A Link Between White Dwarf Pulsars and Polars: Multiwavelength Observations of the 9.36-Minute Period Variable Gaia22ayj
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arXiv
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2025
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| author | Rodriguez, Antonio C. El-Badry, Kareem Hakala, Pasi Rodríguez-Gil, Pablo Bao, Tong Galiullin, Ilkham Kurlander, Jacob A. Law, Casey J. Pelisoli, Ingrid Schreiber, Matthias R. Burdge, Kevin Caiazzo, Ilaria van Roestel, Jan Szkody, Paula Drake, Andrew J. Buckley, David A. H. Potter, Stephen B. Gaensicke, Boris Mori, Kaya Bellm, Eric C. Kulkarni, Shrinivas R. Prince, Thomas A. Graham, Matthew Kasliwal, Mansi M. Rose, Sam Sharma, Yashvi Ahumada, Tomás Anand, Shreya Viitanen, Akke Wold, Avery Chen, Tracy X. Riddle, Reed Smith, Roger |
| author_facet | Rodriguez, Antonio C. El-Badry, Kareem Hakala, Pasi Rodríguez-Gil, Pablo Bao, Tong Galiullin, Ilkham Kurlander, Jacob A. Law, Casey J. Pelisoli, Ingrid Schreiber, Matthias R. Burdge, Kevin Caiazzo, Ilaria van Roestel, Jan Szkody, Paula Drake, Andrew J. Buckley, David A. H. Potter, Stephen B. Gaensicke, Boris Mori, Kaya Bellm, Eric C. Kulkarni, Shrinivas R. Prince, Thomas A. Graham, Matthew Kasliwal, Mansi M. Rose, Sam Sharma, Yashvi Ahumada, Tomás Anand, Shreya Viitanen, Akke Wold, Avery Chen, Tracy X. Riddle, Reed Smith, Roger |
| contents | White dwarfs (WDs) are the most abundant compact objects, and recent surveys have suggested that over a third of WDs in accreting binaries host a strong (B $\gtrsim$ 1 MG) magnetic field. However, the origin and evolution of WD magnetism remain under debate. Two WD pulsars, AR Sco and J191213.72-441045.1 (J1912), have been found, which are non-accreting binaries hosting rapidly spinning (1.97-min and 5.30-min, respectively) magnetic WDs. The WD in AR Sco is slowing down on a $P/\dot{P}\approx 5.6\times 10^6$ yr timescale. It is believed they will eventually become polars, accreting systems in which a magnetic WD (B $\approx 10-240$ MG) accretes from a Roche lobe-filling donor spinning in sync with the orbit ($\gtrsim 78$ min). Here, we present multiwavelength data and analysis of Gaia22ayj, which outbursted in March 2022. We find that Gaia22ayj is a magnetic accreting WD that is rapidly spinning down ($P/\dot{P} = 6.1^{+0.3}_{-0.2}\times 10^6$ yr) like WD pulsars, but shows clear evidence of accretion, like polars. Strong linear polarization (40%) is detected in Gaia22ayj; such high levels have only been seen in the WD pulsar AR Sco and demonstrate the WD is magnetic. High speed photometry reveals a 9.36-min period accompanying a high amplitude ($\sim 2$ mag) modulation. We associate this with a WD spin or spin-orbit beat period, not an orbital period as was previously suggested. Fast (60-s) optical spectroscopy reveals a broad ``hump'', reminiscent of cyclotron emission in polars, between 4000-8000 Angstrom. We find an X-ray luminosity of $L_X = 2.7_{-0.8}^{+6.2}\times10^{32} \textrm{ erg s}^{-1}$ in the 0.3-8 keV energy range, while two VLA radio campaigns resulted in a non-detection with a $F_r < 15.8μ\textrm{Jy}$ 3$ σ$ upper limit. The shared properties of both WD pulsars and polars suggest that Gaia22ayj is a missing link between the two classes of magnetic WD binaries. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_01490 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A Link Between White Dwarf Pulsars and Polars: Multiwavelength Observations of the 9.36-Minute Period Variable Gaia22ayj Rodriguez, Antonio C. El-Badry, Kareem Hakala, Pasi Rodríguez-Gil, Pablo Bao, Tong Galiullin, Ilkham Kurlander, Jacob A. Law, Casey J. Pelisoli, Ingrid Schreiber, Matthias R. Burdge, Kevin Caiazzo, Ilaria van Roestel, Jan Szkody, Paula Drake, Andrew J. Buckley, David A. H. Potter, Stephen B. Gaensicke, Boris Mori, Kaya Bellm, Eric C. Kulkarni, Shrinivas R. Prince, Thomas A. Graham, Matthew Kasliwal, Mansi M. Rose, Sam Sharma, Yashvi Ahumada, Tomás Anand, Shreya Viitanen, Akke Wold, Avery Chen, Tracy X. Riddle, Reed Smith, Roger Solar and Stellar Astrophysics High Energy Astrophysical Phenomena White dwarfs (WDs) are the most abundant compact objects, and recent surveys have suggested that over a third of WDs in accreting binaries host a strong (B $\gtrsim$ 1 MG) magnetic field. However, the origin and evolution of WD magnetism remain under debate. Two WD pulsars, AR Sco and J191213.72-441045.1 (J1912), have been found, which are non-accreting binaries hosting rapidly spinning (1.97-min and 5.30-min, respectively) magnetic WDs. The WD in AR Sco is slowing down on a $P/\dot{P}\approx 5.6\times 10^6$ yr timescale. It is believed they will eventually become polars, accreting systems in which a magnetic WD (B $\approx 10-240$ MG) accretes from a Roche lobe-filling donor spinning in sync with the orbit ($\gtrsim 78$ min). Here, we present multiwavelength data and analysis of Gaia22ayj, which outbursted in March 2022. We find that Gaia22ayj is a magnetic accreting WD that is rapidly spinning down ($P/\dot{P} = 6.1^{+0.3}_{-0.2}\times 10^6$ yr) like WD pulsars, but shows clear evidence of accretion, like polars. Strong linear polarization (40%) is detected in Gaia22ayj; such high levels have only been seen in the WD pulsar AR Sco and demonstrate the WD is magnetic. High speed photometry reveals a 9.36-min period accompanying a high amplitude ($\sim 2$ mag) modulation. We associate this with a WD spin or spin-orbit beat period, not an orbital period as was previously suggested. Fast (60-s) optical spectroscopy reveals a broad ``hump'', reminiscent of cyclotron emission in polars, between 4000-8000 Angstrom. We find an X-ray luminosity of $L_X = 2.7_{-0.8}^{+6.2}\times10^{32} \textrm{ erg s}^{-1}$ in the 0.3-8 keV energy range, while two VLA radio campaigns resulted in a non-detection with a $F_r < 15.8μ\textrm{Jy}$ 3$ σ$ upper limit. The shared properties of both WD pulsars and polars suggest that Gaia22ayj is a missing link between the two classes of magnetic WD binaries. |
| title | A Link Between White Dwarf Pulsars and Polars: Multiwavelength Observations of the 9.36-Minute Period Variable Gaia22ayj |
| topic | Solar and Stellar Astrophysics High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2501.01490 |