February 15, 2007: Dr. Christian Knigge, University of Southampton, England, has requested our assistance in monitoring ten (10) dwarf novae cataclysmic variables as part of a search for radio jet formation during outbursts. Dr. Knigge is attempting to observe a dwarf nova outburst within six hours of the outburst onset using the NRAO Very Large Array (VLA) telescope in New Mexico and the Jodrell Bank MERLIN telescope in the United Kingdom. Rapid optical detection of an outburst onset will be used to trigger target-of-opportunity (TOO) observations with both radio telescopes to study the behavior of dwarf novae outbursts in the radio region of the spectrum, and to determine whether CV systems are capable of forming radio jets similar to those observed in X-ray bursters and other X-ray binaries.
Continuous optical monitoring and rapid reporting of these dwarf novae is requested beginning February 21. The program will continue for at least several weeks, as Dr. Knigge has been allocated six TOO activations of the VLA-MERLIN network.
Rapid reporting of observations is critical to the success of this project. Observers are requested to report observations within one (1) hour to the AAVSO using WebObs or EmailObs, especially if an object appears to be in transition to outburst. Quiescent and full outburst observations are also important, so please report all observations promptly.
Both visual and CCD observations are requested, but CCD time-series should only be performed if the data can be reduced and submitted immediately.
The table below lists the ten target dwarf novae, and for each gives the type, the range according to visual/V observations in the AAVSO International Database, and the outburst threshold, that is, the magnitude that when reached by the star usually indicates an outburst is truly underway.
Desig. Name R.A.(2000) Dec.(2000) Type Range Outburst
(V or visual) threshold
0058+40 RX AND 01:04:35.55 +41:17:58.0 UGZ 10.2 - 15.6 12.5 V
0749+22 U GEM 07:55:05.2 +22:00:04 UGSS+E 8.8 - 15.3 13.5
0803+62 SU UMA 08:12:28.20 +62:36:22.6 UGSU 10.8 - 15.6 13.6
0804+28 YZ CNC 08:10:56.62 +28:08:33.6 UGSU 10.4 - 16.3 13.5
0814+73 Z CAM 08:25:13.20 +73:06:39.23 UGZ 10.2 - 14.0 11.4
0855+18 SY CNC 09:01:03.35 +17:53:56.1 UGZ 10.8 - 14.1 12.7
1804+67 EX DRA 18:04:14.12 +67:54:12.2 UG+E 12.3 - 17.0 14.1
1934+30 EM CYG 19:38:40.10 +30:30:28.0 UGZ 11.8 - 14.4 13.4
1953+77 AB DRA 19:49:06.50 +77:44:23.5 UGZ 12.0 - 15.4 14.0
2138+43 SS CYG 21:42:42.80 +43:35:09.88 UGSS 8.2 - 12.4 11.0
AAVSO charts for these objects may be found at:
RX AND (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=RX%20And )
U GEM (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=U%20Gem )
SU UMA (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=SU%20UMa )
YZ CNC (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=YZ%20Cnc )
Z CAM (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=Z%20Cam )
SY CNC (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=SY%20Cnc )
EX DRA (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=EX%20Dra )
EM CYG (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=EM%20Cyg )
AB DRA (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=AB%20Dra )
SS CYG (http://www.aavso.org/cgi-bin/searchcharts3.pl?name=SS%20Cyg )
[Note 11/5/2013: for charts, go to http://www.aavso.org/vsp ]
As usual, when reporting observations please be sure to indicate the chart(s) and comparison stars used.
Your careful observations and prompt reporting are essential to the success of this ambitious project. Many thanks for your astronomical contributions!
Good observing,
Matthew Templeton
Staff Astronomer
Elizabeth O. Waagen
Senior Technical Assistant
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