Comments on: XMM Newton Zeroes in on Zombie Star

By: Jon Hanford

Jon Hanford — Sat, 17 Jan 2009 17:06:20 +0000

Initially, I thought this object to have a Type Ia progenitor, a probable recurrent novae consisting of a white dwarf drawing matter off its' red giant companion & in the process spinning up the resultant neutron star & winding up its magnetic field as seen in magnetars. GBendt lays out the case that this object was probably a Type II event( subtype non-specified) which implies a 'core-collapse' event by a single star. No mention was made in the ESA press release as to the progenitors' type (Note that a Type II event can also spin-up a neuron star-magnetar)(Thanks GBendt). But nowhere can I pin down exactly what type of SN event produced this SGR-magnetar. Colliding WD-NS and NS-NS scenarios also can't be ruled out. So my question is what was the leading theory for the progenitor(s) of this enigmatic object?

By: Mr.Obvious

Mr.Obvious — Thu, 15 Jan 2009 16:54:31 +0000

If "unique" is defined (and there are many variations) as, "different from the status quo"… then adding a subjective adjective is fine. In this manner, it can be used by the author to communicate some excitement about the object or subject.

Really though… this is a informational site / WEBLOG. Which means it is an INFORMAL means of communication. If you are going to sit in front of your computer, with your ass so puckered up to the point you are going to judge and play "grammar police", I suggest you find someplace else to feed your insecurities and need to be more intelligent than others.

By: Astrofiend

Astrofiend — Thu, 15 Jan 2009 02:05:28 +0000

Silver Thread Says:
January 14th, 2009 at 3:20 pm

Yes Silver Thread – that is the basic principle. Conservation of Angular Momentum it's called.

By: Astrofiend

Astrofiend — Thu, 15 Jan 2009 02:03:47 +0000

# Pedant Says:
January 14th, 2009 at 9:40 am

'revealing it to be extremely unique and unusual'

There is no such thing as 'extremely unique'. Its either unique or it isn't.

>>>Your name says it all Pedant. I'm glad you realise it. Too bad nobody else cares.

By: Silver Thread

Silver Thread — Wed, 14 Jan 2009 22:20:11 +0000

Is the exceptional rotational velocity of a magnetar a result of the original rotational velocity of the star shedding excess mass in an explosion and there by increasing in speed by reducing it's circumference the same way an ice skater spins faster when she draws her arms in close while pirouetting?

By: robby

robby — Wed, 14 Jan 2009 20:39:20 +0000

Somewhat away from the subject, I thought a type 1a supernova was a white dwarf star that gathered enough matter from its companion it will explode like a super nuclear bomb when it neared critical mass of 1.44 solar mass, leaving no remnant. Yet, in 2006, the most powerful type 2 supernova
was observed, at least 100billion times the light,power of the sun, that no remnant was found, not even a black hole-this was at one time a super heavy mass star-perhaps this was one of the last of the modified early type super heavy mass stars the early universe
had, perhaps 300=1000 times the mass of the sun.I sure hope our galaxy don't have one of these super monsters!.

By: robby

robby — Wed, 14 Jan 2009 20:05:17 +0000

There's been so much learned in the period since the space telescope,other orbiting detectors and very large telescopes created. Before about 1990, most thought the universe was relatively quiet, now, there are so many violent events I was able to shut-up most of these wacko co-workers who believes in UFOs and 'aliens' among us when I tell them no amount of technology can overcome the gamma rays bursts,etc which is deadly to advanced life-forms. Perhaps there are many robotic probes roaming deep outer space, millions/billions of years after their living creators ceased to exist.

By: Jon Hanford

Jon Hanford — Wed, 14 Jan 2009 19:52:43 +0000

Hi GBendt, Thanks for your kind response regarding Type Ia and Type II SNe remnants. I take it that no superdense remnants (neutron, quark stars) are produced in Type Ia SN remnants? My initial impression was that millisecond pulsars in globular clusters were due to mass transfer between white dwarfs and red giants although initial conditions between such systems in globular clusters must be quite different than isolated WD-RG systems in interstellar space.Exactly what type of stellar systems are proposed to account for millisecond pulsars in globular clusters? I've read of WD-WD mergers or WD-NS mergers possibly being culprits in millisecond PSRs in globular clusters. Thanks for your thoughtful reply to my inquiry. Regards, Jon

By: Pedant

Pedant — Wed, 14 Jan 2009 16:40:02 +0000

'revealing it to be extremely unique and unusual'

There is no such thing as 'extremely unique'. Its either unique or it isn't.

By: GBendt

GBendt — Wed, 14 Jan 2009 09:05:38 +0000

Hi Jon,
Recurrent novae are close binary systems one partner of which is a White Dwarf, while the other is a Red Giant which fills up its roche volume. Then, mass from the Red Giant falls into the White Dwarf. Such, the mass of the White Dwarf grows, it gets a layer of hydrogen that is highly compressed by gravity and heated up by the infalling matter, and such every now and then nuclear fusion occurs which produces a nova event, again and again in millions of years. Finally, after many novae of that White Dwarf, its mass has grown beyond the chandrasekhar limit of 1,44 solar masses, and the White Dwarf explodes in a Ia supernova.
Pulsars are neutron stars which are the result of a type II supernova, where a very massive star collapses at the end of its life. Neutron stars have masses of two to three solar masses, they are much more smaller and much more denser than White Dwarfs. The fast spinning observed in neutron stars is a result of the conversation of momentum of the core of the progenitor star, not the result of the impact of matter from a partner star.
Pulsars are thought to create eruptions by stellar quakes, while recurrent novae create eruptions by nuclear fusion reactions on their surface. These two scenarios are very differnet one from the other, there is no likely link between the two.

Regards
Günther

By: Jon Hanford

Jon Hanford — Wed, 14 Jan 2009 01:21:41 +0000

After reading about Brad Schaefer's research on recurrent novae (RNe) posted Jan 12, I was curious to know if RNe that occur more frequently may lead to faster spinning, millisecond pulsars (precursors to SGRs and magnetars) due to the spin up effect of mass transfer between the white dwarf progenitor and its stellar companion. While other factors must surely come into play, I'm curious if any research may have been done looking for any link between frequency of of eruption of RNes and SGRs?