Dynamical mass of the white dwarf in XY Ari: a test for intermediate polar X-ray spectral models

Álvarez-Hernández, A.; Torres, M. A. P.; Rodrí, guez-Gil, Pablo; Shahbaz, T.; Sánchez-Sierras, J.; Acosta–Pulido, J. A.; Jonker, P. G.; Gazeas, K.; Hakala, Pasi; Corral-Santana, J. M.

doi:10.1093/mnras/stad2010

Cited by 2 publications

(1 citation statement)

References 67 publications

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“…Our methodology could be applied to other IPs to measure their WD masses more accurately. Notably, recent dynamical measurements of WD masses in GK Per and XY Ari have presented challenges to the previous (and differing) WD mass measurements using X-ray spectroscopy data (Álvarez-Hernández et al 2021(Álvarez-Hernández et al , 2023. To reduce systematic errors, we stress the significance of measuring source distances, detecting or estimating cyclotron emission in the optical/UV band (especially for highly magnetized IPs), and obtaining broadband X-ray spectra beyond 10 keV.…”

Section: Discussionmentioning

confidence: 96%

Constraining the White-dwarf Mass and Magnetic Field Strength of a New Intermediate Polar through X-Ray Observations

Vermette,

Salcedo,

Mori

et al. 2023

ApJ

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We report timing and broadband spectral analysis of a Galactic X-ray source, CXOGBS J174517.0−321356 (J1745), with a 614 s periodicity. Chandra discovered the source in the direction of the Galactic Bulge. Gong proposed that J1745 was either an intermediate polar (IP) with a mass of ∼1 M ⊙, or an ultracompact X-ray binary (UCXB). To confirm J1745's nature, we jointly fit XMM-Newton and NuSTAR spectra, ruling out a UCXB origin. We have developed a physically realistic model that considers a finite magnetosphere radius, X-ray absorption from the preshock region, and reflection from the white-dwarf (WD) surface to properly determine the IP properties, especially its WD mass. To assess systematic errors on the WD mass measurement, we consider a broad range of specific accretion rates ( m ̇ = 0.6 – 44 g cm−2 s−1) based on the uncertain source distance (d = 3–8 kpc) and fractional accretion area (f = 0.001–0.025). Our model properly implements the fitted accretion column height in the X-ray reflection model and accounts for the underestimated mass accretion rate due to the (unobserved) soft X-ray blackbody and cyclotron cooling emissions. We found that the lowest accretion rate of m ̇ = 0.6 g cm−2 s−1, which corresponds to the nearest source distance and maximum f value, yields a WD mass of (0.92 ± 0.08)M ⊙. On the other hand, as long as the accretion rate is m ̇ ≳ 3 g cm−2 s−1, the WD mass is robustly measured to be (0.81 ± 0.06)M ⊙, nearly independent of m ̇ . The derived WD mass range is consistent with the mean WD mass of nearby IPs. Assuming spin equilibrium between the WD and accretion disk, we constrained the WD magnetic field to B ≳ 7 MG, indicating that it could be a highly magnetized IP. Our analysis presents the most comprehensive methodology for constraining the WD mass and B field of an IP by consolidating the effects of cyclotron cooling, finite magnetospheric radius, and accretion column height.

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Section: Discussionmentioning

confidence: 96%

Constraining the White-dwarf Mass and Magnetic Field Strength of a New Intermediate Polar through X-Ray Observations

Vermette,

Salcedo,

Mori

et al. 2023

ApJ

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The mass of the white dwarf in YY Dra (=DO Dra): Dynamical measurement and comparative study with X-ray estimates

Álvarez-Hernández,

Torres,

Shahbaz

et al. 2024

A&A

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We present a dynamical study of the intermediate polar cataclysmic variable based on time-series observations in the $K$ band, where the donor star is known to be the major flux contributor. We covered the $3.97$-h orbital cycle with 44 spectra taken between $2020$ and $2022$ and two epochs of photometry observed in 2021 March and May. One of the light curves was simultaneously obtained with spectroscopy to better account for the effects of irradiation of the donor star and the presence of accretion light. From the spectroscopy, we derived the radial velocity curve of the donor star metallic absorption lines, constrained its spectral type to M0.5--M3.5 with no measurable changes in the effective temperature between the irradiated and non-irradiated hemispheres of the star, and measured its projected rotational velocity $v_ rot i = 103 km s $. Through simultaneous modelling of the radial velocity and light curves, we derived values for the radial velocity semi-amplitude of the donor star, $K_2 = 188^ the donor to white dwarf mass ratio, $q=M_2/M_1 = 0.62 0.02$, and the orbital inclination circ circ circ $. These binary parameters yield dynamical masses of $M_ M odot $ and $M_2 = 0.62^ M odot $ ($68$ per cent confidence level). As found for the intermediate polars GK Per and XY Ari, the white dwarf dynamical mass in YY Dra significantly differs from several estimates obtained by modelling the X-ray spectral continuum.

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Dynamical mass of the white dwarf in XY Ari: a test for intermediate polar X-ray spectral models

Cited by 2 publications

References 67 publications

Constraining the White-dwarf Mass and Magnetic Field Strength of a New Intermediate Polar through X-Ray Observations

Constraining the White-dwarf Mass and Magnetic Field Strength of a New Intermediate Polar through X-Ray Observations

The mass of the white dwarf in YY Dra (=DO Dra): Dynamical measurement and comparative study with X-ray estimates

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