Remarkable white dwarf star possibly coldest, dimmest ever detected

Dne 25.6.2014 21:18, Yousuf Khan napsal(a):
On 25/06/2014 1:38 PM, Poutnik wrote:
In my understanding you need the 1.44 solar mass
for gravity to overcome electron degeneracy pressure
for gravity collapse
and gravity driven kernel - electron fusion.

I suppose there would be a big hysteresis in process reversal.
IMHO, there is not many NS below limit not because they are unstable,
but because there were more strict conditions for their creation.

Some references say the limit is 0.88-1.28 Solar mass.

http://arxiv.org/abs/astro-ph/0012321

Interesting, so you learn something new everyday. So that means at 0.88
solar masses, you may have some neutron stars that weigh less than some
white dwarfs.


Your original post mentions 1.2 SM pulsar,
what is less than maximum of 1.44 SM for dwarfs.

--
Poutnik

Wise man guards the words he says,
as they may speak about him more, than about the subject.

"Yousuf Khan" wrote in message

It's only 3000K in temperature, and possibly 11 billion years old (as
old as the Milky Way)! It was only detected because it was paired up
with a pulsar, which was the first thing detected in the system. They
then noticed some anomalies in the pulsar's timings, and then it was
clear that the pulsar must've had a companion.

The pulsar and the white dwarf are remarkably close in mass to each
other: the pulsar has 1.2 solar masses, while the dwarf has 1.05 solar
masses. The pulsar seems like it's on the low end of the mass scale
for
neutron stars (I always thought they had to be over the Chandrasekhar
Limit of 1.4), while the dwarf seems pretty massive for a dwarf.

http://www.astronomy.com/news/2014/0...-ever-detected

Yousuf Khan

If that 1.44 for is for a "new" neutron star, maybe after 11 billion
years it's radiated away some of its mass.

Mike

--
------------------------------------------------------------

Michael J. Strickland Reston, VA

------------------------------------------------------------

Dne 26.6.2014 2:11, Michael J. Strickland napsal(a):
"Yousuf Khan" wrote in message

It's only 3000K in temperature, and possibly 11 billion years old (as
old as the Milky Way)! It was only detected because it was paired up
with a pulsar, which was the first thing detected in the system. They
then noticed some anomalies in the pulsar's timings, and then it was
clear that the pulsar must've had a companion.

The pulsar and the white dwarf are remarkably close in mass to each
other: the pulsar has 1.2 solar masses, while the dwarf has 1.05 solar
masses. The pulsar seems like it's on the low end of the mass scale
for
neutron stars (I always thought they had to be over the Chandrasekhar
Limit of 1.4), while the dwarf seems pretty massive for a dwarf.

http://www.astronomy.com/news/2014/0...-ever-detected

Yousuf Khan

If that 1.44 for is for a "new" neutron star, maybe after 11 billion
years it's radiated away some of its mass.

Mike


Rather a white dwarf, passing CHS stability limit at 1.44 ,
does not end as 1.44 neutron star
after supernovae 1A explosion.

Part of mass is thrown to space.

The residual mass of neutron star may depends on,
if it is alone or part of binary system,
and on ration of masses and size of the partner.

Supernovas of class 2 can have different parameters
for neutron star creation, as the center of former star
is based rather on iron than on carbon and oxygen.

--
Poutnik

Wise man guards the words he says,
as they may speak about him more, than about the subject.

Poutnik wrote:
Dne 26.6.2014 2:11, Michael J. Strickland napsal(a):
"Yousuf Khan" wrote in message

It's only 3000K in temperature, and possibly 11 billion years old
(as old as the Milky Way)! It was only detected because it was
paired up with a pulsar, which was the first thing detected in the
system. They then noticed some anomalies in the pulsar's timings,
and then it was clear that the pulsar must've had a companion.

The pulsar and the white dwarf are remarkably close in mass to each
other: the pulsar has 1.2 solar masses, while the dwarf has 1.05
solar masses. The pulsar seems like it's on the low end of the mass
scale for
neutron stars (I always thought they had to be over the
Chandrasekhar Limit of 1.4), while the dwarf seems pretty massive
for a dwarf.

http://www.astronomy.com/news/2014/0...-ever-detected

Yousuf Khan

If that 1.44 for is for a "new" neutron star, maybe after 11 billion
years it's radiated away some of its mass.

Mike


Rather a white dwarf, passing CHS stability limit at 1.44 ,
does not end as 1.44 neutron star
after supernovae 1A explosion.

SNIa is due to the complete "deflagration" or rapid nuclear burning of a
carbon or carbon-oxygen white dwarf. It won't leave any sort of remnant
aside from an expanding cloud. Are you thinking of a Type II SN (core
collapse of a Pop I massive star)?


Part of mass is thrown to space.

The residual mass of neutron star may depends on,
if it is alone or part of binary system,
and on ration of masses and size of the partner.

Supernovas of class 2 can have different parameters
for neutron star creation, as the center of former star
is based rather on iron than on carbon and oxygen.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

On 06/26/2014 09:42 AM, Mike Dworetsky wrote:
Poutnik wrote:
Dne 26.6.2014 2:11, Michael J. Strickland napsal(a):


If that 1.44 for is for a "new" neutron star, maybe after 11 billion
years it's radiated away some of its mass.


Rather a white dwarf, passing CHS stability limit at 1.44 ,
does not end as 1.44 neutron star
after supernovae 1A explosion.

SNIa is due to the complete "deflagration" or rapid nuclear burning of a
carbon or carbon-oxygen white dwarf. It won't leave any sort of remnant
aside from an expanding cloud. Are you thinking of a Type II SN (core
collapse of a Pop I massive star)?

Rather I stay corrected here, this I did not know,
not being an expert.



Part of mass is thrown to space.

The residual mass of neutron star may depends on,
if it is alone or part of binary system,
and on ration of masses and size of the partner.

Type-II SN
I had in mind for the below.


Supernovas of class 2 can have different parameters
for neutron star creation, as the center of former star
is based rather on iron than on carbon and oxygen.



--
Poutnik

A wise man guards words he says,
as they may say about him more, than he says about the subject.

On Wednesday, June 25, 2014 8:28:10 AM UTC-7, Yousuf Khan wrote:
On 25/06/2014 10:09 AM, Brad Guth wrote:

And it's likely much older than 16 GY in order to be that cool. Otherwise, what cooled it off so quickly?



Perhaps the interactions with the pulsar's magnetic field? You've heard
of magnetic cooling, right?

Yousuf Khan

That's one possibility (aka theory). Where is this nearest magnetic PSR J2222-0137 pulsar item in relation to this white dwarf, or were there three white dwarfs as a trinary magnetic cooling process?

What came first; (the pulsar or the white dwarf)
http://pl.wikipedia.org/wiki/PSR_J2222-0137

Where did the WD heat go? (into the pulsar?)

On 25/06/2014 3:49 PM, Poutnik wrote:
Dne 25.6.2014 21:18, Yousuf Khan napsal(a):
On 25/06/2014 1:38 PM, Poutnik wrote:
In my understanding you need the 1.44 solar mass
for gravity to overcome electron degeneracy pressure
for gravity collapse
and gravity driven kernel - electron fusion.

I suppose there would be a big hysteresis in process reversal.
IMHO, there is not many NS below limit not because they are unstable,
but because there were more strict conditions for their creation.

Some references say the limit is 0.88-1.28 Solar mass.

http://arxiv.org/abs/astro-ph/0012321

Interesting, so you learn something new everyday. So that means at 0.88
solar masses, you may have some neutron stars that weigh less than some
white dwarfs.


Your original post mentions 1.2 SM pulsar,
what is less than maximum of 1.44 SM for dwarfs.

You're the one who mentioned neutron stars going from 0.88 to 1.28 solar
masses, therefore those would be all less than the 1.44 solar mass limit
for dwarfs.

Yousuf Khan

On 25/06/2014 8:11 PM, Michael J. Strickland wrote:
If that 1.44 for is for a "new" neutron star, maybe after 11 billion
years it's radiated away some of its mass.

Interesting theory. Radiating away 0.24 solar masses in 11 billion years
would make for an extremely bright pulsar, probably brighter than most
supernovas, if it was all done in photons. Of course, it may have
radiated it away in neutrinos, which would be much harder to detect. But
even if radiating it mostly in neutrinos, that would be a considerable
neutrino flux which we should be able to detect on Earth.

Yousuf Khan

On 25/06/2014 11:48 PM, Poutnik wrote:
Dne 26.6.2014 2:11, Michael J. Strickland napsal(a):
If that 1.44 for is for a "new" neutron star, maybe after 11 billion
years it's radiated away some of its mass.

Mike


Rather a white dwarf, passing CHS stability limit at 1.44 ,
does not end as 1.44 neutron star
after supernovae 1A explosion.

Part of mass is thrown to space.

In Type IA supernovas, it's not just a part of the mass that's thrown
into space, it's all of the mass that's thrown into space. There is no
core left behind at all in a Type IA. The white dwarf core is completely
obliterated after the supernova explosion, it doesn't get compacted into
a neutron star core.

However, neutron stars are created in Type Ib, Ic, & II supernovas. In
these types of supernova, the progenitor star is extremely massive so
perhaps the mass of the progenitor is enough to create enough pressure
to crush the core to neutron degeneracy. The core collapses in these
supernova, and then bounces back out, so perhaps the neutron star that
is left behind is simply what's left of the core minus any part of the
core that got bounced out. Afterall, it's the bounced out core material
that becomes the material of planets in subsequent solar systems, such
as carbon, oxygen, iron, etc.

Yousuf Khan

Dne 27.6.2014 6:29, Yousuf Khan napsal(a):
On 25/06/2014 3:49 PM, Poutnik wrote:
Dne 25.6.2014 21:18, Yousuf Khan napsal(a):
On 25/06/2014 1:38 PM, Poutnik wrote:

In my understanding you need the 1.44 solar mass
for gravity to overcome electron degeneracy pressure
for gravity collapse
and gravity driven kernel - electron fusion.

I suppose there would be a big hysteresis in process reversal.
IMHO, there is not many NS below limit not because they are unstable,
but because there were more strict conditions for their creation.

Some references say the limit is 0.88-1.28 Solar mass.

http://arxiv.org/abs/astro-ph/0012321

Interesting, so you learn something new everyday. So that means at 0.88
solar masses, you may have some neutron stars that weigh less than some
white dwarfs.


Your original post mentions 1.2 SM pulsar,
what is less than maximum of 1.44 SM for dwarfs.

You're the one who mentioned neutron stars going from 0.88 to 1.28 solar
masses, therefore those would be all less than the 1.44 solar mass limit
for dwarfs.

No. 0.88-1.28 is estimated lower limit.
Limit is not the same as range.

--
Poutnik

Wise man guards the words he says,
as they may speak about him more, than about the subject.