The Flare-dominated Accretion Mode of a Radio-bright Candidate Transitional Millisecond Pulsar
The Flare-dominated Accretion Mode of a Radio-bright Candidate Transitional Millisecond Pulsar
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DOI：
10.3847/1538-4357/ab8f28
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
Kwan-Lok Li;J. Strader;J. Miller-Jones;C. Heinke;L. Chomiuk
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作者：
Kwan-Lok Li;J. Strader;J. Miller-Jones;C. Heinke;L. Chomiuk
我们报道了3FGL J0427.9−6704的新的同时X射线和射电连续谱观测，3FGL J0427.9是过渡毫秒脉冲星神秘类别的候选成员。这些XMM-牛顿和澳大利亚望远镜紧凑型阵列对这个几乎是边对边的、黯然失色的低质量X射线双星的观测是在亚光盘状态下拍摄的，X射线光度为ERG S−1。与少数几颗研究得很好的过渡毫秒脉冲星不同，3FGL J0427.9−6704在整个∼20小时的X射线观测中一直处于耀斑模式，这些脉冲星的盘状状态大多处于特征的高或低吸积模式，偶尔会出现耀斑。最亮耀斑达到∼2×1034erg S−1。在X射线和光学/紫外线(UV)中，该源在∼10-100erg S的时间尺度上连续表现出耀斑活动。在X射线耀斑和光学/UV耀斑之间没有观测到可测量的时间延迟，但光学/UV耀斑持续时间更长，并且X射线和光学/UV耀斑的相对幅度表现出很大的散射。X射线光谱可以很好地符合部分吸收的幂定律(Γ∼1.41.5)，这可能是由于侧面视角的原因。与稳定的射电外流或急流的存在相一致，在所有历元都存在适度可变的射电连续发射，并且不会被次要辐射遮盖。3FGL J0427.9−6704的同时射电/X射线光度比高于任何已知的过渡毫秒脉冲星，与具有相同X射线光度的恒星质量黑洞的比值相当，为一些中子星可以像黑洞一样具有射电响度提供了额外的证据。
We report new simultaneous X-ray and radio continuum observations of 3FGL J0427.9−6704, a candidate member of the enigmatic class of transitional millisecond pulsars. These XMM-Newton and Australia Telescope Compact Array observations of this nearly edge-on, eclipsing low-mass X-ray binary were taken in the sub-luminous disk state at an X-ray luminosity of erg s−1. Unlike the few well-studied transitional millisecond pulsars, which spend most of their disk state in a characteristic high or low accretion mode with occasional flares, 3FGL J0427.9−6704 stayed in the flare mode for the entire X-ray observation of ∼20 hr, with the brightest flares reaching ∼2 × 1034 erg s−1. The source continuously exhibited flaring activity on timescales of ∼10–100 s in both the X-ray and optical/ultraviolet (UV). No measurable time delay between the X-ray and optical/UV flares is observed, but the optical/UV flares last longer, and the relative amplitudes of the X-ray and optical/UV flares show a large scatter. The X-ray spectrum can be well-fit with a partially absorbed power law (Γ ∼ 1.4–1.5), perhaps due to the edge-on viewing angle. Modestly variable radio continuum emission is present at all epochs, and is not eclipsed by the secondary, consistent with the presence of a steady radio outflow or jet. The simultaneous radio/X-ray luminosity ratio of 3FGL J0427.9−6704 is higher than any known transitional millisecond pulsars and comparable to that of stellar-mass black holes of the same X-ray luminosity, providing additional evidence that some neutron stars can be as radio-loud as black holes.