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\IBVShead{5654}{19 October 2005}

\IBVStitle{GSC\,02050-00745: A New RR Lyrae Star with Blazhko Effect}

\IBVSauth{Antipin, S. V.$^{1,2}$; Sokolovsky, K. V.$^1$; Lebedev, A. A.$^1$}

\IBVSinst{Sternberg Astronomical Institute, 13, University Ave.,
Moscow 119992, Russia; e-mail: antipin@sai.msu.ru}
\IBVSinst{Institute of Astronomy, Russian Academy of Sciences,
48, Pyatnitskaya Str., Moscow 119017, Russia}


\SIMBADobj{GSC 02050-00745}
\SIMBADobj{USNO-B1.0 1175-0308984}

\IBVStyp{  RRAB  }

\IBVSkey{stars: RR Lyrae, Blazhko effect }

\IBVSabs{Our CCD observations show that the newly discovered RR Lyrae star }
\IBVSabs{GSC 02050-00745 definitely shows Blazhko-effect. }
\IBVSabs{The Blazhko period remains unknown.}
\IBVSabs{One more variable star was discovered on the same CCD images.}


\begintext

The variability of GSC\,02050-00745 ($\alpha$ =
16\hr18\mm34\fsec35, $\delta$ = +27\deg28\arcm13\farcs3 (J2000.0))
was discovered and initially investigated on the plates of Moscow
collection taken with the \mbox{40-cm} astrograph in Crimea. The phased
light curve based on the photographic observations (206
estimates, JD2441829--49930) is given in Fig.\,1. The curve's
shape and period permit us to consider the new variable as an RR
Lyrae type star with some peculiarity. The scatter on this phased
curve is fairly large both in maximum (close to phase 0.0) and in
minimum, suggesting some modulation, such as multimodality or
Blazhko effect. To study the effect in more detail, we undertook
additional CCD observations.

Our CCD photometry was carried out using a Pictor 416XTE camera at
the 50-cm reflector of the Crimean Laboratory (Sternberg
Astronomical Institute). The observations in the Johnson $V$ band
continued for two years. 778 brightness measurements were obtained
on 10 nights in 2004 (July 5--28, JD2453192--215), and additional 467 
on 10 nights in 2005 (June 30 -- July 20, JD2453552--572). The
images were dark subtracted, flat-fielded and analyzed with the
aperture photometry package developed by V.P. Goranskij. The
comparison and check stars are marked in Fig.\,2. The
accuracy of our photometry is 0\fmm02.

The phased light curves for two sets of CCD observations are
shown in Fig.\,3. The light elements are the following:
$$
{\rm Max = HJD}2453558.37 + 0\fday508646 \times{\rm E}. \\
$$
Significant changes of the light curve shape and the amplitude of the
variability (from 0\fmm93 in 2004 to 1\fmm34 in 2005) are clearly
seen. The maximum brightness also shows night-to-night
changes which is evident in both sets of observations
(Fig.\,4). This behaviour is most resembling to RR Lyrae
stars with Blazhko effect. To prove the periodic
nature of the effect and to determine the period of the modulation
further observations are needed. 
The only statement we can make now is
that the Blazhko period is fairly long, considerably longer than
the intervals of the observations in each of the two seasons. Note
that the two sets of observations were not specially
planned for maximum and minimum amplitude light variation, 
thus the total effect may be even more significant.

\newpage

Finally, all our CCD observations were analyzed with the package
{\it VAST} 
developed by Sokolovsky \& Lebedev (2005) which aims to detect
new variable stars on series of CCD images. This investigation
resulted in the discovery of a new eclipsing variable USNO-B1.0
1175-0308984 ($\alpha$~=~16\hr18\mm26\fsec91, $\delta$ =
+27\deg33\arcm15\farcs7 (J2000.0), marked in Fig.\,2 as EW). The
star is an EW variable with the following light elements:
$$
{\rm Min I = HJD}2453214.387 + 0\fday336486 \times {\rm E}. \\
$$
The corresponding phased light curve is given in Fig.\,5.


\IBVSfig{7.5cm}{5654-f1.eps}{GSC 02050-00745. The photographic phased
light curve.}
\IBVSfigKey{5654-f1.eps}{GSC 02050-00745}{phased light curve}

\IBVSfig{7cm}{5654-f2.eps}{A V-band image (12\arcm x 8\arcm)
of the field around GSC 02050-00745 (RRAB). The comparison
(comp), the check (check) stars and the newly discovered eclipsing
variable (EW) are marked.}
\IBVSfigKey{5654-f2.eps}{GSC 02050-00745 ; USNO-B1.0 1175-0308984}{finding chart}

\IBVSfig{11cm}{5654-f3.eps}{GSC 02050-00745. The phased light curves
based on CCD observations. Two bottom panels show separate light
curves for the seasons of 2004 and 2005. The changes of the light
curve shape and of the amplitude of variability are clearly seen.}
\IBVSfigKey{5654-f3.eps}{GSC 02050-00745}{phased light curve}

\IBVSfig{6.5cm}{5654-f4.eps}{GSC 02050-00745. Night-to-night variations
in the height of maxima for the two seasons of observations.}
\IBVSfigKey{5654-f4.eps}{GSC 02050-00745}{phased light curve}

\IBVSfig{7.5cm}{5654-f5.eps}{USNO-B1.0 1175-0308984. The phased light
curve of the newly discovered eclipsing variable.}
\IBVSfigKey{5654-f5.eps}{USNO-B1.0 1175-0308984}{phased light curve}


{\bf Acknowledgements:} Two of the authors (S. Antipin and K.
Sokolovsky) are grateful to the Russian Foundation of Basic
Research (grant No. 05-02-16688) for partial support of this
study.


\reference

Sokolovsky, K., Lebedev, A., 2005, in {\it 12th Young Scientists'
Conference on Astronomy and Space Physics}, Kyiv, Ukraine, April
19--23, 2005, eds.: Simon, A.; Golovin, A., p.79
(VAST: {\tt http://saistud.sai.msu.ru/poisk})

\endreferences

\IBVSedata{5654-t1.txt}
\IBVSecomment{Data file for GSC 02050-00745}
\IBVSdataKey{5654-t1.txt}{GSC 02050-00745}{photometry}

\IBVSedata{5654-t2.txt}
\IBVSecomment{Data file for USNO-B1.0 1175-0308984}
\IBVSdataKey{5654-t2.txt}{USNO-B1.0 1175-0308984}{photometry}


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