14 June 2014 at 1:55 pm #573357
CSS 121005:212625+201948, which varies between magnitude 15.5 and >20.5, was identified as a possible ER UMa system by John Greaves from his examination of the CRTS light curve.
In order to find out more about the star’s identity, I am organising a campaign to keep it under observation until the end of the current observing season. We’d like intensive (nightly) measurements of its brightness, to obtain as complete a light curve as possible. Time-resolved photometry during outburst would also be of interest.
If you’d like to know more, there is a link on the BAA VSS pages here: http://www.britastro.org/vss/
Or you can download a note about it, including a chart and sequence, here: http://www.britastro.org/vss/CSS%202126%20campaign_20140511%20(1).pdf
Please submit your obs to the BAA VSS database or AAVSO.
I’ll be speaking briefly about the campaign at next week’s VSS meeting in York (mtg programme: http://www.britastro.org/vss/vss_meeting_2014_jun_21st.htm)
Jeremy15 June 2014 at 9:02 pm #576579Nick JamesParticipant
Jeremy, the chart link in your posting doesn’t work although I can guess what it should be….
Nick.28 June 2014 at 11:58 am #576584
The observing campaign was launched at last week’s VSS meeting in York and there a write-up in the current Section Circular (VSSC 160).
On returning home from the meeting, I found the star rising to outburst (Jun 22.977) at 16.9C and 24 hours later was slightly brighter at 16.2. Since then I haven’t been able to obtain further obs.
Best of luck to anyone wanting to join in the observing fun. Do let me know how you get on.
Go well! Jeremy7 July 2014 at 8:13 am #576597
The star was once again in outburst last night (Jul 6.941 16.0C). Ian Miller carried out time series photometry which reveals what may be a (super)hump, although runs at this time of year are necessarily short. Further photometry encouraged.
Jeremy13 July 2014 at 6:12 pm #576600
This Dwarf Nova has been in outburst since last Sunday (6 July) and was still at 16.9C this morning (Richard Sabo, Bozeman, US).
Time-series photometry conducted on several nights this week by Ian Miller (Swansea, UK) and Richard Sabo has shown superhumps with superhump period, Psh ~ 0.088 d. There is some uncertainty on the period and significant aliasing associated with the short runs that are necessitated by the short nights at these 2 observatories at this time of year. These data are consistent with the dwarf nova being a member of the SU UMa family. The measured value of Psh suggests is is probably not an ER UMa system.
The campaign will continue as we still need to determine the outburst and superoutburst periods. In addition, further photometry during future superoutbursts will help to confirm the Psh of this frequently outbursting dwarf nova. Further info on the BAA VSS website.
Jeremy4 August 2014 at 6:01 pm #576636
The dwarf nova CSS 121005:212625+201948 continues to be active. As previously reported, it was in bright outburst during the first half of July, fading towards quiescence on July 13. There was then a brief outburst (<3 days) around July 20. Recent data from Ian Miller and Juan-Luis Gonzalez Carballo have it currently in outburst (Aug 2, 3, 4) at ~16.4. It will be interesting to see how long this outburst lasts.
Further observations are welcome. For more details go to: http://www.britastro.org/vss/CSS%202126%20campaign_20140511%20(1).pdf
Jeremy4 August 2014 at 9:50 pm #576637Callum PotterKeymaster
if you select the text and use the link tool on the editor bar above (first line) you should be able to fix up the link. e.g.
Cheers, Callum5 August 2014 at 5:45 pm #576580
Thanks Nick. Whenever I try and paste the link it cuts off the .pdf extension. Let’s try again in plain text: http://www.britastro.org/vss/CSS%202126%20campaign_20140511%20(1).pdf
…that doesn’t work either. So for those wanting to look at the doc I suggest either of the following options:
1. cut and paste the complete url (including the .pdf extension) into your browser, or
2. Use the link in my original posting to the BAA VSS web page and then click on the link to the campaign note that you will find there.
Jeremy5 August 2014 at 5:45 pm #576616
This dwarf nova was in bright outburst for about 13 days from July 1 – a light curve with observations by Ian Miller, Roger Pickard, Richard Sabo, Jeremy Shears can be seen on the VSS web site here: http://www.britastro.org/vss/css_121005.htm
At the peak of the outburst it was mag 15.9, ~4 to 4.5 mags above quiescence. Time series photometry revealed humps in the light curve, but the runs weren’t really long enough to draw definitive conclusions about their period. The humps certainly looked like superhumps, although intriguingly there appeared to be more complex structure in them towards the end of the outburst
The most recent observation was on Jul 19.957 when the star was at mag 19.2 (Ian Miller).
We are now eagerly awaiting the next outburst of this frequently outbursting dwarf nova. It will almost certainly be a short, or “normal”, outburst lasting a couple of days. Continued monitoring is needed to determine how often the system goes into outburst, so please feel free to join it (you can upload your data to the VSS and/or AAVSO databases – and do let me know how you get on). In addition, further time series photometry during future long outbursts will be required.
For more details go to: http://www.britastro.org/vss/CSS%202126%20campaign_20140511%20(1).pdf
Jeremy5 August 2014 at 9:05 pm #576638
Thanks for the tip Callum. I have fixed some of the links, but the page keeps crashing when I try to Edit – will try and fix the others soon.
In the meantime I can report that the current outburst of the dwarf nova was a normal outburst of ~3 days as Juan-Luis Gonzalez Carballo had it fading to mag 17.1 last night.
Jeremy23 August 2014 at 10:53 am #576676
In my previous note, I mentioned the brief outburst of CSS from Aug 2 to 5. Since then the star has been languishing at minimum of about ~19 or lower. That is until last night (Aug 22), when it was again in bright outburst. Ian Miller conducted a 2 h time series photometry run in the early hours of today (Aug 23) which showed the star at ~16.0, with a pretty flat light curve. What will tonight bring? A fade or the start of a long outburst? Only further observations will tell!
These notes are based on observations in the BAA VSS Database and the AAVSO International Database by Juan-Luis Gonzalez Carballo, Kenneth Menzies, Ian Miller, Roger Pickard, Richard Sabo and myself. Further observers are welcome.
Jeremy22 September 2014 at 6:25 pm #576692
It’s time for an update on this target – a little overdue as I have been on hols for the last couple of weeks.
In the previous update I reported that at the end of August we had a short outburst. During the first week of September the star was in quiescence. Then a long outburst started on 7 September, lasting at least 12 days. Ian Miller valiantly carried out time-series photometry on several nights during the outburst. This again revealed hump-like features, with a period near 0.0807d, although there was a significant alternative around 0.0881d. Observations during the previous long outburst, in July, suggested a period near 0.0882d, with a significant alternative around 0.0810d. In each case the runs were rather short, introducing the uncertainty in the period. The upshot of all this is that further observations are needed!
So far we have observed long (>10 day) outbursts in late April/early May, early July and mid September, which might point to a ~2 month supercycle. Will we see the next one in early November? Of course there are short (~3 day) between the long outburst that we need to track too.
Many thanks to everyone who has contributed to the campaign so far.
Jeremy10 October 2014 at 6:41 pm #576694
Time for a brief update. In my previous note I mentioned there was a long outburst from Sept 7 to 19. The star was then in quiescence until earlier this week, when it was found on Oct 8 at mag 16.3C. This was one of its brief outbursts, lasting no more than 2 days. Last night (Oct 9) it was back at quiescence again. I still expect a long outburst in early November, but this is by no means certain. Further monitoring is still requested to see if this materialises “on time” and how many brief outbursts there are in the meantime. We need dense coverage (preferably nightly) to be able to discern the brief outbursts and to spot the beginning of a long outburst – an event which would prompt time-resolved photometry. I would like to thank the people who have contributed data so far. I review data in both the BAA VSS and AAVSO databases regularly, which include observations by Ian Miller, Roger Pickard, Kenneth Menzies, Juan-Luis Gonzalez Carballo, David Boyd, Richard Sargent and Richard Sabo. Apologies if I have missed anybody. Go well! Jeremy3 January 2015 at 12:12 pm #576733
I have begun the analysis of the CSS photometry data from the campaign, so I thought a quick update might be helpful. We have 6552 data points from the BAA VSS, AAVSO and CRTS databases, covering the 2013 and the 2014 observing seasons. You can view the 100-day plots for the recent season (data up to 2015 Jan 2) here: http://www.britastro.org/vss/CSS%20plots%202014.pdf
The red dashes are “fainter than” measurements. The blue data are CV or V.
You can see that coverage got better as the campaign took off. The light curve is typical of an SU Uma system (not an ER UMa as once postulated) with frequent outbursts and in my mind is quite beautiful. There are 4 superoutbursts visible, plus many normal outbursts. Analysing the superoutburst times gives a fairly consistent ephemeris, with a period of 66.4 days, taking into account the 4 supers in 2014 and an additional 2 in 2013; or 68.7 days if I only include the 2014 supers. Of course, superoutbursts are only quasi-periodic and it is a mug’s game to try and predict the next. But for a bit of New Year fun I’ll have a go anyway: sometime between Jan 18 and Jan 25, depending on several assumptions – most likely around Jan 23 if I were a betting man. You heard it here first, as they say….
However, given the field is slipping into the west, it will be a challenge to spot the next superoutburst, but it would be fun to try – and would help to update the ephemeris before the seasonal gap. So single shot imaging of the field would be helpful (as would short photometry to look for confirmatory superhumps). The supers last about 13 days.
Of course, this analysis makes use of the hard-won data submitted by many observers – hats off to them! I have used data kindly contributed by: David Boyd, James Boardman, Juan-Luis Gonzalez Carballo, Ian Miller, Ken Menzies, Roger Pickard, Gary Poyner, Richard Sabo, Pavol Dubovsky, Richard Sargent and Denis Buczynski. If you have observed this star and your name is not listed, please contact me as it probably means I have not seen your data.
Good luck and go well! Jeremy29 May 2015 at 8:13 am #576866
Last year a campaign was organised by the BAA Variable Star Section to monitor this dwarf nova.
A paper summarising the results has been accepted for publication by JBAA and a pre-print is available here: http://arxiv.org/abs/1505.07709
Many thanks to all those who contributed to, and supported, the campaign, which shows just what is possible via cooperation and pooling of observations.
Whilst the official campaign finished in January, observers are still welcome to monitor the star, which shows frequent outbursts and superoutbursts. The supercycle is one of the shortest of SU UMa’s on record, at 67 days.
Jeremy Shears1 June 2015 at 7:12 pm #576873
A couple of people have kindly asked if I wish to continue receiving data on this star.
My request is that observations are submitted directly into the BAA VSS Online Database. That’s the safest place for them and will ensure they are available to all researchers in the future.
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