Spectral%20behaviour%20of%20the%20M7%20like%20NS

1
Spectral behaviour of the M7 like NS RX
J0720.4-3125
Markus Hohle Astrophysikalisches Institut und
Universitäts-Sternwarte, Jena Max-Planck-Institu
t für extraterrestrische Physik, Garching
Summer School, Dubna, July 2008
2
What are the M7?

• radio quiet
• isolated
• young
• nearby

Magnificent Seven
Motch et al. (2006)
3
RX J0720
distance 360 pc kT 86-95 eV X ray
period P8.3911s, 0.698
(Kaplan Kerkwijk et al., 2005/07) cyc p
(?) line 301 eV B field 2.4 or 5.6
G line EW, kT, radius long term period p(7.1
/- 0.5) yr (Haberl et al. 2006, Haberl 2007)
4
spectral parameters
Observations in ff thin filter (11 of 14
tot) May 2000 Nov 2007
abs. feature
5
spectral parameters
EPIC-pn, 2006
EPIC-pn ff thin, 2008
6
timing residuals
phase residualsperiod (7.7 /- 0.6) yr
consistent with that derived from former
spectral analysesHaberl (2007), Kaplan
Kerkweijk (2005) 120-1200eV
7
precession
phase residualsperiod (7.7 /- 0.6)
yr spectral variations period (7.1 /- 0.5) yr
8
precession

• - two hot spots and precession
• - small hot spot 1000 days
• - period 22000 days 25.5 yr
• - consistent with period from phase residuals !

9
timing residuals
hard 400-1000 eV soft 120-400 eV
using timing solution from Kaplan Kerkwijk
(2005)
two hot spots switch of phase lag
10
abs(sine) Kaplan Kerkwijk (2005) (10.694 /-
0.058)yr
abs(sine) Kaplan Kerkwijk (2005) linear
(11.504 /- 0.072)yr
abs(sine) Kerkwijk et al. (2007)
linear (10.530 /- 0.069)yr
11
timing residuals
12
timing solution
-hardness changes -phase lag between hard and
soft photons requires energy dependent timing
solution still precessing?
13
precession vs glitch

• dipolar magnetic field -gt hot spots Haberl et al.
  (2006) de Vries et al. (2004)
• -gt precession (RBS 1223) Schwope et al. (2005)
  -gt grav. waves
• no companion found Posselt et al. (2008,
  submitted)
• ISM
• Hohle et al. (will be submitted after Dubna)

14
Thank you very much!
RX J2143
RX J0720
RX J1605
RX J0806
RX J1308
RX J1856
RX J0420