CBA
Observations of Var79 Peg (Oct 2004)
Var79 Peg = 1RXS J215434.4+355023 was
discovered by S. Antipin (2004, IBVS 5573) on plates
of the Moscow collection. The object is located at
R.A.= 21h54m33s.66, DEC.= +35°50'17".4 (J2000.0).
The light curve, published by Antipin, shows two
kinds of outbursts : short-lasting ones and longer
ones. The long-lasting outbursts with flat maxima,
resemble superoutbursts of SU UMa-type dwarf novae.
The amplitude of variability strongly changed during
the interval of observations: before 1980, Var79
Peg's photographic magnitudes changed between 14m.0-<18m.1,
ander after 1982 this became 14m.35-17m.0.
The only exception was 1987, when the star was
fainter than 17m.1 on Moscow plates and
appeared at b=18m.26, as measured in the
GSC 2.2 catalog, on a POSS II blue plate.
Observations on October 29/30,
2004
Var79 Peg was
announced in outburst on 2004, Oct 29.806 UT (visual
detection by Chris Jones, UK) at mag 14.4. Half an
hour later, the outburst was confirmed by myself, on
an unfiltered CCD image. Immediately following the
confirmation, I started an unfiltered time-series
photometry session on Var79 Peg (2004, Oct 29/30),
at CBA Belgium Observatory, using one of the 0.35-m
f/6.3 telescopes, and an SBIG ST-7XME CCD
camera.
The session lasted
for 3.4 hours, resulting in 184 observations, under
moderate sky conditions (cloud fields, strong
moonlight). Ensemble photometry using MIRA AP and
Maxim DL revealed small amplitude modulations
(around 0.1 - 0.15 mag), and a
linear trend of decline (about 0.1 mag over 0.14
d).
Later that night, Lou
Krajci, observing from CBA New Mexico, also started
an unfiltered observing session on Var79 Peg. He
collected a total of 229 observations, showing a
very similar light curve pattern.
Var79 Peg light curve on
Oct 29/30, 2004, composed of CBA Belgium (red dots)
and CBA New Mexico (blue dots)
observations, showing irregular low-amplitude
modulations, but no superhump waves.
Observations on
October 30/31, 2004
Three CBA
observatories participated in this night's session :
Tonny Vanmunster (CBA Belgium), Arto Oksanen (CBA
Finland) and Lou Krajci (CBA New Mexico). The
combined light curve (see below) shows an irregular
modulation of about 0.1 mag .
Var79 Peg light curve on Oct
30/31, 2004, composed of CBA Belgium (cyan dots),
CBA Finland (green dots) and
CBA New Mexico (pink dots) observations, showing
irregular 0.1 mag modulations.
Light curve analysis
Using Peranso,
I performed a detailed period analysis on the
collected observations. I first de-activated
observations, that were considered erroneous, and
then subtracted the average magnitude of each
observation set. This resulted in a total of 942
useful observations. Subsequently, I used the ANOVA
(see figure below) and PDM period analysis
methods to derive the most significant period. This
resulted in a period of 0.0651 +/- 0.0006
d.
The significance of the period (false alarm
probability F.A.P.) then was calculated using the Fisher
Randomization method of Peranso. This is a
Bootstrap approach, and it confirmed the
significance of the above period (F.A.P. of 0.005
only), although the signal is quite weak. The
latter is evident when looking at the phase diagram
(see below), which depicts an average modulation
with an amplitude of 0.04 mag only.
Although the above observations indicate that
superhumps have not (yet) developed, it remains
interesting to continue monitoring this highly
unknown target.
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ANOVA period
analysis on 942 CBA observations of Var79 Peg |
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Phase diagram
resulting from the ANOVA
period analysis |