2021 May 29

Campaign to observe the (very) frequently outbursting dwarf nova CG Dra

Jeremy Shears

CG Draconis was discovered by Hoffmeister in 1965 (1) and he later classified it as a dwarf nova (2). Rather little was known about its outburst frequency until an intensive monitoring campaign was conducted during 2005, the results of which were published in the BAA Journal (3). This revealed that the star has frequent outbursts every 11 days or so and the star spends very little time at quiescence. Two types of outburst were detected: short outbursts lasting about 4 days and long outbursts lasting about 8 days. The range is mag 14.1 to 17.4 as shown in the VSS light curve.

A subsequent paper presented evidence for very shallow (~0.16 mag) eclipses with a duration of about 18 min (4). The times between the eclipses were consistent with an orbital period of 0.18864(4) d, or 4h 31m 38 +/- 3s.

Rather few observations of this star have been made since 2008, according to the BAA and AAVSO databases. Hence the intent of the present campaign is to rectify that situation and check on CG Dra’s current behaviour. Has it changed in the last 15 years?

Two kinds of observation are requested. The first is nightly “snapshot” observations to determine the overall light curve of CG Dra, thus its outburst frequency and duration. These can be digital or visual (if you have a sufficiently large telescope). Secondly, some long runs of time series photometry would help to verify, and time, eclipses. Unfiltered photometry is very suitable for this.

Charts and sequences are available from the AAVSO Variable Star Plotter (e.g. chart). CG Dra is located at RA 19 07 32.63 Dec +52 58 28.1 (J2000.0). The campaign will run until the end of the current observing season, likely early 2022 depending on latitude.

Given that this star undergoes frequent outbursts, it provides much interest for those that decide to follow it, as it is always doing something! Please submit your data to the VSS Database and help us to shed new light on this neglected dwarf nova.

Jeremy Shears

Director, Variable Star Section

1. Hoffmeister C., Mitt. Veranderl. Sterne 2, 96 (1965).

2. Hoffmeister C., Astron. Nachr. 289, 139 (1966).

3. Shears J., Pickard R. and Poyner G., J. Br. Astron. Assoc., 117, 22-24 (2007).

4. Shears J., Boyd D., Brady S. and Pickard R. J. Br. Astron. Assoc., 118, 343-347 (2008).

Teaser image: drawing of a cataclysmic variable by Helena Uthas