2024/08/12 by M. R. Kennedy, P. Callanan, Kennedy, M. R. +41 · 1 voice
Engineering · Physics and Astronomy · #Crystallography and Radiation Phenomena #Laser-Plasma Interactions and Diagnostics #Pulsed Power Technology Applications
paper · doi:10.33232/001c.140729
openalex created_date 2024/09/11 · openalex publication_date 2025/06/10 · openalex updated_date 2026/08/04
UW Coronae Borealis (UW CrB) is a low mass X-ray binary that shows both Type 1 X-ray and optical bursts, which typically last for 20 s. The system has a binary period of close to 2 hours and is thought to have a relatively high inclination due to the presence of an eclipse in the optical light curve. There is also evidence that an asymmetric disc is present in the system, which precesses every 5.5 days based on changes in the depth of the eclipse. In this paper, we present optical photometry and spectroscopy of UW CrB taken over 2 years. We update the orbital ephemeris using observed optical eclipses and refine the orbital period to 110.97680(1) min. A total of 17 new optical bursts are presented, with 10 of these bursts being resolved temporally. The average <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>e</mml:mi> </mml:math> -folding time of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>19</mml:mn> <mml:mo>±</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> s for the bursts is consistent with the previously found value. Optical bursts are observed during a previously identified gap in orbital phase centred on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>ϕ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.967</mml:mn> </mml:mrow> </mml:math> , meaning the reprocessing site is not eclipsed as previously thought. Finally, we find that the apparent P-Cygni profiles present in some of the atomic lines in the optical spectra are due to transient absorption.