Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 12/31/2013 - 17:08
I note that there have been no reported confirmed outbursts of this star since early 2011. Although it has significant seasonal gaps, it seems a little odd to me that potentially multiple maxima might have completely escaped detection during this interval.
The same sort of apparent secession of activity seems to have been exhibited by both CH UMa and V493 Lyr in recent years, two stars that were observed as quite active during their early years under the AAVSO's program. As I recall, several other CVs I've followed over the years ave hinted at having such apparently extended dormant periods as well. It might be something worth looking into.
Just offered as an observation on my part.
J.Bortle (BRJ)
Hi John,
Well looking at LCG for DX And, there is that one "outburst" obs in late 2012, which if true, means the regularity of its outburst would be about normal. That would be 7 outburst in 11 years on the average (64% chance in any year), so a few missed years would be expected just by chance alone.
But, if you dont count that single observed outburst in 2012, there would then be a gap of several years without one. Hmmm. So, it really comes down to the reliability of that one obs!
Best 2014 wishes.
Mike LMK
P.S. Have you checked out the new comet database by Jure http://www.observatorij.org/cobs It is a true step forward in cometary observing and analysis, along the lines of AAVSO WebObs and LCG!
Actually, Mike, if one looks at the 2012 lightcurve data closely it is clear that the single positive October observation is simply an error. There is a negative observation of +14.4 made the very same night. I had checked out the viability of that supposed positive sighting prior to making my original post.
Thus, there indeed appears to be the strong likelihood that DX And has experienced an unusually long period of inactivity recently, a strange and perhaps heretofore unrecognized sort of phenomenon I've seen exhibited in several other CVs over the years.
J.Bortle (BRJ)
John, Thanks for pointing that out. I took a closer look at that obs as well. Actually, the 2 obs - the positive bright one and the <14.4 were made by the same observer (DGP) at exactly the same time (10/19/2012 00:00UT) ! Obviously, an error of some sort, but which obs is the erroneous one? There is a 48 hr period between two positives at around mag 15, with a couple negatives in between. So, it is conceivable the variable rose rapidly to outburst and faded within 24-48 hrs back to quiescence. Now, I am not saying that was likely what happened, only that it is possible given the sparse data in that interval.
I think HQ needs to contact that observer to have him correct the data he submitted. Then, we will know for sure.
Mike LMK
The observer has been contacted.
In the future, you might find that you will get a better response from HQ regarding checking out questionable-looking observations if you email me directly or use Zapper or VStar to flag the observation(s). I don't have time to read closely every forum post every day and could easily have missed this discussion.
Many thanks,
Sara
I looked at my own data since 1993. In that time I've recorded 14 outbursts and missed one for certain (2008). Examining the outburst intervals during this period I find that the shortest time in between outbursts was 264d (Sep 94-Jun 95) and the longest being 688d (Dec 96-Nov 98). There was good coverage in this long gap with no 'major' outburst detected, although DX And did rise to mag 14 in Oct 1997. Was this just an anomoly or a very faint (failed?) outburst? If we count this as an outburst, then that long 600+d gap reduces to just over 300d. Using this number to work out an average outburst cycle along with the others I get 398d for an outburst cycle. If we discount this as an outburst then the figure becomes 437d average.
The time between the last two outbursts was ~460d, and it's been around 1,030 days or so since the last outburst. This would suggest a possible outburst in the summer of 2012 where I note an interesting seasonal gap appears in the AAVSO data. So we might be a couple of months overdue for an outburst, and if I were a betting man I would bet John and Mike's money that we might get an outburst in the next month or two - but don't quote me on that :-)
Gary
Outbursts from CVs is a quasi-periodic, mostly chaotic, phenomena. Having gaps is reasonable, considering the statistical nature of the mass transfer. You might try an estimate of the period and plot an (O-C) diagram of the outbursts, or just do a bar plot of the timeline, and see how often gaps appear; I think there is a standard test to see whether any particular gap is significant. I'm not sure if DX And is within the observation region of CRTS, but you might look there to see if any additional coverage might be available. Looking at the logs, I don't see any 2012 AAVSOnet data.
Observers make submission errors all of the time. Rather than calling any particular observer into question on a public forum, we would much prefer that you use the normal methods of notifying HQ (such as Zapper) so that we can work with the observer and get their mistake corrected privately (or confirm the positive sighting by a re-examination of the estimate by the observer). That said, it would certainly help HQ if every observer looked at the light curves of their stars to confirm that their observations follow the trend of other observers and thereby do their own first-level quality check to save us time!
Arne
Just to close the loop on this, the observation from 10/19/2012 magnitude 11.3 that was in question has been corrected. It was really for RX And.
János Bakos (HAA/VSS) recently reported DX And in outburst. He wrote DX And was around 13.0 mag this morning. He mentioned the star was already visible yesterday too.
Can anyone confirm the outburst?
Clear skies,
Robert
Indeed, DX And does appear to currently be in outburst and the possibility exists that a maximum might have escaped detection during this star's seasonal gap in the summer of 2012. Unfortunately, we'll probably never know for sure.
That said, I would like to point again to the prevailing situation with CH UMA which is not dissimilar to that of DX And. After recording a long series of rather regularly spaced outbursts, this star seems now to not have shown any definite maxima since about early in 2011, at least according to its AAVSO lightcurve. One "might" suspect that the very tail end of an outburst was perhaps recorded last year near the time of the star's solar conjunction (although CH UMa is always situated well outside the twilight regions and should really be much better covered), but that is quite uncertain. With an approximate outburst cycle of 335 days one might anticipate perhaps a couple of missed outburst recently, but their seeming absence since 2011 is just a bit troubling given the usual brightness this star attains at maximum. This is especially so when one considerings that the star's seasonal gap in 2012 was moderately well covered without detection of any outburst.
As I had mentioned upstream, 50 years of following cataclysmic variables leads me to believe that at least a certain few somehow go through seeming long breaks in their outburst rythm. Sadly, I would anticipate such "mysteries" to mount as we progress into the future, in spite of the AAVSO's remote all-sky maging program(s). The AAVSO's once excellent coverage of a great many stars minimized seasonal gaps back in the halcyon days of its broad ranging visual observer corps. Today, lack of serious encouragement aimed at our visual observers has resulted in a steady decline of enthusiasm in this area, reflected in the ever sparser coverage of a great many formerly well observed stars, and a widening of their seasonal gaps, for the most part not counterbalanced by our devoted imagers . Imagining may be seen as our future, but I honestly have my reservations.
J.Bortle (BRJ)
Denisenko of the MASTER team yesterday confirmed the outburst of DX And. [vsnet-alert 17229]
Regarding CH UMa, I regularly observe this star with my DSLR camera (M81, M82 and NGC 3077 is also visible on my CH UMa images, so I can combine supernova-hunting and regular monitoring of CH UMa). Unfortunately CH UMa was always in quiescence since I started to monititor her with my DSLR camera :(
I hope can report all my negative observations soon...
John,
Great comment on achieving better coverage of cataclysmic variables by encouraging visual observers. I have made a similar comment to HQ in the past. Although it's fun to see 4 magnitudes fainter using a CCD, the message that needs to be made is that "coverage" of these variables is usually more important than magnitude depth. This makes observing cataclysmic variables an ideal passtime for visual observers with modest equipment. There are certainly lots of new and not so new variables that need more coverage and can be reached visually at maximum.
Here are some ideas to encourage better coverage:
1) Put out a list of underobserved CVS. This could include months when observations are most needed and required threshold magnitude (don't need a lot of <12 for stars that never reach 14).
2) Resurrect the daily email of newly observed CV maximum (covering the last week or so) with the observer initials of who saw it first (a little recognition can be a motivator).
3) Possibly keep track of "first sightings" and include it in the annual report of the number of observations by each member (do we still put this out?) I remember being motivated to go fainter, back in the "old days", by the listing if "inner sanctums" on the annual report.
Of course the modern emphasis on CCDs and spectroscopy is producing amazing and valuable results. But amateurs without this equipment need to be encouraged. We should never forget the importance of coverage by visual observers as an essential AAVSO contribution to science.
Richard Stanton (STR)
John makes a very good argument that AAVSO coverage of a great number of CVs has declined in recent years. I've been publishing the CV Circular since 2005 and some stars that were once regularly visited by AAVSO observers get almost no love these days.
Richard has some suggestions about how we could encourage more observers to take up the challenge, but most of these suggestions are things we already do in one way or another. You just have to know where to look.
1) Put out a list of underobserved CVS. This could include months when observations are most needed and required threshold magnitude (don't need a lot of <12 for stars that never reach 14).
As Matt pointed out, we already do this, and have a web page with a tool that will generate custom lists for you based on your input.
http://www.aavso.org/program-stars-need-observation
We also have a feature in the newsletter each quarter summarizing which stars have or haven't been getting attention.
You can also subscribe to the CVnet Circular and see at a glance which of your favorite stars are getting plenty of attention and which are not each Monday when it arrives in your inbox.
https://groups.yahoo.com/neo/groups/cvnet-circular/info
2) Resurrect the daily email of newly observed CV maximum (covering the last week or so) with the observer initials of who saw it first (a little recognition can be a motivator).
Those emails were pretty awesome, and I remember the friendly competition (and motivation) they created, but they were complied by hand by the AAVSO staff and took a lot of staff time and resources to publish every day. That whole thing evolved into the MyNewsFlash program, another publication you can subscribe to that you can customize what you get hourly, daily or weekly by star classification, type or name.
http://www.aavso.org/observation-notification#mynewsflash
3) Possibly keep track of "first sightings" and include it in the annual report of the number of observations by each member (do we still put this out?) I remember being motivated to go fainter, back in the "old days", by the listing if "inner sanctums" on the annual report.
The annual observer totals are published in the Annual Report now. We do not keep track of "inner sanctums" any more, however.
http://www.aavso.org/annual-report
Keeping track of "first sightings" and giving credit to observers is problematic, and has led to some famous (infamous) arguments in the past. Determining who gets credit gets to be sticky. Is it the person who first reported it, and how do you tell that? Or is it the person who reports the first sign of activity but perhaps reports it three hours after the other report? Who is going to decide these things, how long do you wait before you declare a winner and who are going to be the outburst police?
We update the Activity At A Glance portion of the CVnet home page daily in real time. We don't hand out credit for "discovering outbursts" unless it is something truly noteworthy like a recurrent nova eruption.
https://sites.google.com/site/aavsocvsection/
You can also subscribe to and contribute to the CVnet-outburst email list, where observers, including John Bortle, report their most recent detections of CV activity, including outbursts, standstills and unusual behavior.
https://groups.yahoo.com/neo/groups/cvnet-outburst/info
Of course the modern emphasis on CCDs and spectroscopy is producing amazing and valuable results. But amateurs without this equipment need to be encouraged. We should never forget the importance of coverage by visual observers as an essential AAVSO contribution to science.
I recently wrote a story about a significant variable star discovery made by Rod Stubbings, a visual observer in Australia, for my blog, that was also featured in the April newsletter.
http://simostronomy.blogspot.com/2014/04/rod-stubbings-patience-persistence-and.html
It is a perfect example of how the ground we visual observers stand on may be shifting or shrinking in some ways, but there is still plenty of good footing if you think about what you are doing and adjust your program to the strengths of visual observing.
Mike Simonsen (SXN)
AAVSO
I agree in large part with what John is saying. The surveys will do a decent job of nightly monitoring of transient objects like CVs, but with many limitations. For example, many surveys (such as CRTS) avoid the galactic plane; others do not observe near the horizon or avoid circumpolar objects. CH UMa is nearly circumpolar for many northern observers, and the visual observers can follow it for months where the surveys will be looking elsewhere. The list of prime parameter-space projects for visual observers is given in the article by Mike Simonsen:
http://www.aavso.org/suggested-stars-visual-observers
Everyone can play an important role!
Arne
Arne-
Thanks for your response. It raises the question, "Are results of automatic surveys being incorporated into AAVSO light curves, both outbursts and fainter thans?" If not, is there any way this could be done? This might be a great way to fill in some of these troublesome coverage gaps.
Just a thought--Richard (STR)
My thanks to Arne and Mike for many informative answers. Maybe there are other solutions out there to the problem identified: With all the 10" to 16" Dobs and other large scopes out there, why are visual observations of so many interesting stars declining? Perhaps we can discuss this more at the June meeting!
Thanks again, Richard (STR)
To quote Richard (STR)
"...why are visual observations of so many interesting stars declining? Perhaps we can discuss this more at the June meeting!"
I can't get to the June meeting and would be interested in feedback to Richard's question now. I have the opportunity to talk about the visual observing of CVs at the Variable Star Symposium after the RASNZ Conference and I would like to encourage more visual observing. Hence my interest in this question. I throw in two more questions:
1. How much has the impact of new technologies had on dragging people away from visual observing? This has two components
(i) Do people now want to use the technologies themselves eg CCDs
(ii) Do people think the automatic surveys take away the need for visual observing (this has been addressed above)
2. Is it that people no longer feel the value of such observations?
3. Has the fun gone out of visual observing for many people?
What other factors are there? We need to identify them so that we can begin to address them.
I look forward to any feedback.
BTW the articles on Rod Stubbing's work are truly inspirational for us visual observers (thanks to both Rod and Mike)
Stephen [HSP]
Pukemaru Observatory, New Zealand
Hy Stephen,
Another reason is that many observatory's, even small backyard ones, are remotely operated.
Cheers, Rolf
Geyserland Observatory
Rotorua NZ
[quote=STR]
With all the 10" to 16" Dobs and other large scopes out there, why are visual observations of so many interesting stars declining?
[/quote]
No doubt there is a huge number of medium and large size "Dobs" out there in the hands of amateur astronomers. However, of all the star parties I have been to over the years, I cannot recall a single owner of these instruments ever observing a variable star!
I think its safe to say that an extremely minute percentage of all Dobs out there are used regularly for variable star observations. And this is a shame of the first magnitude. Just about the only usage of the big ones are to observe faint DSO's, aka "recreational" observing alone.
There are no doubt numerous reasons why this sad situation exists. Disinterest or ignorance of the value of scientific observing is a paramount one, indeed, even among "serious amateurs" with sophisticated equipment. And, certainly the widespread worsening light pollution around the world, makes any visual observing from one's own backyard more and more difficult. If one has to lug a 24" Dob to a remote dark sky site, how often are variable stars going to be followed ?
I have decided to live in a rural area, with excellent dark skies. I can observe variables in the 16-17 magnitude range with my 20" "Dob", which is fairly competitive with the average CCD observer using a modest size SCT in a moderately light polluted area. But, most people nowadays do not or cannot live under dark skies, so to a degree, there goes the decline of visual observing :(
Mike LMK
On the other hand, my experience is that variables are quite suitable objects for visual observing from light polluted locations, compared to diffuse deep sky objects. The trick is of course to use quite high magnification.
Indeed, that is one of the "selling points" I've used when holding an introductory workshop this spring on visual variable star observation at the local astronomy club: variables are objects that you can still observe during sub-optimal conditions, thus giving you something meaningful to do on moonlit nights, summer nights (in Sweden, you don't get dark skies in the summer) or when you don't feel like spending an hour driving to perfect skies.
So, I think your other explanation - disinterest or ignorance of the scientific value - (or something else) is indeed paramount to the decline of observations. Maybe people think with CCDs, old school methods of observation are useless. How wrong they are.
/Gustav, HGUA
At first glance, it seems easy to make the connection between light poluted skies and the decline in visual observations of variable stars. However, upon second glance, deep sky observers and astrophotographers have the same issue with light polution, and though I do not remember seeing any data, it is my impression that those parts of the hobby are growing. Does anyone know to the contrary? How are the DS and Astrophotographers managing? Don't know the answer, but would like to hear what folks think. If those portions of the hobby are growing, then I think we need to take a good look at why.
Gary
WGR
The reasons to the decline in observing variable stars are many, some sociological, some are educational and some based on the general lack of interest in science. I even have a theory that part of the decline in interest is due to the Hubble Space Telescope. This is really not the forum to discuss this topic but I would like to see it on the agenda of both the June meeting and the meeting in November. I am planning on attending the latter and would be interested in such a discussion.
I would like to say that I came to variable stars via being a casual observer. Probably not a very good one, and recently decided that I needed to systematically work on my observing tools. I had an interest in observing variable stars, but never really go involved except for joining the AAVSO. About 4 years ago I learned that Beta Lyrae was a variable star and I have been following since that time. I have only recently started to enter my observations into the AAVSO Data Base. I have also slowly added other stars to my observing list as my skills steadily improve. I still observe deep sky objects, it is just that there are variable stars on the list know. I firmly believe that casual observing is a gateway into variable star observing.
Cheers and clear skies
Bob
Several of the above posters have indicated a need to ascertain just why more hobbyists today (particularly from the U.S.) do not join the ranks of visual variable star observers and how to address that situation. There was even some mention here that some attending the June meeting would like to see some formal, or informal, discussion take place addressing it to hopefully gain a better perspective on the situation, its causes and how to proceed in the future. This is an idea that I heartily support.
Now this is certainly not the first time that this topic has surfaced in recent years. Probably the first occasion it was ever formally address by AAVSO was already back roughly 20 years ago. At the behest of Director Janet Mattei a blue ribbon panel of the AAVSO's best and brightest at the time from all around the New England area was convened at HQ. Broken up into groups, we were asked to discuss throughout the course of that day the problems that AAVSO might, or certainly would, face in the next 10-20 years as we saw it and report back offering potential solutions.
I recall that one of the more serious problems my group felt would confront the organization in the future was the general dumbing down of the hobby and hobbyists. Sadly, this was already becoming apparent even back then. The meeting was too long ago for me to recall in detail our conclusions and suggestions on the matter. However, if any records, or notes, from that conclave held at HQ years ago remain in our archives today and if they could perhaps be brought to the June meeting for examination by any discussion group formed to talk about our current situation, they might prove useful. At the very least the thoughts and ideas put forth by that earlier group of members might serve as a good starting point to work forward from. Certainly, something has to change if we are to maintain a viable visual observer corps into the future.
J.Bortle (BRJ)
A very interesting topic.
Since being on the photometry learning curve I've found a growing interest in monitoring CV's, CH Uma and DX And being a couple of the first CV's I imaged.
Both will be staying on my programme.
Douglas.
Hi,
Just to follow up on one point in Richard's post, the AAVSO does have lists of stars in need of observations that are updated regularly. In the AAVSO Newsletter, we publish quarterly updates on the least-observed LPVs and CVs in the Legacy programs, and we also now have a web feature where you can get a list of Program stars in need of observations on a daily basis:
http://www.aavso.org/program-stars-need-observation
If you are looking for ways to help out in this area, please consult both of those lists.
Clear skies,
Matthew
Just a comment - I don't think lack of encouragement from headquarters can account for much of the decline in visual variable star observing. No doubt the new technologies have siphoned off some potential visual observers. Brightening skies must discourage others. And some of us have simply become old and tired. There must be other reasons.
Hi Richard,
The survey data is not included in the AID, and so therefore does not show up in the light curve generator. We made a decision a few years ago that the survey data should really be kept separate, and leave the AID for individual observers. The intent is to link to those other surveys and include their observations whenever you plot a light curve. That step has been waiting until we had time to rewrite the Light Curve Generator, and that new tool rewrite is now underway. Once it is available, I expect that there will be check-boxes as to which external set of observations you want to display, much like we do with Seqplot today.
Arne
Hello All,
Since the topic of this thread has evolved into discussing the decline of visual observing instead of DX And specifically, we have decided to 1) move the discussion to a separate thread in the General Discussion Forum and 2) lock this thread. I copied John's most recent comment as a starting point and inclued a link back to this thread.
You are encouraged to continue the discussion in the new location. The new thread can be found here.
Thanks!
Rebecca