Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2402.04443

J0526+5934: a peculiar ultra-short period double white dwarf

Alberto Rebassa-Mansergas·Mark Hollands·Steven G. Parsons·Leandro G. Althaus·Ingrid Pelisoli·Puji Irawati·Roberto Raddi·Maria E. Camisassa·Santiago Torres
View original source ↗Read source document ↗Export metadata ↓

Abstract

Ultra-short period compact binaries are important sources of gravitational waves, which include e.g. the progenitors of type Ia supernovae or the progenitors of merger episodes that may lead to massive and magnetic single white dwarfs. J0526+5934 is an unresolved compact binary star with an orbital period of 20.5 minutes that belongs to this category. The visible component of J0526+5934 has been recently claimed to be a hot sub-dwarf star with a CO white dwarf companion. Our aim is to provide strong observational plus theoretical evidence that the primary star is rather an extremely-low mass white dwarf, although the hot subdwarf nature cannot be completely ruled out. We analyse optical spectra together with time-series photometry of the visible component of J0526+5934 to constrain its orbital and stellar parameters. We also employ evolutionary sequences for low-mass white dwarfs to derive independent values of the primary mass. From the analysis of our observational data, we find a stellar mass for the primary star in J0526+5934 of 0.26+-0.05 Msun, which perfectly matches the 0.237+-0.035 Msun independent measurement we derived from the theoretical evolutionary models. This value is considerably lower than the theoretically expected and generally observed mass range of hot subdwarf stars, but falls well within the mass limit values of extremely low-mass white dwarfs. We conclude J0526+5934 is the fifth ultra-short period detached double white dwarf currently known.

Explore related subjects

astro-ph.SRastro-ph.HE

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Alberto Rebassa-Mansergas, Mark Hollands, Steven G. Parsons, Leandro G. Althaus, Ingrid Pelisoli, Puji Irawati, Roberto Raddi, Maria E. Camisassa, Santiago Torres. 2024-02-06. J0526+5934: a peculiar ultra-short period double white dwarf. https://doi.org/10.1051/0004-6361%2F202449519

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Multi-Instrument Analysis of NOAA AR 12781: Coupling Surface Evolution of the AR with Its In-Situ Solar Wind Signatures

Understanding the relationship between photospheric magnetic flux evolution and coronal emission remains an important problem in heliophysics. We investigate the decay of NOAA Active Region 12781 from 7 to 11 November 2020 using observations from the Solar Dynamics Observatory (SDO). Coronal emission was measured from the Atmospheric Imaging Assembly (AIA) 193\~Å images, while the photospheric signed and unsigned magnetic flux was derived from Helioseismic and Magnetic Imager (HMI) observations of the FeĨ 6173\~Å line. The unsigned magnetic flux and mean 193\~Å intensity showed a strong inverse relationship, with Pearson and Spearman correlation coefficients of $r\_p=-0.771$ and $r\_s=-0.758$, respectively. During the five-day decay phase, the unsigned magnetic flux decreased by 36.54\\% from its maximum value, while the coronal emission increased by 21.96\\%. We also compared the remote-sensing observations with near-Earth solar-wind and interplanetary magnetic-field measurements from the OMNI database using an estimated propagation delay. The results show that the coronal emission did not vary directly with the photospheric magnetic flux during the decay of AR\~12781. The possible association with the solar wind is discussed cautiously because a direct source connection cannot be established from the time-delay estimate alone.

astro-ph.SR↗
arXiv2026

Investigating r-Process Diversity in Mildly Metal-Poor Stars Using the Th II 5989 Angstrom Line

The origin of the heaviest elements remains a fundamental mystery, with the "actinide-boost" (Thorium overabundance) serving as a critical diagnostic of r-process nucleosynthesis conditions. While this diversity is well documented in extremely metal-poor (EMP) stars, its frequency in the mildly metal-poor (MMP) regime ($-2.0 < $ [Fe/H] $< -0.5$) is poorly constrained due to blending issues in the commonly used 4019 angstrom line. We present a systematic abundance analysis of mildly metal-poor stars, exploiting the relatively unblended Th II 5989 angstrom line. High-dispersion spectra were obtained using the 1.5 m telescope at Gunma Astronomical Observatory with GAOES, complemented by archival data from the Subaru Telescope/HDS retrieved via SMOKA. We successfully detected Th in 32 out of 42 sample stars. Our analysis demonstrates that the 5989 angstrom line is a useful diagnostic for Th abundance measurements in cool red giants. The mean [Th/Eu] ratio remains nearly constant over the MMP metallicity range, suggesting that progressive homogenization of the interstellar medium during Galactic chemical evolution would reduce abundance variations inherited from individual r-process events, or the dominant r-process events may share similar initial Th/Eu production ratios. While the [Th/Eu] ratio is nearly constant overall in the MMP regime, its dispersion appears to increase toward the metal-rich end of this regime and reaches approximately 1 dex near solar metallicity. This behavior may reflect the combined effects of variations in the initial Th/Eu production ratios of the progenitor objects, the mixing of r-process products in the interstellar medium, and the radioactive decay of Th over stellar lifetimes.

astro-ph.SR↗
arXiv2026

Archival Diagnostics for Potential Background Contaminantsof Project Hephaistos Dyson Sphere Candidates

We report on the diagnostic investigation of nine Project Hephaistos Dyson Sphere candidate M-dwarfs based on archival data. By comparing the Gaia DR3 positions with epoch 2016.0, propagated to the AllWISE epoch, with the mid-infrared centroids measured from the AllWISE images, together with deep archival optical/near-infrared imaging, we identified significant background contamination in candidates B and C--candidate B coincident with a radio counterpart showing a power-law-like spectrum with a radio spectral index alpha = 0.63 +/- 0.11, while candidate C has a near-infrared companion at an offset of 3.75 arcsec. Candidate A provides suggestive evidence through a radio counterpart with spectral index alpha = 0.40 +/- 0.35, while candidates E, F, H and J show marginal evidence. These systems exhibit either significant astrometric offsets or visible interlopers, indicating that the mid-infrared excess likely arises from line-of-sight contamination by hot, dust-obscured galaxies. However, candidates D and I still lack obvious signs of contamination. Dedicated observations are therefore essential to characterise these potential interlopers, eliminate false positives, and ensure that technosignature searches focus on the most robust Dyson Sphere candidates.

astro-ph.SR↗