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\IBVSheadDOI{63}{6259}{29 January 2019}

\IBVStitletl{Detection of a \boldmath{$\delta$} Scuti--type pulsating component}{ in the detached eclipsing binary system  TU CM\lowercase{a} }

\IBVSauth{MKRTICHIAN, D.E.}

\IBVSinsto{National Astronomical Research Institute of Thailand, 260 Moo 4, T. Donkaew, A. Maerim, Chiangmai, 50180
Thailand. e-mail: davidmkrt$@$gmail.com }


\SIMBADobjAlias{TU Cam}{HD 39220}
\IBVSkey{photometry}
\IBVSabs{ We report the detection of 30.5 min low-amplitude (A=0.003 mag)
$\delta$ Scuti-type pulsations in an A5V-A7V type component of the detached
 eclipsing binary system TU CMa.}

\begintext

 TU CMa is a 1.127803854-day (Haans et al.\ 2015) detached eclipsing binary system
with A5V-A7V primary and F8V-G0V secondary components (Garces et al.\ 2017). It
was included in our program to search for pulsating components that have
the primary component lying inside the instability strip and hence can be
potentially pulsating.

Visual inspection of the SWASP data  of TU CMa taken
from their archive\footnote{\tt https://wasp.cerit-sc.cz} revealed about 0.02-day short-period,
low-amplitude light variations.
For the safe detection of possible pulsations, we selected the best
quality nights for TU\,CMa from the
SWASP data, namely HJD 2454105, 2454131, 2454132, 2454133, 2454134, 2454135,
2454433, 2454434, 2454436, 2454456, 2454462 and  2454485.
The pulsation variations were searched for in the out-of-eclipse parts of the light
curves after removal of slow orbital variations using low order polynomial
fits. For the period search, we used the {\sc Period04} software (Lenz \& Breger, 2005)
based on a Discrete Fourier Transform (DFT) analysis.

The DFT amplitude-frequency spectrum of the TU CMa residual data
is shown in Figure 1. We detected a clear signal at 47.3197$\pm$0.0002 c/d ($P=30.5$ min) with an amplitude
of 0.0038 mag. The phased light curve binned into 20-phase intervals is shown
in Figure 2.

Using the mass M=1.761$\pm$0.012 $M_{\odot}$ and the radius R= 1.553$\pm$0.002 $R_{\odot}$ for the
primary component from Garces et al.\ (2017) we calculated the mean density of the pulsating component
as  $\rho$/$\rho \odot$=0.4702. The calculated pulsation constant for the
discovered 30.5 min ($P=0.021$
day) pulsation mode, $Q=P \sqrt{\rho_{\ast}/\rho_{\odot}}= 0.014$, corresponds
to a fourth or fifth
overtone low degree ($\ell=0-3$) mode.

\IBVSfig{8cm}{6259-f1.eps}{The DFT amplitude spectrum of the primary A5V-A7V
component. The dominant peak is at 47.3197 $\pm$0.0002 c/d. }
\IBVSfigKey{6259-f1.eps}{}{}

\IBVSfig{8cm}{6259-f2.eps}{The phase-binned pulsation light variations of
TU CMa. The phase of the maximum light corresponds to HJD 2454107.9776.}
\IBVSfigKey{6259-f2.eps}{TUCMa}{light curve}

Conclusion:
We report the detection of a 30.5 min low amplitude (A=0.003 mag)
$\delta$~Scuti-type pulsation in an A5V-A7V type component of the detached eclipsing binary system
TU CMa. The calculated pulsation constant corresponds to pulsations in the
4-5th overtone low-degree mode (Fitch, 1981).
The parameters of the binary system and components of TU CMa are accurately
determined and are good input parameters for theoretical pulsational modelling.
This binary system can be a good  target for  further
more accurate and detailed photometric observations of pulsations in order
to detect a low-amplitude pulsation spectrum, for the eclipse mode
identification of the dominant mode and for comparison with theoretical
pulsation models.

\vskip 1cm

\noindent{\bf Acknowledgements:} I acknowledge this work as part of the research activity supported by
the National Astronomical Research Institute of Thailand (NARIT),
Ministry of Science and Technology of Thailand.

This paper makes use of data from the DR1 of the WASP data (Butters et al.\ 2010)
as provided by the WASP consortium, and the computing and storage facilities
 at the CERIT Scientific Cloud, reg. no. CZ.1.05/3.2.00/08.0144
which is operated by Masaryk University, Czech Republic (Paunzen et al., 2014).

\references

Butters, O.~W., et al., 2010, {\it A\&A},{\bf 520}, L10 \DOI{10.1051/0004-6361/201015655}

Fitch, W.~S., 1981, {\it ApJ}, {\bf 249}, 218  \DOI{10.1086/159278}

Garc\'es, J.~L.,  Mennickent, R. E., \& Zharikov, S., 2017, {\it PASP} {\bf 129}, 044203 \DOI{10.1088/1538-3873/aa5b7f}

Haans, G.~K., et al., 2015, {\it PKAS}, 30, 205  \DOI{10.5303/PKAS.2015.30.2.205}

Lenz, P., Breger M., 2005, {\it Communications in Asteroseismology},{\bf 146}, 53 \DOI{10.1553/cia146s53}

Paunzen, E., Kuba, M., West, R.G., Zejda, M., 2014, {\it IBVS}, {\bf 6090}
\endreferences


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