A mechanism-independent methodology for modeling γ-ray phaseograms of pulsars in the framework of north-south symmetry
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866908506396819456 |
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| author | Yeung, Paul K. H. Khangulyan, Dmitry Saito, Takayuki |
| author_facet | Yeung, Paul K. H. Khangulyan, Dmitry Saito, Takayuki |
| contents | Fermi-LAT observations revealed that each GeV phase-folded light-curve (aka. phaseogram) of the Crab, Geminga, Dragonfly and Vela pulsars consists of two pulses (P1 & P2) and a "Bridge" between them. There is clearly a "bump" at the Bridge phase of Vela's pulse profiles, that could also be regarded as the third pulse (P3). Differently, the Crab's, Geminga's & Dragonfly's Bridges relatively resemble a "valley floor". Despite such an apparent difference, it is interesting to investigate whether their Bridge emissions are still within the same general picture as Vela's. Assuming the north-south symmetry, we would expect the fourth component (Bridge2/P4) to exist as well. However, such a hypothetical Bridge2/P4 is not intuitively identified on $γ$-ray phaseograms of the Crab, Geminga, Dragonfly and Vela pulsars. It is also intriguing to hint at the rationale for the non-discovery of Bridge2/P4. Our prototypical toy model is free of assumptions on emission regions or radiation mechanisms. Instead, it assumes a north-south symmetric geometry and one circularly symmetric beam per hemisphere, while taking into account Doppler shifts (the most innovative element), time delays and energy-dependent beam shapes. Tentative compatibility of our fitting results with wind models is reported. Notably, for the Crab pulsar, we found a preliminary qualitative correlation between our model predictions and the IXPE results on X-ray polarisation. The softer $γ$-ray pulsation of the Geminga pulsar is found to span over its full phase. Prompted by systematic evaluations, we outline some potential improvements for our toy model. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_03349 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A mechanism-independent methodology for modeling γ-ray phaseograms of pulsars in the framework of north-south symmetry Yeung, Paul K. H. Khangulyan, Dmitry Saito, Takayuki High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Fermi-LAT observations revealed that each GeV phase-folded light-curve (aka. phaseogram) of the Crab, Geminga, Dragonfly and Vela pulsars consists of two pulses (P1 & P2) and a "Bridge" between them. There is clearly a "bump" at the Bridge phase of Vela's pulse profiles, that could also be regarded as the third pulse (P3). Differently, the Crab's, Geminga's & Dragonfly's Bridges relatively resemble a "valley floor". Despite such an apparent difference, it is interesting to investigate whether their Bridge emissions are still within the same general picture as Vela's. Assuming the north-south symmetry, we would expect the fourth component (Bridge2/P4) to exist as well. However, such a hypothetical Bridge2/P4 is not intuitively identified on $γ$-ray phaseograms of the Crab, Geminga, Dragonfly and Vela pulsars. It is also intriguing to hint at the rationale for the non-discovery of Bridge2/P4. Our prototypical toy model is free of assumptions on emission regions or radiation mechanisms. Instead, it assumes a north-south symmetric geometry and one circularly symmetric beam per hemisphere, while taking into account Doppler shifts (the most innovative element), time delays and energy-dependent beam shapes. Tentative compatibility of our fitting results with wind models is reported. Notably, for the Crab pulsar, we found a preliminary qualitative correlation between our model predictions and the IXPE results on X-ray polarisation. The softer $γ$-ray pulsation of the Geminga pulsar is found to span over its full phase. Prompted by systematic evaluations, we outline some potential improvements for our toy model. |
| title | A mechanism-independent methodology for modeling γ-ray phaseograms of pulsars in the framework of north-south symmetry |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2507.03349 |