分类： 天文学 >> 天文学 提交时间： 2023-12-29
Pei Wang
Jian Li
Long Ji
Xian Hou
Erbil Gugercinoglu
Di Li
Diego F. Torres
Yutong Chen
Jiarui Niu
Weiwei Zhu
Bing Zhang
En-wei Liang
Li Zhang
Mingyu Ge
Zigao Dai
Lin Lin
Jinlin Han
Yi Feng
Chenhui Niu
Yongkun Zhang
摘要： Magnetars are neutron stars with extremely strong magnetic fields, frequently powering high-energy activity in X-rays. Pulsed radio emission following some X-ray outbursts have been detected, albeit its physical origin is unclear. It has long been speculated that the origin of magnetars' radio signals is different from those from canonical pulsars, although convincing evidence is still lacking. Five months after magnetar SGR 1935+2154's X-ray outburst and its associated Fast Radio Burst (FRB) 20200428, a radio pulsar phase was discovered. Here we report the discovery of X-ray spectral hardening associated with the emergence of periodic radio pulsations from SGR 1935+2154 and a detailed analysis of the properties of the radio pulses. The complex radio pulse morphology, which contains both narrow-band emission and frequency drifts, has not been seen before in other magnetars, but is similar to those of repeating FRBs - even though the luminosities are many orders of magnitude different. The observations suggest that radio emission originates from the outer magnetosphere of the magnetar, and the surface heating due to the bombardment of inward-going particles from the radio emission region is responsible for the observed X-ray spectral hardening.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies. However, several double-lobed radio sources have been solidly found to be associated with spiral galaxies. By cross-matching $\sim9\times10^5$ spiral galaxies selected from the Sloan Digital Sky Survey DR8 data with the full 1.4-GHz radio source catalogs of NRAO VLA Sky Survey and Faint Images of Radio Sky at Twenty-centimeters, we identify three new spiral galaxies: J0326$-$0623, J1110+0321 and J1134+3046 that produce double radio lobes, and five double-lobed spirals previously known. By combining the newly discovered and all the other known cases in literature, we confirm the relation that more massive spirals could produce more powerful large-scale radio jets. We find that most of these spiral galaxies are located in a galaxy group or a poor cluster, in which the environment is denser than in the field, and about half of them are the central brightest galaxies in their parent system. We therefore suggest that the environment is one of the key factors for a spiral to produce double radio lobes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies. However, several double-lobed radio sources have been solidly found to be associated with spiral galaxies. By cross-matching $\sim9\times10^5$ spiral galaxies selected from the Sloan Digital Sky Survey DR8 data with the full 1.4-GHz radio source catalogs of NRAO VLA Sky Survey and Faint Images of Radio Sky at Twenty-centimeters, we identify three new spiral galaxies: J0326$-$0623, J1110+0321 and J1134+3046 that produce double radio lobes, and five double-lobed spirals previously known. By combining the newly discovered and all the other known cases in literature, we confirm the relation that more massive spirals could produce more powerful large-scale radio jets. We find that most of these spiral galaxies are located in a galaxy group or a poor cluster, in which the environment is denser than in the field, and about half of them are the central brightest galaxies in their parent system. We therefore suggest that the environment is one of the key factors for a spiral to produce double radio lobes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most
sensitive radio telescope for pulsar observations. We make polarimetric
measurements of a large number of faint and distant pulsars using the FAST. We
present the new measurements of Faraday rotation for 134 faint pulsars in the
Galactic halo. Significant improvements are also made for some basic pulsar
parameters for 15 of them. We analyse the newly determined rotation measures
(RMs) for the Galactic magnetic fields by using these 134 halo pulsars,
together with previously available RMs for pulsars and extragalactic radio
sources and also the newly determined RMs for another 311 faint pulsars which
are either newly discovered in the project of the Galactic Plane Pulsar
Snapshot (GPPS) survey or previously known pulsars without RMs. The RM
tomographic analysis in the first Galactic quadrant gives roughly the same
field strength of around 2~$\mu$G for the large-scale toroidal halo magnetic
fields. The scale height of the halo magnetic fields is found to be at least
2.7$\pm$0.3~kpc. The RM differentiation of a large number of pulsars in the
Galactic disk in the Galactic longitude range of $26^{\circ}
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most
sensitive radio telescope for pulsar observations. We make polarimetric
measurements of a large number of faint and distant pulsars using the FAST. We
present the new measurements of Faraday rotation for 134 faint pulsars in the
Galactic halo. Significant improvements are also made for some basic pulsar
parameters for 15 of them. We analyse the newly determined rotation measures
(RMs) for the Galactic magnetic fields by using these 134 halo pulsars,
together with previously available RMs for pulsars and extragalactic radio
sources and also the newly determined RMs for another 311 faint pulsars which
are either newly discovered in the project of the Galactic Plane Pulsar
Snapshot (GPPS) survey or previously known pulsars without RMs. The RM
tomographic analysis in the first Galactic quadrant gives roughly the same
field strength of around 2~$\mu$G for the large-scale toroidal halo magnetic
fields. The scale height of the halo magnetic fields is found to be at least
2.7$\pm$0.3~kpc. The RM differentiation of a large number of pulsars in the
Galactic disk in the Galactic longitude range of $26^{\circ}
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