An international team of astronomers using the ESO Very Large Telescope has detected an unusual arc-shaped shock wave around the binary system RXJ0528+2838. The white dwarf in this pair is producing a powerful bow shock in the interstellar medium, contrary to all existing theoretical models, despite the absence of an accretion disk and any visible mass transfer. The results were published in the journal Nature Astronomy.

An unexpected finding 730 light-years away

RXJ0528+2838 is a binary system located about 730 light-years from Earth. A white dwarf, the dense remnant core of a low-mass star, orbits a Sun-like companion. As the system moves through interstellar gas, a characteristic arc-shaped structure is expected to form ahead of it, similar to the bow wave in front of a ship.

Such shock waves normally arise from strong stellar winds or outflows of matter from a white dwarf fed by an accretion disk. In the case of RXJ0528+2838, however, no such disk is observed, no mass transfer is detected, and the system appears calm and inactive.

Simone Scaringi, associate professor at Durham University and one of the leaders of the study, explained that the team had found something never seen before and, most importantly, completely unexpected.

His colleague Krzysztof Iłkiewicz from the Nicolaus Copernicus Astronomical Center stated that the observations pointed to a strong outflow of matter which, according to current understanding, should not exist in such a system.

How the connection was proven

The strange nebular structure was first noticed in images from the Isaac Newton Telescope in Spain. It was then studied in detail using the MUSE instrument on the ESO Very Large Telescope in Chile. These observations made it possible to establish that the shock wave is indeed physically associated with the binary system and is not a случайный interstellar cloud seen along the line of sight.

The shape and size of the structure indicate that the white dwarf has been expelling matter for at least a thousand years.

A possible explanation

The researchers suggest that a strong magnetic field of the white dwarf may play a key role. Such a field could channel material from the companion star directly onto the surface of the white dwarf, bypassing the formation of an accretion disk. However, calculations show that even with this effect taken into account, current models can explain only part of what is observed.

The discovery challenges standard ideas about the evolution of matter and interactions in binary systems containing white dwarfs. It points to the existence of an unknown energy source or physical mechanism that does not yet fit within established theories.

What comes next

Astronomers hope to find more similar objects using the future ESO Extremely Large Telescope. This will help determine how common such anomalous systems are and clarify which physical processes are responsible for their behavior.

In brief

Astronomers have discovered a powerful shock wave around the binary system RXJ0528+2838, where a white dwarf has been expelling matter for about a thousand years without an accretion disk or visible mass transfer. This contradicts all current models of how such systems should behave. A strong magnetic field is considered a possible explanation, but it accounts for only part of the effect. The finding challenges standard views of binary systems with white dwarfs and opens a new direction for research.