Quadruple system HD 135160 in a unique 2+2 configuration

¹ Astronomical Institute of Charles University, Faculty of Mathematics and Physics, V Holešovičkách 2, CZ-180 00 Praha 8 – Troja, Czech Republic
² Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA
³ Department of Physics and Astronomy, High Point University, High Point, NC, 27268 USA
⁴ Variable Stars South, Congarinni Observatory, Congarinni, NSW, 2447 Australia
⁵ European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Casilla, 19001 Santiago 19, Chile

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 10 October 2025
Accepted: 8 November 2025

Abstract

Analysing a large body of observational data, we found that HD 135160 is a quadruple 2+2 system, composed of a massive ellipsoidal binary (‘heartbeat’ star) with components Aa and Ab in an eccentric 8.234 d orbit and an eclipsing binary (with components Ba and Bb), with a 5.853 d period and partial eclipses that have already been reported from the space photometry secured by the Transiting Exoplanet Survey Satellite (TESS). Our systematic echelle spectroscopy, secured since September 2021, led to the discovery that the optical spectra are dominated by spectral lines of three early-type stars, two moving around each other on a 8.234 d orbit of a high eccentricity, which causes periodic brightenings near the periastron passage, and the third one (component Ba) being the brighter component of the 5.853 d binary. Both pairs are physically bounded and revolve around each other with a period somewhere between 1600 and 2200 days (4.4–6 years). The object exhibits small cyclic light variations of a variable amplitude and characteristic time scale of 0_.^d071 (14.14 c d⁻¹), seen throughout the whole orbit. The nature of these tiny changes deserves further investigation. It also seems that the earlier classification of the object as a Be star is unfounded.