Observing Carbon Stars

[pgc hunter]

Seeing as the moon was making its presence felt, I decided to try something different. I printed off a couple of lists of carbon stars with the intention of doing a carbon star hunt. I used the 10" GSo dob.

Seeing was shocking first thing in the evening, but improved just after midnight before going to hell once again.

At the end of the session, I discovered a bloody spider had set up shop inside the scope AGAIN, during the session. Bloody hell, it seems this scope is a spider magnet for some reason. Luckily there wasnt too many cobwebs and I could easily remove it.

Kaptyen's Star, mag 8.9
This star didn't show any ruddy hue whatsoever.

R Doradus, mag 5.5
Nice and bright, deep orange in colour.

TW Horologium, mag 5.7
Similar brightness to R Doradus, but the colour is not as intense.

NP Puppis, mag 6.3
Appears to be about mid-way between TW Horolgium and R Doradus in terms of its colour intensity and is slightly fainter.

Y Hydra, mag 6.6
An impressive example, this is a deeper orange than R Doradus.

V hydra, mag 6.8
Now this is an impressive sight! Very deep orange, bordering on actual red I'd say, it is certainly redder than X Tra and comes close to DY Crucis, but is 2 magnitudes brighter and there is no bright star nearby to overpower it.

UY Centauri, mag 7.0
Another impressivly coloured star, this one is similar to Y Hydra. A fainter blue star lies just to the SE, creating a nic contrast.

[ngcles]

Hi PGC & All,



Not completely surprising at that magnitude in this aperture but the main reason is that Kapteyn's star isn't a Carbon star -- but is an extremely interesting star in almost all other respects. It is one of the closest stars just under 13ly distant and has the 2nd highest proper-motion of any known star. Only Barnard's star exceeds it.

It is a M0 sub-dwarf star that is the closest "halo-star" to the Sun -- it is not a member of the Milky Way's disc. The reason why it has such a high proper-motion is because it is swimming backwards around the Milky Way (in the opposite direction to the Sun) -- contrary to the motion of the vast majority of stars.

You can read a bit about it here:

http://www.solstation.com/stars/kapteyns.htm

A very interesting star, but not a Carbon Star.


Best,

Les D

[astroron]

Thanks for the link Les, I have observed this star in the past as well as Barnard's.:thumbsup:

[Liz]

Thanks for those obs, PGC, will add to my data, for when things dry out a bit up here, and I can start observing again ;)

[goober]

Nice report! Getting the old scope itch back...

[ngcles]

Hi PGC & All,



Actually just on this I'm pretty sure (please corect me if wrong) but I don't think R Dor is a Carbon star either. It is a very cool and late spectral type Mira star but not a Carbon star. The Spectra is M8 III -- 'bout as cool as you can get in "normal" stars.

R Dor is as a matter of interest one of the brightest things in the sky in the near infra-red. If our eyes could see in either K or J band (1.25 and 2.2 mircometres respectively) R Dor would outshine nearly everything else. In these two bands it would be either the third or second brightest star in the sky at a whopping magnitude -2.6 (Jupiter's brightness) in J-band or in K-band mag -4.2 = :eyepop: Only a little dimmer than Venus.

Check out this table:

http://spider.ipac.caltech.edu/staff/nelson/2mass/brtstar/davystars.txt

To see the brightest stars in the sky in visual light, J and K-band. Very interesting indeed.

Of this list V Hydrae is probably the "best" -- as you have found. Except for Kapteyn's star (discussed previously) all are Mira or pseudo-Mira, or semi-regular type long-period variable stars.

So, you've taken the time to find these, why not then become a variable star observer while you're at it?


Best,

Les D

[pgc hunter]

G'day Les,

I had an inkling that Kaptyen's wasn't any form of red star as it didnt show any colour at all. I got these off a list from the Carbon Stars thread, so that's why I thought that these are actual carbon stars. That is an interesting link, it really makes our little ol' visiual wavelength look pathetic! The sky would be a mighty impressive sight in the K-band!

I'm not interested in variable stars, my forte is galaxies and planetary nebulae.

Is there a list of "real" carbon stars, i.e. stars that are actually red?

cheers

[Coen]

Can not remember which web-site I got this from, see attachment.

Look for the N stars section (second one). It is northern hemisphere dominated.

[pgc hunter]

Cool thanks!

it says that V Hydra is the "reddest known"! I still think DY Crucis is redder than V Hydra. DY is an actual blood red, whereas V Hydra is a very deep orange.

[Coen]

You could also google "carbon star list" to get:

http://www.aho.ch/pilotplanets/files/carbonred1.htm

http://www.astrosurf.com/buil/us/peculiar2/carbon.htm

http://www.nckas.org/carbonstars/

[ngcles]

Hi PGC & All,

Off hand, I don't know where you'd find a dedicated list of Carbon stars but I'll have a poke round and see what I can find some time soon. One place to start a search is via SIMBAD.

http://simbad.u-strasbg.fr/simbad/sim-fid

Do a search on a prominent carbon star (say V Hydrae) and somewhere in the list of references they supply will be a paper that will refer to this star within a list of other similar stars. Just keep poking around in SIMBAD and you come up with something.

BTW, have I mentioned here before how much I hate the SIMBAD interface ...

I know what you mean about PNe and galaxies -- -- I love 'em too. Peter Wiliams tried long and hard to convert me to the "dark side" but I just didn't have it in me ... at that time. Who knows what's down the track though?

Many moons ago, I used to write the deep-sky column for the SASI (Sutherland Astronomical Society) journal and Peter wrote (still writes sometimes) the Variable suff for the same club rag. He'd sometimes shadow what I written the previous edition and point out all the "really interesting variable stars" that were in the same or adjacent fields to the "really boring deep sky objects" I'd written about in the preceding issue.


Best,

Les D

[Coen]

A quick look at Vizer/Simbad and putting Carbon Star into the query gives a number of catalogues with Carbon Star details.

http://vizier.u-strasbg.fr/viz-bin/VizieR-2

CdC also has a carbon star catalogue for it. If you have CdC (Skychart) then you can install and have a look - I do find CdC hard to interact with at times though.

[pgc hunter]

thanks guys. Those lists will keep me occupied for the next few full moons :)

BTW, many sources say that V Hydra is the reddest star known. But to my eyes, DY Crucis is an actual blood red, whereas V Hydra is more of a very deep orange. Does the contrast between it and the bright blue Mimosa make DY appear redder than it really is?

[Lismore Bloke]

Does this link help???


http://www.astr.lu.lv/CGCS/cgcs.htm