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What's Happened To DX AND?

BRJ
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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)

Might be just by chance?
lmk
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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
BRJ
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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)

Data error needs correcting
lmk
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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

DX And observation
BSJ
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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

DX And
PYG
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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

DX And
HQA
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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

DX And observation from 2012
BSJ
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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.

DX And in outburst?
FRF
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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

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484