scenarios to explain our results: 1) Our
observing window was not long enough, and the events were missed with
the estimated 4.8% probability. 2) The events recorded in the K2
observations were time critical, and the mechanism producing them was
either not active in the 2021 and 2022 campaigns or created shallower
events under our detectability level. 3) The enigmatic events in the
K2 data are the result of an unidentified and infrequent instrumental
noise in the original data set or its data treatment.
Description:
CHEOPS light curves used in the paper, with 1-min cadence (raw and
detrended), and 29-min and 1-orbit bins.
Objects:
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RA (2000) DE Designation(s)
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15 37 06.21 -19 08 33.0 HD 139139 = TIC 70652803
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
1min.dat 105 12625 1-min cadence CHEOPS light curve
29min.dat 60 605 29-min bins CHEOPS light curve
1orb.dat 60 188 1-orbit bins CHEOPS light curve
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Byte-by-byte Description of file: 1min.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d Time Time of mid exposure, TDB (BJD-2400000)
20- 37 F18.16 --- Flux Normalised flux
39- 60 F22.20 --- e_Flux Error of normalised flux
62- 79 F18.16 --- Fluxdet Normalised flux, detrended
81-102 F22.20 --- e_Fluxdet Error of detrended normalised flux
104-105 I2 --- Visit [1/15] Id of visit (1)
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Note (1): Table 1. Observing log of the CHEOPS visits used in this work.
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id ObsID File Key Start date (UTC) Obs. Visit
efficiency duration
(%) (h)
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1 1461054 CHPR110046TG000401_V0300 2021-05-01T11:05:38 94.1 19.49
2 1490422 CHPR110046TG000501_V0300 2021-05-11T07:50:18 91.3 19.63
3 1489399 CHPR110046TG000601_V0300 2021-05-12T14:21:18 91.3 19.63
4 1495676 CHPR110046TG000602_V0300 2021-05-17T09:31:17 88.6 19.43
5 1506007 CHPR110046TG000701_V0300 2021-06-02T19:06:18 71.9 19.63
6 1502884 CHPR110046TG000603_V0300 2021-06-06T22:24:19 72.0 19.63
7 1509091 CHPR110046TG000801_V0300 2021-06-08T17:10:18 68.5 22.91
8 1512500 CHPR110046TG000901_V0300 2021-06-13T18:33:16 60.6 26.05
9 1783271 CHPR110046TG001001_V0300 2022-04-14T02:10:38 71.1 19.43
10 1792614 CHPR110046TG001101_V0300 2022-04-27T12:48:40 93.0 19.63
11 1791182 CHPR110046TG001201_V0300 2022-04-28T22:19:37 94.1 19.53
12 1797193 CHPR110046TG001202_V0300 2022-05-07T12:30:38 91.8 22.18
13 1795741 CHPR110046TG001301_V0300 2022-05-09T05:31:39 90.0 19.63
14 1804287 CHPR110046TG001501_V0300 2022-05-20T16:53:39 78.1 19.63
15 1808521 CHPR110046TG001502_V0300 2022-05-22T10:37:17 80.0 19.63
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Byte-by-byte Description of file: 29min.dat 1orb.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.12 d Time Time of mid exposure, TDB (BJD-2400000)
20- 37 F18.16 --- Flux Normalised flux
39- 60 E22.17 --- e_Flux Error of normalised flux
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Acknowledgements:
Roi Alonso, ras(at)iac.es
(End) Patricia Vannier [CDS] 15-Nov-2023