A ∼60 day Super-orbital Period Originating from the Ultraluminous X-Ray Pulsar in M82

被引:34
作者
Brightman, Murray [1 ]
Harrison, Fiona A. [1 ]
Bachetti, Matteo [1 ,2 ]
Xu, Yanjun [1 ]
Furst, Felix [3 ]
Walton, Dominic J. [4 ]
Ptak, Andrew [5 ,6 ]
Yukita, Mihoko [5 ,6 ]
Zezas, Andreas [7 ,8 ,9 ,10 ]
机构
[1] CALTECH, Cahill Ctr Astrophys, 1216 East Calif Blvd, Pasadena, CA 91125 USA
[2] INAF, Osservatorio Astron Cagliari, Via Sci 5, I-09047 Selargius, Italy
[3] ESAC, ESA, Operat Dept, Villanueva De La Canada, Madrid, Spain
[4] Inst Astron, Madingley Rd, Cambridge CB3 0HA, England
[5] Johns Hopkins Univ, Homewood Campus, Baltimore, MD 21218 USA
[6] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[7] Univ Crete, Dept Phys, Iraklion 71003, Greece
[8] Univ Crete, Inst Theoret & Computat Phys, Iraklion 71003, Greece
[9] Fdn Res & Technol Hellas FORTH, Iraklion 71003, Greece
[10] Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA
基金
欧洲研究理事会; 欧盟地平线“2020”; 美国国家航空航天局;
关键词
galaxies: individual (M82); stars: neutron; X-rays: binaries; NEUTRON-STAR; NUSTAR J095551+6940.8; DISCOVERY; ACCRETION; MASS; PULSATIONS; MAGNETAR; ULXS;
D O I
10.3847/1538-4357/ab0215
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Ultraluminous X-ray (ULX) pulsars are a new class of object powered by apparent super-critical accretion onto magnetized neutron stars. Three sources in this class have been identified so far; M82. X-2, NGC. 5907. ULX-1, and NGC. 7793. P13 have been found to have two properties in common; similar to 1 s spin periods, and for NGC. 5907. ULX-1 and NGC. 7793. P13 periodic X-ray flux modulations on timescales of similar to 60-80 days. M82 X-2 resides in a crowded field that includes the ULX M82 X-1 separated from X-2 by 5 '', as well as other bright point sources. A 60 day modulation has been observed from the region, but the origin has been difficult to identify; both M82 X-1 and X-2 have been suggested as the source. In this paper we present the analysis of a systematic monitoring campaign by Chandra, the only X-ray telescope capable of resolving the crowded field. From a simple Lomb-Scargle periodogram analysis and a more sophisticated Gaussian Process analysis we find that only X-2 exhibits a periodic signal around 60 days, supporting previous claims that it is the origin. We also construct a phase-averaged flux profile of the modulations from higher-cadence Swift/XRT data and find that the flux variations in the Chandra data are fully consistent with the flux profile. Since the orbit of the neutron star and its companion is known to be 2.5 days, the similar to 60 day period must be super-orbital in origin. The flux of the modulations varies by a factor of similar to 100 from the minimum to the maximum, with no evidence for spectral variations, making the origin difficult to explain.
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页数:13
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