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Double Stars with Variable Components

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#1 ssmith

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Posted 17 January 2020 - 11:19 AM

It seems that whenever someone has trouble viewing one or more of the components of a double star the possibility of the "Missing" component being variable is posited.  In all the cases that I can recall the missing component either had a incorrect visual magnitude listed or the listed magnitude was in the infrared range leading to the misinterpretation as to its ease of visibility.

 

I know of a couple of doubles where the primary is an algol type eclipsing variable but is anyone aware of a double star where a secondary component exhibits a significant change in magnitude - half a magnitude or more?  True binaries preferred.


Edited by ssmith, 17 January 2020 - 11:33 AM.

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#2 Astrojensen

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Posted 17 January 2020 - 11:30 AM

Mira is actually a double star, but it's currently very close. At the time of its discovery, it was around 0.9", but it has since closed noticeable and is now under 0.3", from what I can find. The companion is faint, and also irregularly variable, between mag 10 to 12. Since it's a close pair, it can only be observed with relatively large scopes and when Mira is at minimum.

 

I'm not sure this pair has ever been observed with an amateur telescope. 

 

 

Clear skies!

Thomas, Denmark


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#3 c2m2t

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Posted 17 January 2020 - 01:20 PM

Hi Steve!

I have to agree with you in that for the vast majority of the double/ multiple stars that I have observed/ imaged, variability is a rare characteristic. As you noted K band magnitude measurements/values are more often the issue and you know I have been caught on that one on several occasions...embarrassing when that happens. frown.gif smile.gif Something that is very beneficial...and I am curious as to how many of the participants on this forum make use of it, and that is the relatively new cabability in Stella Doppie...how many actually call up the 2MASS survey images to track down components that have been listed with K band stellar magnitudes? These 2MASS images can be quite revealing.

 

Cheers, Chris.



#4 OJS

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Posted 17 January 2020 - 05:06 PM

All the ones I know, except for Kruger 60, have A as the variable (WZ Cas, T Dra for e.g.). And K. 60 can be viewed for a lifetime and not see B in outburst. I'm going to scan the impressive list of doubles in 'Burnham's Celestial Handbook', as he has a column for magA and magB; so if B is variable(and say A is mag 3.4), he will have it: '3.4-Var.' Makes it easy to check. Maybe most Bs have insufficient mass to vary much? (I'm not a physicist, but I did stay in a Holiday Inn Express last night).


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#5 ssmith

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Posted 17 January 2020 - 08:06 PM

All carbon stars are variable - usually a 2 to 3 magnitude swing, sometimes more - but all the carbon doubles that I have come across are optical pairs (WZ Cass and T Draconis included).

 

Other cataloged doubles (all optical) that have a carbon primary are:

 

S Scuti  B 969

SV Cygni  BLL 45

UU Aurigae  BLL 17

V Hydrae  BU 1428

X Sagittae  BUP 203


Edited by ssmith, 17 January 2020 - 11:14 PM.

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#6 Rutilus

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Posted 19 January 2020 - 01:30 PM

What about the double star CE Cas.  Both components are Cepheid variables.

David Gray did excellent work here in the sketching forum.

https://www.cloudyni...riables-ce-cas/


Edited by Rutilus, 19 January 2020 - 01:32 PM.

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#7 ssmith

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Posted 19 January 2020 - 08:00 PM

Rutilus -

 

Thanks for the link to the thread on CE Cas - this is exactly the type of observation that I was looking for.

 

A search on CE Cas led me to a recent 2019 paper on Variable Pairs which is a goldmine of information and will take some time to digest.

 

Here is their summary of CE Cas  (CC = Classical Cepheid Variable):

 

"6.1.6. CE Cas AB

 

This visual binary is composed of two CCs, labeled components
A (P = 5.14 d) and B (P = 4.48 d). This is the only such configuration

known in the Milky Way. The projected separation of
the two stars is 7.2 kau, corresponding to an orbital period on
the order of 5000 years. CE Cas A and B are members of the
open cluster NGC 7790 (Majaess et al. 2013), together with the
Cepheid CF Cas (P = 4.875 d). The two components of CE Cas
are present in the GDR2, but with statistically different parallaxes

(Pi A = 0.317 ± 0.031 mas; Pi B = 0.262 ± 0.030 mas). From
their PM vectors, we confirm, however, that the two Cepheids are
gravitationally bound (Fig. A.1). The GDR2 parallax of component

B is likely biased, possibly due to light contamination from
the nearby component A. We did not find any additional resolved
candidate companions of CE Cas."


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#8 Rutilus

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Posted 20 January 2020 - 03:13 PM

I am adding CE Cas to my observing list. Observing an only known example in the Milky Way,

makes the pair kind of cool. I checked out the area  this evening with binoculars, looks like

it will be easy to find. Also it is very well placed in the sky from my location at the moment. 



#9 ssmith

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Posted 21 January 2020 - 09:09 AM

Here is a photo I took of CE Cass.  I  tried to do some photometry on my images but the images were too noisy and the results I was getting weren't correlating well with the field stars so I will try again later.  To my eye it appears that B is brighter than A at this point in time.  

 

NGC7709 LEO55 Cas C9 1-19-20 avg 4fr PCC NonLinear resample.jpg

 


Edited by ssmith, 21 January 2020 - 09:15 AM.

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