[vsnet-alert 10417] 1RXS J180834.7+101041: eclipsing SU UMa or IP?

[Taichi Kato]

   The object is unlikely a polar, but more likely an eclipsing dwarf nova
below the period gap.  However, the presence of He II emission is rather
unusual for a dwarf nova.  The object may be a magnetic system similar
to EX Hya (also with shallow eclipses) and DW Cnc.  A quasi-periodic
feature outside eclipses (see the light curve) may be a signature from
spin modulations.

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The Astronomer's Telegram                   http://www.astronomerstelegram.org 
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Posted: Thu Aug  7 01:30:00 EDT 2008 -- Fri Aug  8 01:30:01 EDT 2008
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ATEL #1648                                                           ATEL #1648

Title:          RTT150 classification of the new cataclysmic variable 1RXS
                J180834.7+101041
Author: I.F.Bikmaev, N.A.Sakhibullin (Kazan State University, Academy
Queries:        Ilfan.Bikmaev at ksu.ru
Posted: 7 Aug 2008;  13:26  UT
Subjects:       Optical, Binaries, Cataclysmic Variables

We have observed new cataclysmic variable 1RXS J180834.7+101041   (ATel
#1640) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,   TUBITAK
National Observatory, Turkey).   11 spectra with resolution of 14 A and
exposure time of 10 min each   have been obtained during the night July
31 / August 01, 2008, by   using TFOSC instrument (3800-8800 A).   The
light curve in SDSS r'- band was also obtained with time resolution of
25 sec by using ANDOR CCD during the night of August 01 / 02, 2008, 
and calibrated against SDSS standard stars.      Spectra show double peaked
emission Balmer lines, He I, and HeII (4686 A)    lines with peak separations
of 500-700 km/s.   It is clear indication on accretion disk.   Moreover,
the classic "S-wave" (due to bright spot presence) is   observed in the
relative intensities of the red and blue emission peaks.      Light curve
shows pronounced asymmetric eclipse (like in UX UMa   system) from r' =
16.1 to 17.0 mag. Brightness of the system    out of eclipse is varied
at the level of 0.2-0.4 mag, without periodic   variations at the time
scale shorter than orbital period indicated in   ATel #1640.        These
data allow us to classify this system as    SU UMa type cataclysmic variable.
The integrated spectrum and light curve are shown at      http://hea.iki.rssi.ru
/~denis/J1808+1010-Sp-Jul31.jpg
and   http://hea.iki.rssi.ru/~denis/J1808+1010-LC-Aug01.jpg       

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