The return to quiescence of Aql X-1 following the 2010 outburst

被引:46
作者
Campana, S. [1 ]
Brivio, F. [1 ,2 ]
Degenaar, N. [3 ]
Mereghetti, S. [4 ]
Wijnands, R. [5 ]
D'Avanzo, P. [1 ]
Israel, G. L. [6 ]
Stella, L. [6 ]
机构
[1] INAF Osservatorio Astron Brera, I-23807 Merate, LC, Italy
[2] Univ Milan, I-20133 Milan, Italy
[3] Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA
[4] INAF IASF Milano, I-20133 Milan, Italy
[5] Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1090 GE Amsterdam, Netherlands
[6] INAF Osservatorio Astron Roma, I-00040 Rome, Italy
关键词
accretion; accretion discs; binaries: close; stars: individual: Aql X-1; stars: neutron; X-rays: binaries; X-RAY BINARY; NEUTRON-STAR CRUST; CHANDRA OBSERVATIONS; MILLISECOND PULSAR; LIGHT CURVES; SWIFT OBSERVATIONS; SAX J1808.4-3658; XTE J1701-462; EXO; 0748-676; KS; 1731-260;
D O I
10.1093/mnras/stu709
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Aql X-1 is the most prolific low-mass X-ray binary transient hosting a neutron star. In this paper we focus on the return to quiescence following the 2010 outburst of the source. This decay was monitored thanks to 11 pointed observations taken with XMM-Newton, Chandra and Swift. The decay from outburst to quiescence is very fast, with an exponential decay characteristic time-scale of similar to 2 d. Once in quiescence the X-ray flux of Aql X-1 remained constant, with no further signs of variability or decay. The comparison with the only other well-monitored outburst from Aql X-1 (1997) is tale-telling. The luminosities at which the fast decay starts are fully compatible for the two outbursts, hinting at a mechanism intrinsic to the system and possibly related to the neutron star rotation and magnetic field (i.e. the propeller effect). In addition, for both outbursts, the decay profiles are also very similar, likely resulting from the shut-off of the accretion process on to the neutron star surface. Finally, the quiescent neutron star temperatures at the end of the outbursts are well consistent with one another, suggesting a hot neutron star core dominating the thermal balance. Small differences in the quiescent X-ray luminosity among the two outbursts can be attributed to a different level of the power-law component.
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页码:1984 / 1991
页数:8
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