J/AJ/170/101 WH & TESS light curves of two eclipsing binaries (Guo+, 2025)
Two ultralow-mass-ratio binary systems at critical evolutionary stages.
Guo D.-F., Li K., Liu F., Wang L.-H., Li H.-Z., Chen Xu, Gao X.
<Astron. J., 170, 101 (2025)>
=2025AJ....170..101G 2025AJ....170..101G
ADC_Keywords: Binaries, eclipsing; Photometry, VRI; Stars, double and multiple
Keywords: Close binary stars ; Contact binary stars ; Semi-
detached binary stars ; Mass ratio
Abstract:
In this paper, we present photometric observations and period analysis
of two totally eclipsing binaries with extremely low-amplitude light
curves. Both binaries exhibit typical W Ursae Majoris-type light
curves with total eclipses, allowing for the precise determination of
the mass ratios. Light-curve solutions were derived using the Python
package PHysics Of Eclipsing BinariEs in combination with a Markov
Chain Monte Carlo framework. Both WISE J053525.4-200442 (hereafter
J053525) and ASASSN-V J175200.35+361805.2 (hereafter J175200) are
identified as shallow contact binaries with ultralow mass ratios.
Specifically, J053525 exhibits a mass ratio of q∼0.124 and a marginal
contact degree of f∼22%, while J175200 has q∼0.027 and a contact
degree of f∼13%. Notably, J175200 represents the most extreme mass
ratio observed in contact binaries to date. However, due to
degeneracies between mass ratio and third-light contributions in
purely photometric analyses, the derived mass ratios should be
interpreted as lower limits, especially for J175200. The evolutionary
states of these systems differ significantly. For J053525, a long-term
period decrease is detected, with the orbital period derivative
calculated as dP/dt=-1.99e-6day/yr. In contrast, J175200 shows a
period increase: dP/dt=1.93e-7day/yr. These contrasting period trends
may be indicative of ongoing mass transfer; however, alternative
explanations such as third-body effects cannot be ruled out.
Nevertheless, the combination of their ultralow mass ratios, shallow
contact configurations, and apparent period evolution highlights their
unique value in testing mass ratio theories and the thermal relaxation
oscillation hypothesis.
Description:
Observations of the complete RcIc-band light curves for the
totally eclipsing binary J053525 (WISE J053525.42-200442.3) were
conducted on 2024 February 11 and 16, using the newly installed 50cm
PlaneWave telescope (WH50) located at Wendeng Biblical Mountain in
Weihai, China. Exposure times were typically set to 70s for the Rc
band and 60s for the Ic band.
Complete V-, Rc-, and Ic-band photometric observations of the
totally eclipsing binary system J175200 (ASASSN-V J175200.35+361805.2)
were conducted using the 100cm telescope at Weihai Observatory
(WH100), China, on 2024 June 2 and 10. The typical exposure times were
50s for the V band, 20s for the Rc band, and 15s for the Ic band.
TESS observed J053525 at a cadence of 30min in sectors 5 and 6
(11/15/18-01/07/19), and at a higher cadence of 10min in sector 32
(11/19/20-12/17/20). Meanwhile, TESS observed J175200 at different
cadences: a 30min cadence in sectors 25 and 26 (05/13/20-07/04/20),
and a higher cadence of 10min in sectors 40 (06/24/21-07/23/21), and
52 and 53 (05/18/22-07/09/22). The relevant data were downloaded from
the Mikulski Archive for Space Telescopes (MAST).
To study the variations of the orbital period, we utilized the 100,
60, and 50cm telescopes at Weihai Observatory, Shandong University,
to obtain eclipsing minima for the binary systems. Additionally, we
used continuous light curves from the Wide Angle Search for Planets
(SuperWASP; Butters+, 2010A&A...520L..10B 2010A&A...520L..10B) and TESS to calculate the
eclipsing times for J053525 and J175200. SuperWASP consists of two
robotic observatories, one on La Palma, Spain, with the Isaac Newton
Group of telescopes (ING), and one at the South African Astronomical
Observatory (SAAO), South Africa. We identified 18 eclipsing minima
for J053525 and 40 eclipsing minima for J175200.
Objects:
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RA (2000) DE Designation(s)
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05 35 25.43 -20 04 42.5 WISE J053525.4-200442 = WISE J053525.42-200442.3
17 52 00.33 +36 18 05.1 ASASSN-V J175200.35+361805.2 = UCAC4 632-056541
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 40 18 The times of minimum light for WISE J053525.4-200442
table2.dat 43 40 The times of minimum light for ASASSN-V
J175200.35+361805.2
lc/* . 5 Normalized, phase-folded light curves files in MRT
format (Data behind Figure 7)
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/AJ/106/2096 : Limb-darkening coefficients in binaries (Van Hamme 1993)
J/ApJ/723/1469 : Flux calibrations and WZ Oph photometry (Wilson+, 2010)
J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJS/237/28 : WISE catalog of periodic variable stars (Chen+, 2018)
J/AJ/158/104 : LL Com BVR bands phot. & times of light minimum (Hu+, 2019)
J/AJ/159/189 : Eclipse timings for 9 contact binaries (Li+, 2020)
J/ApJ/922/122 : BVRcIc LCs of two contact binaries (Li+, 2021)
J/AJ/162/13 : Parameters estimation for 173 eclipsing binaries (Li+, 2021)
J/ApJS/262/12 : Kepler P<2d close binaries (Kobulnicky+, 2022)
J/AJ/164/202 : Extrem. Low Mass Ratio Contact Binar. I. 10 syst. (Li+, 2022)
J/A+A/672/A176 : Mass-ratio distribution of contact binary stars (Pesta+, 2023)
J/A+A/692/L4 : The lowest mass ratio contact binary (Li+, 2024)
http://archive.stsci.edu/ : Mikulski Archive for Space Telescopes (MAST)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.5 d BJD [8443.9/10357.1] Barycentric Julian Date,
BJD-2450000
13 A1 --- Tel Source of observation; telescope used (1)
15- 21 F7.5 d e_BJD [1.3e-4/1.4e-3] Uncertainty in BJD
23- 24 A2 --- Min Light curve minimum, two per phase (9 I, 9 II)
26- 32 F7.1 --- Epoch [-5539.5/0] Epoch in cycles (see Equations 1 & 3)
34- 40 F7.5 d O-C [0/0.01] Residual
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Note (1): Sources as follows:
a = TESS, the Transiting Exoplanet Survey Satellite (12 occurrences)
b = WH100cm, the 100cm telescope at Weihai Observatory, China (2 occurrences)
c = WH60cm, the 60cm telescope at Weihai Observatory, China (2 occurrences)
d = WH50cm, the 50cm telescope at Weihai Observatory, China (2 occurrences)
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.5 d BJD [3137.6/10472.2] Barycentric Julian Date,
BJD-2450000
13 A1 --- Tel Source of observation; telescope used (1)
15- 21 F7.5 d e_BJD [2e-4/2e-3] Uncertainty in BJD
23- 24 A2 --- Min Light curve minimum, two per phase (23 I, 17 II)
26- 33 F8.1 --- Epoch [-18832/4773.5] Epoch in cycles
(see Equations 2 & 4)
35- 43 F9.6 d O-C [-0.1/0.04] Residual
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Note (1): Sources as follows:
a = SuperWASP, the Wide Angle Search for Planets, consisting of two robotic
observatories, one on La Palma, Spain, with the Isaac Newton Group of
telescopes (ING), and one at the South African Astronomical Observatory
(SAAO), South Africa (15 occurrences)
b = TESS, the Transiting Exoplanet Survey Satellite (20 occurrences)
c = WH50cm, the 50cm telescope at Weihai Observatory, China (3 occurrences)
d = WH100cm, the 100cm telescope at Weihai Observatory, China (2 occurrences)
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Robin Leichtnam [CDS] 12-Jun-2026