Summary: SEPARATING THE X-RAY EMISSIONS OF UV CETI A AND B WITH CHANDRA
and Stephen L. Skinner3
Received 2002 October 3; accepted 2003 February 10
We present the first spatially separated X-ray observation of the active UV Ceti binary with Chandra,
providing important new information on the relative X-ray activity levels of its nearly identical dM5.5e com-
ponents. The two components had similar X-ray luminosities during low-level periods, and emission measure
loci derived from Low Energy Transmission Grating spectra reveal similar coronal temperatures (36 MK).
However, the B component showed a higher degree of variability, resulting in a higher average X-ray
luminosity than that of UV Cet A. We discuss possible causes of this enhanced activity in UV Cet B.
Subject headings: binaries: visual -- stars: coronae -- stars: flare -- stars: individual (UV Ceti) --
stars: late-type -- X-rays: stars
The nearby (d ¼ 2:7 pc) binary UV Ceti (GJ 65 AB;
L726-8 AB) is composed of two dM5.5e stars with similar
masses and radii (M % 0:1 M, R % 0:15 R) in a highly
eccentric orbit with a period of 26.5 yr and a semimajor axis
of %200 (5.06 AU; Worley & Behall 1973; Geyer, Harrington,