L dwarfs stars

View previous topic View next topic Go down

L dwarfs stars

Post by Stalker on 24th January 2010, 9:52 am

Hi

I have a small question.

After their formation, the brown and red dwarfs have spectre M. I know that the brown dwarfs become cold and evolve in brown dwarfs L, T, Y...

But why some red dwarfs become L? The temperature of the stars of main sequence must go up with time, and not go down. The red dwarfs do not seem to make exception, since at the end when some dozens one thousand one million years when they evolve in blue dwarfs (in theory).

I also hope for a paper on the dwarfs L, it would be very interessant.

Thank you.
avatar
Stalker
Jovian
Jovian

Number of posts : 526
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: L dwarfs stars

Post by Sirius_Alpha on 24th January 2010, 11:18 am

L, T, and Y dwarfs are sub-stellar, and do not undergo the process of nuclear fusion of hydrogen into helium that main-sequence stars do. As such, their thermal evolution is different.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3484
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: L dwarfs stars

Post by Stalker on 24th January 2010, 11:43 am

The primary component of 2M0746 is a L red dwarf star with 0,085 M_Sol and the secondary is a pulsating L brown dwarf (radio pulsating) with 0,06 M_Sol.

http://www.eso.org/public/news/eso0420/

VB 10:
-mass:0,0779 M_Sol;
-age:~10^9 years;
-temperature: 2600K

2M0746A:
-mass:0,085 M_Sol;
-age:~0,5-1x10^9 years;
--temperature:1800 K

WTF???
avatar
Stalker
Jovian
Jovian

Number of posts : 526
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: L dwarfs stars

Post by marasama on 10th March 2010, 3:58 am

Sirius_Alpha wrote:L, T, and Y dwarfs are sub-stellar
That is incorrect.

L dwarfs house both stars and brown dwarfs.
T dwarfs so far, only house brown dwarfs
Y dwarfs so far, do not exist as none has been found yet (good candidates, but not proven).
http://en.wikipedia.org/wiki/Stellar_classification
http://en.wikipedia.org/wiki/Stellar_classification#Class_L

_________________
Thanks,
CarpD (^_^)
avatar
marasama
SuperEarth
SuperEarth

Number of posts : 212
Location : Earth
Registration date : 2008-04-22

View user profile

Back to top Go down

Re: L dwarfs stars

Post by Sirius_Alpha on 10th March 2010, 7:55 am

Oh, interesting. Thanks for the correction. Smile

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3484
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: L dwarfs stars

Post by Stalker on 10th March 2010, 2:33 pm

In a small sentence in an article about brown dwarfs and small red dwarf, and i remember that the "ultracool stars", the L stellar dwarfs are unable to fuse lithium, but able to fuse hydrogène after the L periode...

Edit:Wrong


Last edited by Stalker on 25th March 2010, 2:42 am; edited 1 time in total
avatar
Stalker
Jovian
Jovian

Number of posts : 526
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: L dwarfs stars

Post by marasama on 10th March 2010, 6:14 pm

I think that was an error. Back when L Dwarfs were assumed L stood for Lithium on the internet.

The correct thing is that L dwarf stars burn all their lithium and no lithium is detected.
While an L brown dwarf does not fuse lithium and thus lithium exist in the atmosphere.
Hence the term, "Lithium Test".
http://en.wikipedia.org/wiki/Brown_dwarf#History
Search for the word "Lithium Test" and you will see the explaination.

As for Ultracool Dwarfs, I am not sure if that proposed name became a term. I can't remember what astronomer did that term. It's in an AJ paper.
However, 2MUCD is associated to the Ultracool Dwarf term.
As 2MUCD = 2MASS UltraCool Dwarf.

_________________
Thanks,
CarpD (^_^)
avatar
marasama
SuperEarth
SuperEarth

Number of posts : 212
Location : Earth
Registration date : 2008-04-22

View user profile

Back to top Go down

Re: L dwarfs stars

Post by Stalker on 11th March 2010, 8:09 am

I don't understand. The ultracool stars and L brown dwarfs should follow the same evolution up to the ignition of the hydrogen. It is proved that the hydrogen burning limit binary L dwarfs show very close temperatures between them.

The temperature of ignition of the lithium is very close to the temperature of ignition of the hydrogen. About its mass is, a star should not have the time to get colder between the stage of lithium and the beginning of main sequence. And even if it's case, impossible to have the same temperature as a brown dwarf of the same age, because energy was fabricated by lithium burning. If episode " L " is intercalated between the stage of fusion of the deuterium and lithium, it is in keeping with observations.

Logically the test of the Lithium should not exist for the L dwarfs.
avatar
Stalker
Jovian
Jovian

Number of posts : 526
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: L dwarfs stars

Post by Stalker on 24th March 2010, 2:38 pm

Theory of Low-Mass Stars and Substellar Objects

The Lithium test cannot make the difference between a young star (deuterium burning or ultracool) and a brown dwarf because young stars doesn't yet destroyed Lithium. And it cannot make the difference between a star and a very massive brown dwarf (between 0,06 and 0,07M_Sol) because it is hot and compact enough to destroy lithium.
avatar
Stalker
Jovian
Jovian

Number of posts : 526
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: L dwarfs stars

Post by Sirius_Alpha on 24th March 2010, 3:07 pm

Interesting. I never knew that Surprised

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3484
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: L dwarfs stars

Post by Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum