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[vsnet-obs 2564] CVC 90 (SW UMa a.o.)
- Date: Fri, 12 Apr 1996 18:14:09 -0100
- To: observations@aavso.org, JBortle@AOL.com, guy@tahq.demon.co.uk, tkato@kusastro.kyoto-u.ac.jp, gp@star.sr.bham.ac.uk, pvancaut@innet.be, bill.worraker@aea.orgn.uk, nogami@kusastro.kyoto-u.ac.jp, safnet@mesiob.obspm.fr, KFA02524@niftyserve.or.jp, sno@iris.elte.hu, vsnet-obs@kusastro.kyoto-u.ac.jp, NAH01147@niftyserve.or.jp, ebroens@innet.be, fidusz@alba.zpok.hu
- From: Tonny Vanmunster <tvanmuns@innet.be>
- Subject: [vsnet-obs 2564] CVC 90 (SW UMa a.o.)
- Sender: owner-vsnet-obs@kusastro.kyoto-u.ac.jp
BELGIAN ASTRONOMICAL SOCIETY V.V.S. - Working Group Variable Stars
Cataclysmic Variables Circular No.90 1996, April 12
Ed.: T. Vanmunster, Walhostraat 1A, 3401 Landen, BELGIUM
Internet: tvanmuns@innet.be TEL. 32-11-831504
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The CATACLYSMIC VARIABLES Home Page: http://vsnet.cv.psi.edu
===================================================================
SW UMa [UGSU/DQ, 10.6v - 16.5v]
===============================
Lasse Jensen, Farum, Denmark reports his discovery of an outburst
of this UGSU-type dwarf nova. He detected the object, while it was
on its rise to maximum :
1996 Apr. 10.903, [14.7 (G. Poyner, 0.40-m refl.);
Apr. 11.847, 14.0 (L. Jensen, 0.33-m refl.);
Apr. 11.875, 13.5 (L. Jensen);
Apr. 11.955, 11.7 (L. Jensen);
Apr. 11.969, 11.4 (L. Jensen);
SW UMa was last seen in outburst on August 10, 1993 (G. Dyck, USA),
when it reached mag. 11.6. This was a normal outburst. In March 1992,
SW UMa was observed in superoutburst (H. Dahle, Norway and R. Stewart,
USA).
Orbital and superhump periods of SW UMa are well determined. The
following values are given in [1] : orbital period 1.36356 h, super-
hump period 1.3999 h.
This object provides a lot of interesting observing opportunities,
both for amateurs and professionals :
- Superhumps in SW UMa can easily be detected and followed visually.
Bjorn Granslo, Norway has presented an interesting account of his
attempts during the March 1990 superoutburst in [2].
- Astronomers with CCD equipment should look for QPOs (quasi-periodic
oscillations). QPOs are oscillations of short coherence lengths, and
are a widely observed phenomenon in cataclysmic binaries. During the
above mentioned 1992 superoutburst of SW UMa, Taichi Kato of Ouda
Observatory, Kyoto University, Japan, detected QPOs with gigantic
amplitudes (~20%). This type of QPOs are called "super-QPOs". Super-
imposed with the superhumps, they observed QPOs with a mean period
of 6.1 minutes and an unprecedented large amplitude of 0.2 mag. [3].
References :
------------
[1] Cataclysmic Variable Stars, B. Warner, Cambridge Astrophysics
Series, No. 28, Cambridge University Press, 1995.
[2] Variable Star Research: An International Perspective, ed. J.R.
Percy et al., Cambridge University Press, 1992.
[3] Kato et al. 1992, PASJ 44, L215
GO Com [UGSU, 13.1 - 20.0p]
===========================
The GO Com outburst, announced in our previous circular, apparently
has been a short one, as indicated by the list of photometric
observations below. Referring to the peculiar outburst behaviour in
1995, it nevertheless remains important to closely monitor this
variable, since unexpected brightenings may occur in the weeks
following an outburst.
-----------------------------------------------------------------------
DATE (UT) MAGN MS SEQ OBSERVER REMARKS SOURCE
-----------------------------------------------------------------------
1996 03 25.008 [14.4 mv GSC Vanmunster, T. CVC 89
1996 03 26.555 14.4 CU Iida, M. VSNET
1996 03 26.574 14.2 CU Iida, M. VSNET
1996 03 26.597 14.6 CU Iida, M. VSNET
1996 03 26.634 14.84 CV Ouda Team VSNET
1996 03 26.830 14.5 mv GSC Jensen, L. VSNET
1996 03 26.976 14.5 mv GSC Jensen, L. VSNET
1996 03 27.135 14.7 mv GSC Vanmunster, T. CVC 89
1996 03 27.928 [14.4 mv GSC Broens, E. VSNET
1996 03 27.940 14.5 mv GSC Vanmunster, T. VSNET
1996 04 03.995 [14.4 mv TA Poyner, G. VSNET
UV Per [UGSU, 11.0v - 17.5v]
============================
The UV Per outburst, first announced in CVC 86, is over now. It has
turned out to be a most exciting outburst : the initial normal
outburst triggered a bright superoutburst, which once again was
followed by a short post-superoutburst brightening. Taichi Kato, Kyoto
University, Japan remarks in a recent VSNET message : "Concerning post-
superoutburst brightenings, UV Per had a well observed example in 1989
October - November, whose light curve can be seen on the VSNET Home
Page (UV Per page). Examples of superoutbursts triggered by normal
outbursts, later followed by post-superoutburst brightenings have been
well observed in T Leo in at least two occasions: 1991 December -
1992 January, and 1993 January."
Other examples of post-superoutburst brightenings have furthermore
been reported in UZ Boo and VY Aqr (see CVC 16) and in V1028 Cyg
(CVC 53). Some of these brightenings are short-lived ones (like a
normal outburst), while others are long-lived (like the post-dip
behaviour of AL Com).
We have compiled a complete light curve, clearly showing the above
mentioned features, on the basis of 74 photometric observations. It
will be made available on the Cataclysmic Variables Home Page shortly.
GK Per [NA/DQ, 0.2v - 13.0V]
============================
The outburst of GK Per (see CVC 83), which started in February 1996,
is still ungoing. An intermediate light curve has been compiled on
the basis of 274 photometric observations. It is available on the
Cataclysmic Variables Home Page.
S10932 [UG:+E, 13.4 - 18.5p]
============================
This object underwent a very short and faint outburst end of March
1996. It was detected by Makoto Iida, VSOLJ, Japan, using a CCD.
The eclipsing dwarf nova S10932 is part of the Belgian Cataclysmic
Variables Alert Programme.
The photometric summary below shows all available observations :
-----------------------------------------------------------------------
DATE (UT) MAGN MS SEQ OBSERVER REMARKS SOURCE
-----------------------------------------------------------------------
1996 03 25.011 [14.6 mv GSC Vanmunster, T. VSNET
1996 03 26.611 14.7 CU Iida, M. VSNET
1996 03 26.614 14.8 CU Iida, M. VSNET
1996 03 26.616 14.6 CU Iida, M. VSNET
1996 03 26.618 15.1 CU Iida, M. VSNET
1996 03 26.621 16.7 CU Iida, M. VSNET
1996 03 26.623 15.4 CU Iida, M. VSNET
1996 03 26.625 15.0 CU Iida, M. VSNET
1996 03 26.627 14.5 CU Iida, M. VSNET
1996 03 27.017 [14.3 mv GSC Jensen, L. VSNET
1996 03 27.142 [15.0 mv GSC Vanmunster, T. VSNET
1996 03 27.162 [15.0 mv GSC Vanmunster, T. VSNET
1996 03 27.915 [14.6 mv GSC Broens, E. VSNET
1996 03 27.943 [15.0 mv GSC Vanmunster, T. VSNET
The previous outburst of this object was seen on January 1st, 1996 by
the Ouda Team, Kyoto University, Japan [CVC 77], at mag. 13.5. Eclipses
as deep as 3.2 V magnitudes were observed by T. Kato and the Ouda Team.
This is one of the deepest known eclipse amplitudes among outbursting
dwarf novae. Similar deep eclipses were also reported by German
astronomers Peter Kroll and Gerold Richter of Sonneberg Observatory,
who measured an amplitude of about 4.4 mag (R band) [CVC 78].
P. Kroll and G. Richter derived the following ephemeris for mid-eclipse
timings : Min (HJD) = J.D. 2449486.48166 + 0.0870386727 * E.
Tonny Vanmunster