I.F.Malov

1
Do magnetars really exist?
I.F.Malov Pushchino Radio Astronomy Observatory,
Lebedev Physical Institute RUSSIA malov_at_prao.ru
AXPs and SGRs
Magnetars
The cyclotron instability causes the generation
of transverse waves at the frequency 4
?B3 ?p3 ? , ?p2 ?b where
e B
8 p np e2 ?B is the cyclotron
frequency, ?p m c

m plasma frequency , ?p Lorentz-factor of the
secondary plasma, ?b Lorentz-factor of the
primary beam.
What the word magnetar means ? 1) Is the
supercritical dipole magnetic field ? But
magnetic field of SGR 04185729 is less than 7.5
x 1012 G 2)Is the bursting behaviour? Normal
pulsars have the burst components and giant
pulses. 3) Is the low rotational power with
respect to their X-ray luminosity? The young
pulsar PSR J1846-0258 in the SNR Kes 75 (t 884
years), P 326 msec show X-ray bursts, similar
to ???s and SGRs. However its X-ray luminosity Lx
4.1 x 1034 erg/sec can be provided by the
losses of the rotation energy dE/dt 8.1x1036
erg/sec. 4) Is the black body plus power-law
X-ray spectrum? Normal radio pulsars emit thermal
and non-thermal radiation outside the radio
range. 5) Is the erratic radio pulse behaviour?
Individual pulses of radio pulsars have different
forms and spectra. So, there is no one criterion
defining the magnetar type.
The oscillating behaviour of the angle between
the axis of the emission cone and the line of
sight
The distance of generation of radio waves r
r e2 Bs2 ?p4 P
r ( ) 1 / 6
1,76 103 ?8 -1/6
R 2p2 m2 c2 ?b 2 ?
R is
of order of the light cylinder radius. The
increment of the cyclotron instability
p ? 2?p res ??
????? ?
?T 2 p e Bs ?b ( R / r )3
??t ?????????? ?2 ( R / r )3 ? -1
m c P ? ?T ?t gives
the amplification of waves with
dr 3 ?2 R3 t ? ? ??
?????? 62.6 ?8 -1
c 8 ? rLC2 ? This amplification
must be effective at low frequencies. So, we must
expect high fluxes at ? 100 MHz and much less
at ? gtgt ?.

Energy of a giant burst must be equal to magnetic
energy B2 4 p R03 B2
R03 1046 erg
8 p 3 6 It is
necessary to draw through the crust a sphere with
R0 1 km, i.e. 0.1 R if an efficiency of
transformation of magnetic energy to radiation is
100 . Such an event must cause some catastrofic
changes in the neutron star. There are no
observational evidences of these changes.
Drift waves
For this model the angle ß between the rotation
axis and the magnetic moment must be small.
Indeed our calculations have shown that in PSR
J1642-4950 ß 150. 6, in AXP J1810-197 and 1E
1547.0-5408 ß lt 200.
(dPdr/dt)-11
?(sec)8.32x10-2 2/5 ,
(Lx)34 (W/Pdr)2 Pdr ƒpl
   P (dPdr/dt)
dP/dt ,
2 Pdr  
B (G) 22.45 Pdr/?2
CONCLUSIONS

1) There is no one criterion defining the
magnetar type. The answer the question in
the title must be negative, as we believe.
2) The detection of SGR 04185729 with magnetic
field of order of 7.5 x 1012 G gives birth doubts
on the supercritical magnetic fields as the main
peculiarity of ???s and SGRs. 3) It is not enough
to have magnetic fields 1016 G to provide bursts
with energies 1046 erg. 4) The angle between
magnetic and rotation axes in ??? PSR J1642-4950
is equal to 150.6. This gives the possibility to
use the drift model for the description of
AXPs. 5) In the frames of this model parameters
of PSR J1642-4950 are the rotation period ?
0.32 sec, the strength of magnetic field in the
region of generation of observed emission ? 950
G and at the surface of the neutron star Bs
3.39 x 1012 G. 6) It is shown that the cyclotron
instability near the light cylinder of the PSR
J1642-4950 can cause the generation of radio
radiation. This radiation must be located in the
narrow laye near the light cylindrr and the flux
at low frequences ( 100 MHz) is expected much
more intense than at higher frequences.
In the frame of the drift model we estimate the
rotation period ? 0.32 sec, dP/dt 6.29 x
10-13 , logBs 12.53 for PSR J1642-4950.
The geometry of the magnetosphere considered