VY Aquarii (UGSU)
Visual magnitude estimates by P. Schmeer, Bischmisheim, Germany:
AQRVY 20201105.74 <130 SPK
AQRVY 20201106.742 112 SPK
Sequence: AAVSO (V magnitudes)
Instrument: 203-mm SCT
Confirmed by Gary Poyner (Birmingham, UK) as follows:
Nov 06.777 11.4 22cm
The previously recorded outburst (a normal one?) was observed from 2015 March 28 to April 1.
Time-resolved photometry during the current outburst is encouraged.
I'd love to start a campaign on this object without supplanting Patrick. Christian Knigge, severall collaborators, and myself are looking to put together as much as we can on this outburst. In particular, we are also hoping to get radio data (likely due to a relativistic jet) to complement the optical and UV data that largely trace the accretion disk. Multiple filters allow us to constrain the broad band spectrum of the source, which is often an important constraint for science. Elizabeth, can we start a co-requested alert, keeping Patrick involved?
We are still working on setting filter, candence, and SNR requirements. We will update you when we can.
At a minimum I would love to get multiple filters (including Visual, U, B, V, R, I, to your best abilities) a day, perhaps even once per hour. I am unsure if we will request higher cadence observations. Spectroscopy around H alpha (6563 Angstrom) and 5000 Angstrom would be interesting as well.
The source is currently brighter than 11th magnitude (and maybe even brigther than 10th magnitude). The quiescent level is more along 17 th magnitude. We have requested and been granted Swift observations to capture the X-rays and the simultaneous UV, U, B, V magnitude once per day, likely from November 11-20 (we're trying to get on scope faster). We will observe with the South African MeerKAT radio telescope at least once on November 8 at 11:40-13:40 UT. We will likely observe multiple times with MeerKAT.
Oftentimes dwarf nova outbursts only last a week or so, so let's all cross our fingers for clear skies and fireworks.
Greg, Christian, et al., thanks a lot for the proposal!
Quote: "Oftentimes dwarf nova outbursts only last a week or so, ..."
The current outburst of VY Aquarii is very likely a superoutburst and is expected to last about two weeks (the usual duration of standard SU UMa-type outbursts).
According to AAVSO data, a normal outburst was observed 2006 October 7–11, and a superoutburst 2008 July 1–16 (followed by a rebrightening July 21–23). An outburst of unclear nature was observed from 2015 March 28 to April 1 by Rod Stubbings and the All-Sky Automated Survey for Supernovae (ASAS-SN).
CBA has also been alerted, but since not everyone here is part of that. Here's Christian and my rough plan.
This white dwarf has a companion that orbits it every 0.06309 d (90.85 min) that supplies the material the white dwarf accretes. So changes to the source emission may happen on more rapid timescale than daily observations. AAVSO observers can play a major role in this campaign. To first order, a superoutburst will likely last around two weeks, as Patrick said. Towards the end of the outburst, the source will decay towards its quiescent emission (mostly from the companion star) of 17th mag Visual. So we expect around 7 mags of changing optical emission over the outburst, with the AAVSO observers playing critical roles.
We have six priorities for AAVSO observers. Please pick one given your capacity and interest.
- Capture B V timeseries data at as rapidly as possible a cadence given the magnitude of the source when you observe. Please observe B V B V B V ....
- Capture V timeseries data at as rapidly as possible a cadence given the magnitude of the source when you observe.
- Capture Visual (Vis or CV) timeseries data at as rapidly as a possible cadence given the magnitude of the source when you observe.
- Capture U B V timeseries data at as rapidly as possible a cadence given the magnitude of the source when you observe. Please observe U B V U B V U B V ....
- Capture spectra across as much of the optical range as possible (6563 Angstrom and ~5000 Angstrom are the most critical) at least once per day. It is important to be sensitive to absorption lines that will be fainter than the continuum level in your spectra.
- Capture spectra across as much of the optical range as possible (6563 Angstrom and ~5000 Angstrom are the most critical) as rapidly as your instrument will allow. It is important to be sensitive to absorption lines that will be fainter than the continuum level in your spectra.
AAVSO Alert Notice 724 announces an observing campaign on the cataclysmic variable VY Aqr. Please see the notice for details and observing instructions.
There are threads for this campaign under the following forums:
- Campaigns and Observation Reports: https://www.aavso.org/vy-aqr-campaign
- Cataclysmic Variables: https://www.aavso.org/vy-aqr-outburst
- Spectroscopy: https://www.aavso.org/vy-aqr-campain
- Time-Sensitive Alerts: https://www.aavso.org/comment/74849
Please subscribe to these threads if you are participating in the campaign so you can be updated by the astronomers and by HQ. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
A sharp fade started on 11/26 (JD 59179), with VY Aqr fading 3 magnitudes in less than two days. However, it's still sitting around V=15.1, almost 2 mags about quiescence. As is typical for SU UMa star superoutbursts, VY Aqr should experience a smaller, shorter rebrightening in the next few days. One or more additional "echo" outbursts may also occur over the next few weeks, so keep observing it as long as possible. Runs are getting shorter this late in its observing season, but snapshot and even short (1-2 hour) time series are still possible.
Copy of my alert message (the fading started already on November 25 IMO):
Recent ASAS-SN Sky Patrol (Shappee et al. 2014ApJ...788...48S and Kochanek et al. 2017PASP..129j4502K) light curve and data: https://asas-sn.osu.edu/light_curves/a7ed8a21-0df0-4f55-aef0-cf1ab6b9d6…
Zwicky Transient Facility (ZTF) light curve and data: https://lasair.roe.ac.uk/object/ZTF18abskpen/
Time-resolved photometry is still encouraged.
Patrick Schmeer wrote on 26 November:
VY Aqr rapidly fading (since Nov. 25)
VY Aquarii (UGSU)
Recent ASAS-SN Sky Patrol (Shappee et al. 2014ApJ...788...48S and Kochanek et al. 2017PASP..129j4502K) light curve and data: https://asas-sn.osu.edu/light_curves/87bb45f1-bc31-443b-a438-581e63bf33…
The rapid fading began on 2020 November 25, i.e. 19 days after the onset of the superoutburst and 18 days after optical peak; the duration of the supermaximum was a few days longer than that of a standard UGSU supermaximum (~14 days).
Last night remote from Chile brightness slightly brighter than the day before at around mag. 14.6 compared to Nov. 30 at around mag. 15.2.
I just posted data from last night--20201201--JD 2459185.5 to 9185.7. HMB and WGR show it brightened 2.5 mags from the previous night. Both show a nice downward fading of nearly the same slope. Observed at slightly different times. Something interesting going on. Suggest keeping on it.
Strange your V data from last night are about 0.5 mag brighter than mine and the night before we had similar downward trends in V-band. What comp stars are you using?
So far V and B band data had been very close for VY Aqr. YOurs are about 0.5 mag apart.
I am using 000-BKF-582 (V mag 10.657) as Ref star and 000-BCN-525 (V mag 10.957) as check star.
I double checked and reduced that nights data again. You are correct. I have deleted and reloaded the correct data.
BTW: what exposure are you using?
I apologize that I have not been able to keep you all updated, especially during the echo outburst. I have been dealing with both COVID-19 related administration issues at my University, and then the moment those cleared, I was dealt two health setbacks (I am currently doing ok).
Thank you so much for the incredible data that you all have collected. Combined with the AAVSO historical record, on the raido side we were able to time our observations when we wanted them to occur during the decay!! I will be checking in with that time to find out if we got any detections from imaging within individual epochs, imaging over a full individual epoch, or stacked analyses of multiple epochs. I will also check in with Professor Knigge to find out what we got from Swift X-ray and Ultraviolet observations.
Due to my health issues, I cannot guarantee that I will get back to you before the new year. If I do not, I wish you all a happy holiday season, clear skies, and safety for you and your families.
- Greg Sivakoff