Extreme quiescent variability of the transient neutron star low-mass X-ray binary EXO 1745-248 in Terzan 5

被引：0

作者：

Sandoval L.E.R. ^{[1
,2
]}

Wijnands R. ^{[1
]}

Degenaar N. ^{[1
]}

Cavecchi Y. ^{[3
,4
]}

Heinke C.O. ^{[5
]}

Cackett E.M. ^{[6
]}

Homan J. ^{[7
,8
,9
]}

Altamirano D. ^{[10
]}

Bahramian A. ^{[11
]}

Sivakoff G.R. ^{[5
]}

Miller J.M. ^{[12
]}

Parikh A.S. ^{[1
]}

机构：

[1] Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, Amsterdam

[2] Department of Physics, Texas Tech University, Box 41051, Science Building, Lubbock, 79409-1051, TX

[3] Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, 08544, NJ

[4] Mathematical Sciences and STAG Research Centre, University of Southampton, Southampton

[5] Department of Physics, University of Alberta, CCIS 4-183, Edmonton, T6G 2E1, AB

[6] Department of Physics and Astronomy, Wayne State University, 666 W. Hancock St, Detroit, 48201, MI

[7] MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue 37-582D, Cambridge, 02139, MA

[8] SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, Utrecht

[9] Eureka Scientific Inc., 2452 Delmer Street, Oakland, 94602, CA

[10] Physics and Astronomy, University of Southampton, Southampton

[11] Department of Physics and Astronomy, Michigan State University, East Lansing, 48824, MI

[12] Department of Astronomy, University of Michigan, 1085 South University Ave, Ann Arbor, 48109-1107, MI

来源：

Sandoval, L.E. Rivera (liliana.rivera@ttu.edu) | 2018年 / Oxford University Press卷 / 479期

基金：

加拿大自然科学与工程研究理事会; 美国国家航空航天局; 欧盟地平线“2020”;

关键词：

Globular clusters: individual: Terzan 5-X-rays: binaries;

D O I：

10.1093/MNRAS/STY1535

中图分类号：

学科分类号：

摘要：

EXO 1745-248 is a transient neutron star low-mass X-ray binary that resides in the globular cluster Terzan 5. We studied the transient during its quiescent state using 18 Chandra observations of the cluster acquired between 2003 and 2016. We found an extremely variable source, with a luminosity variation in the 0.5-10 keV energy range of approximately three orders of magnitude (between 3 × 1031 and 2 × 1034 erg s-1) on time-scales from years down to only a few days. Using an absorbed power-law model to fit its quiescent spectra, we obtained a typical photon index of ~1.4, indicating that the source is even harder than during outburst and much harder than typical quiescent neutron stars if their quiescent X-ray spectra are also described by a single power-law model. This indicates that EXO 1745-248 is very hard throughout the entire observed X-ray luminosity range. At the highest luminosity, the spectrum fits better when an additional (soft) component is added to the model. All these quiescent properties are likely related to strong variability in the low-level accretion rate in the system. However, its extreme variable behaviour is strikingly different from the one observed for other neutron star transients that are thought to still accrete in quiescence. We compare our results to these systems. We also discuss similarities and differences between our target and the transitional millisecond pulsar IGR J18245-2452, which also has hard spectra and strong variability during quiescence. © 2018 The Author(s).

引用

页码：2777 / 2788

页数：11

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