Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/external/xmm_sw_cal/icwg/presentations/rxj1856_haberl.pdf Дата изменения: Mon Jun 19 13:01:34 2006 Дата индексирования: Sat Dec 22 14:56:43 2007 Кодировка: Поисковые слова: роберт годдард

RX J1856.5-3754 as standard calibration target for soft X-rays

Frank Haberl ICWG meeting, Iceland, 14-16 June 2006


The Magnificent Seven: Thermal, radio-quiet neutron stars Soft X-ray spectrum + faint in optical


Walter et al. (1996)

PSPC 0.15 ± 0.23 ± 0.29 ± 0.38 ± 0.78 ± 1.82 ± 3.08 ±

cts/s 0.01 0.03 0.02 0.03 0.02 0.02 0.02

H -0.96 -0.06 -0.20 -0.74 -0.67 -0.82 -0.96

R1 ± 0.03 ± 0.12 ± 0.08 ± 0.02 ± 0.02 ± 0.01 ± 0.01

HR2 -0.45 ± -0.60 ± -0.51 ± -0.66 ± -0.68 ± -0.77 ± -0.94 ±

0.73 0.17 0.11 0.08 0.04 0.03 0.02

Name RX J0420.0-5022 RBS1774 = 1RXS J214303.7+065419 RBS1223 = 1RXS J130848.6+212708 RX J0806.4-4123 RBS1556 = RX J1605.3+3249 RX J0720.4-3125 RX J1856.5-3754


Chandra and XMM spectra
nH kT R Lbol = = = = (9.5 ± 0.03) · 1019 cm 63.5 ± 0.2 eV 4.4 ± 0.1 km (120pc) 4.1 · 1031 erg s-1
Burwitz et al. (2003)

RX J1856.5­3754
Black-body fit

No narrow absorption features !

Chandra LETGS

XMM EPIC-pn

Photon Energy (keV)

Spectrum constant over time scales of years
Haberl (2006)


A `stable` neutron star
Model: tbabs*bbody
Simultaneous fit with all parameters linked except norm: 1.000 1.008 0.995 0.983 0.989 · 5 observations in FF mode + thin1 filter · 1 observation in timing mode + thin1 filter ± ± ± ± 0.005 0.005 0.005 (*) 0.004

(*) 69 intervals in STDGTI extension


Cross calibration
Individual fits with all parameters free:

· · · ·

Model: tbabs*bbody Low column density requires energies down to 0.1-0.15 keV No full agreement between different instruments yet For broad band spectroscopy EPIC-pn has largest sensitivity and is the most stable instrument

Simultaneous fits with NH linked:

relative accuracy ± 0.5 eV ± 0.2 km


LETG spectrum with best fit EPIC-pn model


Summary
Source properties: · Simple continuum spectrum below ~1 keV · Constant source (spectrum, intensity) · Low absorption · Not too bright/faint · Point source Calibration aims: · Stability of detector at soft X-rays · Contamination · Re-distribution (CCDs) Standard source + standard model