An Estimation of the White Dwarf Mass in the Dwarf Nova GK Persei with NuSTAR Observations of Two States

Abstract

We report on X-ray observations of the Dwarf Nova GK Persei performed by {\it NuSTAR} in 2015. GK Persei, behaving also as an Intermediate Polar, exhibited a Dwarf Nova outburst in 2015 March--April. The object was observed with {\sl NuSTAR} during the outburst state, and again in a quiescent state wherein the 15--50 keV flux was 33 times lower. Using a multi-temperature plasma emission and reflection model, the highest plasma temperature in the accretion column was measured as $19.7_{-1.0}^{+1.3}$~keV in outburst and $36.2_{-3.2}^{+3.5}$~keV in quiescence. The significant change of the maximum temperature is considered to reflect an accretion-induced decrease of the inner-disk radius $R_{\mathrm{in}}$, where accreting gas is captured by the magnetosphere. Assuming this radius scales as $R_{\mathrm{in}}\propto {\dot{M}}^{-2/7}$ where $\dot{M}$ is the mass accretion rate, we obtain $R_{\mathrm{in}}=1.9_{-0.2}^{+0.4}{R}_{\mathrm{WD}}$ and $R_{\mathrm{in}}=7.4_{-1.2}^{+2.1}{R}_{\mathrm{WD}}$ in outburst and quiescence respectively, where $R_{\mathrm{WD}}$ is the white-dwarf radius of this system. Utilising the measured temperatures and fluxes, as well as the standard mass-radius relation of white dwarfs, we estimate the white-dwarf mass as $M_{\mathrm{WD}}=0.87\pm 0.08M_{\odot }$ including typical systematic uncertainties by 7%. The surface magnetic field is also measured as $B\sim 5\times 10^5$~G. These results exemplify a new X-ray method of estimating $M_{\mathrm{WD}}$ and $B$ of white dwarfs by using large changes in $\dot{M}$.

arXiv comment8 pages, 4 figures, accepted for publication in MNRAS

References in corpus (17)

• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• The Swift/BAT Hard X-ray Transient Monitor
• RXTE broadband X-ray spectra of intermediate polars and white dwarf mass estimates
• Analytical Hot Spot Shapes and Magnetospheric Radius from 3D Simulations of Magnetospheric Accretion
• White dwarf masses in intermediate polars observed with the Suzaku satellite
• Quenching of the accretion disk strong aperiodic variability at the magnetospheric boundary
• Intermediate polars in the Swift/BAT survey: Spectra and white dwarf masses
• A Universal Decline Law of Classical Novae. II. GK Persei 1901 and Novae in 2005
• The X-ray Spectrum of the Dwarf Nova SS Cyg in quiescence and outburst
• GK Per and EX Hya: Intermediate polars with small magnetospheres
• The stellar mass ratio of GK Persei
• HST Fine Guidance Sensor Parallaxes for Four Classical Novae
• V405 Aurigae: A High Magnetic Field Intermediate Polar
• Application of the Ghosh & Lamb Relation to the Spin-up/down Behavior in the X-ray Binary Pulsar 4U 1626-67
• INTEGRAL Broadband X-ray spectrum of the intermediate polar V709 Cas
• Multi-mission observations of the old nova GK Per during the 2015 outburst
• Influence of Compton scattering on the broad-band X-ray spectra of intermediate polars

Cited by in corpus (9)

• Hard X-ray view on intermediate polars in the Gaia era
• Hard X-ray Cataclysmic Variables
• INTEGRAL view on Cataclysmic Variables and Symbiotic Binaries
• The intermediate polar cataclysmic variable GK Persei 120 years after the nova explosion: a first dynamical mass study
• Photoionization modelling of quiescence phase spectra of novae & symbiotic star
• A search for cool molecular gas in GK Persei and other classical novae
• MASTER OT J030227.28+191754.5: a dwarf nova at a massive oxygen-neon white-dwarf system ?
• X-ray spectroscopy method of white dwarf mass determination in intermediate polars. External systematic uncertainties
• Constraints on the magnetic field structure in accreting compact objects from aperiodic variability