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\IBVShead{6148}{14 September 2015}

\IBVStitletl{Study of Pulsation Spectrum of Mass-accreting}{ Component of Algol-type system VV\,UM\lowercase{a}}

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

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

\SIMBADobj{VV UMa}


\begintext
VV\,UMa is an eclipsing,  semi-detached (Algol-type) close binary  system with a short period of
0.6873801 day. It was found to be a variable by Gitz (1936) based on
the photographic plates taken at the Moscow Observatory. Afterwards,
Struve (1950) classified VV\,UMa as a single-lined spectroscopic binary
with spectral type A0V,  a mass ratio
q$\sim$0.23 and  semi-amplitude $K_1=59\,{\rm km\,s}^{-1}$. Hill et
al. (1975) classified the primary component as A2V. The first set of
complete uvby light curves of VV\,UMa was acquired in 2000 January and
analyzed by L\'{a}zaro et al. (2001). They reported about detection of
pulsational light variations  with periodicity of about 0.048  days (20.88 c/d) and
 0.020 days (50.76 c/d).  Later, with new observations, L\'{a}zaro et al.
(2002) confirmed the periodicity of about 0.0216 days (46.2
c/d) and  derived  effective temperatures of the primary and the secondary
as $T_{\rm eff}$=9250$\pm$150 K and $T_{\rm eff}$=5600$\pm$100 K, respectively.
Kim et al. (2005) confirmed the pulsations and assign VV\,UMa system to so
called new class of oEA stars suggested  by Mkrtichian et al. (2002, 2004).
Kim et al. $B$-filter CCD photometric light curve and period search analysis
definitely show of 51.239 c/d (0.0195 day) and 47.46 c/d (0.0211 day)
pulsations.


We conducted a new photometric observations of VV\,UMa within frames of
Thai Sky Survey for oEA Stars (THASSOS) in
order to get improved information about oscillation spectrum. The
photometric observations were acquired  from 26 December 2013 to 23
March 2014 at the Thai National Observatory (TNO,
$18^\circ$~$35^\prime$~$17^{\prime\prime}$~N,
$98^\circ$~$29^\prime$~$11^{\prime\prime}$~E).  The 0.5 meter Cassegrain
Telescope, the Apogee Alta U9000 $3056\times3056$ pixels CCD camera and 10
seconds exposure times though V filter were used. The data were reduced
by using Maxim DL5 program. Comparison stars are listed in Table 1. The
phased, differential light curve folded with the period of 0.6873801 day
is plotted in Figure 1.


\begin{table}[h]
\centering
\caption{Data on VV\,UMa,  comparison and check stars.}
 	\begin{tabular}{llll}
        \hline
        \hline
Star&	 RA  (J2000)	& DEC (J2000) &	\textit{V} \\
         \hline
VV UMa	& 09\hr 38\mm 06\fsec72	&+56\deg$ $01\arcm  07\farcs25	&10.28\\
TYC 3810-1503-1 (Comparison Star)&	09\hr 38\mm 32\fsec22	&+55\deg 52\arcm 06\farcs52	&10.17\\
TYC 3810-1120-1 (Check Star)&	09\hr 37\mm 43\fsec28	& +55\deg 49\arcm 19\farcs76	&10.36\\
	\hline
	\hline
		\end{tabular}
\label{tab:dataobserve}
\end{table}


\IBVSfig{8cm}{6148-f1.eps}{The phased V-filter light curve of VVUMa folded on the period of 0.68738 days.}

Times of binary curve minima were measured using quadratic polynomial
fitting method and are presented in the Table\,2. The residuals from the
out-of-eclipse light curves were obtained by removal of low-degree
polinomial fits to the light curves of every night and are shown in
Figure 2. Residuals exhibit strong amplitude modulation -- an indicator
of multiperiodiciy of pulsations.


\begin{table}[h]
\centering
\caption{Times of light minima of VV UMa.}
 	\begin{tabular}{lll}
        \hline
        \hline
Date 	& Minima HJD time &	Type of eclipse \\
         \hline
3 January 2014	& 2456661.44963	& primary  \\
9 February 2014  & 2456698.23069	& secondary  \\
11 February 2014	& 2456700.28931	& secondary  \\
13 March 2014 	& 2456730.18678 & primary \\
	\hline
	\hline
		\end{tabular}
\label{tab:dataobserve}
\end{table}

\begin{table}[h]
\centering
\caption{Pulsation frequencies and amplitudes  found in the primary component.}
 	\begin{tabular}{cc}
        \hline
        \hline

Frequency (c/d)    &   Amplitude (mag)  \\
         \hline
$F_1$=48.8483$\pm$0.0003   &     0.0028$\pm$0.0001  \\
$F_2$=47.0152$\pm$0.0005   &     0.0018$\pm$0.0001  \\
$F_3$=19.4359$\pm$0.0008   &     0.0018$\pm$0.0001  \\
	\hline
	\hline
		\end{tabular}
\label{tab:dataobserve}
\end{table}


The Discrete Fourier Transform (DFT) analysis was applied to the residual
data to find the pulsation frequencies  of the primary component. We use
a pre-whitening technique for consecutive detections of signals. The
periodograms of consecutive steps of the DFT analyses of the primary
component of VV UMa are  shown in Figure 3 from top to bottom. We
detected three oscillation frequencies  listed in Table 3.

In summary, during new photometric study of pulsations in  a  primary,
mass-accreting component of Algol-type system VV\,UMa we found four new
times of binary light minima. We confirmed pulsations of the primary
component and found three pulsation periods at frequencies of  48.8483
c/d (0.0205 d), 47.0152 c/d (0.0213) and  19.4359 c/d (0.0515 d). First
two frequencies are close to the values reported by Kim et al. (2005),
but we believe that our frequencies are more accurate. We are going to
combine our photometric results with results of spectroscopic
observations of VV\,UMa obtained by us in 2014-2015 using 2.4\,m telescope at
TNO in order to get accurate orbital parameters of VV\,UMa system.


\IBVSfig{15cm}{6148-f2.eps}{The nightly residual light variations (HJD time zero point is 2456000).
Pulsational multiperiodic fits to the light curves are shown by solid line.}

\IBVSfig{10cm}{6148-f3.eps}{The DFT amplitude spectra of the primary component after consecutive
(from top to bottom) pre-whitening procedures.}

{\bf Acknowledgements:} Department of Physics and Materials Science
Chiang Mai University thanked for support, this work is a part of research activity
of the  National Astronomical Research Institute of Thailand (NARIT).

\newpage

\references 

Gitz, H., 1936, {\it Perem. Zvezdy}, {\bf 5}, 65

 Hill, G., Hilditch, R. W., Younger, F., \& Fisher, W. A., 1975, {\it MmRAS}, {\bf 79}, 131

 Kim, S.-L., Lee, J.W., Lee, C.-U., Kang, Y.B., Koo, J-R., Mkrtichian, D.E., 2005, {\it IBVS}, {\bf 5598}

 L\'{a}zaro, C., \& Ar\'{e}valo, M. J., Mart\'{i}nez-Pais, I.G., Dom\'{i}nguez, R.M., 2002, {\it AJ}, {\bf 123}, 2733

L\'{a}zaro, C., Ar\'{e}valo, M. J., Claret, A., Rodriguez, E., \& Olivares, I., 2001, {\it MNRAS}, {\bf 325}, 617

Mkrtichian, D.~E.,  Kusakin, A.~V., Gamarova, A.~Yu. \& Nazarenko, V., 2002, {\it ASPC}, {\bf 259}, 96

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

Struve, O., 1950, {\it ApJ}, {\bf 112}, 184

\endreferences

\IBVSedata{6148-t4.txt}
\IBVSdataKey{6148-t4.txt}{VV UMa}{photometry}

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