[IAUC] CBET 664: 20061010 : VY AQUARII

[IAUC mailing list]

                                                  Electronic Telegram No. 664
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS en CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT en CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html


VY AQUARII
     E. O. Waagen, American Association of Variable Star Observers (AAVSO),
writes that the SU UMa-type (possibly WZ Sge-type) cataclysmic variable
VY Aqr is in outburst for the first time since 1994, as reported by H.
Maehara (Tokyo, Japan), who observed the variable at V magnitude 12.46 on
Oct. 7.563 UT (via the 'vsnet' and 'baavss-alert' Internet groups), and
confirmed by P. Schmeer (Bischmisheim, Germany) at visual magnitude 11.3 on
Oct. 7.749.  The outburst does not appear to be a superoutburst, according
to observations reported to the AAVSO.
     The last observed superoutburst of VY Aqr occurred in April 1993 (see
AAVSO Alert Notice 171), when it reached visual magnitude 10.0 and was
brighter than 13.0 for 15 days.  The last regular outburst to be observed
occurred in April 1994, when VY Aqr reached visual magnitude 11.3 and was
brighter than 13.0 for 3 days.  The true nature of VY Aqr is not known, as
its superhump behavior during the 1993 superoutburst did not fit the
classical pattern for WZ Sge-type stars (see Patterson et al. 1993, PASP
105, 69).  There is a very interesting pattern to the outbursts of VY Aqr:
For four of the five superoutbursts recorded in the AAVSO International
Database, there is a "regular" outburst approximately 1 year later.  For the
fifth superoutburst, there there are three 5- or 6-day gaps during the time
when this "follow-up" regular outburst might have been expected.
     Superoutbursts were reported on 1983 Nov. 30, 1986 May 3, 1988 Sept.
1, 1990 June 30, and 1993 Apr. 25.  Regular outbursts were reported on 1984
Dec. 17, 1987 July 1, 1989 Aug. 12, 1994 Apr. 23, and now 2006 Oct. 7.  Among
the five superoutbursts, the average inter-outburst interval is approximately
859 days (+/- 192 days).  After onset of four of the five superoutbursts, a
regular outburst is seen approximately 379 days (+/- 46 days) later.  Also,
during the approximately-11.5-year interval covered by these five
superoutbursts and follow-up regular outbursts, no other confirmed regular
outbursts were observed.  A search of ASAS2 and ASAS3 data by A. Henden,
AAVSO, shows no reliable observations for 1997-2004; the 2005 ASAS3 data were
not available.  Two positive observations (D, or very poor, quality) in the
ASAS2 data were contradicted by numerous fainter-than observations in the
AAVSO International Database and so are discounted.
     Selected visual magnitude estimates reported to the AAVSO:
2006 Oct. 4.8201, [13.8 (E. Muyllaert, Oostende, Belgium); 6.8139, [12.5,
(Muyllaert); 7.4280, [13.0 (R. Stubbings, Warragul, Victoria, Australia);
7.7490, 11.3 (P. Schmeer, Bischmisheim, Germany); 7.7604, 11.4 (Muyllaert);
7.7743, 11.2 (H. Hautecler, Boutersem, Belgium); 7.7810, 11.3 (Schmeer);
7.7950, 10.9 (G. Krisch, Bockenem, Germany); 7.7979, 11.2 (W. Kriebel,
Schierling/Walkenstetten, Germany); 7.8060, 11.2 (G. Poyner, Birmingham,
England); 7.8021, 11.4 (Muyllaert); 7.8431, 11.2 (A. Gonzalez Herrera,
Ferrol, Spain); 7.8542, 11.2 (Muyllaert); 7.8620, 11.3 (M. Jacquesson,
Sevigny, Waleppe, France); 7.8740, 11.1 (Poyner); 7.9931, 11.1 (J. Bortle,
Stormville, NY); 8.0340, 11.0 (A. Tekatch, Hamilton, Ontario, Canada);
8.3960, 11.4 (Stubbings); 8.4549, 11.3 (H. Matsuyama, Kanimbla, Queensland,
Australia); 8.7375, 11.5 (S. Swierczynski, Dobczyce, Poland); 8.7528, 11.6,
(Kriebel); 8.7650, 11.7 (Schmeer); 8.7847, 11.8 (Muyllaert); 8.9993, 11.7
(Bortle); 9.1021, 11.9 (Tekatch); 9.2333, 11.9 (M. Linnolt, Honolulu, HI);
9.4020, 12.6 (Stubbings); 9.4460, 12.7 (Stubbings); 9.8153, 12.5 (K. Geary,
Kingscourt, Ireland.  CCD V magnitudes reported to the AAVSO (selected from
long runs):  Oct. 7.7739, 11.40 (D. Boyd, West Challow, England); 7.8621,
11.33 (Boyd); 7.8681, 11.29 (J. Temprano, Santander, Spain); 7.9927, 11.24
(J. Blackwell, Northwood, NH); 8.2287, 11.37 (D. Starkey, Auburn, IN);
8.3871, 11.52 (N. Butterworth, Mt. Louisa, Queensland, Australia); 9.0400,
12.21 (Blackwell); 9.0672, 12.24 (J. Carlson, Hyannis, MA).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 October 10                  (CBET 664)               Daniel W. E. Green