British astronomers have discovered a new type of starburst. This is how researchers at Durham University report a micronova. The scientists published their results in the journal Nature. Much smaller than traditional supernovae, these new explosions occur when a white dwarf sucks material from a companion star, causing nuclear fusion and an explosion in the process. Strong magnetic fields also play a role in such a micronova, which confines the chain reaction to certain regions in the binary constellation.
Observations over the past 40 years might now be given an explanation
Already in the last 40 years there have been several reports of unexplained rapid outbursts from the binary star system TV Columbae. During these outbursts, the optical/ultraviolet luminosity increases more than threefold in less than an hour and fades once more following regarding ten hours. The cause of these outbursts was previously unknown, but it has long been suggested that they may be related to the accretion of mass onto a moderately magnetized white dwarf by a low-mass companion. The new investigations have now been able to determine the nature of these outbursts and their impact on the binary star system.
Fast outflows were observed in the ultraviolet spectral lines with the help of NASA’s TESS space telescope and the Very Large Telescope of the European Southern Observatory (ESO) in Chile. The velocities of these currents were more than 3,500 kilometers per second, comparable to the escape velocity from the surface of a white dwarf. The researchers were able to detect the explosions in TV Columbae and in two other accretion systems, EI Ursae Majoris and ASASSN-19bh. The bursts have a total energy that is regarding 10−6 the energy of classical nova explosions and show a strong resemblance to type I X-ray bursts.
Explosion only affects certain star regions
“This event challenges our understanding of how thermonuclear explosions occur in stars,” quoted Science magazine Scinexx Research director Simone Scaringi. “Given the short duration and energies released, this thermonuclear reaction must be confined to a small area of the stellar surface, burning only a limited amount of material.” The reason for this might be the existence of strong magnetic fields.
Astronomers have long been fascinated by the explosive phenomena known as nova bursts. These outbursts are believed to be caused by a sudden release of energy as nuclear reactions take place in the surface layers of an accreting white dwarf star. This process occurs when the temperature and pressure of stellar material become so high that nuclear fusion reactions proceed in a self-sustaining manner.
So far, it has only been theoretically predicted that the same process might also lead to localized thermonuclear outbursts, similar to those observed in accreting neutron stars. Now the British researchers have probably been able to provide actual evidence of such micronovae. Although research into nova explosions is still in its infancy, it is hoped that further research will help shed light on these mysterious events.
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