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[I81] C 8 observed

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#1 flt158

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Posted 31 October 2020 - 01:21 PM

Hello, everyone here who is interested in carbon stars. 

 

On Friday night 30th October 2020 I set up my Williams Optics 158 mm F/7 apochromatic refractor in my Bortle 9 back garden.

There was the problem of an almost Full Moon to contend with. 

Sunset occurred at 4.55 pm.

The air temperatures dropped from 4 degrees to 2 degrees Celsius during my time of observation.

But the sky was very clear and no wind between 5 and 7 pm over Dublin, Ireland. 

 

I very much required those conditions because the particular carbon star was going to prove a very faint one. 

You see, [I81] C 8 is seriously faint. 

Simbad says the magnitude is 11.5, and then adds the ~ symbol which suggests it is variable. 

My Guide 9.1 DVD gives 14.0. But I reckon neither of these sources have it fully correct. 

I agree 100% with our friends on AAVSO which state its magnitude is +12.9. 

[I81] C 8 is in Cassiopeia right next to TYC 4018 1946 whose magnitude is 11.5. 

[I81] C 8 is not a strong orange carbon star although it still has a spectral class of C.  

There is another orange star very close by which has the designation 3UC307-007505. 

Its magnitude is +12.3. 

Therefore if you have the desire to hunt down [I81] C 8, please be careful that you do see both stars. 

 

I know some of you like the designations which start with the letters GSC.

[I81] C 8 is also called GSC 04018-00410. 

The right ascension is: 00 hours 15 minutes and 01.46 seconds. 

The declination is +63 degrees 12 minutes and 09.8 seconds. 

 

Another question I was asking was: what does [I81] refer to or who?

Simbad helped out very well. 

It refers to Takashi Ichikawa who is a Japanese astronomer. 

I presume he is still alive and well.  

 

To successfully observe GSC 04018-00410 I had to use my most powerful eyepiece - a Radian 3 mm. 

It gives my scope 374X. 

But I have to state I only once saw this carbon star directly. 

I kept seeing it with averted vision and especially as I gave the scope very slight side to side movements. 

Still I am greatly relived to say I saw the star!

 

GSC 04018-00410 or [I81] C 8 is the 15th carbon star I have observed in Cassiopeia and my 92nd overall. 

 

Thank you for reading my latest report 

 

Comments, corrections and especially images are very welcome. 

 

Clear skies from Aubrey. 

 

 


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#2 Rich5567

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Posted 01 November 2020 - 04:14 AM

Hi Aubrey,

 

Great observation report there, you really like those red stars don't you,

 

Whats the plan, are you trying to reach 100 and then stop, or trying to see as many as your scope will show you?. Whatever it is it's a great little project.waytogo.gif.

 

If you like objets with a red tinge to then you should observe variables more, it may be right up your alley.

 

I've being lucky with clear skies at this end, with four clear nights this last week, I even manged last night for three hours before the rain came over. Haven't observed any doubles for a while, its being variables the last month or so.

 

Cheers,

 

Rich.


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#3 flt158

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Posted 01 November 2020 - 05:07 AM

Hello, Rich. 

 

It is very good to hear from you. 

I would love to reach 100 carbon stars before the end of 2020. 

But right now I do have the desire to seek out all the carbon stars in Cassiopeia which are available with my scope. 

There are quite a number of them still.

I don't know how many there are though. 

 

Most carbon stars appear orange to me and my apochromatic refractor. 

But some do have a slight redness also.

 

I find that I am settling on observing some variable stars and I do record their magnitudes on www.aavso.org

And I'm fine with that. 

 

Of course it is perfectly good for you to have a break from observing double stars for a while, Rich.

My next new double is going to be a double star with a carbon star companion. 

 

Therefore watch this space, Rich. 

 

Clear skies to you, 

 

Aubrey. 


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#4 chrysalis

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Posted 01 November 2020 - 05:12 AM

Hello, Rich. 

 

It is very good to hear from you. 

I would love to reach 100 carbon stars before the end of 2020. 

But right now I do have the desire to seek out all the carbon stars in Cassiopeia which are available with my scope. 

There are quite a number of them still.

I don't know how many there are though. 

 

Most carbon stars appear orange to me and my apochromatic refractor. 

But some do have a slight redness also.

 

I find that I am settling on observing some variable stars and I do record their magnitudes on www.aavso.org

And I'm fine with that. 

 

Of course it is perfectly good for you to have a break from observing double stars for a while, Rich.

My next new double is going to be a double star with a carbon star companion. 

 

Therefore watch this space, Rich. 

 

Clear skies to you, 

 

Aubrey. 

Hi Aubrey - see here for some. Excellent website. Links to Red Stars in CAS as well as the entry page (shorter string).

 

http://www.virtualco...on=CAS&order=ra

 

http://www.virtualcolony.com/sac/


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#5 flt158

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Posted 01 November 2020 - 06:47 AM

Hello, Mark. 

 

As usual I'm delighted to hear from you. waytogo.gif

Thank you for providing us all with those extraordinary lists of carbon stars.  

 

I must make sure I will get to observe each one of them - no matter how long it takes!  

 

Best regards from Aubrey. applause.gif



#6 Organic Astrochemist

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Posted 01 November 2020 - 04:30 PM

I think that if Aubrey wants to keep looking at the reddest stars, he should stick to the carbon stars, which are dependably red, some of the other red stars are giants and Miras that have variable magnitude and color.

In some respects carbon stars are a rather homogeneous group and that can be quite an advantage when comparing observations.

Consider this article and especially the table at the end which conveniently has both distance and bolometric absolute magnitude of carbon stars right next to each other.

https://arxiv.org/pdf/1911.09413.pdf

All the carbon stars roughly have the same bolometric magnitude Mbol ~ -5. So the closer ones should appear brighter and the farther ones should appear dimmer. Except the visible apparent magnitude will also depend on how much dust is around the star. So if you find two stars at roughly the same distance and one is much fainter than the other, it is likely because the fainter one is surrounded by much more dust.
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#7 flt158

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Posted 01 November 2020 - 05:35 PM

Thank you, Organic Astrochemist for your advice.

I am planning on sticking to the carbon stars for the foreseeable future alright. 

And many of us love to observe Mira from time to time. 

providing

I do fully realise that [I81] C 8 doesn't exactly stir the senses. 

I'm just glad to have said that I saw it. 

 

Simbad has helped me to locate other carbon stars in Cassiopeia.

Therefore I will have some more for you all.  

 

Organic Astrochemist, I would also like to thank you for providing that Astronomy & Astrophysics link. 

 

Can I ask you what does bolometric magnitude mean?

I can see in the 7th column from the left at the end. 

It's always good to learn something new. 

 

Thank you in advance, Aubrey. 



#8 Organic Astrochemist

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Posted 01 November 2020 - 08:27 PM

Hi Aubrey,
Bolometric magnitude is just a measure of the luminosity of a star at all wavelengths. So you can use that 7th column to see the total luminosity of the stars you have observed (more negative is brighter). The 6th column gives you the distance in parsecs.

I’m pretty curious, what are the five carbon stars that appeared the faintest to you? Do they all have roughly the same distance? Did they all have the roughly the same bolometric magnitude?

What about the five closest carbon stars; did any appear to you to be much dimmer than the rest? Did they all have roughly the same bolometric magnitude?

#9 flt158

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Posted 02 November 2020 - 09:14 AM

Hello, Organic Astrochemist. 

 

I thank you very much for explaining what bolometric magnitude is. 

I did Google the term last night and got the very same description as you did.

It just goes to show that the term luminosity is important. 

Robert Burnham give the luminosities of many stars in his Celestial Handbooks Volumes 1, 2 and 3. 

I see he lists the classes as Ia, Ib II, III, IV, V and VI - from most luminous supergiant down to Subdwarfs stars. 

I'm only saying this for those who are learning.

 

Now to answer your main question, Organic Astrochemist, 

I hope you don't mind if I keep to the faintest carbon stars I have observed in Cassiopeia. 

These are:

 

1. Case 271. 12.1 Mag. 

2. Case 270: 12.8 Mag. 

3. [I81} C 8: 12.9 Mag. 

 

In regards to distance: it was some time ago when I was given a mathematical formula in regards to the issue of distance here on Cloudy Nights. 

But I do very much remember the consternation I caused; and so I decided not to pursue it any further. 

I know it is to do with the Parallaxes figure on Simbad. 

I don't see a measurement Mbol on Simbad for any carbon stars. 

 

Of the brighter carbon stars in Cassiopeia, I have observed these four which I see on the Astronomy and Astrophysics link you provided above. 

Each one of them are variable of course. 

But they are all bright in the general sense. 

 

1. WZ Cas. D = 482.6 parsecs. Varies from 6.8 to 11.4 in magnitude. But it always seems to be bright when I observe it. Mbol: -4.83

2. V623 Cas. D = 556.2 parsecs. Its magnitude I did estimate at 7.8. Mbol:-4.61.  

3 WW Cas. D = 1065 parsecs. Its magnitude I did estimate at 9.7. Mbol: -4.99. 

4. X Cas. D = 1229.7 parsecs. Its magnitude I did estimate at 10.2. Mbol: -5.36. 

 

I take it these distances are reliable figures. 

 

Therefore there is very much some similarity on the issue of the bolometric magnitude of the brighter carbon stars.

 

So although it is not possible to give you all the details, please feel free to help us out with the fainter carbons. 

 

Very best regards to you, Organic Astrochemist. 

 

Aubrey.  



#10 Organic Astrochemist

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Posted 02 November 2020 - 04:05 PM

Thanks for your observations Aubrey.

With respect to the reliability of the distances (or the bolometric magnitudes), some level of the uncertainties Are provided in the paper, but in general I defer to those more knowledgeable than myself.

But I think it’s interesting that the four brightest carbon stars you saw in Cassiopeia had roughly the same bolometric magnitude. This likely suggests they are of similar masses, ages and luminosity. Not surprisingly WZ Cas and V623 Cas appear the brightest because they are the closest. WW Cas and X Cas appear dimmer because they are farther away.

The dimmest carbon stars in Cassiopeia that you have observed likely appear faint because they are far away, beyond 2 kpc (outside of the range of the paper).

It would be quite remarkable to see WZ Cas at mag 11.4 because it is so close and bright. It would have to be surrounded by a lot of dust to make it appear as faint as similar stars over three times as far away. But that is what carbon stars do and I am sure that you will find them doing it.
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#11 flt158

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Posted 02 November 2020 - 04:49 PM

I thank you very much indeed for your response, friend. 

 

Can I ask you for your Christian or first name? 

I'm sure it's far shorter than Organic Astrochemist. grin.gif

 

It's wonderful that I keep learning about such details, for example, bolometric magnitudes, luminosities and the distances of these extraordinary carbon stars.

How vast our Milky Way truly is! shocked.gif  

 

Those very dim carbons which I have observed must, as you say, be much farther away alright. 

 

Now in regards to WZ Cas. I have since visited www.aavso.org and some folk who are observing this carbon star have given magnitudes as high as +6.5 and as faint as +8.1 so far in 2020. 

So I very much doubt if anyone will see it as faint as +11.4. 

As you say, the star would need a serious amount of dust to occult the star's photosphere. 

 

I would be delighted to hear from others here on the Observational Astrophysics Forum who would observe these fascinating celestial bodies.

Even brief reports would suffice. 

I would most certainly read their account. 

 

And I am by no means getting near to finish observing them in Cassiopeia.  

 

Meteorologists are promising some clear and calm skies over Ireland over the next few nights. 

 

One friend has asked me to report on a double star whose companion is a carbon star in Cassiopeia. 

So I do plan to find it tomorrow night (Tuesday). 

 

And on that note, I wish you all clear skies, 

 

Aubrey.  



#12 Organic Astrochemist

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Posted 02 November 2020 - 10:53 PM

Hi Aubrey,
My name is Jim. flt158 is also not as sociable as Aubrey.

I use Sky Safari and Simbad for information about my observing targets. Unfortunately I think both of these don’t provide as reliable information about distances to carbon stars as the paper I cited. In general, I think the best distance information can be useful for observing. I agree that AAVSO is also a treasure.

There are some interesting stars in that list, some very bright, some very dim, some very near and some very far.
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#13 flt158

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Posted 03 November 2020 - 07:38 AM

Thank you, Jim!

 

It is my mother who saw the Aubrey on the TV. 

I believe the actor's name was Aubrey C. Smith. 

 

Please keep up the good work here on the Observational Astrophysics Forum, Jim. 

It's great to have you here as some of us are always willing to learn something new.

 

And I thank you also for pointing out that Sky Safari and Simbad don't provide reliable information in regards to the distances of carbon stars. 

It's good that you recognise that the Astronomy and Astrophysics paper is more reliable that either of those programmes. 

 

Isn't there i recent school of thought that astronomers are not sure what the distance of Betelgeuse (Alpha Orionis) is?

 

Very best regards and clear skies from Aubrey.  




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