An Alternative Explanation for the Helium Star Pulsar Binary J1928$+$1815: The Most Heavyweight Black Widow System to Date
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| Natura: | Preprint |
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2025
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| author | Gong, Hang Bobrick, Alexey Garzón, Francisco Bhakta, Deven Maccarone, Thomas Kumari, Sangita Rodríguez, Nieves Castro Cabrera-Lavers, Antonio Bahramian, Arash Liu, Jifeng |
| author_facet | Gong, Hang Bobrick, Alexey Garzón, Francisco Bhakta, Deven Maccarone, Thomas Kumari, Sangita Rodríguez, Nieves Castro Cabrera-Lavers, Antonio Bahramian, Arash Liu, Jifeng |
| contents | We present the results of deep near-infrared imaging of the recently discovered helium star pulsar binary J1928$+$1815 situated in the Galactic plane. Our observations did not achieve significant detections, providing limiting magnitudes of J=23.7 and H=22.2, which are both 2.4\,magnitudes deeper than the expected J and H magnitudes for a modeled stripped helium star with a mass of 1\,$\rm M_{\odot}$ after extinction. Although we cannot completely rule out the possibility of more significant extinction and the exact evolutionary status of the supposed helium star is uncertain, by comparing J1928$+$1815 with other pulsar binaries, we propose a natural alternative solution: that J1928$+$1815 is a heavyweight black widow system with a massive ablated white dwarf. Due to the pulsar's relatively high spin-down power and short orbital separation, the irradiation heating timescale is uniquely shorter than the cooling timescale for the WD companion. As a result, the WD effectively boils, with its outer layers expanding, overfilling the Roche lobe and producing low-density binary-scale haze opaque in the radio band. If this interpretation is correct, J1928$+$1815 would represent a new category distinct from canonical lightweight black widow systems. Radio eclipses can occur in pulsar binaries across a wider range of WD companion masses than previously thought. Therefore, they do not serve as a definitive indicator of a helium star without its direct detection. We contend that a spectroscopic identification remains the smoking gun for its existence. Given the crowding in this field, an \textit{HST} imaging in the near-infrared band would provide even better constraints. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_17248 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | An Alternative Explanation for the Helium Star Pulsar Binary J1928$+$1815: The Most Heavyweight Black Widow System to Date Gong, Hang Bobrick, Alexey Garzón, Francisco Bhakta, Deven Maccarone, Thomas Kumari, Sangita Rodríguez, Nieves Castro Cabrera-Lavers, Antonio Bahramian, Arash Liu, Jifeng High Energy Astrophysical Phenomena We present the results of deep near-infrared imaging of the recently discovered helium star pulsar binary J1928$+$1815 situated in the Galactic plane. Our observations did not achieve significant detections, providing limiting magnitudes of J=23.7 and H=22.2, which are both 2.4\,magnitudes deeper than the expected J and H magnitudes for a modeled stripped helium star with a mass of 1\,$\rm M_{\odot}$ after extinction. Although we cannot completely rule out the possibility of more significant extinction and the exact evolutionary status of the supposed helium star is uncertain, by comparing J1928$+$1815 with other pulsar binaries, we propose a natural alternative solution: that J1928$+$1815 is a heavyweight black widow system with a massive ablated white dwarf. Due to the pulsar's relatively high spin-down power and short orbital separation, the irradiation heating timescale is uniquely shorter than the cooling timescale for the WD companion. As a result, the WD effectively boils, with its outer layers expanding, overfilling the Roche lobe and producing low-density binary-scale haze opaque in the radio band. If this interpretation is correct, J1928$+$1815 would represent a new category distinct from canonical lightweight black widow systems. Radio eclipses can occur in pulsar binaries across a wider range of WD companion masses than previously thought. Therefore, they do not serve as a definitive indicator of a helium star without its direct detection. We contend that a spectroscopic identification remains the smoking gun for its existence. Given the crowding in this field, an \textit{HST} imaging in the near-infrared band would provide even better constraints. |
| title | An Alternative Explanation for the Helium Star Pulsar Binary J1928$+$1815: The Most Heavyweight Black Widow System to Date |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2511.17248 |