Magnetars in Binaries - ISDC, Data Centre for Astrophysics€¦ · Magnetar activity in 1E...
Transcript of Magnetars in Binaries - ISDC, Data Centre for Astrophysics€¦ · Magnetar activity in 1E...
Magnetars in Binaries
Wei Wang
National Astronomical Observatories, China
High Throughput X-ray Astronomy in the eXTP Era conference
Rome, Feb 6-8 2017
Contents
• Magnetar family: isolated magentars (AXP & SGR); accreting magnetars in binaries
• Superslow pulsation X-ray pulsars
• Super-luminous X-ray pulsars: extragalactic magnetars
• Prospects for eXTP
Pulsar FamilyAnomalous X-ray pulsars(AXPs) & Soft gamma
repeaters (SGRs)
Millisecond pulsars
Radio young pulsars
Observed characteristics of AXPs and SGRs
• Pspin = 2 – 12 sec
• period derivatives: 10-14 – 10-10 s/s
• Dipole magnetic field: 1013 – 1015 G
• They have a persistent X-ray luminosity (1033-1035 erg/s) higher than their spin-down power – different from other pulsars!
• X-ray Bursts/flares are detected:
luminosity > 1037 erg/s
giant bursts Lx > 1042 erg/s
• No companion
• Magnetic field provides energy
• Isolated magnetars !
Pulsar populations
single binary
MSPs
Young pulsars
magnetars
LMXBs
HMXBsAccreting magnetars
?
Magnetars in binaries:accreting magnetars
• Superslow pulsation X-ray pulsars (Pspin>1000 s)
• Super-luminous X-ray pulsars :
extragalactic magnetars
• Neutron stars in high-mass X-ray binaries:
Be X-ray transients
(main-sequence companion star)
Supergiant binaries
(supergiant companion)
Corbet diagram
Pspin ≈0.1 - 1000 sec
The Pspin- Porbit diagram for Superslow X-ray pulsars in HMXBs
Recently some very slowly pulsation neutron stars are discovered in some binaries: Pspin>1000 s !
2S 0114+65 : 9700 s(Wang 2011)
4U 2206+54 : 5560 s
SXP 1062: 1062 sX-ray transient (Haberl et al. 2012)
(Wang 2009;Wang 2010;Wang 2013)
Spin-up trend of 2S 0114+65 from 1986 - 2008
6.2x10-7 s s-1
8.9x 10-7 s s-1
1.06x 10-6 s s-1
Spin-up trend seems acceleratingin last 20 years
Wang 2011
Fast spin period evolution of these pulsars:
Spin-down trend of 4U 2206+54 in last 20 years
Average Spin–down rate of 5x10-7 s s-1
(Wang 2012,2013; Reig et al. 2012)
Phase-shift method finds the spin-down behavior in haft year in 4U 2206+54 (2006 May -Dec): \dot P ~ (6± 2)x10-7 s s-1
Be X transient SXP 1062• Located in the Small Magellanic Cloud, associated with a SNR ( 2-4x104 yr)
• A large spin-down rate of 3x10-6 s/s during an outburst in 2010.
Haberl et al. 2012
From 2010-2012average rate:~ 10-7 s/s
Sturn et al. 2013
• 1E 1613.48−5055 in a young supernova remnant RCW 103 (Central Compact Object, CCO)
P = 6.67 hours
(single or binary?)
Other candidates of superslow pulsation pulsars
Magnetar activity in 1E 1613.48−5055
2016 June 22
Rea et al. 2016D’Ai et al. 2016
CCO in RCW 103 should be a magnetar!
Possible picture:Fall-back accretion after the supernova explosion (Tong, Wang, + 2016 ApJ)
Origin of spin period in X-ray pulsarsStandard evolution of neutron star binaries:a) ejector state: spin-down like radio pulsars;b) propeller state: spin-down by interaction between magnetosphere
and stellar winds;c) accretor state: Pspin reaches a critical value; switch on as X-ray
pulsars as observed.
(Pringle & Rees 1972 Ghosh & Lamb 1978)
The maximum spin period which can be reached in different observed conditions (magnetic field; accretion rate) : from several seconds up to near 1000 s.Then what channels produce the long spin period higher 1000 s ? It is a key question we need understand here.
Why special for superslow pulsation X-ray pulsars?
What is physical origin for long spin period?
• Li & van den Heuvel (1999): born as a magnetar with B>1014 G, allow for the neutron star to spin down slower than 1000 s in Myrs, and field decays to 1012 G at present (difficulty in time scales)
• Ikhsanov (2007): a phase “subsonic propeller” between the transition from known supersonic propeller state to accretorstate would allow for the long spin period :
Applying the above formulae to the case of 4U 2206+54/2S 0114+65, one derives the magnetic field of higher than ~ 1014 G!
Alternative approaches:• Spin-down rate in accreting state in standard model
(Lipunov 1992)
• Recently , a new theory of quasi-spherical accretion for X-ray pulsars is developed (Shakura et al. 2012):the magnetic field in wind-fed neutron star systems is given by
However, with both approaches we still find the derived magnetic field of
> 1014 G for 4U 2206+54; SXP 1062; 2S 0114+65
These super-slow pulsation pulsars then are defined as accreting magnetars.
2. Ultra-luminous X-ray sources (ULXs)
M31 X-rays
ULXs : X-ray luminosity > 1039 erg/s(1) intermediate mass BH 100-1000 M⊙;(2) 10 M⊙ BH and jet effect
A neutron star discovered in a ULX in M82
NuStar found a pulsation of 1.37 s in X-ray toward M82 X-2(Bachetti et al. 2014) .
Lx ~ 1040 erg/s; Orbital period: 2.5 day Neutron star mass 1.4 M⊙; Ledd~ 1038 erg/sRequiring an ultra-strong magnetic field >1014 G to produce high X-ray luminosity
• ULX NGC 7793 P13: (Furst et al. 2016)
P=0.42 s, Lx =1040 erg/sspin-up: \dot P= -2x10-11 s/s
• ULX-1 in NGC 5907: (Israel et al. 2016)
P=1.43 (2003), P=1.13 (2014) ( \dot P= -8x10-10 s/s )Lx=1041 erg/s (500*LEdd)
• Strong multipolar magnetic field (similar to magnetars) needed
• Many ULXs may harbor neutron stars – super-luminous X-ray pulsars – extragalactic accreting magnetars
Ultra-luminous X-ray bursts NGC 4636 d=14 Mpc (Irwin et al. 2016)
Lx ~ 1039 -1040 erg/s; durations ~ 1 hr; rise time <1 min
Origins: X-ray flares in magnetars (similar to observed flares in AXP and SGR)? - extragalactic magnetars?
Magnetar studies in binaries with eXTP
• Magnetars: AXP/SGR
powered by magnetic energy
• Accreting magnetar candidates powered by accretion not magnetic energy:
• Identifying a real magnetar in accreting systems requires –
searching for features of magnetar activities :
X-ray bursts
accreting neutron stars with high dipole magnetic field
Science goals
• Find more candidates with WFM
• Detect X-ray bursts in accretion magnetar systems with WFM
• Timing: spin evolution of accretion magnetars, QPOs
• Precise spectral measurements to find cyclotron absorption lines with LAD and SFA
• Better X-ray spectra and timing for ULX pulsars /bursts with LAD and SFA: weak sources (1-10x10-12
erg/cm2/s, 0.5-10keV)
– search for extragalactic magnetars
Thank you for your attention!