Rapid bursts of magnetically gated accretion in the intermediate polar V1025 Cen

TL;DR

This paper reports the first detection of magnetically gated accretion bursts in a confirmed intermediate polar white dwarf system, V1025 Cen, validating a theoretical instability model originally proposed for neutron stars.

Contribution

It provides observational evidence of magnetically gated accretion bursts in a confirmed intermediate polar, confirming the applicability of the Spruit & Taam model to white dwarfs.

Findings

12 short accretion bursts observed over 27 days

Bursts last less than six hours and recur every 1-3 days

Supports the magnetic gating mechanism in white dwarf accretion processes

Abstract

Magnetically gated accretion has emerged as a proposed mechanism for producing extremely short, repetitive bursts of accretion onto magnetized white dwarfs in intermediate polars (IPs), but this phenomenon has not been detected previously in a confirmed IP. We report the 27-day TESS light curve of V1025 Cen, an IP that shows a remarkable series of twelve bursts of accretion, each lasting for less than six hours. The extreme brevity of the bursts and their short recurrence times (~1-3 days) are incompatible with the dwarf-nova instability, but they are natural consequences of the magnetic gating mechanism developed by Spruit & Taam to explain the Type II bursts of the accreting neutron star known as the Rapid Burster. In this model, the accretion flow piles up at the magnetospheric boundary and presses inward until it couples with the star's magnetic field, producing an abrupt burst of accretion. After each burst, the reservoir of matter at the edge of the magnetosphere is replenished, leading to cyclical bursts of accretion. A pair of recent studies applied this instability to the suspected IPs MV Lyr and TW Pic, but the magnetic nature of these two systems has not been independently confirmed. In contrast, previous studies have unambiguously established the white dwarf in V1025 Cen to be significantly magnetized. The detection of magnetically gated bursts in a confirmed IP therefore validates the extension of the Spruit & Taam instability to magnetized white dwarfs.