Nature of the exploding star revealed

(ORDO NEWS) — US and Israeli astronomers have revealed that CT Eridani is a repeated nova, that is, an object that generates bright flashes with a period of several tens of years.

A preprint with the results of the study is published on the arXiv website.

A nova is a star that suddenly increases in brightness by a thousand or million times and slowly returns to its original state, which can take several months.

This phenomenon occurs in binary systems consisting of a white dwarf and a main sequence star that is a material donor.

Matter flows from it to the white dwarf, forming an accretion disk. As hydrogen accumulates in the surface layer of the dwarf, nuclear reactions begin to occur, the speed of which at some point increases explosively.

Eridani’s CT is a nova that was discovered in 2009 when it peaked at magnitude 5.42 (November 14).

By November 25, the brightness had fallen by three magnitudes, which allowed it to be classified as a very fast nova.

To better understand the nature of the object, the researchers analyzed large sets of photometric data collected by various instruments, including the TESS and Gaia space telescopes.

The results showed that a white dwarf with a mass of 1.25 solar masses has an orbital period of about 2.61 days and is located at a distance of about 16,600 light years.

Its companion has already ceased to be a main sequence star and is now a subgiant with a radius of about 3.7 solar radii and a temperature of 6200 kelvins.

The accretion rate is 3.5 times 10 to the minus 7th power of solar masses per year.

Due to the large mass of the white dwarf and the very high accretion rate of the Eridanian CT, it will take a short time to accumulate the necessary mass to trigger the next nova event.

Calculations give a return period of 12 years, but with a possible range of 5 to 50 years.

Combined with archival data, the researchers concluded that the most likely recurrence period should be between 40 and 50 years.

Thus, Eridani’s CT is a repeated nova, and the previous outburst remained undiscovered during the period of the solar survey from 1959 to 1969.


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