J/MNRAS/499/4011 New periodic signals detected in TESS (Chakraborty+, 2020)
Hundreds of new periodic signals detected in the first year of TESS with the
weirddetector.
Chakraborty J., Wheeler A., Kipping D.
<Mon. Not. R. Astron. Soc., 499, 4011-4023 (2020)>
=2020MNRAS.499.4011C 2020MNRAS.499.4011C (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Stars, double and multiple ;
Effective temperatures ; Photometry ; Optical
Keywords: methods: numerical - methods: statistical -
planets and satellites: detection
Abstract:
We apply the weirddetector, a non-parametric signal detection
algorithm based on phase dispersion minimization, in a search for low
duty-cycle periodic signals in the Transiting Exoplanet Survey
Satellite (TESS) photometry. Our approach, in contrast to commonly
used model-based approaches specifically for flagging transits,
eclipsing binaries, or other similarly periodic events, makes minimal
assumptions about the shape of a periodic signal, with the goal of
finding 'weird' signals of unexpected or arbitrary shape. In total,
248301 TESS sources from the first-year Southern sky survey are run
through the weirddetector, of which we manually inspect the top 21500
for periodicity. To minimize false-positives, we here only report on
the upper decile in terms of signal score, a sample for which we
obtain 97% recall of TESS eclipsing binaries and 62% of the TOIs. In
our sample, we find 377 previously unreported periodic signals, for
which we make a first-pass assignment that 26 are ultra-short periods
(<0.3d), 313 are likely eclipsing binaries, 28 appear planet-like, and
10 are miscellaneous signals.
Description:
The basic principle of the weirddetector is to identify
high-likelihood periodic signals for manual inspection while
abandoning any parametric function to describe the transit shape.
We ran the weirddetector on all light-curve files in sectors 1-13
available at http://archive.stsci.edu/tess/bulk_downloads/bulk_downloads_
ffi-tp-lc-dv.html MAST (248301 not including overlap of targets
between sectors; 223087 unique targets after considering overlap). We
remove probable outliers from each PDC light curve by removing points
more than 6*MAD away from the median in an 11-point rolling window. We
also removed all points with non-zero quality flags in the FITS files.
In each sector, we split each PDC time-series into two segments
('semisectors') before and after the ∼1d data gap. Within each
segment, we used linear interpolation to fill in missing data and
detrended with a moving median filter, using a 1-d bandwidth, to
remove long-term trends, following (Wheeler and Kipping
2019MNRAS.485.5498W 2019MNRAS.485.5498W). After detrending, we removed the interpolated
points and recombined the segments. The weirddetector was then run on
the 24567 trial periods for 248301 unique light curves.
After filtering, we flag 377 previously unidentified targets (dubbed
Weird Objects of Interest, or WOIs) that appear to contain some
periodic signal. The signals were selected manually based on whether
their phase curves showed a clear signal (or multiple clear signals,
in the case of aliases). In Table A1, we present the ζpeak and
periods, along with accompanying information, for the WOI signals
reported in this work.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 88 377 Parameters for all 377 WOIs
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See also:
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- TIC TIC source identifier
11- 17 F7.4 d P Period
19- 26 E8.3 --- zetapeak Merit function (1)
28- 35 E8.3 --- Dchi2 Δχ2=median(χ2)-χ2
37- 44 E8.3 --- kappa Kurtosis (2)
46- 50 I5 K Teff ? Effective temperature
52- 55 F4.2 [cm/s2] logg ? Surface gravity
57 I1 --- dips Number of significant dips
59- 67 F9.4 % delta Depth of the dip (in percentage)
69- 74 F6.2 deg RAdeg Right ascension (J2000)
76- 81 F6.2 deg DEdeg Declination (J2000)
83 A1 --- Flat [y/n] Indicates if the baseline is flat
85- 88 A4 --- Class Classification of the signal (3)
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Note (1): The merit function ζ is defined for each period value as
ζ(P)=κ'(P)Δχ2(P)/σ(P), see section 2.1
for details
Note (2): The kurtosis reflects the weight of a distribution's tail relative to
its peak
Note (3): Class as follows:
eb = Eclipsing binary 'EB'. It displays (a) two dips per period, or
(b) one dip and noticeable phase-curve variations, or (c) one dip with
a depth greater than 2 per cent. Using this criterion, we classify 313
of the WOIs as likely EBs.
misc = WOI without a clear classification - within which we suspect stellar
activity may be broadly responsible (10/377).
pl = 'Planet-like' (PL). Signal which appear consistent with a transiting
planet from the phase curve morphology alone, but has not been subject
to any further vetting. We classify signals as PL if they show no
noticeable phase-curve variations and have one-dip per period which is
less than 2 per cent in depth. We also impose the condition that the
duration of the dip must be less than one-sixth of the orbital period
(which corresponds to a planet with a/R*>2). This results in 28 PLs.
usp = Extremely short flagged periods, less than 0.3d, which we classify as
'ultra short period' (USP). If correct, these are unlikely to be
eclipses since for a Solar-like host the orbital period would be
grazing or inside the star. We classify 26 of the cases as USPs.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 07-Sep-2023