\documentstyle[twoside, epsf]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{5752}{22 January 2007}

\IBVStitletl{Photometry of 39 PMS Variables}{ in the Taurus-Auriga Region}

\IBVSauth{Grankin, K.N.; Artemenko, S.A.; Melnikov, S.Y.}

\IBVSinsto{Astronomical Institute, Uzbek Akademy of Sciences, 33
Astronomicheskaya str., Tashkent 100052, Uzbekistan\\
email: kn@astrin.uzsci.net, sveta@astrin.uzsci.net, stas @astrin.uzsci.net}

\SIMBADobj{GSC 00697-00960}
\SIMBADobj{GSC 01258-00338}
\SIMBADobj{GSC 01259-00232}
\SIMBADobj{GSC 01266-01121}
\SIMBADobj{GSC 01267-00362}
\SIMBADobj{GSC 01270-00230}
\SIMBADobj{GSC 01270-00735}
\SIMBADobj{GSC 01274-01076}
\SIMBADobj{GSC 01274-01491}
\SIMBADobj{GSC 01275-00669}
\SIMBADobj{GSC 01281-00398}
\SIMBADobj{GSC 01281-01906}
\SIMBADobj{GSC 01284-00930}
\SIMBADobj{GSC 01284-01283}
\SIMBADobj{GSC 01288-00790}
\SIMBADobj{GSC 01289-00513}
\SIMBADobj{GSC 01292-00639}
\SIMBADobj{GSC 01838-00189}
\SIMBADobj{GSC 01843-00400}
\SIMBADobj{GSC 02371-02073}
\SIMBADobj{GSC 02373-00920}
\SIMBADobj{GSC 02391-00494}
\SIMBADobj{HD 28150}
\SIMBADobj{HD 283323}
\SIMBADobj{HD 283782}
\SIMBADobj{HD 283798}
\SIMBADobj{HD 284135}
\SIMBADobj{HD 284149}
\SIMBADobj{HD 284503}
\SIMBADobj{HD 285281}
\SIMBADobj{HD 285579}
\SIMBADobj{HD 31281}
\SIMBADobj{RX J0409.8+2446}
\SIMBADobj{[WKS96] RX J0424.8+2643A}
\SIMBADobj{RX J0435.9+2352}
\SIMBADobj{[WKS96] RX J0439.4+3332A}
\SIMBADobj{RX J0446.8+2255}
\SIMBADobj{[WKS96] RX J0451.9+2849A}
\SIMBADobj{V1117 Tau}

\IBVSabs{Thirty nine PMS variable stars were observed in the}
\IBVSabs{direction of the Taurus-Auriga star-forming region.}

\begintext

The previous studies have shown that most of the well known Pre-Main Sequence
(PMS) stars in the Tau-Aur region demonstrate some periodic light variations
(Grankin, 1997). Such periodicities can be interpreted as the rotational
modulation of the stellar flux by a group of dark surface spots. Thus, the
photometric observations of spotted PMS stars allow to measure their rotational
periods with high accuracy. The aim of our research is an extension of PMS
stars sample with known rotational periods, which are fundamental stellar
parameters. Unfortunately, most of the spotted PMS stars show the periodic light
variations very seldom, when spots are disposed on a star surface extremely
inhomogeneously (Grankin, 2005). Therefore, it is necessary to make some
long-term observations of such PMS star to discover its rotational period with
confidence. In this connection, we have made long-term observations of
representative sample of new PMS stars in Tau-Aur region.

We present a photometric study of 39 PMS stars discovered in the
Taurus-Auriga star-forming region, based on high-resolution echelle spectroscopy
and proper motion data (Wichmann et al., 2000). Photometric data were collected
with three 60-cm telescopes at the Mt.~Maidanak Observatory (Uzbekistan) during
several runs from 2000 to 2006. Each telescope was equipped with a pulse
counting FEU-79 photomultiplier tube and a set of standard $BV$ Johnson and $R$
Kron--Cousins filters.

The light curves obtained during our campaign were analyzed with use the
string-length algorithm (Dworetsky, 1983). The spacing of our observations in
time (one day) causes so-called false periods (Tanner, 1948). Both true and
false periods produce fully equivalent folded light curves. In order to
determine the true period it is necessary to carry out some intensive
monitorings within several nights. Unfortunately, we could make such intensive
observations only for several objects from our list.

In Table 1 we present first detection of periodic light variations for 15 PMS
stars, for which a few monitorings have been made. Their phased light curves in
$V$ band are shown in Figure 1. We found periodic variations for other seven
PMS stars, without any monitorings. Therefore, we could not select the true
period for them. These seven PMS stars are listed in Table 2 and their phased
light curves are displayed in Figure~2. In Table 2 only the two most probable
periods for these stars are presented. At last, we could not discover any
periodicity for 17 PMS stars from our list. All these stars are the irregular
variables. These seventeen irregular PMS stars are listed in Table~3. The
original photometric data for all 39 PMS stars is available at the IBVS website as {\tt 5752-t4.txt}.

\IBVSedata{5752-t4.txt}
\IBVSdataKey{5752-t4.txt}{}{photometry}

\begin{table}[h]
\normalsize
\begin{center}
{\normalsize {\bf Table 1.} List of new regular PMS stars with a few
monitorings. Columns are: star's name, Right Ascension and Declination of the
star calculated for J2000.0, SpT -- spectral type, $N_{s}$ -- number of
observational seasons, $\Delta$$m_{V}$ -- observed maximal amplitude of
variation in Johnson $V$ band for one of observational seasons, range $V$ --
photometric range in the $V$ band for all observational seasons, $P$ -- period
of variation in days}
 \vskip 2mm
\begin{tabular}{rrrrrrcr}
\hline Star Name & RA (2000) & Dec (2000)& SpT & $N_{s}$ & $\Delta$$m_{V}$ & 
range $V$ &
$P$ [days]\\ \hline
 HD 285281      & 04 00 31.07 & 19 35 20.8 & K1 & 4 & 0.16 & 10.12--10.29 & 
1.1683 \\
 HD 283323      & 04 05 12.34 & 26 32 43.6 & K2 & 6 & 0.12 & 11.21--11.49 & 
1.9610 \\
 HD 284135      & 04 05 40.58 & 22 48 12.0 & G3 & 5 & 0.06 & 9.29--9.44   & 
0.8160 \\
 HD 284149      & 04 06 38.80 & 20 18 11.2 & G1 & 5 & 0.07 & 9.62--9.75   & 
1.0790 \\
RXJ0424.8+2643A & 04 24 48.18 & 26 43 16.0 & K1 & 6 & 0.17 & 11.22--11.42 & 
3.2100 \\
 HD 28150       & 04 27 04.86 & 18 12 27.2 & G5 & 6 & 0.12 & 9.30--9.51   & 
0.6962 \\
 HD 284503      & 04 30 49.19 & 21 14 10.7 & G8 & 4 & 0.13 & 10.26--10.40 & 
0.7360 \\
GSC 01274-01076 & 04 38 13.04 & 20 22 47.0 & K2 & 5 & 0.15 & 12.12--12.28 & 
2.9600 \\
 HD 283798      & 04 41 55.16 & 26 58 49.4 & G7 & 5 & 0.05 & 9.61--9.69   & 
0.6000 \\
RXJ0446.8+2255  & 04 46 53.22 & 22 55 13.1 & M1 & 3 & 0.14 & 12.80--12.97 & 
3.7620 \\
GSC 01292-00639 & 04 50 00.18 & 22 29 57.7 & K1 & 4 & 0.15 & 11.15--11.31 & 
0.4778 \\
GSC 01284-00930 & 04 52 30.76 & 17 30 25.8 & K4 & 6 & 0.09 & 12.00--12.11 & 
0.8204 \\
GSC 01281-00398 & 04 56 13.56 & 15 54 22.0 & K7 & 3 & 0.14 & 12.58--12.76 & 
5.6400 \\
GSC 01289-00513 & 04 57 30.63 & 20 14 28.6 & K3 & 4 & 0.19 & 10.96--11.20 & 
1.4600 \\
GSC 00697-00960 & 04 59 46.14 & 14 30 55.2 & K4 & 7 & 0.26 & 11.56--11.89 & 
1.2308 \\
\hline
\end{tabular}
\end{center}
\end{table}

\begin{table}
\normalsize
\begin{center}
{\normalsize {\bf Table 2.} List of new regular PMS stars without
any monitorings. Columns are: star's name, Right Ascension and
Declination of a star calculated for J2000.0, SpT -- spectral type,
$N_{s}$ -- number of observational seasons, $\Delta$$m_{V}$ --
observed maximal amplitude of variation in Johnson $V$ band for one
of observational seasons, range $V$ -- photometric range in the $V$
band for all observational seasons, $P$ -- period of variation in
days}\vskip 2mm

\begin{tabular}{rrrrrrcr}
\hline Star Name & RA (2000) & Dec (2000)& SpT & $N_{s}$ & $\Delta$$m_{V}$ & 
range $V$ & $P$ [days]\\
\hline
GSC 01258-00338  & 04 05 19.61 & 20 09 25.2 &   K1 & 4 & 0.16 & 10.31--10.54 & 
2.86 (0.741) \\
RXJ0409.8+2446   & 04 09 51.11 & 24 46 21.5 & M1.5 & 3 & 0.20 & 13.38--13.59 & 
5.58 (1.214) \\
GSC 01274-01491  & 04 33 34.68 & 19 16 48.6 &   G6 & 3 & 0.10 & 13.08--13.20 & 
1.41 (0.585) \\
GSC 01266-01121  & 04 38 27.63 & 15 43 38.2 &   K3 & 4 & 0.10 & 13.22--13.50 & 
2.54 (1.651) \\
RXJ0439.4+3332A  & 04 39 25.47 & 33 32 44.8 &   K5 & 5 & 0.16 & 11.39--11.56 & 
2.43 (0.708) \\
RXJ0451.9+2849A  & 04 51 56.90 & 28 49 42.7 &   K4 & 2 & 0.20 & 13.25--13.45 & 
0.921 (11.66)\\
GSC 01281-01906  & 04 56 56.54 & 16 00 24.8 &   M1 & 2 & 0.25 & 14.23--14.50 & 
0.884 (7.62)\\
\hline
\end{tabular}
\end{center}
\end{table}

\begin{table}
\normalsize
\begin{center}
{\normalsize {\bf Table 3.} List of new irregular PMS stars.
Columns are: star's name, Right Ascension and Declination of a star
calculated for J2000.0, SpT -- spectral type, $N_{s}$ -- number of
observational seasons, $\Delta$$m_{V}$ -- observed maximal
amplitude of variation in Johnson $V$ band for one of observational
seasons, range $V$ -- photometric range in the $V$ band for all
observational seasons, $P$ -- period of variation in days} \vskip
2mm

\begin{tabular}{rrrrrrcr}
\hline Star Name & RA (2000) & Dec (2000)& SpT & $N_{s}$ & $\Delta$$m_{V}$ & 
range $V$ &
$P$ [days]\\ \hline

GSC 01259-00232 & 04 12 50.65 & 19 36 58.0 & K6 & 4 & 0.10 & 12.51--12.65 & 
1.569? \\
 HD 285579      & 04 12 59.87 & 16 11 47.8 &   G1 & 5 & 0.07 & 10.95--11.12 &      
- \\
GSC 02371-02073 & 04 15 51.42 & 31 00 36.0 &   G6 & 4 & 0.12 & 12.34--12.47 & 
0.414? \\
GSC 01270-00735 & 04 32 53.22 & 17 35 34.0 &   M2 & 2 & 0.07 & 13.64--13.77 & 
0.857? \\
GSC 01270-00230 & 04 33 42.01 & 18 24 27.4 &   G6 & 3 & 0.06 & 12.04--12.12 & 
1.122? \\
RXJ0435.9+2352  & 04 35 56.81 & 23 52 05.4 & M1.5 & 2 & 0.16 & 13.31--13.49 &      
- \\
GSC 02373-00920 & 04 37 16.87 & 31 08 19.8 &   K4 & 3 & 0.09 & 13.12--13.31 & 
1.429? \\
V1117 Tau       & 04 38 15.59 & 23 02 28.1 &   M1 & 2 & 0.12 & 13.74--13.90 & 
1.185? \\
GSC 01838-00189 & 04 41 24.00 & 27 15 13.2 &   G8 & 3 & 0.05 & 13.05--13.15 &      
- \\
GSC 01267-00362 & 04 43 25.98 & 15 46 03.6 &   G7 & 6 & 0.13 & 12.81--12.97 &  
1.11? \\
GSC 01275-00669 & 04 44 26.78 & 19 52 17.5 &   M1 & 4 & 0.11 & 12.53--12.64 &      
- \\
 HD 283782      & 04 44 54.40 & 27 17 45.5 &   K1 & 4 & 0.07 & 9.48--9.55   &      
- \\
GSC 01284-01283 & 04 51 54.24 & 17 58 28.1 & M1.5 & 2 & 0.18 & 13.89--14.08 & 
1.348? \\
GSC 01843-00400 & 04 51 56.52 & 28 49 26.2 &   K2 & 2 & 0.12 & 14.08--14.20 &      
- \\
GSC 01288-00790 & 04 52 57.07 & 19 19 50.1 &   K5 & 6 & 0.09 & 12.05--12.29 &      
- \\
GSC 02391-00494 & 04 53 08.69 & 33 12 01.6 &   G8 & 2 & 0.14 & 13.69--13.88 &      
- \\
  HD 31281      & 04 55 09.62 & 18 26 31.1 &   G1 & 4 & 0.07 & 9.16--9.27   &      
- \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSfig{12.7cm}{5752-f1.eps}{Light curves of new regular PMS stars with a few
monitorings}
 \IBVSfigKey{5752-f1.eps}{}{light curve}

\IBVSfig{8cm}{5752-f2.eps}{Light curves of new regular PMS stars without any
monitorings}
 \IBVSfigKey{5752-f2.eps}{}{light curve}

Previously to our study the rotational periods for 24 PMS stars from the
Wichmann's list were known (Bouvier et al., 1997; Broeg et al., 2006). Now the
sample of the PMS stars with known periods in this star-forming region has
increased almost twice. We hope that this result will allow to study the
evolution of an angular moment of young stars in the Tau-Aur region more
carefully.

\newpage

\references

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Bouvier, J., Wichmann, R., Grankin, K., Allainet, S., Covino, E., Fernandez, M.,
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Dworetsky, M.M., 1983, {\it MNRAS}, {\bf 203}, 917

Grankin, K.N., 1997, {\it IAU Symposium}, {\bf 182}, \nobibcode 281 \ADSBIBCODE{1997IAUS..182P.281G}

Grankin, K.N., 2005, {\it LPI Contributions}, No.\ 1286

Tanner, R.W., 1948, {\it JRASC}, {\bf 42}, 177

Wichmann, R., Torres, G., Melo, C.H.F., Frink, S., Allain, S.,
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\endreferences

\end{document}
