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\input ibvs2.sty

\begin{document}
\IBVShead{5556}{6 August 2004}

\IBVStitle{UBVRI Observations of V350 C\lowercase{ep} in the Period 2002-2004}

\IBVSauth{SEMKOV, E.H.}

\IBVSinsto{Institute of Astronomy, Bulgarian Academy of Sciences,
72, Tsarigradsko Shose blvd., BG-1784 Sofia, Bulgaria, e-mail: evgeni@skyarchive.org}


\SIMBADobj{V350 Cep}
\IBVStyp{  TTau  }
\IBVSkey{photometry}
\IBVSabs{Results from UBVRI photometric observations of the pre-main sequence }
\IBVSabs{star V350 Cep are present.}
\IBVSabs{The historical light curve of V350 Cep resembles the FUOR type stars}
\IBVSabs{but its spectrum is similar to the Classical T Tauri stars.}
\IBVSabs{Our observations suggest that during the period 2002-2004 V350 Cep}
\IBVSabs{be still near to the maximum value.}

\begintext

The pre-main sequence (PMS) star V350 Cep lies in the region of
active star formation NGC 7129. The historical light curve of V350
Cep resembles the FU Orionis (FUOR) type stars (Semkov et al. 1999) but its
spectrum is similar to the Classical T Tauri stars (Magakian et al. 1999).
Since 1970 a gradual increasing of star brightness has begun and the $R$ magnitude
of V350 Cep increased with $\sim$$5^{\rm m}$ until 1977.
Since 1977 the stellar brightness varies around the maximal value with an amplitude
of about $1\fmm5 $ ($B$).


The present data are a continuation of our
investigation of V350 Cep (Semkov 1993; Semkov 1996; Semkov et al. 1999; Semkov 2002).
Our photometric data were performed in two observatories with three telescopes:
the 2-m Ritchey-Cretien-Coude and 50/70/172~cm Schmidt telescopes of
the National Astronomical Observatory Rozhen (Bulgaria) and
the 1.3-m Ritchey-Cretien telescope of the Skinakas Observatory\footnote{Skinakas
Observatory is a collaborative project of the University of Crete,
the Foundation for Research and Technology - Hellas, and
the Max-Planck-Institut f\"{u}r extraterrestrische Physik.}
of the Institute of Astronomy, University of Crete (Greece).
All frames ware taken through a standard Johnson-Cousins set of filters.
The technical parameters for the CCD cameras used, observational procedure
and data reduction process are described in Semkov (2002).
As a reference the $\it UBVRI$ comparison sequence reported in Semkov (2002) was used.
The results of our photometric observations of V350 Cep are summarized in Table 1.
The table contains the date of observation, the Julian Date, the $V$ magnitude,
$U-B$, $B-V$, $V-R$ and $V-I$ indices and the used telescope.

Herbst et al. (1994) defined three basic types of brightness variation concerning PMS stars.
Type I of variability is typical for Weak line T Tauri Stars (WTTSs).
The variability is due to rotation of large cool surface spots.
Periods of variability on time scales of days and amplitudes up to $0\fmm8 $ in $\it V$
are observed in WTTSs.
Type II of variability occurs predominantly on Classical T Tauri Stars (CTTS) and it is
caused by superposition of cool and hot surface spots.
Non-periodic variations with amplitudes up to $3^{\rm m}$ in $\it V$ are often observed on CTTSs.
Type III is a more complicated variability observed on Herbig Ae/Be stars (HAEBESs)
and some early F-G type CTTSs.
The brightness variations are supposed to be produced by obscuration from circumstellar dust.
The variability is either irregular or periodic on time scales of days or weeks and
the observed amplitudes exceed up to $2\fmm8 $ in extreme cases.



\newpage
\begin{table}[!ht]
\centerline{Table 1. Photometric observations of V350 Cep in the period
February 2002 - May 2004}
\small
\vskip 3mm
\begin{center}
\begin{tabular}{cccccccc}
\hline
\noalign{\smallskip}
Date       & J.D.(24...) & $V $  & $U-B$ & $B-V$ & $V-R_C$ & $V-I_C$ & Tel. \\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
~~5.02.2002 &  52311.226 & 16.08  &   $-$  & 0.97  & 0.84  & 2.04  & Scm\\
~~6.02.2002 &  52312.219 & 16.22  &   $-$  &  $-$    & 0.92  & 2.12  & Scm\\
~~7.02.2002 &  52313.213 & 16.09  &   $-$  & 1.18  & 0.82  & 2.04  & Scm\\
~~8.06.2002 &  52433.502 & 16.344 &   $-$  & 1.054 & 1.012 & 2.160 & 1.3m\\
24.06.2002 &   52449.552 & 16.168 &   $-$  & 1.014 &  $-$    & 2.060 & 1.3m\\
~~2.07.2002 &  52457.533 & 16.105 & $-$0.31& 1.040 & 0.914 &  $-$    & 1.3m\\
~~3.07.2002 &  52458.546 & 16.193 &   $-$  & 1.015 & 0.962 & 2.076 & 1.3m\\
15.07.2002 &   52471.496 & 16.093 &   $-$  & 1.103 &  $-$    & 2.016 & 1.3m\\
22.08.2002 &   52508.543 & 16.199 &   $-$  & 1.071 & 0.953 & 2.055 & 1.3m\\
23.08.2002 &   52509.557 & 16.321 &   $-$  & 1.037 &  $-$    & 2.137 & 1.3m\\
24.08.2002 &   52510.549 & 16.374 &   $-$  &  $-$    &  $-$    & 2.150 & 1.3m\\
25.08.2002 &   52511.562 & 16.315 & $-$0.15& 0.978 & 0.985 & 2.134 & 1.3m\\
~~3.10.2002 &  52551.424 & 16.25  &   $-$  & 1.19  & 1.07  & 2.14  & Scm\\
~~4.10.2002 &  52552.435 & 16.25  &   $-$  & 1.20  & 0.92  & 2.14  & Scm\\
~~5.10.2002 &  52553.448 & 16.16  &   $-$  &  $-$    & 0.86  & 2.07  & Scm\\
29.10.2002 &   52577.376 & 16.14  &   $-$  & 1.05  & 0.91  & 2.06  & Scm\\
30.10.2002 &   52578.327 & 16.05  & $-$0.36& 1.00  & 0.89  & 1.98  & Scm\\
31.10.2002 &   52579.214 & 16.07  & $-$0.38& 1.04  & 0.94  & 2.02  & Scm\\
~1.11.2002 &   52580.230 & 16.10  &   $-$  & 1.04  & 0.89  & 2.05  & Scm\\
26.11.2002 &   52605.196 & 16.19  &   $-$  &  $-$    & 0.81  & 2.06  & Scm\\
28.11.2002 &   52607.258 & 16.46  & $-$0.45& 1.10  & 1.01  & 2.27  & Scm\\
29.11.2002 &   52608.220 & 16.38  &   $-$  & 1.23  & 0.97  & 2.22  & Scm\\
28.02.2003 &   52698.592 & 16.391 & $-$0.29& 1.047 & 1.069 & 2.101 & 2m\\
~~2.03.2003 &  52700.581 & 16.398 & $-$0.42& 1.072 & 1.069 & 2.084 & 2m\\
~~3.03.2003 &  52701.568 & 16.247 & $-$0.27& 1.060 & 1.018 & 1.982 & 2m\\
~~3.04.2003 &  52732.587 & 16.32  &   $-$  & 1.04  & 0.97  & 2.17  & Scm\\
~~1.05.2003 &  52761.461 & 16.29  &   $-$  &  $-$    & 0.97  & 2.15  & Scm\\
~~2.05.2003 &  52762.440 & 16.24  &   $-$  & 1.01  & 0.90  & 2.14  & Scm\\
~~5.05.2003 &  52765.448 & 16.21  &   $-$  & 0.93  & 0.96  & 2.11  & Scm\\
11.06.2003 &   52801.544 & 16.273 &   $-$  &  $-$    &  $-$    & 2.136 & 1.3m\\
12.06.2003 &   52802.565 & 16.301 & $-$0.34& 1.039 &  $-$    & 2.136 & 1.3m\\
15.06.2003 &   52805.578 & 16.224 &   $-$  &  $-$    &  $-$    & 2.110 & 1.3m\\
16.06.2003 &   52806.570 & 16.108 &   $-$  & 1.006 &  $-$    & 2.057 & 1.3m\\
17.06.2003 &   52807.570 & 16.088 &   $-$  & 1.022 &  $-$    & 2.014 & 1.3m\\
18.06.2003 &   52808.569 & 16.221 &   $-$  & 1.043 &  $-$    & 2.028 & 1.3m\\
19.06.2003 &   52809.566 & 16.269 & $-$0.24& 1.069 &  $-$    & 2.080 & 1.3m\\
21.06.2003 &   52812.465 & 16.127 &   $-$  &  $-$    &  $-$    & 2.048 & 1.3m\\
23.06.2003 &   52813.573 & 16.173 &   $-$  &  $-$    &  $-$    & 2.077 & 1.3m\\
24.06.2003 &   52814.553 & 16.235 &   $-$  &  $-$    & 0.990 & 2.125 & 1.3m\\
25.06.2003 &   52815.563 & 16.326 &   $-$  &  $-$    & 0.993 & 2.171 & 1.3m\\
26.06.2003 &   52816.576 & 16.241 &   $-$  &  $-$    &  $-$    & 2.123 & 1.3m\\
27.06.2003 &   52817.561 & 16.111 &   $-$  &  $-$    &  $-$    &  $-$    & 1.3m\\
10.07.2003 &   52831.386 & 16.149 &   $-$  & 1.071 &  $-$    & 2.075 & 1.3m\\
12.07.2003 &   52832.565 & 16.134 &   $-$  & 1.040 &  $-$    & 2.057 & 1.3m\\
12.07.2003 &   52833.408 & 16.129 &   $-$  & 1.025 &  $-$    & 2.054 & 1.3m\\
13.07.2003 &   52834.424 & 16.044 &   $-$  & 1.031 &  $-$    & 2.026 & 1.3m\\
25.07.2003 &   52845.547 & 16.151 &   $-$  & 1.030 &  $-$    & 2.088 & 1.3m\\
26.07.2003 &   52846.581 & 16.065 &   $-$  & 1.021 &  $-$    & 2.070 & 1.3m\\
30.07.2003 &   52850.575 & 15.889 &   $-$  & 1.001 & 0.887 & 1.926 & 1.3m\\
~~9.08.2003 &  52860.539 & 15.990 &   $-$  &  $-$    &  $-$    & 1.981 & 1.3m\\
~~9.08.2003 &  52861.355 & 16.148 &   $-$  & 1.048 &  $-$    & 2.090 & 1.3m\\
10.08.2003 &   52862.416 & 16.179 &   $-$  & 1.076 &  $-$    & 2.101 & 1.3m\\
27.09.2003 &   52910.283 & 16.21  &   $-$  & 1.01  & 0.93  & 2.18  & Scm\\
28.09.2003 &   52911.263 & 16.38  &   $-$  &  $-$    &  $-$    & 2.24  & Scm\\
29.09.2003 &   52912.249 & 16.28  &   $-$  & 1.16  & 0.93  & 2.19  & Scm\\
~~1.10.2003 &  52914.480 & 16.27  &   $-$  & 1.12  & 1.00  & 2.22  & Scm\\
~~2.10.2003 &  52915.321 & 16.28  &   $-$  & 1.03  & 0.99  & 2.24  & Scm\\
~~3.10.2003 &  52916.285 & 16.16  & $-$0.25& 1.04  & 0.97  & 2.16  & Scm\\
\noalign{\smallskip}
\hline
\end{tabular}
\end{center}
\end{table}


\clearpage
\begin{table}[!ht]
\centerline{Table 1. (continuation)}
\vskip 3mm
\small
\begin{center}
\begin{tabular}{cccccccc}
\hline
\noalign{\smallskip}
Date       & J.D.(24...) & $V $  & $U-B$ & $B-V$ & $V-R_C$ & $V-I_C$ & Tel. \\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
24.10.2003 &   52968.410 & 15.88  &   $-$  &  $-$    &  $-$    & 1.96  & 2m\\
25.11.2003 &   52969.241 & 15.94  &   $-$  & 0.95  & 0.91  & 2.01  & Scm\\
19.12.2003 &   52993.185 & 15.83  &   $-$  & 0.97  & 0.95  & 1.97  & Scm\\
10.02.2003 &   53046.210 & 15.70  &   $-$  &  $-$    & 0.84  & 1.88  & Scm\\
20.03.2003 &   53084.553 & 15.770 &   $-$  &  $-$    & 0.863 & 1.908 & 2m\\
21.03.2003 &   53085.578 & 15.963 &   $-$  &  $-$    & 0.923 & 2.046 & 2m\\
22.03.2003 &   53086.522 & 15.884 &   $-$  &  $-$    & 0.884 & 1.932 & 2m\\
13.05.2003 &   53138.513 & 15.97  &   $-$  & 0.99  & 0.90  & 2.03  & Scm\\
13.06.2004 &   53170.440 & 15.87  &   $-$  &  $-$    & 0.91  & 1.96  & Scm\\
15.07.2004 &   53201.407 & 15.89  &   $-$  &  $-$    & 0.85  & 1.98  & Scm\\
16.07.2004 &   53202.433 & 16.03  &   $-$  & 1.05  & 0.93  & 2.05  & Scm\\
\noalign{\smallskip}
\hline
\end{tabular}
\end{center}
\end{table}

The $V$-light curve of V350 Cep from all our CCD observations (Semkov 1996;
Semkov et al. 1999; Semkov 2002 and this paper) is shown in Fig. 1.
It is seen from the figure that for the ten years period of observations
the star shows a long-term brightness variations on a time-scale of about one thousand days.
Such long-term variability is also seen and from our photographic observations
made in the period 1985-1994 (Semkov 1993; Semkov 1996).
The long-term brightness variations are typical of HAEBE stars or related objects
called UXors (Herbst and Shevchenko, 1999).
The cause of variability of UXors can be obscuration from orbiting circumstellar matter
or variable accretion from a circumstellar disk.
In contrast to HAEBE stars and UXors V350 Cep is a low-mass star of M2 spectral type.
The observed amplitude in $V$-light in the period 1994-2004 is only 0\fmm8.

\IBVSfig{7cm}{5556-f1.eps}{V-light curve of V350 Cep in the period August 1994 - July 2004}
\IBVSfigKey{5556-f1.eps}{V350 Cep}{light curve}

Another important result from our photometric study is the variation of color indices
with stellar brightness.
The measured color indices $\it V-I$ and $\it B-V$ versus stellar magnitude $V$ during the period
of our CCD observations are plotted in Fig. 2 and Fig. 3 respectively.
A clear dependence can be seen from the figures: the star becomes redder as it fades.
Such color variations are typical of stars with large cool spots whose variability
is produced by rotation of the spotted surface (WTTs).
Consequently, V350~Cep shows photometric characteristics of FUORs (5 magnitudes outburst),
UXors (long-term brightness variations) and WTTs
(variability with small amplitude in time scale of days).
On the other hand, the observed spectra of V350 Cep can be classified as a
CTTs spectrum (Magakian et al. 1999).
As is seen from Table 1 V350 Cep shows a very strong ultraviolet excess a characteristic
also typical of CTTs.
These discrepancies make V350~Cep a unique object very difficult for exact classification.

The author thanks the Director of Skinakas Observatory Prof. I. Papamastorakis
and Dr. I. Papadakis for the telescope time.

\IBVSfig{5cm}{5556-f2.eps}{Relationship between V magnitude and V-I color index in the period of observations}
\IBVSfigKey{5556-f2.eps}{V350 Cep}{}

\IBVSfig{5cm}{5556-f3.eps}{Relationship between V magnitude and B-V color index in the period of observations}
\IBVSfigKey{5556-f3.eps}{V350 Cep}{}

\references

Herbst, W., Shevchenko, V.S., 1999, {\it AJ}, {\bf 118}, 1043

Herbst, W., Herbst, D. K., Grossman, E. J., Weinstein, D. 1994, {\it AJ}, {\bf 108}, 1906

Magakian, T.Y., Movsesian, T.A., Hovhannesian, E.R., 1999, {\it Astrofizika},
{\bf 42}, 121 \BIBCODE{1999Ap.....42..121M}

Semkov, E.H., 1993, {\it IBVS}, No. 3825

Semkov, E.H., 1996, {\it IBVS}, No. 4339

Semkov, E.H., Mutafov, A.S., Munari, U., Rejkuba, M., 1999,
{\it AN}, {\bf 320}, 57

Semkov, E.H., 2002, {\it IBVS}, No. 5214

\endreferences

\end{document}
