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\IBVShead{6182}{8 September 2016}

\IBVStitletl{Detection of multiperiodic oscillations}{ in the mass-accreting component of GQ T\lowercase{r}a}

\IBVSauth{Mkrtichian, D.E.$^1$; Gunsriwiwat, K.$^2$; Komonjinda, S.$^2$ }

\IBVSinst{National Astronomical Research Institute of Thailand, 191 Siriphanich Bldg., Huay Kaew Rd., Suthep, Muang, 50200 Chiang Mai, Thailand.}
\IBVSinst{Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Muang, 50200 Chiang Mai, Thailand}

\SIMBADobj{GQ TrA}


\begintext

The ``{\bf Tha}i {\bf S}ky {\bf S}urvey for {\bf o}EA {\bf S}tars" (THASSOS)
project is focused on searching for and studies of new mass-accreting pulsating
components of a semi-detached Algol-type systems, the class called oEA stars
(Mkrtichian et al., 2002, 2004).
From the point of view of stellar evolution, this class of pulsating stars
is different from pulsating $\delta$ Scuti type stars in the detached
eclipsing binary systems, showing similar pulsational characteristics.

GQ TrA is a southern semi-detached Algol type eclipsing binary system
with A3V primary component and 2.339450-day orbital period. It was discovered
and classified as an Algol type star by Hoffmeister (1949).

The new CCD photometric observations for GQ TrA were obtained during 7
nights from 16 to 22 April 2014 using the Thai
Southern Hemisphere Telescope (TST, PROMPT-8) at Cerro Tololo
Inter-American Observatory (CTIO) in Chile. Ten second exposures through
B-filter were used. All stars in the field of view were reduced by
MaxIm DL 5 software using aperture photometry,  TYC 9049-1892-1 star
(RA = 16\hr 22\mm 07\fsec19 DEC= $-$65\deg46\arcm34\farcs7) was used as a comparison star.
Phased differential light curve folded according to ${\rm HJD} =
2452501.01   + 2.339450 \times E$ is shown in Figure 1. Times of GQ TrA light
minima were measured using quadratic polynomial fitting method.  The
Heliocentric Julian Day (HJD) of a primary minimum measured on
18 April 2014 is 2456765.7942. 

The pulsations variations were searched for in the out-of-eclipse parts
of light curves after removal of slow orbital variations using the low order
polynomial fits. Residual light curves are shown in Figure 2.
The periodic variations in the residual data were analysed  using the {\sc Period04}
software (Lenz \& Breger, 2005).
We use a Discrete Fourier Transform (DFT) and pre-whitening technique
for consecutive detection of signals in the data. The steps of DFT
analyses and consecutive pre-whitenings of found frequencies are shown
in Figure 3 from top to bottom. We detected eight oscillation
frequencies in the interval of 39.0 - 47.9 c/d (30-36.9 min).
Frequencies are listed in Table 1.

Conclusion: We found a new time of primary minima. We conclude that GQ
TrA is a new member of oEA group of pulsators, showing a rich spectrum
of relatively high amplitude, low-degree oscillations. It is a
promising target for further photometric and especially spectroscopic
line profile detection of the full (low- and high-degree) spectrum of
non-radial oscillations.

\IBVSfig{8cm}{6182-f1.eps}{The phased B-filter light curve of GQ TrA
folded with the period of 2.339450 days.}
\IBVSfigKey{6182-f1.eps}{GQ TrA}{light curve}

\IBVSfig{12cm}{6182-f2.eps}{The nightly residual light variations (HJD
time zero point is 2456000+).}
\IBVSfigKey{6182-f2.eps}{GQ TrA}{other}

\IBVSfig{13cm}{6182-f3.eps}{The DFT amplitude spectra of the primary component
after consecutive (from top to bottom) pre-whitening procedures.}
\IBVSfigKey{6182-f3.eps}{GQ TrA}{periodogram}


\begin{table}
\centering
\caption{Pulsation frequencies and amplitudes.}
 	\begin{tabular}{cc}
        \hline
        \hline

Frequency (c/d)/($\sigma$)    &   Amplitude ( mag )/($\sigma$)   \\
         \hline
$f_1$=45.644(2)	&	0.0060(1)	\\
$f_2$=47.900(3)	&	0.0044(1)       \\
$f_3$=44.954(4)	&	0.0028(1)	\\
$f_4$=39.669(4)	&	0.0033(1)	\\
$f_5$=46.201(6)	&	0.0020(1)	\\
$f_6$=39.409(5)	&	0.0023(1)	\\
$f_7$=39.094(6)	&	0.0020(1)	\\
$f_8$=46.542(5)	&	0.0024(1)	\\
	\hline
	\hline
		\end{tabular}
\label{tab:dataobserve}
\end{table}


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


\references

Hoffmeister C., 1949, {\it Erg. AN}, {\bf 12}, No. 1

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

Mkrtichian D. et al., 2002, {\it ASP Conf. Ser.}, {\bf 259}, 96

Mkrtichian, D.E., Kusakin, A.V., Rodriguez, E., et al., 2004, {\it A\&A}, {\bf 419}, 1015

\endreferences

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