J/AJ/149/120 Times of minimum light for TY UMa (Li+, 2015)
The active contact binary TY UMa revisited: is it a quadruple star?
Li K., Hu S.-M., Guo D.-F., Jiang Y.-G., Gao Y.-G., Chen X., Odell A.P.
<Astron. J., 149, 120 (2015)>
=2015AJ....149..120L 2015AJ....149..120L (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Radial velocities
Keywords: binaries: close - binaries: eclipsing - stars: individual: TY UMa
Abstract:
TY UMa is an F-type eclipsing binary star. Four-color light curves and
radial velocities of this system were presented and simultaneously
analyzed using the W-D code. It is found that TY UMa is a W-subtype
shallow contact binary system (f=13.4%) with a mass ratio of q=2.523.
In order to explain the asymmetric light curve of this binary, a dark
spot on the less massive component was employed. Our newly determined
31 times of minimum light, including those collected from the
literature, have been used to analyze orbital period changes of TY
UMa. The complicated period variation could be sorted into a secular
period increase at a rate of dp/dt=+5.18(±0.21)x10-7days/yr, a
51.7yr periodic modulation (A3=0.0182days), and a very small
amplitude cyclic oscillation with a period of 10.0yr
(A4=0.0015days). The long-term increase of the period can be
explained by mass transfer from the less massive component to the more
massive one. The Applegate mechanism may impossibly explain the two
cyclic components in the period. The two cyclic variations are very
likely caused by the light travel time effect of third and fourth
components, suggesting that TY UMa is a quadruple system.
Description:
CCD observations of TY UMa were taken with the Weihai Observatory 1.0m
telescope of Shandong University (WHOT). Observations were carried out
on three nights (UT 2014 February 20 and 25 and May 21). The PIXIS
2048B CCD camera was used.
We obtained nine spectra of TY UMa on UT 2014 November 3 with the B&C
spectrograph on the Steward Observatory 2.3m Bok telescope. Spectra
were also obtained for spectral and radial velocity standard stars.
The spectrograph configuration was such as to produce 1.35Å
resolution (2 pixel), using the 832/mm grating in second order and a
slit width of 1.5''. Wavelength coverage was about 3850 to 4700Å.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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12 09 02.49 +56 01 54.0 V* TY UMa = NSVS 2614576 (P=0.3545)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 39 9 Heliocentric radial velocities of TY UMa
table3.dat 60 305 Observed times of minimum light for TY UMa
refs.dat 159 85 References
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
J/AJ/147/98 : Times of minimum light for EQ Tau (Li+, 2014)
J/AJ/143/99 : Photometry of W UMa eclipsing binaries (Terrell+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 F9.4 d HJD Heliocentric Julian Date (HJD-2450000)
11- 16 F6.4 --- Phase [0/1] Phase (1)
18- 22 F5.1 km/s HRV1 [-100/109] Primary heliocentric radial velocity
24- 27 F4.1 km/s e_HRV1 Uncertainty in HRV1
29- 34 F6.1 km/s HRV2 [-276/247] Secondary heliocentric radial velocity
36- 39 F4.1 km/s e_HRV2 Uncertainty in HRV2
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Note (1): Computed with Eq.(1): Min.I=HJD2456714.1341+0.35454813E.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d HJD Heliocentric Julian Date of minimum light
(HJD-2400000)
12- 14 A3 --- Meth Detection method (ccd, phg, pe, or vis) (1)
16 A1 --- Type [ps] Type of minimum light (p=primary, s=secondary)
18- 25 F8.1 --- E [-37907/48701] Epoch (cycle) (2)
27- 33 F7.4 d O-C1 Primary O-C residual (2)
35- 41 F7.4 d O-C2 Secondary O-C residual (3)
43- 49 F7.4 d O-C3 Tertiary O-C residual (4)
51- 57 F7.4 d Res ? Quadruple O-C residual (5)
59- 60 I2 --- Ref [1/85] Reference; in refs.dat file
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Note (1): The detection methods are defined as follows:
ccd = charge coupled device;
phg = photographic;
pe = photoelectric;
vis = visual.
Note (2): Calculated using the same linear ephemeris as Kang et al.
(2002MNRAS.331..707K 2002MNRAS.331..707K), 2439532.4951+0.35453954E (Eq.(2)) which can be
fitted by Eq.(3).
Note (3): Represents the residual after removal of the the quadratic term of
Eq.(3), where the cyclic oscillation can be seen more clearly.
Note (4): After both the long term increase and the cyclic change are
subtracted, the (O-C)3 values are displayed in the lowest panel of Fig.5.
We found that the pe and ccd data of the (O-C)3 values may show a cyclic
oscillation. A nonlinear least-squares solution for the pe and ccd data of
(O-C)3 values leads to Eq.(4). A cyclic oscillation with a very small
amplitude of 0.0015days and a period of 10.0yr is determined. The
corresponding fitting curve is shown in the upper panel of Fig.6.
Note (5): When the cyclic term is removed (lower panel of Fig.6).
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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
45-159 A115 --- Com Comments
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 21-Apr-2015