An international team of astronomers has discovered a new cataclysmic variable (CV) using NASA’s Swift spacecraft. It lies six arc minutes from the center of the spiral galaxy NGC 4945, 11.7 million light-years from the Milky Way. The discovery is announced in a preprint published in the arXiv repository.
The object, which exhibits burst activity in the ultraviolet range, was designated TUVO-21acq because it was found by the Transient UV Objects Project (TUVO). It, like other cataclysmic variables, is a binary star system consisting of a white dwarf that pulls matter from a companion star. Due to accretion, the white dwarf increases its brightness several times, and then again loses its brightness. In addition, the accretion disk, due to thermal instability, can produce powerful explosions known as dwarf novae (DN).
In total, astronomers recorded two outbreaks, one in February 2021, and the other in January 2022. The results of observations showed that during the first outburst the brightness of the source increased by at least 4.1, 2.4 and 3.5 magnitudes, and during the second outburst – by 4.4, 3.4 and 3.6 magnitudes in three UV ranges. Scientists have also determined lower limits for the duration of the first and second outbreaks, which are estimated at 6.1 and 10.7 days, respectively. The upper limits for the first and second outbreaks are 21.1 and 45 days, respectively.
Scientists note that the parameters of the flares turned out to be fully compatible with the model of dwarf novae. Therefore, the authors of the study classified TUVO-21acq as DN CV.