Skip to main content

Web Publications

AAVSO Alert Notice 360: Request to Monitor U Gem and SS Cyg for Radio Observations AAVSO HOME > publications > alert notice

AAVSO Alert Notice 360

Request to Monitor U Gem and SS Cyg for Radio Observations
November 5, 2007

Dr. Elmar Koerding, University of Southampton, England, and his
collaborators have requested our assistance in a continuing project to
monitor two dwarf novae -- U Geminorum (0749+22) and SS Cygni (2138+43)
-- in support of radio observations with the MERLIN and VLA telescopes. 
This new campaign is a continuation of the project described in AAVSO
Alert Notice 345.  Koerding and collaborators are attempting to detect
and characterize radio emission from dwarf novae during outbursts. 
Rapid optical detection of an outburst onset will be used to trigger
target-of-opportunity (TOO) observations with the MERLIN Array at
Jodrell Bank, UK and with the NRAO Very Large Array (VLA) in New Mexico. 
Observations of SS Cygni during the first campaign yielded important new
results, and a paper on those observations will be submitted for
publication in late 2007. 

Continuous optical monitoring and rapid reporting of observations of U
Gem and SS Cyg is requested beginning 2007 November 5 (JD 2454410). This
campaign will continue for at least several months, until a total of
four outbursts are detected in either of these systems and TOO
observations are obtained with the VLA and MERLIN.

Rapid reporting of observations is again critical to the success of this
campaign.  Observers are requested to report their observations to the
AAVSO within one (1) hour using WebObs or EmailObs, especially if an
object appears to be in transition to outburst.  Quiescent and full
outburst observations are also important as they can be used to
constrain when an outburst begins and and ends.  This includes
"fainter-than" observations during quiescence, so please submit any and
all observations you make as soon as you are able.

Both visual and CCD observations are requested, but CCD time-series
observations should only be performed if the data can be reduced and
submitted immediately if an outburst has not yet been reported.  Once 
an outburst has been detected and acknowledged by the radio 
observatories, time-series observations will then be very useful, and 
observers capable of performing filtered time series are encouraged 
to do so.

The table below lists the (J2000) coordinates, V-band ranges, and V-band
outburst thresholds for U Gem and SS Cyg.  The outburst threshold is the
magnitude at which the star is highly likely to go into outburst if it
reaches this point.  Please report any observations equal to or brighter
than the given threshold to the AAVSO immediately.

Desig.  Name    RA(2000)        Dec(2000)       Range(V)        Thresh.(V)
0749+22 U GEM   07:55:05.2      +22:00:04       8.8-15.3        13.5 V
2138+43 SS CYG  21:42:42.8      +43:35:10       8.2-12.4        11.0 V

AAVSO Charts for these objects may be generated at:



Please indicate the chart IDs and comparison stars used when reporting
all observations.

For more information on this project, please visit:

Your careful observations and prompt reporting are essential to the
success of this important project.  Many thanks from the Principal
Investigator and collaborators, and from AAVSO Headquarters for your
astronomical contributions!

Clear skies, & good observing,

Matthew Templeton
AAVSO Headquarters


Information on submitting observations to the AAVSO may be found at:


An Alert Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484