Scientists find eclipsing binary system of M-dwarf stars
Faint stars are tidally locked to one another in a close, circular orbit.

Laurel Kornfeld | Apr 19, 2018

A group of scientists studying archival data collected by the Sloan Digital Sky Survey (SDSS) and the Catalina Sky Survey (CSS) discovered a never before seen binary star system composed of two low-mass M-dwarf stars in a close orbit around one another.

Eclipsing binaries are binary star systems in which the orbital plane of both stars line up with an observer's line of sight, enabling the observer to see each of the stars eclipse the other.

An advantage of binary systems is that scientists can directly measure the mass, radius, and even temperature of both stars in the system.

Designated SDSS1156-0207, the newly-found system is composed of two very faint stars that orbit each other every 0.3 days.

The larger star measures 0.46 solar radii and has 0.54 solar masses. Its smaller companion has a radius about 30 percent that of the Sun and just 0.19 solar masses.

Separated by just 0.0077 AU (astronomical units, with one AU equal to the average Earth-Sun distance or 93 million miles), both stars are tidally locked to each other, meaning each has one hemisphere that always faces its companion and another hemisphere that always faces away from its companion.

They orbit one another in circular rather than elliptical orbits.

While the larger star is estimated to have a temperature of 3,101 degrees Kelvin (5,122 degrees Fahrenheit), its partner is cooler, with an estimated temperature of 2,899 degrees Kelvin (4,759 degrees Fahrenheit).

In contrast, the Sun's temperature is about 5,778 degrees Kelvin (9,941 degrees Fahrenheit).

After the system was found in both the SDSS and CSS archives, the researchers conducted followup radial velocity observations using the Gemini Multi-Object Spectrograph (GMOS) on Hawaii's Gemini North telescope.

"In this work, we present a double-lined, M dwarf eclipsing binary discovered from cross matching Catalina Sky Surveys and Sloan Digital Sky Survey. The physical properties of this system are further characterized using the Gemini telescope," they wrote in a paper accepted for publication in the journal Solar and Stellar Astrophysics.

As a next step, the researchers plan to use high-resolution spectroscopy to learn more about the activity level of each star and the system's general properties.

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