Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S....
-
Upload
kelvin-hargrave -
Category
Documents
-
view
213 -
download
1
Transcript of Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S....
![Page 1: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/1.jpg)
Be born slow or die fast
Spin evolution of neutron stars with alignment and counteralignment
S. Eliseeva, S. Popov, V. Beskin
astro-ph/0611320
![Page 2: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/2.jpg)
Neutron star evolution: the main parameters
P, dot P, B, ………. χ
χ
The latter one is often ignored.
We revisit magneto-rotationalevolution of NSs taking intoaccount the evolution of theinclination angle using twomodels of spin-down:• magneto-dipole• longitudinal current losses
Our aim is to compare the standard assumptions made inNSs studies with theoreticalmodels and to analyse the obtained results.
![Page 3: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/3.jpg)
Evolution of the angle χ
We study magneto-rotational evolution of neutron stars taking into account evolution of the angle between spin and magnetic axis.
It is important that in both models, magneto-dipole and current losses,there are invariants:
Magneto-dipole losses Current losses
![Page 4: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/4.jpg)
Magneto-dipole losses
P0/cos
t1/2
P0
P
t
![Page 5: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/5.jpg)
Death line for mag-d. losses
log P
log P•
•••
••
•
•
••
••
•
Usually any possible dependenceof the death line on the inclinationangle is ignored.
![Page 6: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/6.jpg)
Lifetime as an active pulsar
This value significantly differs from the one without accounting for theevolution of the inclination angle.
![Page 7: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/7.jpg)
Braking index
All known nbr are smaller than 3
Name n P
J1842-0258 2.65 0.326
B9531+21 2.51 0.033
B1509-58 2.84 0.151
J1119-6127 2.91 0.408
B0540-69 2.14 0.050
B0833-45 1.4 0.089
(Livingstone et al. astro-ph/0601530)
There are many attempts to solve this problem (discs, internal structure, etc.)
![Page 8: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/8.jpg)
Age estimates for mag-d.
Pulsars faster becomealigned rotators thancross the death line.
For small initial periodsno significant spin-downis possible, unless the initial angle was very closeto 90 degrees.
Highly magnetized NSsreach the stage of aligned rotators very quickly.
![Page 9: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/9.jpg)
Longitudinal current losses
![Page 10: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/10.jpg)
Longitudinal current losses
cosi4 03
6420
2*
tot c
RBfW
t
P
P0
t14/13
P/sin
![Page 11: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/11.jpg)
Tracks on P-Pdot diagram
B=const, χ=const
B=const, χ≠const
Evolution with changing χ on the P-Pdot diagram issomehow similar to theevolution with decaying B.
![Page 12: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/12.jpg)
Death line for current losses
1
P
sin χ
(Beskin, Gurevich, Istomin 1993)
![Page 13: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/13.jpg)
Orthogonal rotators
See detailed explanation in (Beskin, Nokhrina 2004)
P
sin χ
![Page 14: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/14.jpg)
2/1
22
c
R
ccGJ BB
A3
6420
3*
tot i64
c
R
c
RBfW
dS ][[1tot BJr ScW
cj GJ||A /i Beskin, Gurevich & Istomin, JETP,1983, Beskin & Nokhrina, Astr. Lett, 2004
Orthogonal rotators: details
![Page 15: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/15.jpg)
Age estim. for current losses
Pulsars usually faster become orthogonal rotators than cross the deathline.
![Page 16: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/16.jpg)
Period distributions
37 active PSRs with τch > τkin 1523 active PSRs from the ATNF
![Page 17: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/17.jpg)
Inclination angle distribution
107 active PSRs (Rankin 1990)
43 active PSRs (Beskin et al. 1993)
![Page 18: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/18.jpg)
Initial periods
The initial periods areclose to the observed.
![Page 19: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/19.jpg)
Different neutron stars
HB-PSRs
SGRs
AXPs
The Mag. Seven
RRATs
![Page 20: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/20.jpg)
Age estimates
Accounting for the evolution of the inclination angle has a strong impactonto age estimates of NSs of different types.We give estimates of ages of neutron stars of different types fortwo models of energy losses: magneto-dipole and longitudinal currents.
![Page 21: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/21.jpg)
Age estimates and χmaxχmax corresponds to the moment when aNS leaves the stage of active PSRs.
With χmax we havelower age estimates.
![Page 22: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/22.jpg)
Evolutionary tracks
Arons(free)
RS(hindered)
Beskin, Eliseeva 2005
![Page 23: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/23.jpg)
Track reconstruction
We follow the procedure which we call “inverse track reconstruction”.Knowing the present-day period, angle χ, and the magnetic fieldwe reconstruct the track backwards in time.The procedures is done only for the current losses model.
![Page 24: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/24.jpg)
Track reconstruction
Time of evolution as an active PSR
Time of evolution as an extinct PSR
![Page 25: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/25.jpg)
XDINS RX J0720.4-3125
Pobs=8.39 sec
B=1014 G
Χobs = 50o
Pobs=8.39 sec
B=1013.5 G
Χobs = 50o
Pobs=8.39 sec
B=1013 G
Χobs = 50o
Τ ind = 1 Myr
![Page 26: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/26.jpg)
AXP 1E 2259+586
Pobs=6.98 sec
B=6 1013 G
Χobs = 70o
B=6 1013 G
Χobs = 85o
B=6 1013 G
Χobs = 80o
B=1014 G
Χobs = 85o
Τ ind = 0.01 Myr
![Page 27: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/27.jpg)
XDINS RX J0720.4-3125
Pobs=8.39 sec
B=1013 G
Χobs = 5o
Τ ind = 1 Myr
Pobs=8.39 sec
B=1014 G
Χobs = 5o
![Page 28: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/28.jpg)
Discussion: role of invariants
In both models we discussed quick evolution of NSs towards low losses is due to the existence of invariants.
Of course, the invariants exist only under specific ideal assumptions.
Even without changes in the electro-magnetic “sector” of models,there is a possibility that some non-EM mechanism (like thosediscussed by Macy 1974 or debris discs) are important.
Other possibilities can be related to debris discs (Menou et al. 2001)and vortex line migration (Ruderman).
![Page 29: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/29.jpg)
Discussion: particle escape
In the case of current losses information about distribution of χ behindthe death line can help to choose between free and hindered particle escape.
For free escape all NSs should have sin χ close to 1.However, it is necessary to be sure that significant evolution of theinclination angle took place.
![Page 30: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/30.jpg)
Discussion: AXPs and SGRs
AXPs and SGRs should be born with long periods, if any of the twomodels of energy losses is directly applicable.
Highly magnetized NSs are ideal to test models and to learn something about initial parameters:• Their magneto-rotational evolution is very rapid• There are estimates of their inclination angles (from X-ray light curves, for example)• There are independent age estimates
Observations show that highly magnetized NSs cover a widerange of χ.
![Page 31: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/31.jpg)
Discussion: population synthesis
The usual assumption is that sin χ = 1 = const Somehow, this can be applied also to the case of slowly varying χ, unless it is close to 0 (or 90 in the current losses model).
At the moment there is no theoretical reason to expect slowly varying χ. As we demonstrated,in both models χ varies on the same time scale as P.On the other hand, observational data do not requirestrong evolution of χ during PSR life.
So, assumptions of popsynthesis models are incontradiction with models of spin-down.
Even if both models of energy losses are not correct, the evolution of the inclination angle is a skeleton in a cupboard of popsynthesis models
![Page 32: Be born slow or die fast Spin evolution of neutron stars with alignment and counteralignment S. Eliseeva, S. Popov, V. Beskin astro-ph/0611320.](https://reader030.fdocument.pub/reader030/viewer/2022032517/56649cb85503460f9497f6ad/html5/thumbnails/32.jpg)
Summary
We demonstrate that direct application of both – magneto-dipole andcurrent losses – models of radio pulsars leads to absurd results, unlesssome specific assumptions are made:
• initial periods are close to the observed ones or• initial inclination angles are within 1 degree from maximum losses
Both options can be seriously criticized, and detailed population synthesiswhich takes into account the evolution of the inclination angle is necessary.
So, we conclude, that direct application of both models is inappropriate.However, the standard assumption is also not absolutely reliable.
We do not understand well enough how pulsars spin down