J/A+A/703/A166 Orbital periods of polars from TESS (Hernandez-Diaz+, 2025)
A systematic search for orbital periods of polars with TESS.
Methods, detection limits, and results.
Hernandez-Diaz S., Stelzer B., Schwope A., Munoz-Giraldo D.
<Astron. Astrophys. 703, A166 (2025)>
=2025A&A...703A.166H 2025A&A...703A.166H (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, cataclysmic ; Binaries, orbits ; Photometry ; Optical
Keywords: stars: cataclysmic variables - stars: magnetic field -
techniques: photometric - methods: data analysis -
methods: statistical
Abstract:
Determining the orbital periods of cataclysmic variable stars (CVs) is
essential for confirming candidates and for the understanding of their
evolutionary state. The Transiting Exoplanet Survey Satellite (TESS)
provides month-long photometric data across nearly the entire sky that
can be used to search for periodic variability in such systems.
This study aims to identify and confirm the orbital periods for
members of a recent compilation of magnetic CVs (known as polars)
using TESS light curves. In addition to providing the periods, we set
out to investigate their reliability, and hence the relevance of TESS
for variability studies of CVs.
Four period-search methods were used, namely the Lomb-Scargle
periodogram, the autocorrelation function (ACF), sine fitting, and
Fourier power spectrum analysis, to detect periodic signals in TESS
light curves. We investigated the correlation between noise level and
TESS magnitude by "flattening" the observed TESS light curves,
effectively isolating the noise from the periodic modulation. To
evaluate the reliability of the period detections, we developed a
probabilistic framework for the detection success across
signal-to-noise ratios in the power spectral density of observed light
curves.
Ninety-five of the 217 polars in our sample have pipeline-produced
TESS two-minute cadence light curves available. The results from our
period search are overall in good agreement with the previously
reported values. Out of the 95 analysed systems, 85 exhibit periods
consistent with the literature values. Among the remaining ten
objects, four are asynchronous polars, where TESS light curves resolve
the orbital period, the white dwarf's spin period, and additional
beat frequencies. For four systems, the periods detected from the TESS
data differ from those previously reported. For two systems, a period
detection was not possible due to the high noise levels in their light
curves. Our analysis of the flattened TESS light curves reveals a
positive correlation between noise levels - expressed as the
standard deviation of the flattened light curve - and TESS magnitude.
Our noise level estimates resemble the rmsCDPP, a measure of white
noise provided with the TESS pipeline products. However, our values
for the noise level are systematically higher than the rmsCDPP
indicating red noise and high-frequency signals hidden in the
flattened light curves. Additionally, we present a statistical
methodology to assess the reliability of period detections in TESS
light curves. We find that for TESS magnitudes ≳17, period
detections become increasingly unreliable.
Our study shows that TESS data can be used to reliably and efficiently
determine orbital periods in CVs. The developed methodology for period
detection, noise characterisation, and reliability assessment can be
systematically applied to other variable star studies, thus improving
the robustness of period measurements in large photometric data sets.
Description:
We present the results of a systematic study aimed at identifying and
confirming the orbital periods for members of a recent compilation of
magnetic cataclysmic variable stars (known as polars) from Schwope
(2025A&A...698A.106S 2025A&A...698A.106S) using optical light curves obtained by the
Transiting Exoplanet Survey Satellite (TESS). Four period-search
methods were employed: Lomb-Scargle periodogram, autocorrelation
function, sine fitting, and Fourier power spectrum analysis.
Ninety-five of the 217 polars in our sample have pipeline-produced
TESS two-minute cadence light curves available. The derived orbital
periods are compared with values previously reported in the
literature. Out of the 95 analysed systems, 85 exhibit periods
consistent with the literature values. Among the remaining ten
objects, four are asynchronous polars. For four systems, the periods
detected from the TESS data differ from those previously reported. For
two systems, a period detection was not possible due to the high noise
levels in their light curves. Our study shows that TESS data can be
used to reliably and efficiently determine orbital periods in
cataclysmic variable stars. The developed methodology can be
systematically applied to other variable star studies, improving the
robustness of period measurements in large photometric data sets.
Sample properties and results from period search for the catalogue of
polars using TESS light curves. The table includes identifiers,
coordinates, photometry from TESS and Gaia, orbital period
measurements, and references.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 373 95 Sample properties and period search results for
95 polars with TESS 2-minute cadence light
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 29 A29 --- System Object's common name
31- 49 I19 --- GaiaDR3 Gaia identifier from data release 3
51- 69 F19.15 deg RAdeg Gaia DR3 Right Ascension (ICRS) at Ep=2016.0
71- 90 F20.16 deg DEdeg Gaia DR3 Declination (ICRS) at Ep=2016.0
92-101 I10 --- TIC TESS Input Catalogue identifier
103-210 A108 --- Sectors Observed TESS sectors
212-217 F6.3 mag Tmag TESS magnitude
219-223 F5.3 mag e_Tmag Uncertainty in TESS magnitude
225-230 F6.3 mag BPmag Gaia BP mean magnitude
232-237 F6.3 mag RPmag Gaia RP mean magnitude
239-244 F6.3 mag Gmag Gaia G mean magnitude
246-255 F10.5 min PorbLS ? Lomb-Scargle sector-average orbital period
257-264 F8.5 min e_PorbLS ? Uncertainty in PorbLS
266-274 F9.4 min PorbACF ? Autocorrelation function sector-average
orbital period
276-281 F6.3 min e_PorbACF ? Uncertainty in PorbACF
283-291 F9.4 min PorbSINE ? Sine fitting sector-average orbital period
293-299 F7.4 min e_PorbSINE ? Uncertainty in PorbSINE
301-310 F10.5 min PorbFS ? Fourier power spectrum sector-average
orbital period
312-319 F8.5 min e_PorbFS ? Uncertainty in PorbFS
321-330 F10.5 min Porb ? Final adopted orbital period
332-339 F8.5 min e_Porb ? Uncertainty in final Porb
341 I1 --- CorrFlag [0/1] 1/2Porb correction flag (1)
343-353 F11.7 min Porblit Literature-reported orbital period
355-373 A19 --- r_Porblit Literature source for Porblit
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Note (1): A total of 38 systems were corrected for dominant modulations at half
the orbital period (1/2 Porb):
1 = at least one of the individual period determinations used to compute the
final orbital period was corrected
0 = no correction applied
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Acknowledgements:
Santiago Hernandez-Diaz, hernandez(at)astro.uni-tuebingen.de
(End) Patricia Vannier [CDS] 15-Oct-2025