Monitoring of Northern dwarf novae for radio jets campaign

[PTS]

AAVSO Alert Notice 505
October 24, 2014

Monitoring of Northern dwarf novae for radio jets campaign

Ms. Deanne Coppejans (PhD candidate, Radboud University Nijmegen
(Netherlands) and University of Cape Town) and colleagues have
requested AAVSO observer assistance in monitoring several dwarf
novae in support of their campaign to observe them in outburst
with the Very Large Array (VLA) to search for radio jets.

They will observe 5 targets from the following list: U Gem*,
EX Dra, Z Cam*, RX And*, EM Cyg, AB Dra, SY Cnc, SU UMa*, and
YZ Cnc*. Stars with an asterisk (*) will be given higher priority,
so if two targets were to go into outburst simultaneously, the
high-priority one would be selected by them to trigger VLA
observations.

The campaign will begin now and run through September 2015, or
until all five VLA triggers have been used.

This campaign is similar to previous AAVSO campaigns, namely the
2007 campaign to monitor a sample of 10 dwarf novae (AAVSO Alert
Notice 345, which resulted in the first detection of a radio jet in
a dwarf nova system (Koerding et al. 2008, Science, 320, 1318), and
the ones carried out at the request of Dr. James Miller-Jones and
colleagues on SS Cyg in 2010-2011 (AAVSO Special Notices #204,
#206, Alert Notice 445). The latter resulted in an accurate
distance determination to SS Cyg, thereby reconciling its behavior
with our understanding of accretion disc theory in accreting
compact objects (Miller-Jones et al. 2013, Science, 340, 950).

Ms. Coppejans writes: "The relation between accretion and outflow is
one of the basic problems in modern astrophysics. It has long been
thought that CVs are the only accreting systems that do not produce
jets, and this notion has even been used to constrain jet models.
However, there are now some indications that CVs do show jets,
possibly allowing a universal link between accretion and ejection.
Radio observations provide the best unambiguous tracer of the
corresponding jet or directed outflow, but there are only two clear
detections. By observing a more extensive sample of cataclysmic
variables in outburst we will determine the existence of jets or
other outflows in these accreting binary systems. These observations
will decide if either CVs do show jets and thus support a universal
link between accretion and ejection, or if they do not show jets,
further constraining future jet models."

The radio jet, if it exists in any of these nine systems, is
expected to be seen shortly after the beginning of the outburst (as
it was in SS Cyg). Catching the outburst as it is just starting and
reporting that information to AAVSO HQ immediately is crucial, as
the astronomers need to be alerted, make their decision whether to
trigger the VLA observations, and allow enough time for the VLA
to start the observations.

The first two systems you are asked to monitor are RX And and EM
Cyg, as they are in a good position for observing. Please observe
these systems NIGHTLY and report all observations as soon as is
practical. In the event of an outburst, please report your
observations as quickly as you can via WebObs, and also notify
Dr. Matthew Templeton and Elizabeth Waagen at AAVSO Headquarters
and Deanne Coppejans (matthewt@aavso.org, eowaagen@aavso.org,
d.coppejans@astro.ru.nl).

Visual magnitude estimates are a fast and effective means of
monitoring these dwarf novae. CCD observations are also useful;
please reduce your frames and report your data as soon as possible
following an observing run. CCD time-series are not required for
this project.

Coordinates (2000) and Range
Name R.A. Dec. Max Min Type Date last outburst 2014
RX And* 01 04 35.52 +41 17 57.8 10.8 vis 15.5 vis ZCAM Oct 16 (2456946)
U Gem* 07 55 05.21 +22 00 04.8 8.9 vis 15.4 V UGSS May 22 (2456799)
YZ Cnc* 08 10 56.65 +28 08 33.2 10.4 vis 15.7 V UGSU Oct 02 (2456933)
SU UMa* 08 12 28.28 +62 36 22.3 10.9 vis 14.9 vis UGSU Jul 02 (2456840)
Z Cam* 08 25 13.20 +73 06 39.2 10.4 vis 13.8 vis ZCAM Oct 18 (2456949)
SY Cnc 09 01 03.31 +17 53 56.0 10.6 vis 13.8 vis ZCAM Oct 12 (2456941)
EX Dra 18 04 14.11 +67 54 12.2 13.0 vis 16.7 V UG+E Oct 10 (2456940)
EM Cyg 19 38 40.11 +30 30 28.4 12.1 vis 14.2 vis ZCAM Oct 20 (2456950)
AB Dra 19 49 06.54 +77 44 23.4 12.2 vis 15.5 vis UGSS Sep 27 (2456927)

Charts with comparison stars for these stars may be created using
the AAVSO VariableStar Plotter (VSP, http://www.aavso.org/vsp).

Please report observations to the AAVSO International Database
using the names above (do not include the asterisk). As said
earlier, timely reporting is essential, especially if you see a
star possibly going into outburst. Time is critical!

Your observations and timely notice will be crucial to the success
of this campaign. Many thanks for your participation.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen and
Matthew R. Templeton.

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