An international team of astronomers have discovered a new binary system consisting of an M dwarf orbiting its star. A passing dwarf star allows you to see the so-called relativistic radiant effect. This is reported in a document posted on August 20 in arXiv pre-print.
The relativistic aurora effect, also known as Doppler amplification, is the process by which relativistic effects alter the apparent luminosity of an emitting substance moving at a speed close to the speed of light. The process is caused by the reflex motion of the stars, introducing changes in the photometric flux due to the Doppler effect.
Radial effect measurements are important for binary astronomers because they allow an independent estimate of the radial velocity of the secondary components. This can be critical in uncovering the physical parameters and nature of such systems.
Now, using data from NASA's Kepler spacecraft's extended mission known as K2, a team of researchers led by Philip Eigmuller of the German Aerospace Center (DLR) has studied the star EPIC 219654213, which was originally identified as a potential host for the planetary system.
However, the K2 data, supplemented by subsequent spectroscopic observations from ground-based observatories including the Keck Telescope, the Northern Optical Telescope (NOT) and MacDonald Observatory, show that EPIC 219654213 is a binary star. The observation campaign also allowed scientists to determine the fundamental parameters of the newly found system.
“In this article, we provide a detailed description of the OBZ [detached binary eclipse] formed by the main star of the sequence and the companion of M-dwarfs with accurate K2 photometry and subsequent observation of radial velocity on earth,” the astronomers write in the article.
The primary component of the system is a slightly developed main sequence star of the spectral type F7V. The star, about 4.1 billion years from Earth, has a radius of about 1.52 solar radii and a mass similar to that of our Sun.
The companion is a dwarf star of the spectral type M5V, which is about five times smaller and less massive than the Sun. The dwarf is in an almost circular orbit around the primary star, orbiting it every 5.44 days. The system components are divided by approximately 0.065 AU.
The study authors also went into detail about the radiant effect observed in the system, focusing on its amplitude:
“The results show a 35 ppm radiant effect amplitude variation, accounting for 50 percent of the observed discrepancy between expected and observed radiance effects,” the paper said.
In their concluding remarks, the researchers noted that EPIC 219654213 should be further explored through exoplanet hunting missions such as NASA Transiting Exoplanet Survey Satellite (TESS) and PLAnetary Transits and EZA (ESA) and star hunting (PLATO). More observations of this system may confirm that its smaller component is indeed an M dwarf or brown dwarf, or, which is also possible, a highly bloated exoplanet – 'hot Jupiter'.
