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What is NSV 1436?

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lmk
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I noticed its in outburst again last night v=13.0, but for those unfamiliar of it, this is one of the enigmatic Ross variables discovered to be variable photographically about a century ago. What's so strange about it?

Well, primarily it has only been found in regular cv-like outbursts to magnitude 13 or so in the past couple years. For at least a decade before that, it had not been observed in such outburst. As far as I know this is the only cv-like variable that stops outbursting for extended periods and then apparently resumes a regular cycle.

Also, it appears that from the limited number of faint positive observations, it may have 2 "minima", down around mag 18 and around mag 16-17.

This seems to be an extremely unusual behavior, and no apparent physical mechanism to explain it!? What sort of campaign or observations could be performed on it to try elucidate its peculiar nature? I think this really deserves a lot of attention. It certainly is bugging me.

Mike LMK

I've been shooting NSV
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I've been shooting NSV 1436 the last 3 weeks.....I probably should look at my data rather then waiting another 2 months to "harvest" 3 months at a time.  Thanks for the heads-up!

James Foster,

Los Angeles, CA

Close companions
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The main issue with this variable for most of us amateurs are the 2 close companions to it, a 17-ish magnitude star 4 arcsec south and an 19-ish one 2.5 arcsecs to the south. I suspect a lot of the CCD data is contaminated by one or both of these stars in the aperture. A few images made a decade ago with a 2.5-m scope clearly shows NSV 1436 can be faint, around 19th magnitude.

The big questions are - what percentage of the amateur measurements in the 16-mag range are contaminated by these companions, and what percentage of the time the variable actually spends in the 16-mag range vs. the 18-19 range?

Mike LMK

DSLR imaging NSV1436
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I already wanted to observe this star, but didn't remember the proper name. As I can recall Mike several times wrote about this star on the [AAVSO-DIS] list in the past. Thanx for informing us about the recent aboutburst. This morning I managed to make 10x30s images with my Canon EOS 1000D using a 300mm focus (zoom) telephoto lens. I'll process the images during the day.

Specify aperture size important here!
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I might suggest all CCD observers put their aperture size in the "comments" section of each set of observations of this star.  Also, whether or not the 17 mag companion 4"S was included or excluded.

(See attached finder chart).

This would be of immense help for the future analysis of the data of this star when it is in its low states.

Mike LMK

I'm going to hazard a guess,
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I'm going to hazard a guess, and that's that virtually all of the amateur CCD obs are contaminated with light from the two nearby stars.  I think the only way to get to the bottom of it is going to be by doing spectroscopy with a big telescope.  We don't really know what it does at minimum.  I'd guess it is an eclipsing cataclysmic variable, with the faint images we did with the UH 2.2m telescope taken during an eclipse.

Constraints on an eclipser
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Well, thats an interesting guess, Jim. However, does it fit the observations? We have been watching it fairly well over the past dozen years, and only in the last 2 years has it gone into regular ~monthly oubursts. Over the period from 2001-2010 no sign of it brighter than 16th mag, even though the coverage has not been dense enough to be certain there haven't been a few isolated bright outbursts.

But, assuming it had not shown any ouburst for ten years or more, it would imply: 1) A nearly edge-on orbit to our line of sight  2) the larger component would need to be big enough to completely obscure most of the accretion disk/hot spot  3) A long orbital period, where the hot spot stays hidden behind the larger star for a decade or longer.

I am not a physicist/expert on cv's but it would seem such a long orbital period would require the stars to be very far apart, and so there wouldn't be any way one could accrete from the other?

Mike LMK

I looked at the data in the
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I looked at the data in the AID, and personally, I think coverage is pretty spotty.  There are outbursts around the following JDs:

2416786
2424492
2432885
2455629 LMK
2455928 LMK
2456009 LTE
2456206 LTE
2456244 LMK

The later outbursts with the initials were detected by those visual observers, which apparently keyed the CCD crowd to to start observing.  Unless LMK and LTE are looking, coverage is fairly slim! 

The eclipser thing goes out the window, there's good time series stuff that would show an eclipse at any reasonable CV orbital period, and it's not there.  So barring some unusual configuration like a CV orbiting a third star, eclipses are out.  I think we need spectroscopy.

Jim

NSV 1436 in outburst
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I uploaded all 31 observation I made for this object today, but for some reason, the last 12 were omitted; the 12 that showed this star in outburst!  I'll try again latter to re-upload.

I made a note to myself to reshoot this field with 1x1 (unbinned) exposures.  At my image scale (0.76" per pixel) and focal length (2419mm) I can resolve NSV 1436 from the nearby 17th magnitude companions.  Of course this is assuming good seeing (<3")  and good tracking which is kinda a crap shoot since I'm usually not at the computer when I'm shooting autonomously.  Hope to pick-up on this variable again when the rain stops....rare event here in Southern California!

James

NSV 1436 Graph
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Here is a little graph of my observation for the variable.  My earlier problem with the "missing" 12 observation was due to an erroneous reference star being used.  This was corrected and re-submitted  successfully.  If I can get steady-guiding/good-seeing, I'll re-shoot all future observations of this obect with 150 sec. Vp exposures at 1x1 bin.  If the seeing and guiding cooperate, I can seperate NSV 1436 from the nearby 17th magnitude "companions."

Resolving the variable
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James, that's really excellent. If you can consistently resolve the variable alone over a period of time in your submitted observations, that would go a long ways towards determining its true minimum state. eg. Why and how often does it drop to v=19?

Mike LMK

Nsv 1436
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To Michael,

Yes I can can resolve it from the 17th magnitude double nearby, but only if I shoot at 1x1 bin and the seeing/guiding are good.  I'm sure i have contanmination from these nearby stars on my last observations (10-14Nov12) since I shot at 2x2 bin.  Rain has finally stopped in LA, so I'll be shooting NSV 1436 tonite 5 x 150 sec.'s 1x1 bin though the Vp filter guided.  

I'm doing the same exposure/binning for V452 Cas since its also very close to a dim star and has a range of brightness close to NSV 1436. 

James-FJQ 

NSV 1436 revised graph
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Here is another graph with the Bp data included from its recent outburst.  I haven't looked at last night's data, but NSV 1436 seemed to be in its "quiescent" phase more or less.

James-FJQ

Cv at all?
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Is it possible that this star is an EX Lupi type object? They show occasional, semi-regular eruptions.

Just a thought!

Maybe or not?
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Thats an interesting idea Michael.  Superficially, NSV 1436 and EX Lup have a resemblance. A long period of low state with about 2 mag variation, then a period of bright state, with 5-6 mags total range from max to min.

However, when I zoom in to EX Lup last bright outburst state in 2008, the light curve doesn't really resemble NSV 1436 so much. NSV 1436 exhibits regular short cv-like outbursts about on monthly schedule, but EX Lup seems to more or less stay bright with 1 mag variation after the bright state begins, slowly declineing back to the minimum state.

Of course, there could be variable behaviors between different EX Lupis too?

How about the spectra? That would be a big help to compare for some unique signatures of the EX Lupi stars.

Mike LMK

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