Gravitational Redshift Detection from the Magnetic White Dwarf Harbored in RX J1712.6-2414

Abstract

Gravitational redshift is a fundamental parameter that allows us to determine the mass-to-radius ratio of compact stellar objects, such as black holes, neutron stars, and white dwarfs (WDs). In the X-ray spectra of the close binary system, RX J1712.6$-$2414, obtained from the Chandra High-Energy Transmission Grating observation, we detected significant redshifts for characteristic X-rays emitted from hydrogen-like magnesium, silicon ($\Delta E/E_{\mathrm{rest}}\sim 7\times 10^{-4}$), and sulfur ($\Delta E/E_{\mathrm{rest}}\sim 15\times 10^{-4}$) ions, which are over the instrumental absolute energy accuracy ($\Delta E/E_{\mathrm{rest}}\sim 3.3\times 10^{-4}$). Considering some possible factors, such as Doppler shifts associated with the plasma flow, systemic velocity, and optical depth, we concluded that the major contributor to the observed redshift is the gravitational redshift of the WD harbored in the binary system, which is the first gravitational redshift detection from a magnetic WD. Moreover, the gravitational redshift provides us with a new method of the WD mass measurement by invoking the plasma-flow theory with strong magnetic fields in close binaries. Regardless of large uncertainty, our new method estimated the WD mass to be $M_{\mathrm{WD}}>0.9M_{\odot }$.

13 pages, 5 figures. Accepted for publication in ApJ

References in corpus (11)

• Gaia Data Release 3: Summary of the content and survey properties
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Testing the white dwarf mass-radius relationship with eclipsing binaries
• Measuring the masses of magnetic white dwarfs: A NuSTAR Legacy Survey
• Dynamical constraints on the component masses of the cataclysmic variable WZ Sge
• A possible evolutionary scenario of highly magnetized super-Chandrasekhar white dwarfs: progenitors of peculiar type Ia supernovae
• Chandra/HETGS Observations of the Capella System: the Primary as a Dominating X-ray Source
• VW Hyi: optical spectroscopy and Doppler tomography
• Masses of the Hyades white dwarfs: A gravitational redshift measurement
• Application of a new X-ray reflection model to V1223 Sagittarii
• Breaking the degeneracy in magnetic cataclysmic variable X-ray spectral modeling using X-ray light curves

Cited by in corpus (1)

• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras