Astronomers detect a new catastrophic variable system

Using NASA’s Swift spacecraft, astronomers have discovered a new catastrophic variable (CV) from its ultraviolet (UV) burst activity. The renewed CV, designated TUVO-21acq, was detected as part of the Transient UV Objects Project (TUVO). The finding is reported in a paper published June 21 on arXiv.org.

Cataclysmic variables (CVs) are: binary star systems consisting of a primary white dwarf accreting matter from a normal companion of a star. They increase in brightness irregularly by a large factor and then fall back to a resting state. These binary stars have been found in many environments, such as the center of the Milky Way galaxy, the solar environment, and within open and globular clusters. in resumes, mass transfer of the companion star often occurs through a accretion disk around the white dwarf and in some cases thermal instability in the disk causes an outburst known as a dwarf nova (DN).

Now, a team of astronomers led by David Modiano of the University of Amsterdam, the Netherlands, reports the finding of a new CV in the field targeting the spiral galaxy NGC 4945. The new transient was detected in the UV band, about six arc minutes from the center of this galaxy. The discovery was made using data from the Ultraviolet Optical Telescope (UVOT) aboard Swift.

“Within our TUVO project, we have discovered and characterized a new catastrophic variable in the UV, which we have designated TUVO-21acq. The first detection was made in February 2021 using our dedicated TUVOpipe pipeline, which analyzes daily UVOT data. to look for transients. A second UV burst was detected in January 2022,” the researchers explained.

The astronomers used UVOT to narrow down the properties of TUVO-21acq, focusing mainly on the amplitudes and time scales of the two eruptions. They found that during the first eruption, the source’s brightness increased by at least 4.1, 2.4 and 3.5 magnitudes, and by 4.4, 3.4 and 3.6 magnitudes in the second eruption. three UV bands.

By calculating the time between the first and last detection of each burst of TUVO-21acq, the researchers determined lower limits for the duration of the first and second burst, which were estimated to be 6.1 and 10.7 days, respectively. The upper limits for the first and second eruptions were calculated to be 21.1 and 45 days, respectively.

According to the study, key parameters of TUVO-21acq’s outbursts derived from UVOT photometry, including the amplitudes, duration and recurrence time, were found to be completely consistent with dwarf novae. In addition, the general shape and key emission features shown in the spectrum suggest that the source is a quiescent, catastrophic variable. Therefore, the astronomers classified TUVO-21acq as a DN CV.

“We confirm the nature of the source as a growing white dwarf that has undergone DN. eruption based on photometric and spectroscopic properties,” the scientists concluded.

They added that their finding demonstrates TUVO’s capabilities in discovering new, previously unclassified transients in the UV wavelength range.

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