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Fraser
2011-Dec-05, 11:20 PM
Located in the Large Magellanic Cloud, a star named VFTS 102 is spinning its heart out… Literally. Rotating at a mind-numbing speed of a million miles per hour (2 million kmph), this hot blue giant has reached the edge where centrifugal forces could tear it apart. It’s the fastest ever recorded – 300 times faster [...]

More... (http://www.universetoday.com/91579/incredible-spinning-star-rotates-at-a-million-miles-per-hour/)

Cougar
2011-Dec-06, 12:27 AM
Its possible that if the two stars were very close that streaming gases could have started the incredible rotation. Then the more massive of the pair blew its stack expelling the star into space.

Just to clarify, I don't think the explosion would do that much to impart much velocity to the companion star. If the two were in a pretty tight orbit, though, and one went supernova, with most of its mass essentially "disappearing" from the standpoint of the orbiting companion, then all the companion's orbital speed would turn into a linear speed, sending it off at a good clip. This should be able to be tested by tracing the companion's motion backwards to see if there's a supernova remnant back there.

But "streaming gases" would have been in the direction of the more massive star that went supernova, so I still don't see how this star's spinrate got so high....

PraedSt
2011-Dec-06, 10:09 AM
Perhaps the expanding debris hit the star at a tangent?

Trakar
2011-Dec-06, 06:17 PM
Just to clarify, I don't think the explosion would do that much to impart much velocity to the companion star. If the two were in a pretty tight orbit, though, and one went supernova, with most of its mass essentially "disappearing" from the standpoint of the orbiting companion, then all the companion's orbital speed would turn into a linear speed, sending it off at a good clip. This should be able to be tested by tracing the companion's motion backwards to see if there's a supernova remnant back there.

But "streaming gases" would have been in the direction of the more massive star that went supernova, so I still don't see how this star's spinrate got so high....

Why would streaming gases be going to the unstable larger star?

As the Larger star built up more layers and became less stable it was probably puffing out large amounts of its outermost layers. If this young blue giant was in a tight orbit (given its current velocity) It would have been sweeping up a lot of this blown off mass.

http://www.astronomycafe.net/qadir/q2954.html

http://www.spitzer.caltech.edu/news/1203-feature10-17-Giant-Star-Goes-Supernova-and-is-Smothered-by-its-Own-Dust

PraedSt
2011-Dec-06, 08:52 PM
I think Cougar was referring to the mass transfer that happens when one of the binaries grows beyond its Roche lobe, not the blowing off of layers.

Trakar
2011-Dec-07, 04:02 AM
I think Cougar was referring to the mass transfer that happens when one of the binaries grows beyond its Roche lobe, not the blowing off of layers.

But in a type II SN which is what that sounds like, it isn't the more massive star that gains mass , it is the white dwarf. Perhaps Cougar was just confusing different types of SN mechanisms?

PraedSt
2011-Dec-07, 12:15 PM
But in a type II SN which is what that sounds like, it isn't the more massive star that gains mass , it is the white dwarf.Aren't white dwarfs (dwarves?) type I? As I understand it, since this spinning star is big and blue, its exploding companion must have been born too massive to form a white dwarf.

So the primary probably evolved into a giant star before exploding, and the mass transfer might have happened both ways- throwing off layers like you suggested, and also Roche lobe transfer.

Trakar
2011-Dec-08, 12:55 AM
Aren't white dwarfs (dwarves?) type I?

quite right!

When speaking of binary stars and supernovae it is quite easy to get the terminologies conflated, which was my concern.

http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html



As I understand it, since this spinning star is big and blue, its exploding companion must have been born too massive to form a white dwarf.

not sure that the mass of the blue giant companion was relevent to the size of the earlier SN progenitor star, yeah, if it blew its lid, it was too big to puff off the outer layers and calm down into a more sedate White Dwarf retiree stage of existence. This doesn't mean that in the period before its detonation it didn't blow off some mass (ref. Eta Carinae - http://rst.gsfc.nasa.gov/Sect20/ETACARC.jpg)



So the primary probably evolved into a giant star before exploding, and the mass transfer might have happened both ways- throwing off layers like you suggested, and also Roche lobe transfer.

The young blue giant is pretty stable right now, and no real reason to think that it would have been loosing any mass to its partner. Its spin rate is the only reason to suspect that it was sipping its partner's mass. It's certainly possible, I guess, I just don't see any evidence in support of that supposition.

PraedSt
2011-Dec-08, 09:05 AM
Sorry, I think I was loose with my description. Just to clear up:

(1) I think there were originally two stars, A and B. B is the massive, spinning star in the article. A was the star that exploded.

(2) Because A exploded before B, and because more massive stars evolve quicker, I reckon A started off more massive than B.

(3) As far as I understand, stars that start off really massive, like A, never evolve into a white dwarf. They evolve into giant stars and eventually explode as a TII SN.

(4) In order to explain B's spin rate, mass transfer was unidirectional: A to B.

(5) This transfer could have happened by A throwing off mass &/or if A grew beyond its Roche lobe.

Hope that makes sense :)