\documentstyle[twoside,epsf,hyperref]{article}
\input ibvs2.sty
\input ibvst.sty
\begin{document}
\IBVSheadDOI{63}{6210}{13 July 2017}


\IBVStitletl{Discovery of short-period oscillations}{ in the mass-accreting component of BD V\lowercase{ir}}

\IBVSauth{Mkrtichian, D.E.; A-thano, N.; Awiphan, S}


\IBVSinsto{National Astronomical Research Institute of Thailand, 191 Siriphanich Bldg., Huay Kaew Rd., Suthep, Muang, 50200 Chiang Mai,
Thailand.}

\SIMBADobj{BD Vir}

\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, so called class of oEA stars suggested by Mkrtichian et al.
(2002, 2004). oEA components of binaries have been evolved into the
instability strip after the first high- mass transfer stage and show
$\delta$ Sct-like oscillations like classical $\delta$ Sct-type stars in
well detached eclipsing binary systems, without any history of mass
transfer.
BD Vir is a 2.548572-day semi-detached Algol type eclipsing binary
system with an A8\,V primary component, showing long-term orbital period
variation (Kreiner, 2004).

The new CCD photometric observations for
BD\,Vir were obtained during 4 nights (February 13, March 13, 31 and
April 20, 2017) using the 0.5m telescope of Thai National Observatory in
Thailand. All observations were made  at the orbital phase interval
0.45-0.72.  Johnson B-filter was used, exposures varied from 20 to 80
seconds depending on seeing and the weather conditions. All stars in the
field of view were reduced by SExtractor  and the Python written codes
for differential photometry. Exposures were binned by 4 points to get a
better accuracy. The comparison star TYC 6120-50-1 (RA = 13\hr 27\mm
16\fsec245 DEC= $-$16\deg 07\arcm 45\farcs85) was
used.


Pulsational variations were searched for in the out-of-eclipse parts
of the light curve after removal of slow orbital light variations using the
low order polynomial fits. Residual light curves are shown in Figure 1.
We searched for periodic variations in the residual data  by using the
Period04 software (Lenz \& Breger, 2005).

We applied the Discrete Fourier Transforms (DFT) and the signal
pre-whitening techniques for consecutive detection of signals in the
data. Steps of DFT analyses and consecutive pre-whitenings of found
frequencies are shown in Figure 2 from top to bottom. We detected two
pulsation frequencies at 34.159 c/d and 29.735 c/d.  Frequencies,
amplitudes of oscillations and their accuracies are listed in Table 1.



\IBVSfig{16cm}{6210-f1.eps}{The nightly residual light variations of BD
Vir (dots). Solid line is a two frequency fit to the data.}
\IBVSfigKey{6210-f1.eps}{BD Vir}{light curve}

\IBVSfig{20cm}{6210-f2.eps}{The DFT amplitude spectra of the primary
component. Top panel - the DFT of the residual light curve, highest peak
is at 34.16 c/d.  Middle panel - the DFT of residuals after removal of 34.16 c/d,
highest peak at 29.73 c/d.
Bottom panel - the DFT after removal of 34.16 and 29.73 c/d.}
\IBVSfigKey{6210-f2.eps}{BD Vir}{periodogram}


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

Frequency (c/d)/($\sigma$)    &   Amplitude (mag)/($\sigma$)   \\
         \hline
$f_1$=34.1599(4)	&	0.0045(2)	\\
$f_2$=29.7353(6)	&	0.0030(2)       \\
	\hline
	\hline
		\end{tabular}
\label{tab:dataobserve}
\end{table}


Conclusion: We discovered short-period pulsational light oscillations in a primary
mass-accreting component of the semi-detached eclipsing binary system BD
Vir. We conclude, that BD Vir is a new member of oEA group of pulsators
suggested by Mkrtichian et al. (2002, 2004).

\pagebreak

{\bf Acknowledgements:}

We 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.


\references

Kreiner J.M., 2004, {\it AcA}, {\bf 54}, 207

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

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 \DOI{10.1051/0004-6361:20040095}

\end{document}
