The Accretion Geometry of the Asynchronous Polar V1432 Aql

TL;DR

This study uses X-ray observations to analyze the accretion geometry of the unique eclipsing asynchronous polar V1432 Aql, revealing insights into its high-temperature emission, accretion rate, and magnetic interactions.

Contribution

It provides a detailed physical model of the accretion geometry in V1432 Aql, highlighting the effects of inefficient accretion and deep stream penetration into the magnetosphere.

Findings

Detection of significant Compton reflection.

Confirmation of high soft X-ray temperature (~52 keV).

Low total accretion rate contradicts recent nova hypothesis.

Abstract

As the only eclipsing asynchronous polar (AP), V1432 Aql provides an excellent laboratory to study the interaction between the accreted matter and the magnetic field. However, due to its complex emission, a more physical understanding of its accretion geometry is still outstanding. Here, we report an X-ray spectral study using contemporaneous observations from \nustar\ and \swift. We detect significant Compton reflection and confirm earlier reports of a high soft X-ray temperature $\sim52$ keV. We suggest that the multi-temperature emission is due to a distribution of the specific accretion rate over the accretion region, which leads to a continuous temperature distribution over the heated area and explains the high temperature of the soft X-rays. We interpret these characteristics as the results of the inefficient accretion in APs. Thus the accretion stream can punch deeply into the magnetosphere and feed the white dwarf (WD) over a much narrower accretion region near its equator. Additionally, the broad-band X-rays provide details of the accretion; the low total accretion rate of $\sim 1 \times 10^{-10} ~M_{\odot} ~yr^{-1}$ contradicts the speculation that V1432 Aql was a recent nova, while the high specific accretion rate of $\sim 5.6 ~g ~cm^{-2} ~s^{-1}$ explains the significant reflection from the surface of the WD.