2009/06/29 by Marcel A. Agüeros, Marcel Agueros, Craig Heinke +13
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Compact star #Gamma-ray bursts and supernovae #Millisecond pulsar #Neutron star #Physics #Pulsar #Pulsars and Gravitational Waves Research #Radio telescope #Stars #Telescope #White dwarf #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/700/2/l123
published as Astrophys.J.700:L123-L126,2009 · 4 pages, 1 table; to appear in the Astrophysical Journal Letters
arxiv created 2009/06/29 · openalex publication_date 2009/07/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
SDSS J091709.55+463821.8 (hereafter J0917+4638) is the lowest surface gravity white dwarf (WD) currently known, with log g = 5.55 ± 0.05 ( M ≈ 0.17 M ☉ ). Such low-mass white dwarfs (LMWDs) are believed to originate in binaries that evolve into WD/WD or WD/neutron star (NS) systems. An optical search for J0917+4638's companion showed that it must be a compact object with a mass ⩾0.28 M ☉ . Here we report on Green Bank Telescope 820 MHz and XMM-Newton X-ray observations of J0917+4638 intended to uncover a potential NS companion to the LMWD. No convincing pulsar signal is detected in our radio data. Our X-ray observation also failed to detect X-ray emission from J0917+4638's companion, while we would have detected any of the millisecond radio pulsars in 47 Tuc. We conclude that the companion is almost certainly another WD.