1. Spectral behaviour of the M7 like NS RX J0720.4-3125
Markus Hohle
Astrophysikalisches Institut und Universitäts-Sternwarte, Jena
&
Max-Planck-Institut 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 : eV
X ray period : P=8.3911s, =0.698
(Kaplan & Kerkwijk et al., 2005/07)
cyc p+ (?) line : 301 eV
B field : 2.4 or 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)
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.1
0.2 5 10 15 20 25
log
(energy [keV])
cts/s
0078
0533
0534
0815
0986
1060
1086
1181
1265
1356
1454
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 residuals period : (7.7 +/- 0.6) yr consistent with that derived from former spectral analyses Haberl (2007), Kaplan & Kerkweijk (2005) eV

7. precession
phase residuals period: (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: ~2*2000 days = 2*5.5 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)
( / )yr
abs(sine) Kaplan & Kerkwijk (2005)
+ linear
( / )yr
abs(sine) Kerkwijk et al. (2007)
+ linear
( / )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 (RBS 1223) Schwope et al. (2005) -> grav. waves
precession vs glitch 84 86 88 90 92 94 96 98
100
-100
-80
-60
-40
-20 20 40
kT [eV]
EW [eV]
0078
0533
0534
1454
dipolar magnetic field -> hot spots Haberl et al. (2006) & de Vries et al. (2004)
-> precession (RBS 1223) Schwope et al. (2005) -> 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