J/A+A/589/A94 TU UMa light curves and maxima, CL Aur minima (Liska+, 2016)
New analysis of the light time effect in TU Ursae Majoris.
Liska J., Skarka M., Mikulasek Z., Zejda M., Chrastina M.
<Astron. Astrophys. 589, A94 (2016)>
=2016A&A...589A..94L 2016A&A...589A..94L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, horizontal branch ; Binaries, orbits ;
Photometry, CCD
Keywords: binaries: general - techniques: photometric -
techniques: radial velocities - stars: variables: RR Lyrae -
methods: data analysis
Abstract:
Recent statistical studies prove that the percentage of RR Lyrae
pulsators that are located in binaries or multiple stellar systems is
considerably lower than might be expected. This can be better
understood from an in-depth analysis of individual candidates. We
investigate in detail the light time effect of the most probable
binary candidate TU UMa. This is complicated because the pulsation
period shows secular variation.
We model possible light time effect of TU UMa using a new code applied
on previously available and newly determined maxima timings to confirm
binarity and refine parameters of the orbit of the RRab component in
the binary system. The binary hypothesis is also tested using radial
velocity measurements.
We used new approach to determine brightness maxima timings based on
template fitting. This can also be used on sparse or scattered data.
This approach was successfully applied on measurements from different
sources. To determine the orbital parameters of the double star TU
UMa, we developed a new code to analyse light time effect that also
includes secular variation in the pulsation period. Its usability was
successfully tested on CL Aur, an eclipsing binary with mass-transfer
in a triple system that shows similar changes in the O-C diagram.
Since orbital motion would cause systematic shifts in mean radial
velocities (dominated by pulsations), we computed and compared our
model with centre-of-mass velocities. They were determined using
high-quality templates of radial velocity curves of RRab stars.
Maxima timings adopted from the GEOS database (168) together with
those newly determined from sky surveys and new measurements (85) were
used to construct an O-C diagram spanning almost five proposed orbital
cycles. This data set is three times larger than data sets used by
previous authors. Modelling of the O-C dependence resulted in
23.3-year orbital period, which translates into a minimum mass of the
second component of about 0.33Ms. Secular changes in the pulsation
period of TU UMa over the whole O-C diagram were satisfactorily
approximated by a parabolic trend with a rate of -2.2ms/yr. To confirm
binarity, we used radial velocity measurements from nine independent
sources. Although our results are convincing, additional long-term
monitoring is necessary to unambiguously confirm the binarity of
TU UMa.
Description:
Differential photometry for RR Lyrae star TU UMa in the 1st and 2nd file.
The measurements were obtained using 24-inch and 1-inch telescopes,
respectively. The observations were performed at the Masaryk
University Observatory in Brno (3 nights, 24-inch), and at the private
observatory in Brno (16 nights, 1-inch) in the Czech Republic from
December 2013 to June 2014. Observing equipments consisted of 24-inch
Newtonian telescope (600/2780mm, diameter/focal length) and a
Moravian Instruments CCD camera G2-4000 with Stromgren photometric
filters vby, and of 1-inch refractor (a photographic lens Sonnar
4/135mm, lens focal ratio/focal length) and ATIK 16IC CCD camera with
green photometric filter with similar throughput as the Johnson V
filter. Exposures were v - 60s, b - 30s, y - 30s, green - 30s. For the
small aperture telescope, five frames were combined to a single image
to achieve a better signal-to-noise ratio. The time resolution of a
such combined frame is about 170s.
CCD images were calibrated in a standard way (dark frame and flat
field corrections). The C-Munipack software (Motl 2009) was used for
this processing as well as for differential photometry.
The comparison star BD+30 2165 was the same for both instruments, but
the control stars were BD+30 2164 (for the 24-inch telescope) and
HD 99593 (for the 1-inch telescope).
The 3rd file contains maxima timings of TU UMa adopted from the GEOS
RR Lyr database, from the latest publications, together with maxima
timings determined in our study. Times of maxima were calculated from
our observations, sky-surveys data (Hipparcos, NSVS, Pi of the Sky,
SuperWASP), photographic measurements (project DASCH), and from
several published datasets, in which the maxima were omitted or badly
determined - Boenigk (1958AcA.....8...13B 1958AcA.....8...13B), Liakos, Niarchos
(2011IBVS.6099....1L 2011IBVS.6099....1L, 2011IBVS.5990....1L 2011IBVS.5990....1L), Liu, Janes
(1989ApJS...69..593L 1989ApJS...69..593L), Preston et al. (1961ApJ...133..484P 1961ApJ...133..484P).
The 4th file contains minima timings of eclipsing binary CL Aur
adopted from O-C Gateway database.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------
11 29 48.49 +30 04 02.4 TU UMa = BD+30 2162
05 12 54.19 +33 30 28.1 CL Aur = SV* HV 6886
-------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 28 433 vby differential photometry of TU UMa
table2.dat 32 703 Green differential photometry of TU UMa
table3.dat 157 253 Maxima timings of TU UMa
table4.dat 64 203 Minima timings of CL Aur
refs.dat 115 102 References
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Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
15- 20 F6.3 mag mag Magnitude in Band
22- 26 F5.3 mag e_mag Uncertainty of magnitude
28- 32 A5 --- Band [vby green ] Photometric band (1)
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Note (1): vby Stromgren bands and green band, similar to V-Johnson.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date, time of maximum
14- 19 F6.4 d e_HJD ?=9.9999 Uncertainty of time of maximum (1)
21- 49 A29 --- Ref Reference, in refs.dat file
51- 71 A21 --- Obs Observer
73- 76 A4 --- Met Observation method
78-157 A80 --- Comm Comments (2)
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Note (1): value 9.9999 = unknown uncertainty.
Note (2): References in refs.dat file.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian Date, time of minimum
14 A1 --- Type [ps] Type of minimum,
p for primary, s for secondary
16- 42 A27 --- Ref Reference, in refs.dat file
44- 59 A16 --- Obs Observer
61- 64 A4 --- Met Observation method
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 29 A29 --- Ref Reference code
31- 49 A19 --- BibCode BibCode
51-115 A65 --- Com Comments
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Acknowledgements:
Jiri Liska, jiriliska(at)post.cz,
DTPA, Masaryk University, Czech Republic
(End) Jiri Liska [DTPA, Czech Republic], Patricia Vannier [CDS] 12-Feb-2016