XMM-Newton reveals a candidate period for the spin of the “Magnificent Seven” neutron star RX J1605.3+3249
XMM-Newton reveals a candidate period for the spin of the “Magnificent Seven” neutron star RX J1605.3+3249
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DOI：
10.1051/0004-6361/201423380
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发表时间：
2014-01
影响因子：
6.5
通讯作者：
A. Pires;F. Haberl;V. Zavlin;C. Motch;S. Zane;M. Potsdam;M. F. Physik;NASA's Goddard Space Flight Center;Cnrs;U. Strasbourg;Observatoire Astronomique;Mullard Space Science Laboratory;A. Jena
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文献类型：
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作者：
A. Pires;F. Haberl;V. Zavlin;C. Motch;S. Zane;M. Potsdam;M. F. Physik;NASA's Goddard Space Flight Center;Cnrs;U. Strasbourg;Observatoire Astronomique;Mullard Space Science Laboratory;A. Jena
上下文由ROSAT发现的七颗热发射孤立中子星（INS）被称为“壮丽七星”（M7），在各种中子星星群中是独一无二的。通过磁场衰减的地壳加热和与磁星的进化联系可以解释为什么这些物体旋转得更慢，并且比类似年龄的标准旋转动力磁星具有更高的热光度和磁场强度。目标。第三明亮的INS，RX J1605.3+3249，是七个仍然缺乏检测到的周期性的对象中的唯一对象。源光谱，而纯粹的热没有显着的磁层发射，是复杂的，并显示窄和宽的吸收功能，可以潜在地被用来限制磁场的表面成分，以及质量-半径比的中子星星。方法.我们使用XMM-牛顿天文台对该源进行了60 ks的观测，旨在揭示中子星星的旋转速率并详细研究其光谱。我们面对我们的结果与以前的观察来源，并讨论其属性的上下文中的M7作为一个群体和已知的人口银河系INS。结果在4σ置信水平下，探测到P = 3.387864（16）s的周期信号，很可能是中子星星的自旋周期。发现调制的幅度与能量有关，并且当定时搜索仅限于能量高于10.5 keV的光子时，调制的幅度会更显着地被检测到。新数据与过去XMM-Newton EPIC-pn观测源的相干组合将脉冲星自旋下降速率限制在2σ置信水平u ν ε − 1.39 × 10 −13 Hz s −1，这意味着偶极磁场Bdip = 7.4 × 10 13 G。如果得到证实，RX J1605.3+3249将是M7中偶极磁场最高的中子星星。源的光谱显示了冷黑体成分的证据，以及两个广泛的吸收功能的存在。此外，RGS相机的高分辨率光谱证实了在源的共同添加的光谱中存在能量为0.57 keV的窄吸收特征，这在其他热发射孤立中子星中也可见。结论.相位分辨光谱学以及旨在确定时间解决方案的专门观测活动将对中子星星的几何形状提供宝贵的约束，并将允许人们确认自旋下降的高值，这将使源比任何其他M7 INS更接近磁星。
Context. The group of seven thermally emitting isolated neutron stars (INSs) discovered by ROSAT and known as the “Magnificent Seven” (M7) is unique among the various neutron star populations. Crustal heating by means of magnetic field decay and an evolutionary link with magnetars may explain why these objects rotate more slowly and have higher thermal luminosities and magnetic field intensities than standard rotation-powered pulsars of similar age. Aims. The third brightest INS, RX J1605.3+3249, is the only object amidst the seven still lacking a detected periodicity. The source spectrum, while purely thermal with no significant magnetospheric emission, is complex and displays both narrow and broad absorption features that can potentially be used to constrain the surface component of the magnetic field, as well as the mass-to-radius ratio of the neutron star. Methods. We observed the source with the XMM-Newton Observatory for 60 ks aiming at unveiling the neutron star rotation rate and investigating its spectrum in detail. We confront our results with previous observations of the source and discuss its properties in the context of the M7 as a group and of the known population of Galactic INSs. Results. A periodic signal at P = 3.387864(16) s, most likely the neutron star spin period, is detected at the 4σ confidence level. The amplitude of the modulation was found to be energy dependent and is more significantly detected when the timing search is restricted to photons with energy higher than ∼0.5 keV. The coherent combination of the new data with a past XMM-Newton EPIC-pn observation of the source constrains the pulsar spin-down rate at the 2σ confidence level, u ν ∼− 1.39 × 10 −13 Hz s −1 , implying a dipolar magnetic field of Bdip ∼ 7.4 × 10 13 G. If confirmed, RX J1605.3+3249 would be the neutron star with the highest dipolar field amongst the M7. The spectrum of the source shows evidence of a cool blackbody component, as well as for the presence of two broad absorption features. Furthermore, high-resolution spectroscopy with the RGS cameras confirms the presence of a narrow absorption feature at energy ∼0.57 keV in the co-added spectrum of the source, also seen in other thermally emitting isolated neutron stars. Conclusions. Phase-resolved spectroscopy, as well as a dedicated observing campaign aimed at determining a timing solution, will give invaluable constraints on the neutron star geometry and will allow one to confirm the high value of spin down, which would place the source closer to a magnetar than any other M7 INS.