J/A+A/630/A114 TESS light curves detection limits (Tregloan-Reed+, 2019)
Simulations of starspot anomalies within TESS exoplanetary transit light curves.
I. The detection limits of starspot anomalies in TESS light curves.
Tregloan-Reed J., Unda-Sanzana E.
<Astron. Astrophys. 630, A114 (2019)>
=2019A&A...630A.114T 2019A&A...630A.114T (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Exoplanets ; Photometry ; Stars, M-type ; Stars, K-type ;
Stars, late-type
Keywords: stars: late-type - stars: activity - stars: starspots -
planets and satellites: general - methods: numerical -
techniques: photometric
Abstract:
The primary targets of the NASA Transiting Exoplanet Survey Satellite
will be K and M dwarf stars within our solar neighbourhood. Young K
and M dwarf stars are known to exhibit a high starspot coverage
(∼50%), however, older stars are known to show fewer starspots. This
implies that TESS 2 min cadence transit light curves may contain
starspot anomalies, and if so, will require transit-starspot models to
accurately determine the properties of the system.
The goals are to determine if starspot anomalies can manifest in TESS
transit light curves, to determine the detection limits of the
starspot anomalies and to examine the relationship between the change
in flux caused by the starspot anomaly and the planetary transit.
20573 simulations of planetary transits around spotted stars were
conducted using the transit-starspot model, PRISM. In total 3888
different scenarios were considered using three different host star
spectral types, M4V, M1V and K5V. The mean amplitude of the starspot
anomaly was measured and compared to the photometric precision of the
light curve, to determine if the starspot anomaly's characteristic
"blip" was noticeable in the light curve. Results. The simulations
show that, starspot anomalies will be observable in TESS 2 min cadence
data. The smallest starspot detectable in TESS transit light curves
has a radius of ∼1900km. The starspot detection limits for the three
host stars are: 4900±1700km (M4V), 13800±6000km (M1V) and
15900±6800km (K5V). The smallest change in flux of the starspot
(ΔFspot=0.00015±0.00001) can be detected when the ratio
between the planetary and stellar radii, k=0.082±0.004.
The results confirm known dependencies between the amplitude of the
starspot anomaly and the photometric parameters of the light curve.
The results allowed the characterisation of the relationship between
the change in flux of the starspot anomaly and the change in flux of
the planetary transit for TESS transit light curves.
Description:
Light curve files for the 20573 simulated TESS light curves. The
directory structure flows through the different parameters used in the
simulations: Spectral class > Planetary radius > observational
wavelength > orbital period > spot temperature > photometric
precision. The individual file names are the starspot angular radius
in the light curve (e.g.,
K5V3.0600237001001.0deg.dat is
the light curve file for a 1.0 degree starspot with a temperature of
3700K, observed at 600nm with a photometric precision of 100ppm, and a
3R_Earth planet orbiting a K5V star with an orbital period of 2 days).
The largest numbered file in the bottom directories are when the
starspot anomaly is considered detected (e.g., for
K5V3.060023700100*deg the largest
numbered file is 1.5deg.dat which indicates that the smallest starspot
detectable in the given example is 1.5 degrees).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 72 21263 List of light curves
lc/* . 21263 Individual light curves
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- SpC Spectral class (1)
11- 14 F4.2 Rgeo rp Planetary radius (2)
16- 19 I4 nm lambda Observational wavelength (3)
21 I1 d Porb orbital period (4)
23- 26 I4 K Tspot Spot temperature (5)
28- 30 I3 ppm Phot Photometric precision (6)
32- 35 F4.1 deg Size Smallest starspot size detectable in this
sample (7)
37- 72 A36 --- FileName Name of the light curve file
in subdirectory lc
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Note (1): Spectral classes are K5V, M1V and M4V.
Note (2): Planetary radius could be, in Earth radius:
1.00, 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, 2.75, 3.00, 3.0, 3.25, 3.50,
3.5, 3.75, 4.00, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0
Note (3): Observational wavelength could be 600, 785 or 1000nm.
Note (4): Orbital period could be 1, 2, 3, 4 or 6=days.
Note (5): Spot temperature could be 3000, 3050, 3100, 3150, 3400, 3475, 3550,
3625, 3700, 3800, 3900 and 4000K.
Note (6): Photometric precision could be 50, 100, 150 or 200ppm.
Note (7): Starspot size from 0.5 to 20.0deg, by 0.5deg steps.
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Byte-by-byte Description of file (#): lc/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 13 F11.6 min Data-time ?=0 Spot free light curve time
19- 26 F8.6 --- Data-flux ?=0 Spot free light curve flux
29- 39 F11.6 min Model-time Light curve with spot time
45- 52 F8.6 --- Model-Flux Light curve with spot flux
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Acknowledgements:
Jeremy Tregloan-Reed, jeremy.tregloanreed(at)uantof.cl
(End) J. Tregloan-Reed [Univ. Antofagasta, Chile], P. Vannier [CDS] 22-Aug-2019