Magnetic field evolutionMagnetic field evolutionof neutron stars:of neutron stars:

linking magnetars and linking magnetars and antimagnetarsantimagnetars

Sergei PopovSergei Popov(SAI MSU)(SAI MSU)

(co-authors: A. Kaurov, A. Kaminker)PASA vol. 32, id.e018 (2015)

arXiv: 1504.03279

Pires et al. (2015)

NS birth rateNS birth rate

[Keane, Kramer 2008, arXiv: 0810.1512]

CCOsCCOs

Puppis ASee list in: 1301.2717

For three sources there are strong indications for large (>~100 msec) initial spin periods and low magnetic fields:1E 1207.4-5209 in PKS 1209-51/52,RX J0822-43 in Pup A andPSR J1852+0040 in Kesteven 79

Anti-magnetarsAnti-magnetarsStar marks the CCO in Kes 79(from 0911.0093)

Note, that there is no roomfor antimagnetars from thepoint of view of birthratein many studies of differentNS populations.

Further evolution of CCOsFurther evolution of CCOs

B

PSRs+Magnetars+Close-by coolersCCOs

1010 1012 B1011 1013

HMXBs

Among young isolated NSs about 1/3 can be related to CCOs.If they are anti-magnetars, then we can expect that 1/3 of NSsin HMXBs are also low-magnetized objects.They are expected to have short spin periods <1 sec.However, there are no many sources with such properties.

Possible solution: emergence of magnetic field (see Ho 2011).

Chashkina,Popov 2012

Popov et al. MNRAS 2010

Halpern, Gotthelf

Where are old CCOs?Where are old CCOs?

Yak

ovle

v, P

ethi

ck 2

004

According to cooling studies they have to be bright till at least 105 years.But there are no candidates in the solar vicinity.

We propose that a large set of data on HMXBs and cooling NSsis in favour of field emergence on the time scale 104 ≤ τ ≤ 105 years.

Some PSRs with thermal emission for which additional heating was proposedcan be descendants of CCOs with emerged field.

The final element for the GUNS?The final element for the GUNS?

Vigano, Pons 2012Bernal, Page, Lee 2013

The field is buried by fall-back, and then re-emerges on the scale ~104 yrs.

Emerged pulsars in the P-Pdot diagramEmerged pulsars in the P-Pdot diagram

Emerged pulsars are expected to haveP~0.1-0.5 secB~1011-1012 GNegative braking indices or at least n<2.About 20-40 of such objects are known.

Parameters of emerged PSRs: similar to “injected” PSRs (Vivekanand, Narayan, Ostriker).

The existence of significant fractionof “injected” pulsars formallydo not contradict recent pulsar current studies(Vranesevic, Melrose 2011).

Part of PSRs supposed to be born withlong (0.1-0.5 s) spin periods can bematured CCOs.

Espinoza et al. arXiv: 1109.2740

““Hidden” magnetarsHidden” magnetars

Kes 79

Halp

ern

, Gotth

elf 2

010

Kes 79. PSR J1852+0040. P~0.1 s

Shabaltas & Lai (2012) show that large pulse fraction of the NS in Kes 79 can be explained if its magnetic field in the crust is very strong:few ×1014 G.

• If submergence of the field happens rapidly, so the present day period represents the initial one• Then, the field of PSR 1852 was not enhanced via a dynamo mechanism• Detection of millisecond “hidden” magnetars will be a strong argument in favour of dynamo.

arXiv: 1307.3127

Magnetar burstsMagnetar bursts

Growing twistGrowing twist

(images from Mereghetti arXiv: 0804.0250)

Non-global twist modelNon-global twist model

1306.4335

What causes what?What causes what?The chicken or the egg? Crust or magnetosphere?

It would be nice to havemagnetars without crust,and magnetars withoutmagnetospheres.

Hypothetical highly magnetizedquark stars can be the first of them,and “frozen” (aka “hidden”) magnetars – can be testbedsto study crustal processes withoutmagnetospheric phenomena.

Crust of magnetosphere?Crust of magnetosphere?

Beloborodov, Levin 2014

Lander et al. 2014M

asa

da e

t al. 2

010

What triggers the burst?What provides energy?

How often do magnetars burst?How often do magnetars burst?

Perna, Pons 2011

Visibility of the thermal effectVisibility of the thermal effect

Pons, Rea 2012

If a NS has low quiescent luminosity, then an additional release ofthermal energy during an outburst can be well visible.If the luminosity was already high – then it is very difficultto observe an outburst.

What about Kes 79?What about Kes 79?

Halpern, Gotthelf 2010

Very stableflux for years!(see also Bogdanov 2014)

Why?

Always in a highstate? Or nearly no activity for years?

AXP CXO J010043.1-7211is known to haveconstant fluxfor a long time.

RCW 103 as a “hidden” magnetarRCW 103 as a “hidden” magnetarwith active crustwith active crust

De Luca et al. (2006)

• Fluxes• Temperatures• Variability• Pulse profile changes

Kes 79 looks very quiet, stable .... ...but RCW 103 – not.

Only thermal radiation!No traces of any kind ofmagnetospheric activity.

Let us model RCW103!Let us model RCW103!

Kaminker et al. 2014

Cartoon of the modelCartoon of the model

Photons and neutrinosPhotons and neutrinos

Kaminker et al. 2014

Mostly released heatis carried away by νs.

How bright it can be?How bright it can be?If we move the heating layer down (towards higherdensity) – then the surfaceemission is not stronglyenhanced.

It is shown, how muchbrighter a NS can beif we put the heatinglayer for 120 days.

Modeling RCW103Modeling RCW103

Calculations by A. Kaurov

Heating was on for 120 days.

Different curves correspond to different composition ofthe heat blanketing layer.

ConclusionsConclusions•Studies of “hidden” magnetars can be used to probe processes in the crust of strongly magnetized NSs.• Kes 79 looks very stable, which is strange for a “hidden” magnetar• RCW103 can be a ”hidden” magnetar, and its activity can be explained in this model.

A compact object in SN1987Acan be ``hidden’’ magnetar,as it was born soon after acoalescence (Morris, Podsiadlowski 2007)and strong fall-back has beenproposed to explain its properties(Chevalier 1989, Bernal et al. 2010).

PASA vol. 32, id.e018 (2015)arXiv: 1504.03279