Low-Energy X-Ray Observations of the Wolf 630 System

Abstract

The septuplet of M dwarfs is resolved into three components, Wolf 630ABab, Wolf 629ab, and VB 8AB, with the EXOSAT channel multiplier array (CMA). W 630 and VB 8 have previously been observed with the Einstein high resolution imager (HRI). The ratio of CMA to HRI count rates for VB 8 can be produced with an isothermal plasma model temperature T = 6.4×10⁵K, which is exceptionally low in the known range of coronal temperatures. The count rate during 18,112 s of effective exposure with EXOSAT shows that VB 8 flared once in 0.05 - 2 keV flux.