MAXI J1820+070 with NuSTAR - II. Flaring during the hard to soft state transition with a long soft lag

被引：9

作者：

Buisson, D. J. K. ^{[1
,2
]}

Fabian, A. C. ^{[2
]}

Gandhi, P. ^{[1
]}

Kara, E. ^{[3
]}

Parker, M. L. ^{[4
]}

Shaw, A. W. ^{[5
]}

Tomsick, J. A. ^{[6
]}

Walton, D. J. ^{[2
]}

Wang, J. ^{[3
]}

机构：

[1] Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England

[2] Inst Astron, Madingley Rd, Cambridge CB3 0HA, England

[3] MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA

[4] European Space Astron Ctr ESA ESAC, E-28691 Madrid, Spain

[5] Univ Nevada, Dept Phys, Reno, NV 89557 USA

[6] Univ Calif Berkeley, Space Sci Lab, 7 Gauss Way, Berkeley, CA 94720 USA

来源：

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | 2021年 / 500卷 / 03期

基金：

英国科学技术设施理事会; 美国国家航空航天局;

关键词：

accretion; accretion discs; black hole physics; X-rays: binaries; QUASI-PERIODIC OSCILLATIONS; X-RAY BINARY; ACCRETION DISC VISCOSITY; NGC; 5408; X-1; BLACK-HOLE; DOMINATED ACCRETION; XTE J1550-564; LIGHT CURVES; CYGNUS X-1; TIME LAGS;

D O I：

10.1093/mnras/staa3510

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We continue the analysis of NuSTAR data from the recent discovery outburst of MAXI J1820+070 (optical counterpart ASASSN-18ey), focussing on an observation including unusual flaring behaviour during the hard to soft state transition, which is a short phase of outbursts and so comparatively rarely observed. Two plateaus in flux are separated by a variable interval lasting similar to 10 ks, which shows dipping then flaring stages. The variability is strongest (with fractional variability up to F-Var similar to 10 per cent) at high energies and reduces as the contribution from disc emission becomes stronger. Flux-resolved spectra show that the variability is primarily due to the power-law flux changing. We also find a long soft lag of the thermal behind the power-law emission, which is 20(-1.2)(+1.6) s during the flaring phase. The lag during the dipping stage has a different lag-energy spectrum, which may be due to a wave passing outwards through the disc. Time-resolved spectral fitting suggests that the lag during the flaring stage may be due to the disc re-filling after being disrupted to produce the power-law flare, perhaps related to the system settling after the jet ejection which occurred around 1 d before. The time-scales of these phenomena imply a low viscosity parameter, alpha similar to 10(-3), for the inner region of the disc.

引用

页码：3976 / 3986

页数：11