Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 03/07/2013 - 14:58
As we begin year four of the campaign, let me bring you all up to date on progress, and there is a lot to report!
The first draft of the summary paper of the results from the first three years has been written and is in preparation for publication. It is 27 pages with copious light curves and data provided by the AAVSO and Z CamPaign participants who are specifically acknowledged in the credits. As soon as it is available on arXiv I will share the paper with all of you.
At the risk of scooping my own publication, I will summarize our results to date.
You can read the full update here.
Excuse my ignorance, you say only nine of the Z Cam stars go into outburst from standstill but don't they all do it? Isn't that the essence of a Z Cam, that they go into and out of standstill from a more-or-less agitated state? For example, ES Dra is not on your list of confirmed "outbursters" but it spent most of last year in a standstill and since about 1 September it has been varying over a range of three magnitudes or so. Maybe I'm missing the definition of an outburst?
Jim Roe [ROE]
Hi Jim,
A standstill is defined as a period of more or less constant light at a level about 30% less (or often quoted as 1- 1.5 magnitudes) below maximum light. Like this classical example below.
For many years it has been assumed and stated in Text books and papers that a Z Cam always returns to minimum after a standstill, in fact the theories explaining what causes standstills need for this to happen for their models to work.
There were three Z Cams we were pretty sure had gone back into outburst (maximum light) from standstill in the past, and Z CamPaign efforts and an exhaustive search of the light curves of the other stars has revealed at least six others, including Z Cam itself!
Actually, I was under the impression that it has been known for years that several Z Cams, TZ Per for example, went from standstill to maximum. There are definitely records for this phenomenon in the BAAVSS.
From memory it was the case of HX Peg outbursting from standstill a number of years ago which started people looking back in the records for instances where UGZ stars have apparently entered outburst from standstill. Certainly it can be argued that BAAVSS data does show this.
But I wonder.... Is there an instance where t/s photometry has shown a UGZ star to rise directly from a standstill state, or are we looking at data where there is x number of hours with no data at all where the star might have dipped before rising again? I'm not saying for a moment that this is what happens, but for it to be categorically stated that standstills sometimes end with an outburst, we must have this sort of proof surely? We all know how a CV can change it's photometric state quite dramatically in a small number of hours. Long enough for a standstill to end and a new outburst to begin?
I do wonder at that...
Gary [PYG]
Hi Mike,
has that paper ever been published or put on ARXIV?
Josch
Hi Josch,
I passed it by some of the leading authorities before submitting it, and I've been working to improve it based on their pre-submission comments. Most of the remaining changes are simple bookkeeping and caption edits, but they take time. I hope to finish it this month.
Mike
Hi Mike,
thanks for the reply.
Would be interested in receiving a copy as soon as available.
Josch