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The Current Situation With FN SGR?

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BRJ
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The Z AND-type variable 1848-19 FN SGR is one of the most peculiar objects on my regular observing program and long a favorite of mine. It is subject to exceedingly protracted episodes of recurring outbursts, such that the star is rarely found at minimum light during most observing seasons. Over much of the 2013 observing season this variable was near minimum and reported at roughly magnitude 13.0 or fainter, although there may be some suggestions of a small rise taking place toward late summer shortly before FN entered the twilight.

This past spring Steve O'Connor submitted the only estimates reported to the AAVSO during the early portion of FN SGR's 2014 observing season. These came in the form of two CCD values.  One is dated near the end of February, the other about ten days later. These put the star at a moderately bright 12.0 and well above minimum. However, two months later at the beginning of June 2014 Andy Pearce reported a single fainter than magnitude 13.5 for FN SGR. Nevertheless, when I looked in on the star on June 20th and 23rd, I recorded brightnesses in the mid 12's, or once again well above normal minimum. 

Now I've known both Steve and Andy over many years and both are very trustworthy observers. So just what is FN doing? It certainly would be uncustomary for FN SGR to behave in such a manner over such a short interval. I would thus ask if perhaps someone could take the time to look into one of the sky survey data banks for a 2014 lightcurve of FN SGR and inform us of just what those say has been going on lately with this most unusual variable. 

J.Bortle   (BRJ)

 

 

FN Sgr New Brighter Phase
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Hi John

A very interesting post on truly a terrific system. I also liked seeing your classic Harvard designation in there too! I've always thought it was a neat and simple way of listing (them) and keeping the charts. I actually still use the same mode for listing nowadays, the only difference being the use of 2000.0 coords instead of 1900.0.

As far as FN Sgr goes, it was your inclusion of it in the early days of The Circular that originally caught my attention. I've actually got a bunch of (unpublished) observations of it taken subsequent to the early season ones you mentioned and will do my best to put them up later this week (probably Thursday). Between pulsations, eclipses and outbursts there's alot going on there ! Really a classic symbiotic. Thanks again for your post.

By the way, I'll soon be putting up my 2014 observations of V348 Sgr, in a long (for this star) protracted minimum around 165-180V. My memory of this one, from the Circular days, was that it seemed more or less always on the move, seemingly not content at max or min for very long. Not so right now. The minimum has been ongoing for months now.

best regards,

Steve

  

    

 

1848-19 FN SGR
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Thanks for your response to this thread, Steve. I very much look forward to seeing your as yet un-submitted recent data when added to the AAVSO lightcurve for FN SGR.

In the meantime, I note that an activity update for FN SGR from the Kyoto University was by chance received this morning listing a number of additional visual and CCD datapoints taken within the period of questionable recent activity. These do indeed indicate the star seemingly at constant minimum from last autumn until the very beginning of June of this year, then abruptly rising. The observations listed in the e-mail were as follows:

  20130503.774  13.13V  (Seiichiro Kiyota)
  20130520.883   134  (Andrew Pearce)
  20130523.866   135  (Andrew Pearce)
  20130524.658  11.16Ic  (Seiichiro Kiyota)
  20130524.660  12.26Rc  (Seiichiro Kiyota)
  20130524.661  13.25V  (Seiichiro Kiyota)
  20130615.819   135  (Andrew Pearce)
  20130705.651   134  (Andrew Pearce)
  20140605.841  <135  (Andrew Pearce)
  20140624.619   124  (Andrew Pearce)

This would initially seem to infer a difficulty with the two bright datapoints taken via CCD during late February/early March. But perhaps not. FN SGR is known to be much brighter in the red and I am unsure about any peculiar emission lines. As I've related previously, such can sometimes raise havoc with detectors and result in overly bright readings relative to the visual. And observations in anything but very restricted "V" consistently do give bright magnitude values for FN. 

Now Steve indicated his CCD observations so far reported as being taken in "V", but I think we do need to see the rest of his "V" data for FN for this season to ascertain what may be going on here. As I noted, Andy Pearce is an equally experienced observer as Steve, so initially there would seem no obvious reason to doubt either one of these gentlemen. We simply need to take time to resolve this situation.

However...prior to that I think it quite important to convey that FN SGR currently does seem to be experiencing the onset of yet another abrupt rise potentially to a new maximum and should be carefully watched over the course of the coming summer months. 

J.Bortle   (BRJ)

 

  

 

FN Sgr New Brighter Phase
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Greetings Once Again,

All my 2014 obs for FN Sgr are in the DB now. That V runs a few tenths brighter than vis for exotic symbiotics like this isn't especially rare. Just from memory I think the same thing goes on with ones like BX Mon, V694 Mon, V4018 Sgr, CH Cyg, AS 270 etc. All the emission features and the late-type giants typically present in these systems register smartly on the detector, even with the usual photometric filters in place. Many of the symbiotics sport 'AS' alias names, their strong H-alpha signatures having been noted, sometimes for the first time, by Merrill and Burwell back in the 1950's and published in their MWC and AS 'Additional Stars' lists. That's where I picked up on another symbiotic in Sgr, AS 270, which I was lucky enough to catch in outburst (perhaps for the first time) back in 2001. For those observers who can reach far enough south to get FN Sgr, AS 270 is only a little bit lower in declination. Try it as well. It's currently slowly settling down from an (11th mag) 'outburst' and is now about the same brightness as its' better known neighbor, FN Sgr.       

On the VSX page for FN Sgr, see the excellent, modern reference on ZAND types - Gromadzki et al.

Good observing !

Steve

 

 

 

1848-19 FN SGR
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Ah ha! Now that we have a much better lightcurve to work with (thanks to Steve) the picture changes completely. It is apparent that FN SGR must have begun a new rise at, or very near to, the end of its last observing season and attained a new 11th magnitude maximum sometime between early last December and the beginning of February this year. The indication is now that the 13th magnitude negative observation reported by Andy may be the one with difficulties, the unobserved interval surrounding this observation probably being too brief to truly represent any sort of eclipse event. Only further data can confirm this. We'll see if perhaps Andy monitors this forum and can supply more information regarding his early June observation.

At least what is clear now is that FN SGR has experienced a new brightening, which peaked during its last solar conjunction and it is currently fading very slowly near magnitude 12. The whole situation once again points up just how critical reasonably good coverage is, particularly for the odd-ball variables. There are far too many highly interesting stars on our program and far too few observers, both visual and CCD, these days to maintain the sort of coverage that would truly be desirable. Certainly if we only have the willingness to address the situation, the days of the visual observer need not be viewed as coming to a close.

J.Bortle   

FN Sgr
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I will add this to my regular observations.

For interest I also took a spectra of the star. It shows a slightly red continuum with lots of strong emission lines of H and He. Doesn't lend itself to accurate transforms.

http://i566.photobucket.com/albums/ss109/TCB168/_fnsgr_20140626_447_TBoh...

Terry

FN Sgr Visual Observations
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Hi John and all

Sorry for not responding sooner but I've been very busy.  Thanks to John for pointing out these observations as I've revisited my log book and realised I made a pretty basic mistake of recording the incorrect comparison star I used as the basis for the estimate.  I have revised the estimate now in the database.  I still did not make a positive observation on June 5th but have revised this to <12.8 rather than <13.5.  The observation was however impacted by the telescope being close to one of the walls of my flip top roof observatory.  This made it difficult to insert a higher power eyepiece into the telescope and therefore the low power and bright sky consipired to make the observation difficult.  I was reasonably confident I could glimpse the 128 comparison star but not confident that I could see FN Sgr.  However the observation is probably not the most accurate it could be and I've adjusted the observation in the database to reflect this.

Apologies for prolonging the confusion for a few days and thanks again to John for pointing out the discrepancy.

Regards

Andrew Pearce (PEX)

FN SGR
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Hi Andy and thanks for chiming in. Your explanation/details concerning your early June reported negative observation of FN SGR helps to further clarify what it has been doing recently and I've noticed a number of your recent follow up observations as well. It's unfortunate that the most recent new brightening of this star happened to occur while it was in solar conjunction. However, since its subsequent activity upon reappearance in the morning sky now seems to be reasonably well documented and with the original questions all having been addressed, I imagine we can get back to regularly monitoring how the current brightening evolves in coming months.

As a P.S., how are you making out these days in the comet arena? I do see you name pop up from time to time on the comet related forums, but we haven't communicated directly with one another in quite a while. Should you get the chance, give me an update on your current efforts.

John               (J.Bortle   BRJ)

  

FN Sgr
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Hi John

Unfortunately my comet observing has sort of stopped. I live in Perth which is the capital city of Western Australia and over the last 10 years has grown enormously with a population of about 1.5 million. My backyard observatory is only 7 kms from the city centre so light pollution is just too bad to follow all but the brightest comets. However my skies are still good enough to observe 16th mag variables on nights of good seeing. So my focus is now on variable stars.

I've also become concerned as to where visual comet observing is going in the future. With the apparent demise of the ICQ, I haven't been able to work out the continued scientific value of comet observing.  Obviously comets can be observed for their aesthetic attractiveness but I think variable star observers are a bit more fortunate that we have a pretty strong and vibrant AAVSO!

Regards

Andrew

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