Observational evidence

1
Observational evidence
From Gravitationally-redshifted absorption lines
in the X-ray burst spectra of a neutron star,
Cottam et al., 2002, Nature (in press)
http//xxx.lanl.gov/ftp/astro-ph/papers/0211/0
211126.pdf
Investigating the low-mass X-ray binary
EXO0748-676 Neutron star primary accreting matter
from an evolved red dwarf secondary star via
Roche Lobe overflow through an accretion
disc. 335ksec observation with XMM-Newton in 2000
http//sci.esa.int/home/xmm-ne
wton/index.cfm
2
Low mass X-ray binary
Neutron star primary
Evolved red dwarf secondary
Roche point
Accretion disk
3
Outbursts
Total exposure time 335,000 sec in XMM-Newton
RGS 28 X-ray bursts, typically lasting 100
sec X-ray count rate in quiescence 0.5
cts/sec Burst count rate typically 9 ct/sec
4
X-ray absorption lines
hot bursts (gt1.2keV)
cold bursts (lt1.2keV)
quiescence
low-ionization circumstellar absorber
redshifted, highly ionized gas
z 0.35 M 1.4-1.8
solar masses R 9-12 km
5
EXO0748-676
origin of X-ray bursts
circumstellar material