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RE 0618 + 7 5 - A very short-period, binary dMe system

Jeffries, R.D.; Elliott, K.H.; Kellett, B.J.; Bromage, G.E.


K.H. Elliott

B.J. Kellett

G.E. Bromage


We report on the discovery of a new, very short-period, chromospherically active, late-type binary system. Observations performed with the ROSAT Wide Field Camera revealed the EUV source RE 0618 + 75, and subsequent optical spectroscopy identified this source as a chromospherically active, double dMe star with intense Ca II H and K and Hα emission lines. Further spectroscopy revealed that the object is a binary system with a period of 0.539 d, a mass ratio of unity and a systemic velocity of – 14 km s–1. Spectral types of M3 for both components are deduced from low-resolution spectra, and this yields a system inclination of 34° and component separation of 2.4 R⊙. RE 0618 + 75 is the most rapidly rotating, binary dMe system known, yet the magnetic activity observed is no greater than many similar, but more slowly rotating, dMe stars. This reinforces the concept of activity saturation in rapidly rotating stars.


Jeffries, R., Elliott, K., Kellett, B., & Bromage, G. (1993). RE 0618 + 7 5 - A very short-period, binary dMe system. Monthly Notices of the Royal Astronomical Society, 265(1),

Journal Article Type Article
Acceptance Date May 10, 1993
Online Publication Date Nov 1, 1993
Publication Date 1993-11
Deposit Date Feb 8, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 265
Issue 1
Publisher URL