[Message Prev][Message Next][Thread Prev][Thread Next][Message Index][Thread Index]
[vsnet-preprint 10] IBVS submission "1432-0033 : A New Eclipsing SU UMa-type Dwarf Nova"
Dear colleagues,
We have pleasure to herewith include a manuscript that has been submitted to the IBVS. It describes the June 2000 outburst of the cataclysmic variable 1432-0033, and our most important findings on this object.
Kind regards,
Tonny Vanmunster - CBA Belgium
Fred Velthuis - CBA Pakuranga, NZ
Jennie McCormick - CBA Pakuranga, NZ
\documentstyle[twoside,epsf]{article}
\input{ibvs2.sty}
\begin{document}
\IBVShead{XXXX}{XX August 2000}
\IBVStitle{1432-0033 : A NEW ECLIPSING SU UMa-TYPE DWARF NOVA }
\IBVSauth{Tonny Vanmunster$^1$, Fred Velthuis$^2$, Jennie McCormick$^2$}
\IBVSinst{Center for Backyard Astrophysics (Belgium),Walhostraat 1A, B-3401
Landen, Belgium, \\ \indent email: Tonny.Vanmunster@advalvas.be}
\IBVSinst{Center for Backyard Astrophysics (Pakuranga), Farm Cove Observatory,
2/24 Rapallo Place, \\ \indent Pakuranga, Auckland, NZ, email: fredvelt@ihug.co.nz}
\IBVSobj{1432-0033}
\IBVStyp{ cataclysmic }
\IBVSkey{Cataclysmic variables -- photometry}
\begintext
The object 1432-0033 was detected as a cataclysmic variable (CV) of unknown type
by C. Berg during the course of his QSO (Quasi Stellar Objects) spectroscopic
survey (Berg et al. 1992). He reported 1432-0033 at a quiescent magnitude of 18.5B, and
showing typical emission lines. He also was the first to point out the
resemblance to the dwarf novae HT Cas and U Gem. The J2000.0
co-ordinates for 1432-0033 are $\alpha$ = 14\hr 35\mm 00\fsec 14,
$\delta$ = -00\deg 46\arcm 07\farcs 0 (Downes et al. 1997), while astrometry by
Arne Henden (Henden 2000) yields a position of $\alpha$ = 14\hr 35\mm 00\fsec 24,
$\delta$ = -00\deg 46\arcm 05\farcs 8 (J2000.0).
\smallskip
\noindent
Here we report differential time-series photometry of 1432-0033 during the June
2000 outburst, by two observatories from the Center for Backyard Astrophysics. We
detected superhumps with a period of 0.078 ($\pm$ 0.002) d and also
found eclipses in 1432-0033, yielding an orbital period of 0.07273 ($\pm$ 0.00001)
d. Our observations firmly establish 1432-0033 as a genuine eclipsing
SU UMa-type dwarf nova.
\bigskip
\noindent
{\bf Outburst history}
\bigskip
The first detected outburst of 1432-033 was observed visually by
Rod Stubbings (Stubbings 1999a) on 2000, May 10.446 UT with a reported magnitude
of mv = 15.0. The outburst, presumably a superoutburst, lasted at least 10 days
(Stubbings 1999b).
\smallskip
\noindent
A next outburst was reported by Patrick Schmeer (Schmeer 2000), who found the
object around mag 14.5 on unfiltered CCD images taken with the Iowa Robotic
Observatory (IRO 2000) telescope on 2000, April 06.378 UT. While 1432-0033 was
still faint on an image taken on April 04.378 UT, it was clearly rising on
April 05.376 UT. This outburst was probably a normal, faint outburst, as indicated
by visual observations (Pearce 2000).
\smallskip
\noindent
1432-0033 was again reported in outburst at a visual magnitude of mv = 14.9, on
2000, June 24.419 UT (Stubbings 2000). For the first time, this outburst was
monitored intensively by CCD photometry, the results of which are discussed below.
\smallskip
\noindent
The shortest likely interval between outbursts of 1432-0033 is about 79 days.
The maximum superoutburst cycle, derived from the above observations, is about
411 days, although there is a high likelihood that the true supercycle value will
be smaller. More intensive monitoring of 1432-0033 will be required to further
refine this value. The outburst amplitude is about 4 magnitudes.
\bigskip
\noindent
{\bf CCD photometry during the June 2000 outburst}
\bigskip
\noindent
Upon notification of the outburst of 1432-0033, a small observing campaign was
launched by the Center for Backyard Astrophysics (CBA). The CBA is a multi-
longitude network of professional and amateur astronomers (Patterson 1998), who
study periodic phenomena in cataclysmic variables. Target campaigns and results
of the CBA are regularly reviewed on the CBA Web site
(http://vsnet.astro.bio2.edu/cba).
\smallskip
\noindent
The CBA campaign on 1432-0033 accumulated 11.3 hours of coverage over 4 nights
and 844 datapoints. Details are listed in table 1.
\smallskip
\begin{table}
\begin{center}
\begin{tabular}{ccccc}
\hline
UT Date & JD Start$^1$ & Length (hr) & Telescope$^2$ & Points \\
\hline
26-Jun-2000 & 1722.4075 & 2.33 & 1 & 74 \\
28-Jun-2000 & 1724.4007 & 2.09 & 1 & 47 \\
29-Jun-2000 & 1724.9994 & 0.95 & 2 & 111 \\
30-Jun-2000 & 1725.7665 & 5.89 & 2 & 612 \\
\hline \\
\multicolumn{5}{l}{$^1$ 2,450,000+ } \\
\multicolumn{5}{l}{$^2$ (1)=CBA Belgium, 0.35-m; (2)=CBA Pakuranga, 0.25-m } \\
\\
\end{tabular}
\end{center}
\caption{Log of photometry }
\end{table}
\medskip
\noindent
Time-resolved and differential (variable - comparison) CCD photometry of 1432-
0033 was started at CBA Belgium on June 26, 2000, using a 0.35-m f/6.3
Schmidt-Cassegrain telescope, mounted on an AstroTechniek FM-98 German
equatorial mount, and equipped with a SBIG ST-7 CCD camera (Kodak KAF-0400 CCD
for imaging and Texas Instruments TC211 CCD for guiding). For a complete
description of the CBA Belgium Observatory equipment and software, see (Vanmunster
et al. 2000a). We used GSC 4984 691 (mag 12.7) as the comparison star, whose
constancy was confirmed by other check
stars. Camera control, telescope guiding and photometric imaging were all done
using {\it MaxIm DL/CCD} (Cyanogen Productions Inc.). Images were stored as FITS
files and were corrected for standard debiasing and flat fielding. Data
reduction was completed using the profile fitting algorithm (PSF) of {\it MIPS}
(Buil et al. 1993), immediately following image acquisition, allowing incoming
observations of 1432-0033 to be monitored in a quasi-real-time mode. This
approach revealed the 喪eal-timedevelopment of superhumps in the system and
allowed the immediate classification of the object as a new SU UMa-type
cataclysmic variable (Vanmunster 2000b).
\IBVSfig{8.0cm}{s1432-f1.eps}{Period analysis of 1432-0033.}
\IBVSfig{8.0cm}{s1432-f2.eps}{Eclipses in the light curve of 1432-0033.}
\smallskip
\noindent
Further observations at CBA Belgium and CBA Pakuranga were obtained over the
next nights (table 1), allowing a more detailed analysis of the superhump
period. After removing linear trends in the light curve, we performed a period
analysis using the Phase Dispersion Minimization PDM method (Stellingwerf 1978).
The resulting theta diagram is shown in Figure 1. The best superhump period is
0.078 ($\pm$ 0.002) d. Given the rather limited amount of observations and the
baseline of 5 nights only, we could not derive a more accurate superhump period
value. The superhump full amplitude was about 0.2 magnitudes.
\smallskip
\noindent
Next to the detection of superhumps, we also found eclipses in 1432-0033, as
shown in Figure 2, that depicts CBA Pakuranga observations between JD 2451725.77
and JD 2451726.01. Observations at this observatory were made with a 0.25-m f/10
Schmidt-Cassegrain telescope and SBIG ST-6 CCD camera. There are only a very
limited number of SU UMa-type cataclysmic
variables exhibiting eclipses. Yet, they provide the unique opportunity to
reconstruct the brightness distribution of the accretion disk from the observed
light curve, and to study the evolution of the accretion disk structure over
time. Eclipses in 1432-0033 had a more or less symmetric profile and an average
duration of 23 minutes. The eclipses showed an average depth of 0.6 - 0.7
magnitudes.
\bigskip
\noindent
Over the course of the outburst, we were able to make 6 useful mid-eclipse
timings of 1432-0033. From these, we derived an orbital period of 0.07273 ($\pm$
0.00001) d. We also derived a heliocentric mid-eclipse ephemeris :
$$ \begin{array}{r@{}r@{}l}
{\rm T = } $\space$ 2451725.03349 & {} $\space$ + $\space$ 0.072727 & {} \times E \\
$\space$ \pm 0.00053 & $\space$ $\space$ \pm 0.000013 \\
\end{array} $$
where E is a cycle number, and T is a HJD (Heliocentric Julian Date) value.
\bigskip
\noindent
The superhump excess value {\it $\epsilon$ = (Psh - Porb) / Porb }
where {\it Psh} and {\it Porb} denote the superhump and orbital period
respectively, is 7.8 percent. Knowing that typical $\epsilon$ values are around
2 to 3 percent, the high $\epsilon$ value for 1432-0033 is likely to be
explained by the uncertainty of the {\it Psh} value.
\bigskip
\noindent
A next superoutburst of 1432-0033, hopefully during a better visibility season,
will not only allow a more accurate determination of the superhump period (and
hence the $\epsilon$), but will definitely provide a great opportunity to study
the eclipses and accretion disk structure in full detail.
\bigskip
{\bf Acknowledgements.} We are grateful to the Center for Backyard Astrophysics
for their continuous support in our stellar CCD photometry research work.
\medskip
\begin{references}
Berg, C., et al., 1992, {\it Astrophys. J. Sup.}, {\bf 78}, 409
Buil, C., Klotz, A. et al., 1993, {\it Manual for the Microcomputer Image Processing System}, V2.0
Downes, R., Webbink, R., Shara, M., 1997, {\it PASP}, {\bf 109}, 345
IRO, 2000, {\it http://denali.physics.uiowa.edu/IRO/index.shtml}
Henden, A., 2000, {\it vsnet-alert 5030}
Patterson, J., 1998, {\it Sky and Telescope}, {\bf October 1998}, 77
Pearce, A., 2000, {\it vsnet-alert 5034}
Schmeer, P., 2000, {\it vsnet-alert 4571}
Stellingwerf R.F. 1978, {\it ApJ}, {\bf 224}, 953
Stubbings, R., 1999a, vsnet-alert 2965
Stubbings, R., 1999b, vsnet-obs 20713
Stubbings, R., 2000, vsnet-alert 5030
Vanmunster, T., et al., 2000a, {\it IBVS 4940}
Vanmunster, T., 2000b, {\it vsnet-alert 5037}
\end{references}
\end{document}
vsnet-adm@kusastro.kyoto-u.ac.jp
Return to Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
VSNET Home Page