Taking the pulse of the shortest orbital period binary system RX J0806.3+1527

TL;DR

This study presents detailed optical timing and polarization measurements of RX J0806.3+1527, confirming its orbital period derivative, polarization, and spectral properties, supporting its status as a strong gravitational wave source candidate.

Contribution

The paper provides the first extended optical timing analysis, polarization detection, and spectral study of RX J0806.3+1527, confirming its orbital evolution and emission characteristics.

Findings

Detected orbital period derivative indicating spin-up.

Measured linear polarization at about 2%.

Extended the timing solution back to 1994 observations.

Abstract

RX J0806.3+1527 is thought to be a 321s orbital period (the shortest known) double white dwarf binary system. According to the double degenerate binary (DDB) scenario this source is expected to be one of the strongest gravitational wave (GW) emitter candidates. In the last years RX J0806.3+1527 has been studied in great details, through multiwavelength observational campaigns and from the point of view of data analysis result interpretations. We present here the timing results obtained thanks to a 3.5-year long optical monitoring campaign carried out by the Very Large Telescope (VLT) and the Telescopio Nazionale Galileo (TNG) which allowed us to detect and study the orbital period derivative (spin-up at a rate of about 10^-3 s/yr) of the 321s modulation, to detect the linear polarisation (at a level of about 2%), and to study the broad band energy spectrum. The VLT/TNG observational strategy we used allowed us to rely upon a P-Pdot coherent solution which we finally extended backward to the 1994 ROSAT observation of RX J0806.3+1527.