TY - JOUR
T1 - Understanding the LMXB X2127+119 in M 15
T2 - I. X-ray eclipses and dips
AU - Ioannou, Zac
AU - Naylor, T.
AU - Smale, A. P.
AU - Charles, P. A.
AU - Mukai, K.
PY - 2002
Y1 - 2002
N2 - We present X-ray observations of the high-inclination low-mass X-ray binary system X2127+119 (AC211) in the globular cluster M 15 (NGC 7078). The observations consist of data acquired in 1996 with the RXTE satellite and in 1995 with the ASCA satellite. Also, the MPC1 data from the 1988 GINGA observations were de-archived and re-analysed. The phase-folded 2-10 keV hardness ratios from all three missions differ significantly indicating that the system can exhibit different spectral behaviours. We find that the X-ray eclipse profiles can be described relatively well using a simple model where the secondary star passes in front of a large X-ray emitting region. For this we require a mass ratio (q = M1/M2) of about one. The radius of this X-ray emitting region is ∼0.8 RL1 and its vertical extent ∼60° above the orbital plane. We suggest that if this X-ray emitting region were an optically thick corona, it would explain various puzzling aspects of this system. We also show that the X-ray dip observed at phases around 0.65 does not conform with the idea that the dip is caused by vertically extended material associated with the stream/disc impact region, but that it could be due to structure in the inner parts of the disc.
AB - We present X-ray observations of the high-inclination low-mass X-ray binary system X2127+119 (AC211) in the globular cluster M 15 (NGC 7078). The observations consist of data acquired in 1996 with the RXTE satellite and in 1995 with the ASCA satellite. Also, the MPC1 data from the 1988 GINGA observations were de-archived and re-analysed. The phase-folded 2-10 keV hardness ratios from all three missions differ significantly indicating that the system can exhibit different spectral behaviours. We find that the X-ray eclipse profiles can be described relatively well using a simple model where the secondary star passes in front of a large X-ray emitting region. For this we require a mass ratio (q = M1/M2) of about one. The radius of this X-ray emitting region is ∼0.8 RL1 and its vertical extent ∼60° above the orbital plane. We suggest that if this X-ray emitting region were an optically thick corona, it would explain various puzzling aspects of this system. We also show that the X-ray dip observed at phases around 0.65 does not conform with the idea that the dip is caused by vertically extended material associated with the stream/disc impact region, but that it could be due to structure in the inner parts of the disc.
KW - Accretion, accretion discs
KW - Stars: binaries: eclipsing, coronae
KW - Stars: individual: X2127+119, AC211
KW - X-rays: binaries
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U2 - 10.1051/0004-6361:20011581
DO - 10.1051/0004-6361:20011581
M3 - Article
AN - SCOPUS:0036184407
SN - 0004-6361
VL - 382
SP - 130
EP - 140
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
IS - 1
ER -