\documentstyle[twoside,epsf]{article}

\input{ibvs2.sty}

\begin{document}

\IBVShead{5123}{18 June 2001}

\IBVStitle{Outburst Photometry of T\lowercase{mz}V34}

\IBVSauth{Kato, Taichi$^1$; Uemura, Makoto$^1$; Buczynski, Denis$^2$; Schmeer, Patrick$^3$}

\IBVSinst{Dept.\ of Astronomy, Kyoto University, Kyoto 606-8502, Japan,\\ \indent
e-mail: tkato@kusastro.kyoto-u.ac.jp, uemura@kusastro.kyoto-u.ac.jp}

\IBVSinst{Conder Brow Observatory, Littlefell Lane, Lancaster LA2 ORQ,
England,\\ \indent e-mail: denis@cb978iau.demon.co.uk}

\IBVSinst{Bischmisheim, Am Probstbaum 10, 66132 Saarbr\"{u}cken,
Germany, e-mail: extpasc@rz.uni-sb.de}

\SIMBADobj{Tmz V34}
\IBVStyp{ UGSS }
\IBVSkey{dwarf nova, photometry}

\begintext

TmzV34 is a variable star discovered by Takamizawa (1998).  The J2000.0
coordinates are 09\hr15\mm51\fsec69, +09\deg00\arcm49\farcs9.  Although
Takamizawa's initial observations suggested rather irregular
variations, a noticeable brightening to 13\fmm1 was recored on films
taken on 1994 November 30.  The star was also likely identified with
the ROSAT source 1RXS J091552.3+090056 = RX J0915.8+0900, which led to
a possible classification as a cataclysmic variable.  The ROSAT source
was independently identified with the same star through the
Hamburg/RASS Optical Identifications (Bade et al.\ 1998).  The star was
also recorded bright ($V = 12.99$) in GSC, which made the dwarf
nova-type variability likely.  Since then, the star has been monitored
as a part of VSNET Collaboration
(http://www.kusastro.kyoto-u.ac.jp/vsnet/).  The first outburst since
the discovery was detected by T. Watanabe (Watanabe and Kato 1999) at
visual magnitude 13.6 on 1999 April 8, which made the secure
identification of the variable as a dwarf nova.  This outburst,
however, was not fully followed because of unfavorable observing
condition.

The next outburst detection was made by one of the authors (P.
Schmeer), who observed the object using the Iowa Robotic Observatory
(IRO) 0.5-m telescope and an AP-8 CCD, and found it slowly brightening
from unfiltered CCD magnitude of 15.4 on 2000 February 3.444 UT to 14.2
on February 8.319 UT (Schmeer 2000).  Upon this detection, we started
time-resolved CCD photometry.  The CCD observations at Kyoto University
were done using an unfiltered ST-7 camera attached to the Meade 25-cm
Schmidt-Cassegrain telescope.  The exposure time was 30 s. The images
were dark-subtracted, flat-fielded, and analyzed using the Java$^{\rm
TM}$-based aperture photometry package developed by one of the authors
(TK)\@.  The CCD observations at Conder Brow Observatory were done using
an SXL8 CCD attached to a 33-cm reflector.  The exposure time was 45
s.  The Kyoto and Conder Brow observations used different comparison
stars, GSC 819.542 (GSC magnitude 13.07) and GSC 819.281 (GSC magnitude
13.41), respectively, because of the different field-of-view of the
images.  We therefore treat these observations separately.
Barycentric corrections were applied to the observed times before the
following analysis.  Table 1 lists the log of observations, together
with nightly averaged magnitudes.  Table 2 lists the snapshot
observations by P. Schmeer.

\begin{table}
\begin{center}
\caption{Log of time-series observations of TmzV34}
\begin{tabular}{cccccl}
\hline
start$^a$ & end$^a$ & mean mag$^b$ & error$^c$ & $N^d$ & Observatory \\
\hline
51584.228 & 51584.296 & 0.234 & 0.014 &  82 & Kyoto \\
51585.195 & 51585.335 & 0.611 & 0.012 & 221 & Kyoto \\
51585.388 & 51585.517 & 0.320 & 0.006 & 168 & Conder Brow (CB)\\
\hline
\end{tabular}

{\normalsize
\begin{tabular}{l@{ }l}
$^a$ & BJD${}-{}$2400000\\
$^b$ & Magnitude relative to GSC 819.542 (Kyoto) or GSC 819.281 (CB)\\
$^c$ & Standard error of nightly average\\
$^d$ & Number of frames\\
\end{tabular}
}

\bigskip

\caption{Snapshot observations of TmzV34}
\begin{tabular}{cc}
\hline
BJD${}-{}$2400000 & unfiltered CCD mag \\
\hline
51577.949 & 15.4 \\
51578.797 & 15.2 \\
51579.824 & 15.1 \\
51581.938 & 14.4 \\
51582.824 & 14.2 \\
51584.811 & 14.0 \\
\hline
\end{tabular}
\end{center}
\end{table}

\IBVSfig{10cm}{5123-f1.ps}{Light curves of Kyoto Observations.  The relatively
large scatter was due to passing clouds}

\IBVSfig{8cm}{5123-f2.ps}{Light curves of Conder Brow Observations}

Figures 1 and 2 show the result of Kyoto and Conder Brow Observations,
respectively.  The Kyoto observations show only slow fading, and the
fading almost stopped in the Conder Brow Observations.  No apparent
superhumps were detected.  The Kyoto observations having been affected
by clouds, the Conder Brow observations (Figure 2) more adequately
represent the absence of regular superhump-type oscillations.  These
observations qualifies TmzV34 as an SS Cyg-type (UGSS in GCVS) dwarf
nova.  The slow rising at an almost constant rate of 0.22 mag\,d$^{-1}$
(as calculated from Table 2) also supports the SS Cyg-type
classification.  The low outburst amplitude and the slow rise make
TmzV34 as a good candidate for a dwarf nova with a long orbital
period.

\bigskip

The authors are grateful to VSNET members for providing visual observations
covering years.  P. Schmeer's observations were made with the Iowa
Robotic Observatory, and he wishes to thank Robert Mutel and his students.
Part of this work is supported by a Research Fellowship of the
Japan Society for the Promotion of Science for Young Scientists (MU).

\references

Bade, N., Engels, D., Voges, W., Beckmann, V., Boller, Th., Cordis, L.,
Dahlem, M., Englhauser, J., Molthagen, K., Nass, P., Studt, J.,
Reimers, D., 1998, {\it A\&AS}, {\bf 127}, 145

Schmeer, P., 2000, {\it VSNET alert circulation}, No.\ 4160 (available from\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert4000/msg00160.html)

Takamizawa, K., 1998, {\it VSNET observations}, No.\ 10504 (available from\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/obs10000/msg00504.html)

Watanabe, T., Kato, T., 1999, {\it VSNET alert circulation}, No.\ 2854 (available from\\
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/alert2000/msg00854.html)

\end{document}
