During a pointed 2018 NuSTAR observation, we detected a flare with a 2.2 hour duration from the magnetar 1RXS J170849.0$-$400910. The flare, which rose in $\sim25$ seconds to a maximum flux 6 times larger than the persistent emission, is highly pulsed with an rms pulsed fraction of $53\%$. The pulse profile shape consists of two peaks separated by half a rotational cycle, with a peak flux ratio of $\sim$2. The flare spectrum is thermal with an average temperature of 2.1 keV. Phase resolved spectroscopy show that the two peaks possess the same temperature, but differ in size. These observational results along with simple light curve modeling indicate that two identical antipodal spots, likely the magnetic poles, are heated simultaneously at the onset of the flare and for its full duration. Hence, the origin of the flare has to be connected to the global dipolar structure of the magnetar. This might best be achieved externally, via twists to closed magnetospheric dipolar field lines seeding bombardment of polar footpoint locales with energetic pairs. Approximately 1.86 hours following the onset of the flare, a short burst with its own 3-minute thermal tail occurred. The burst tail is also pulsating at the spin period of the source and phase-aligned with the flare profile, implying an intimate connection between the two phenomena. The burst may have been caused by a magnetic reconnection event in the same twisted dipolar field lines anchored to the surface hot spots, with subsequent return currents supplying extra heat to these polar caps.
Constraints on Late-Time Flaring from Luminous Fast Blue Optical Transients using the Transiting Exoplanet Survey Satellite and the Zwicky Transient Facility
Cornell University（康奈尔大学）；Texas Tech University（德克萨斯理工大学）；Weizmann Institute of Science（魏茨曼科学研究所）；Liverpool John Moores University（利物浦约翰摩尔斯大学）；California Institute of Technology（加州理工学院）；University of Minnesota（明尼苏达大学）
Gamma Rays from ALP-Photon Conversion and Inverse Compton Reprocessing in Neutron Star Magnetospheres
University of Salamanca（萨拉曼卡大学）；INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano（意大利国家天体物理研究所米兰空间天体物理与宇宙学研究所）；INFN, Sezione di Pavia（意大利国家核物理学院帕维亚分部）；Instituto de Fısica de Cantabria (IFCA, UC-CSIC)（坎塔布里亚物理研究所）
