Related Experiment Video
Updated: Jan 8, 2026
05:54
Author Spotlight: Non-Invasive Imaging of Complex Bio-Structures Using Polarization-Sensitive Two-Photon Microscopy
Published on: September 8, 2023
1.7K
Pulse and Polarization Structures in Axion-Converted X-Rays from Pulsars
JiJi Fan1, Lingfeng Li2, Chen Sun3
1Brown University, Department of Physics and Brown Theoretical Physics Center, Providence, Rhode Island 02912, USA.
Physical Review Letters
|December 19, 2025
Summary
Pulsation patterns in neutron star X-rays may reveal axions, feebly coupled particles. Analyzing X-ray Dim Isolated Neutron Star RX J1856.6-3754 shows axion signals are possible but require reduced uncertainties for definitive conclusions.
Area of Science:
- Astrophysics
- Particle Physics
Background:
- Neutron stars (NSs) possess extreme magnetic fields and dense cores, making them potential sources for axion production.
- Axions are hypothetical feebly coupled particles, and their detection could signify new physics beyond the Standard Model.
Purpose of the Study:
- To investigate the potential of X-ray pulsation structures from NSs as probes for axions.
- To develop analytical formalisms for analyzing axion-induced X-ray intensity and polarization pulsations.
Main Methods:
- Development of new analytical formalisms for pulsation-polarization structure analysis in axion scenarios.
- Application of the formalism to X-ray Dim Isolated Neutron Star RX J1856.6-3754, analyzing its hard X-ray excess.
- Updated fitting of intensity and pulsation data to assess axion compatibility.
Main Results:
- The axion explanation for the hard X-ray excess in RX J1856.6-3754 is compatible with available intensity and pulsation data.
- Incorporating pulsation data shifts the posterior by less than 1σ.
- The preferred parameter space for axions is nearing exclusion by other astrophysical constraints.
Conclusions:
- X-ray pulsation structures offer valuable insights into axion properties and couplings.
- Further reduction in pulsation data uncertainties (aiming for 75%) could lead to a >3σ conclusion on axion-induced X-rays.
- Continued study is crucial for definitively confirming or excluding axion signals from neutron stars.
Related Concept Videos
01:17NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences
1.6K
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
1.6K
01:23Atomic Nuclei: Nuclear Relaxation Processes
1.2K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
1.2K
01:13¹H NMR Signal Multiplicity: Splitting Patterns
6.5K
When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...
6.5K
01:05Atomic Nuclei: Magnetic Resonance
1.1K
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
1.1K
01:29Potential Due to a Polarized Object
702
A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
702
01:10Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule
2.4K
In the AX proton spin system, proton A can sense the two spin states of a coupled proton X, resulting in a doublet NMR signal with two peaks of equal (1:1) intensity. When proton A is coupled to two equivalent protons (AX2 spin system), the spin states of each X can be aligned with or against the external field, creating three possible scenarios. This results in a 1:2:1 triplet signal, where the central peak corresponds to the chemical shift of A and is twice as large or intense as the...
2.4K