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\begin{document}
\IBVShead{5038}{7 March 2001}

\IBVStitletl{Times of Minimum of Eclipsing Binaries from ROTSE1 CCD}{ Data, II: Suspected and Recently Named Variables}

\IBVSauth{Diethelm, R.}
\IBVSinsto{BBSAG and Astron.\ Institut der Universit\"at Basel, Rennweg 1,
CH--4118 Rodersdorf, Switzerland\\
\indent e-mail: diethelm@astro.unibas.ch}

\IBVStyp{ E }
\IBVSkey{CCD photometry}

\begintext

In the first part of a series of papers (Diethelm, 2001), we have reported
the timings of minimum light of known eclipsing binaries extracted from
ROTSE-1 (Robotic Optical Transient Search Experiment 1) survey data, as reported
in Akerlof et al.\ (2000). The original measurements are publicly available
through the internet (http://www.umich.edu/ \~{}rotse).

In Table 1 of this second paper in the series, the derived timings are
presented for the suspected and recently named variables according to the New
Catalogue of Suspected Variable Stars (NSV)\@. In each case, the data have been
folded into a seasonal light curve using the ROTSE1 period value or the recently
published elements of variation (see remarks on individual stars below). The
time of minimum was then found with the help of the Kwee--Van Woerden
algorithm (Kwee and Van Woerden, 1956).

\begin{table}[h]
\caption{Times of minimum of eclipsing binaries}
\begin{center}
\begin{tabular}{lcll}
\hline
\lower8pt\hbox{Star} & Type & JD(hel,min) & est.\ error\\[-2pt]
  &  of min. & \multicolumn{2}{c}{(days)}\\
\hline
ROTSE1\,J124337.15+384415.1 = GSC\,3021.2642 & p &
2451305.7378 & 0.0007\\
 & s & 2451306.8821 & 0.0004\\
ROTSE1\,J125241.77+261637.4 = GSC\,1995.2249  & p & 2451277.8543
& 0.0014\\
 & s & 2451288.8720 & 0.0015\\
ROTSE1\,J131759.92+300801.0 = GSC\,2535.670
& s & 2451260.8492 & 0.0001\\
 & p & 2451275.7062 & 0.0004\\
ROTSE1\,J134651.80+225714.7 = GSC\,1999.518 & p & 2451260.7047 &
0.0007\\
 & s & 2451286.8695 & 0.0007\\
ROTSE1\,J181210.81+305512.9 = GSC\,2622.1151 & p &
2451259.8761 & 0.0017\\
ROTSE1\,J184241.47+452902.9 = GSC\,3527.1195 & s &
2451304.860 & 0.002\\
 & p & 2451312.864 & 0.002\\
\hline
\end{tabular}
\end{center}
\end{table}

{\bf Remarks on individual variables:}

ROTSE1\,J124337.15+384415.1 = NSV\,5904 = GSC\,3021.2642 = WR\,125:
Very recently, Vandenbroere et al.\ (2001) have reported a complete CCD
light curve of this EW type eclipsing binary. Our minima fit their
elements of variation well ($O-C = -0.0030$ and $-0.0028$ days).

ROTSE1\,J125241.77+261637.4 = NSV\,19516 = GSC\,1995.2249: This
eclipsing binary is of the EB type ($m_{\rm p} = 10.74$; $m_{\rm s} =
10.68$). The maximum following the primary minimum is slightly brighter
(10.53 mag) than the one following the secondary (10\fmm55).

ROTSE1\,J131759.92+300801.0 = NSV\,6177 = SVS\,1257 = GSC\,2535.670 =
LL Com: During the course of this work, we became aware of the fact,
that this EB type variable has already been investigated (Frank et al.,
1996) and given a official name (LL Com). The minima reported in Table
1 yield $O-C$ values of +0.0439 and +0.0386 days in respect to the
elements of variation given by Frank et al.\ (1996), indicating the
necessity of a slight correction to their period (new value: 0.4069125
days), in good agreement with the period reported by the ROTSE team. We
have also used the photographic data from the paper in which the
variability of SVS\,1257 was announced (Kurochkin, 1959) to deduce
times of minimum light. These turn out to be: JDH2434127.370(2),
JDH2435540.545(2) and JDH2435929.531(5), all of which are timing of
primary minima. Since we have no additional timings in the large time
gap between these measurements and our current data, no refinement of
the period value is possible.

ROTSE1\,J134651.80+225714.7 = GSC\,1999.518 = S\,8090: This variable is
of the EW type with deep minima (13\fmm1--13\fmm8) and a rather short
period (0\fday241168 days)

ROTSE1\,J181210.81+305512.9 = NSV\,10369 = GSC\,2622.1151 = S\,8606: A close
inspection of the ROTSE light curve made it plausible, that the value of the
period has to be doubled to 1.123874 days. Although no observations around
the phase of the secondary minimum are available, we are confident that this
interpretation is correct. We find this variable to be an Algol type eclipsing
binary with a primary minimum lasting for $D = 0\fper18 = 0\fday19$ with an
amplitude of 0\fmm65 (12.65--13.3).

ROTSE1\,J184241.47+452902.9 = NSV\,11259 = GSC\,3527.1195 = S\,9326: This is
another close binary of the EW type.

We would like to express our gratitude towards the ROTSE team for making
their data available to the general public. In addition, the cross-reference
table provided by B.~Skiff through M.~Baldwin of the AAVSO is thankfully
acknowledged. It proved to be very helpful for the identification of the ROTSE
sources.

\references

Akerlof, C., Amrose, S., Balsano, R., Bloch, J., Casperson, D., Fletcher,
S., Gisler, G., Hills, J., Kehoe, R., Lee, B., Marshall, S., McKay, T., Pawl,
A., Schaefer, J., Szymanski, J., Wren, J., 2000, {\it AJ}, {\bf 119}, 1901

Diethelm, R., 2001, {\it IBVS}, No.\ 5027

Frank, P., Moschner, J., Moschner, W., 1996, {\it IBVS}, No.\ 4386

Kurochkin, N.E., 1959, {\it Perem.\ Zv.}, {\bf 12}, 409

Kwee, K.K., Van Woerden, H., 1956, {\it Bull.\ Astron.\ Inst.\ Neth.}, {\bf
12}, 111

Vandenbroere, J., Martignoni, M., Verrot, J.P., Acerbi, F., 2001,
{\it IBVS}, No.\ 5021

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