J/AJ/147/98 Times of minimum light for EQ Tau (Li+, 2014)
The triple binary star EQ Tau with an active component.
Li K., Qian S.-B., Hu S.-M., He J.-J.
<Astron. J., 147, 98 (2014)>
=2014AJ....147...98L 2014AJ....147...98L
ADC_Keywords: Binaries, eclipsing
Keywords: binaries: close - binaries: eclipsing - stars: individual: EQ Tau
Abstract:
New photometric data of EQ Tau observed in 2010 and 2013 are
presented. Light curves obtained in 2000 and 2004 by Yuan & Qian and
2001 by Yang & Liu, together with our two newly determined sets of
light curves, were analyzed using the Wilson-Devinney code. The five
sets of light curves exhibit very obvious variations, implying that
the light curves of EQ Tau show a strong O'Connell effect. We found
that EQ Tau is an A-type shallow contact binary with a contact degree
of f=11.8%; variable dark spots on the primary component of EQ Tau
were also observed. Using 10 new times of minimum light, together with
those collected from the literature, the orbital period change of EQ
Tau was analyzed. We found that its orbital period includes a secular
decrease (dP/dt=-3.63x10-8days/yr) and a cyclic oscillation
(A3=0.0058 days and P3=22.7 yr). The secular increase of the
period can be explained by mass transfer from the more massive
component to the less massive one or/and angular momentum loss due to
a magnetic stellar wind. The Applegate mechanism cannot explain the
cyclic orbital period change. A probable transit-like event was
observed in 2010. Therefore, the cyclic orbital period change of EQ
Tau may be due to the light time effect of a third body.
Description:
The CCD photometric observations of EQ Tau were first carried out
using the 60cm telescope at Yunnan Observatory from 2009 to 2012,
during which some new times of minimum light were determined. Then, EQ
Tau was observed using the 1m telescope at Yunnan Observatory on 2010
October 30 and November 1, and complete V, R, and I light curves were
derived. Finally, EQ Tau was observed by using the 85cm telescope at
Xinglong station of the National Astronomical Observatories of China
(NAOC) on 2013 January 8 and 11, and complete B, V, R, and I light
curves were obtained. All telescopes were equipped with the standard
Johnson-Cousin-Bessel UBVRI CCD photometric system.
Objects:
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RA (ICRS) DE Designation(s)
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03 48 13.43 +22 18 50.9 V* EQ Tau = V* EQ Tau = CSV 347
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 32 23 Newly determined times of minimum light for EQ Tau
table2.dat 62 272 Times of minimum light for EQ Tau
refs.dat 115 66 References
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
J/MNRAS/381/602 : BV differential light curves of EQ Tau (Yuan+, 2007)
J/AJ/132/960 : V(RI)c light-curves of EQ Tauri (Hrivnak+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date
14- 19 F6.4 d e_HJD Uncertainty in HJD
21 A1 --- Type [ps] Minimum type (p=primary, s=secondary)
23- 27 A5 --- Flt Filter (B, V, R, I, Clear)
29- 32 A4 --- Tel Telescope (1)
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Note (1): Telescope codes defined as follows:
1m = 1m telescope at Yunnan Observatory;
60cm = 60cm telescope at Yunnan Observatory;
85cm = 85cm telescope at Xinglong station of the National Astronomical
Observatories of China (NAOC).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date
14- 15 A2 --- Type Miminum type (I or II)
17- 19 A3 --- Meth Observation method (ccd=charge-coupled device,
pe=photoelectric, pg=photographic)
21- 26 F6.4 d e_HJD Error in the time of light minimum (1)
28- 35 F8.1 --- E Epoch (cycle)
37- 43 F7.4 d O-C1 The (O-C)1 value (2)
45- 51 F7.4 d O-C2 The (O-C)2 value (2)
53- 59 F7.4 d Res Residual (2)
61- 62 I2 --- Ref Reference code; in refs.dat file
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Note (1): Some references do not show the errors of the times of light
minimum. We set the errors of pe and CCD data as 0.0010 and the errors
of pg data as 0.0100.
Note (2): The different resoiduals are:
* (O-C)1 is calculated from 2440213.325+0.341347E (top panel of Fig.4),
which can be fitted by Eq.(2).
* (O-C)2 represents the residuals after removal of the secular decrease
of 3.63x10-8d/yr (middle panel of Fig.4).
* Res represents the residuals after both the secular decrease and
the periodic variation (P3=8305d)
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference identifier
4- 22 A19 --- BibCode Bibliographic code
24- 43 A20 --- Aut Author's name
45-115 A71 --- Com Comments
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 12-Sep-2014