Hard X-Ray Excess from the Magnificent Seven Neutron Stars

被引：23

作者：

Dessert, Christopher ^{[1
]}

Foster, Joshua W. ^{[1
]}

Safdi, Benjamin R. ^{[1
]}

机构：

[1] Univ Michigan, Dept Phys, Leinweber Ctr Theoret Phys, Ann Arbor, MI 48109 USA

来源：

ASTROPHYSICAL JOURNAL | 2020年 / 904卷 / 01期

基金：

美国国家科学基金会;

关键词：

Neutron star cores; Neutron stars; X-ray point sources; X-ray stars; X-ray astronomy; COHERENT TIMING SOLUTION; SPIN-DOWN; OPTICAL COUNTERPART; MAGNETIC-FIELDS; RX J0720.4-3125; RADIO-EMISSION; PROPER MOTIONS; ABSORPTION; CANDIDATE; ATMOSPHERES;

D O I：

10.3847/1538-4357/abb4ea

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We report significant hard X-ray excesses in the energy range 2-8 keV for two nearby isolated neutron stars: RX J1856.6-3754 and RX J0420.0-5022. These neutron stars have previously been observed in soft X-rays to have nearly thermal spectra at temperatures similar to 100 eV, which are thought to arise from the warm neutron star surfaces. We find nontrivial hard X-ray spectra well above the thermal surface predictions with archival data from the XMM-Newton and Chandra X-ray telescopes. We analyze possible systematic effects that could generate such spurious signals, such as nearby X-ray point sources and pileup of soft X-rays, but we find that the hard X-ray excesses are robust to these systematics to the extent that is possible to test. We also investigate possible sources of hard X-ray emission from the neutron stars and find no satisfactory explanation with known mechanisms, suggesting that a novel source of X-ray emission is at play. We do not find high-significance hard X-ray excesses from the other five Magnificent Seven isolated neutron stars.

引用

页数：34

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