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Superhumps in VW CrB: UBVRI and CCD data
VW CrB has been observed at HJD 2452848.3212-.4966 using the 38cm telescope
of the Crimean Astrophysical Observatory equipped with the SB ST-7 CCD
camera with the R filter (197 observations), and at the 1.25m telescope
equipped with UBVRI photometer-polarimeter at .35483-.41049 (227
observations). The mean brightness was nearly the same as we got at the
previous night [vsnet-campaign-dn 3877].
From the longer CCD run, we have detected two sharp superhump maxima at HJD
2452848.3668 and .4491 with a corresponding period of 0.0723 d.
The periodogram analysis using the trigonometric polynomial fit (Andronov,
Odessa Astro. Publ., 1994, 7, 49, http:il-a.pochta.ru/oap7_049.ps [gzipped
PostScript]) has been applied to both nights simultaneously. The
statistically optimal value of the degree of trigonometric polynomial is 2
(false alarm probability is 10^{-5.9}).
The ephemeris for the superhump maxima is
HJD=52848.2220 + 0.07267 E
+/-.0009 .00016
(Var-Comp=1.725+/-0.015)
The minima occur (.324+/-.014)P earlier than the maximum,
with the mean initial epoch HJD=52848.2711+/-0.0011.
(Var-Comp=1.935+/-0.012), so the mean amplitude of the superhump is
.210+/-.012 mag.
The preliminary estimated value of the superhump period from these two
nights is slightly shorter than that P=0.0743+/-0.0006 reported by R.Novak
(IBVS 4489) based on his 4-hour run in 1997. However, this difference is not
statistically significant because of relatively large error estimate based
on a short run.
However, our new period estimate quantitatively supports the conclusion of
T.Kato [vsnet-campaign-dn 3878] that "The measured superhump period from the
preliminary analysis is slightly shorter than the literature value".
From the UBVRI observations, the moment of maximum
occurred at HJD 2453214.3680+/-0.0013, in an excellent agreement with the
CCD data. The minimum timing is
HJD 2553214.4094+/-.0106. The comparison star for these observations was
C1 GSC 02576-01733 (16 00 39.29 +33 15 03.7), contrary to the comparison
C2 GSC 2576.2027 used for the CCD data.
In the table below, the mean instrumental magnitude difference Var-C1 is
shown, arguing that the comparison star has similar spectral energy
distribution at the wavelengths longer than that of V. Of course, there is
an UV excess in the dwarf nova. The linking to the standard UBVRI system is
planned.
Var-C1 Delta mag
U 2.368 (8) 0.157+/-.018
B 2.978 (5) 0.184 .014
V 3.128 (8) 0.250 .025
R 3.090 (4) 0.134 .014
I 3.111 (7) 0.147 .025
I.L.Andronov (il-a@mail.ru)
K.A.Antoniuk (antoniuk@crao.crimea.ua)
A.V.Baklanov (alex-baklanov@mail.ru)
S.V.Kolesnikov (sv-k@mail.ru)
E.P.Pavlenko (pavlenko@crao.crimea.ua)
N.M.Shakhovskoy (shakh@crao.crimea.ua)
Department of Astronomy and Astronomical Observatory, Odessa National University
Crimean Astrophysical Observatory
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