2025/05/09 by P. Barrett, Mark Gurwell, Barrett, Paul E. +1 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2505.06468
openalex publication_date 2025/05/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
AR Scorpii, the so called white dwarf pulsar, contains a rapidly rotating magnetic white dwarf (WD; Pspin = 117.0564 s) interacting with a cool, red dwarf (RD) companion in a 3.56 hour orbit. It is a strong radio source with an inverted spectral index between 1-200 GHz that is indicative of synchrotron emission. This paper presents the first submillimeter observations of AR Scorpii using the Submillimeter Array, helping to fill a critical gap in the spectral energy distribution between 10-600 GHz. The average flux densities at 220 and 345 GHz are 124 and 86 mJy, respectively. The lower than expected flux density at 345 GHz suggests a break in the synchrotron emission at about 200 GHz. A periodogram analysis of the 220 GHz observations shows a modulation with an amplitude of ~6% at a period of 58.26 s or at twice the spin frequency of the white dwarf. This modulation is the first direct detection of the WD spin period at radio frequencies and implies that the synchrotron emission arises near the WD and and not from an interaction with the photosphere of the RD. A fit to the spectral energy distribution shows that the synchrotron emission arises from a small, low density region with a magnetic field of 43 MG at a distance of 0.6 orbital radii from the WD. This result implies that AR Scorpii contains a weakly magnetic WD (~15 MG) and not a strongly magnetic WD (~500 MG) as previously asserted.