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V1666 Cyg disappears

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mpr
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Hello,

V1666 Cyg is a SRA carbon star with a period of 376d and an amplitude of 10.9-12.9V. According to Alksne, Alksnis, Dzervitis: Properties of Galactic Carbon Stars, 1991 a secondary variability component exists. So far so good. My first observations around JD 2450490 till 2452200 matching good to this data.

Unfortunately I can not observe variable stars during the next years. Later I am starting again and try V1666 Cyg two times. But it seems that the star only shows slight variations. Therefore I was not sure whether I should start with V1666 agian or not.  

The third time I look at V1666 the variable was fainther as I ever has seen it. Therefore I put V1666 on my list again and was very surprised about what happens now. Please be aware by looking at my observations that I have used different sequences and look at my comments about the first minimum (was around 14mag).

So far so nice! But now V1666 Cyg was to faint for my instrument. I ask for help from someone who can carry one my observations to see how faint V1666 Cyg will get. A cart is available but only with comp. stars up to 14.4 mag.

Because V1666 Cyg is a carbon stars this behavior may is connected with some kind of dust shell like CW Leo or RW LMi. Maybe therefore V1666 Cyg is also interesting for spectral analysis.

Peter Maurer

 

 

 

 

V1666 Cyg sequence extended
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SXN
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Joined: 2010-03-12

Hi Peter,

The latest release of APASS reaches just to the east of this star, so I have extended the sequence into the 16th magnitude range with some overlap on the existing sequence which is much closer to the variable. Most of these new comps will be too far away for a typical CCD system, but a visual observer with a large aperture could use these to see if they can estimate V1666 Cyg.

Of course, with it being a carbon star, and very red visually, it may have faded beyond even what a visual observer with an 18-20" can see.

Mike

V1666 Cyg - check old observations against current sequence
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weo
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Hi Peter,

Your report on V1666 Cyg is very interesting! Would it be possible for you to compare your earlier observations made with a different sequence to the current sequence and convert them to values based on the new sequence? If you can do this, all your observations can be looked at together and we will better know what is happening. (if you are able to do this and want to update your observations with the revised magnitudes, please let me know and I will help you make the update.) Many thanks!

Good observing, Elizabeth Waagen

V1666 Cyg - revised magnitudes
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mpr
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Hi Elizabeth,

I think I can do. Should I edit them via WebObs (and mark them as new?) or should I give you the revised magnitudes?

Peter Maurer

 

V1666 Cyg - revised magnitudes
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Hi Peter,

Sorry for the delay in getting back to you. Regarding replacing your observations with new ones with revised magnitudes, the best way depends on how you have the data at home. If you have the data in electronic form at home, edit a file to upload using WebObs.  If you do not have the observations in electronic form, download your data from the AAVSO archive, edit the observations, and prepare a new file for uploading via WebObs. When you have your file of revised observations ready to upload, let me know.  I will remove your old observations, and then tell you when you may upload your revised file. If you have questions about any of this, just let me know.  Elizabeth

V1666 Cyg - revised magnitudes
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Hi Elizabeth,

because I have not to correct all observations is it not more simple I edit them via WebObs. I would let the early observations untouched. Also the brighter ones. Only the two first minima of the new observations must been corrected. For all other observations the difference will be around 0.1-0.2mag. Therefore within the accuracy of visual observations.

Peter Maurer

 

This underlines the
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This underlines the importance of keeping good observing records. I know the BAAVSS requires observers to submit the estimate (not just the comp stars used) along with the deduced mag, and I'd encourage us to do the same. Just think... if this had been done, you'd only need to bring up the historical estimate (say 123-3 127+1) and revise the deduced mag based on the new values for 123 and 127.

I have all my obs, together with estimates, from about 1987-95 but none after that. It'd be great if we could have a text field for the actual estimate. Too late now of course for historical estimates, but we'd have to start somewhere; and there's no time like the present. You'd only need an extra text field in the DB.

V1666 is at v=15.2 (plus a bad comp star!)
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Estimated with some difficulty visually, using the new seq far to the east (even beyond the fov of my Ethos ep :). Definitely fainter than the published range!

Important note: The 144 comp directly N of the variable is completely wrong. Its very faint, guestimated around 16th magnitude or a bit less. Is this a mis-ID, bad photometry, or is it clearly variable itself? I'll file a CHET report.

Mike LMK

V1666 Cyg - observations adapted
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First thanks to Thomas Lloyd Evans and Michael Linnolt for their observations. V1666 should be near minimum now. It will be interesting to see if he gets brighter again or more and more fainth.

I have adapted my observations to the better sequence. Now it looks very good to me. Estimates brighter than 11.7 are the same as before. The other estimates lowered the stronger the fainter the estimate was up to 0.7 mag.   

The 144 comp. star. May I was confused by the star more east? ~14.5 mag is what I can see under my conditions at clear nights.

Peter Maurer

 

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