October 24, 2014: 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: RX And*, U Gem*, YZ Cnc*, SU UMa*, Z Cam*, SY Cnc, EX Dra, EM Cyg, and AB Dra. 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, whichever comes first.
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 2008Sci...320.1318K), 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 2013Sci...340..950M).
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), Range, Type, and Date of most recent outburst in 2014
| Name | R.A.(2000) | Dec.(2000) | Max | Min | Type | Date latest 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 possbily going into outburst. Minutes will count!
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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