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    THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
           25 Birch Street, Cambridge, MA 02138 USA
                      aavso@aavso.org
         Tel. 617-354-0484       Fax 617-354-0665

AAVSO ALERT NOTICE 342  (October 9, 2006)

SUBJECT: OUTBURST OF 2106-09 VY AQUARII - PROBABLY NOT A SUPEROUTBURST

Object: 2106-09 VY AQR

Coordinates: R.A. 21h 12m 09.20s Dec. -08o 49' 36.5" (2000.0)

The SU UMa-type (possibly WZ Sge-type) cataclysmic variable VY Aqr is in outburst for the first time since 1994. The outburst was discovered by VSOLJ member Hiroyuki Maehara, Tokyo, Japan, who observed VY Aqr at 12.46V on October 7.5633 UT (announced via vsnet and baavss-alert), and confirmed by Patrick Schmeer, Bischmisheim, Germany, who reported it at visual magnitude 11.3 on October 7.749 UT. The outburst is probably not a superoutburst, according to observations reported to the AAVSO.

The last superoutburst of VY Aqr observed 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 observed occurred in April 1994, when it 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 stars (see Patterson et al. 1993, PASP 105, 69). Thus, if the current outburst is a superoutburst, time series photometry throughout the outburst may help determine the nature of this star. To date, the data received at the AAVSO do not show any obvious evidence of superhumps.

CCD observers are asked to carry out as long CCD time series runs (V filter) as possible, with a cadence such that each observation has at least S/N=50. If observations with more than one filter are possible, all should be made within the same S/N=50 constraint. Visual observations are welcome; please observe several times during the night and at regular, frequent intervals (~10 minutes) if you see VY Aqr changing significantly between observations.

For all observations reported to the AAVSO to date, please see the AAVSO website. Selected recent observations reported to the AAVSO include (note that all CCD observations are selected from long runs):

04.8201, <13.8, E. Muyllaert, Oostende, Belgium;
06.8139, <12.5, Muyllaert;
07.4280, <13.0, R. Stubbings, Warragul, Victoria, Australia;
07.7490, 11.3, P. Schmeer, Bischmisheim, Germany;
07.7604, 11.4, Muyllaert;
07.7739, 11.400V, D. Boyd, West Challow, England;
07.7743, 11.2, H. Hautecler, Boutersem, Belgium;
07.7810, 11.3, Schmeer;
07.7950, 10.9, G. Krisch, Bockenem, Germany;
07.7979, 11.2, W. Kriebel, Schierling/Walkenstetten, Germany;
07.8060, 11.2, G. Poyner, Birmingham, England;
07.8021,11.4; Muyllaert;
07.8424, 11.469 unfiltered, J. Shears, Bunbury, Cheshire, England;
07.8431, 11.2, A. Gonzalez Herrera, Ferrol, Spain;
07.8542, 11.2, Muyllaert;
07.8620, 11.3, M. Jacquesson, Sevigny, Waleppe, France;
07.8621, 11.33V, Boyd;
07.8681, 11.29V, J. Temprano, Santander, Spain;
07.8740, 11.1, Poyner;
07.9927, 11.243V, J. Blackwell, Northwood, NH;
07.9931, 11.1, J. Bortle, Stormville, NY;
08.0340, 11.0, A. Tekatch, Hamilton, Ontario, Canada;
08.2287, 11.372V, D. Starkey, Auburn, IN;
08.3871, 11.522V, N. Butterworth, Mt. Louisa, Queensland, Australia;
08.3960, 11.4, Stubbings;
08.4549, 11.3, H. Matsuyama, Kanimbla, Queensland, Australia;
08.7375, 11.5, S. Swierczynski, Dobczyce, Poland;
08.7528, 11.6, Kriebel;
08.7650, 11.7, Schmeer;
08.7847, 11.8, Muyllaert;
08.9993, 11.7, Bortle;
09.0400, 12.21V, Blackwell;
09.0672, 12.238V, J. Carlson, Hyannis, MA;
09.1021, 11.9, Tekatch;
09.2333, 11.9, M. Linnolt, Honolulu, HI;
09.4020, 12.6, Stubbings;
09.4460, 12.7, Stubbings;
09.8153, 12.5, K. Geary, Kingscourt, Ireland.

There is a very interesting pattern to the superoutbursts and outbursts of VY Aqr. For 4 of the 5 superoutbursts recorded in the AAVSO International Database, there is a "regular" outburst approximately 1 year later. For the fifth superoutburst, there are three 5- or 6-day gaps in observations during the time when this "follow-up" regular outburst would have been expected. Data in the AAVSO International Database show the following:

     Outburst date         Vis.Mag.  Duration   Observer    Type OB
   JD           UT                    days
2445668.5:   11/30/1983     10.7      ~14        BRJ        superoutburst
2446051.5    12/17/1984     10.6       3         PZA,STI    regular outburst

2446553.8:    05/03/1986    10.1      ~13        MOW        superoutburst
2446978.3     07/01/1987    10.6       3         ILS        regular

2447406.2     09/01/1988    10.1       17        ILS        superoutburst
2447750.794   08/12/1989    11.3       3         STI        regular

2448073.0     06/30/1990    10.5       15        AB         superoutburst
in 1991 season, no outburst observed; good coverage         ---
  w/5-day gap in July, 5-day gap in Aug, 6-day gap in Sep

2449103.0     04/25/1993    10.0       15        AB         superoutburst
2449466.2     04/23/1994    11.3      ~3         JA         regular
.....
current outburst
2454015.9     10/07/2006   <13.0                 SRX
2454016.2     10/07/2006    11.3                 SPK
2454017.7     10/09/2006    11.7                 BRJ
2454017.902                 12.6                 SRX
2454017.946                 12.7                 SRX

Among the 5 superoutbursts, the average interoutburst interval is approximately 859 days (+/-192 days; 885, 853, 667, 1030). After onset of 4 of the 5 superoutbursts, a regular outburst is seen approximately 379 days (+/-46 days; 383, 425, 344, 363) later.

Also, during the ~11.5-year interval covered by these 5 superoutbursts and follow-up regular outbursts, no other confirmed regular outbursts are observed. A search of ASAS2 and ASAS3 data by Arne Henden, AAVSO, shows no reliable observations from 1997-2004; the 2005 ASAS3 data were not available. Two positive observations (D (very poor) quality) in the ASAS2 data were contradicted by numerous fainter-than observations in the AAVSO International Database and so are discounted.

AAVSO charts for VY Aqr, as well as sequence information for CCD observations, are available at

http://www.aavso.org/cgi-bin/searchcharts3.pl?name=vy%20aqr

Please observe VY Aqr through this outburst and the rest of the observing season, and report your observations to the AAVSO as 2106-09 VY AQR.

Also, in a plea for observations next spring, please add VY Aqr to your morning objects when it comes back into view in March. Since we are no longer receiving observations from Bill Albrecht (AB) or Danie Overbeek (OB), Albert Jones (JA) and Rod Stubbings (SRX) have been our main morning twilight observers, and in some years we are losing up to 6 weeks of coverage at this very important time!

Thank you very much for your astronomical contributions and efforts.

Good observing!

Elizabeth O. Waagen
Senior Technical Assistant

SUBMIT OBSERVATIONS TO THE AAVSO

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If you cannot access this URL, please contact us for submission details. You may also use our charge-free number (888-802-STAR = 888-802-7827) or our fax (617-354-0665) to report your observations.

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